A grading system for direct laryngoscopy

Anaesthesia, 1999, 54, pages 1007±1024 ................................................................................................................................................................................................................................................

Correspondence Vaporisers

The editorial on vaporisers (Anaesthesia 1999; 54: 519±20) is very good as far as it goes. Does it go far enough? I think not. The reader will look in vain for mention of the electronic and technical revolutions in monitoring. These have enabled the anaesthetist to analyse and measure with great accuracy, breath by breath, the inhaled and exhaled concentrations of the gases and volatile agents which are the current tools of the trade; and even, by computer wizardry, to display, numerically and graphically, the MAC values. All these values (including many physiological ones) can be taken off the screen and printed so as to provide a permanent record of a patient's anaesthetic. Given our new-found monitoring abilities, do we really need the expensive, clumsy and complex calibrated vaporisers of which the editorial speaks? Do they have to be temperature and ¯ow compensated? The Goldman, or equivalent, used as a vaporiser-in-thecircle (VIC), is a perfect example of a simple, cheap apparatus neither calibrated nor ¯ow- and temperature-compensated but, when used with modern technology, is both effective and safe. In the same way we might even ®nd, if we really wanted a vaporiser mounted on an anaesthetic machine backbar, that the old-fashioned Boyle's bottle would be good enough. Admittedly, good enough is not good enough: we need something better. Both we and the manufacturers should start thinking. As the editorial points out, we only buy anaesthetic equipment

the way they are because `the manufacturers produce them like that'. Not only do they produce them like that, they design them like that. On whose say-so? Why do they design them like that? Take vaporisers. Suppose we said to the manufacturer: `Volatile anaesthetics come to us as liquids stored in bottles. We would like to see them as a gel stored in something analogous to the ink-jet cartridge of a computer's printer. You would simply slot the cartridge into a newly designed `ùniversal'' vaporiser. Each cartridge would incorporate a device which would tell both the vaporiser and the anaesthetist which agent was in use; although, with modern vapour analysers that would simply act as a safety device. Changing the chosen agent to a different agent, or replacing an empty cartridge, would be simplicity itself. There should be no need for more than one such `ùniversal'' vaporiser for each anaesthetic machine backbar, and one for each VIC circle system''. That might raise some hackles. The time has come, it seems to me, when we, as anaesthetists, should tell the manufacturers what we want, and not take from them what they want. We should not continue to allow them to lead us down blind and expensive alleys; and we should insist on innovation: affordable innovation, but still ÿ innovation. We could help ÿ if only they would ask us. P. V. Scott Alexandra Healthcare NHS Trust, Redditch, Worcestershire B98 7UB, UK

Ventricular ®brillation during spinal surgery

I was interested to read the case report of ventricular ®brillation in the prone position during back stabilisation surgery in a boy with Duchenne's muscular dystrophy (Anaesthesia 1999; 54: 364±7) and feel that its publication raises a couple of important issues. Firstly, it reinforces the view that correction of scoliosis surgery should not be taken lightly, as it is indeed life-threatening surgery, especially as many of the children have concomitant disease that complicates anaesthesia, as in the case described. Second, it does raise the problem of cardiopulmonary resuscitation in the prone position. However, my main concern is the sentence in the discussion that reads `However, the application of commercially available stick-on precordial de®brillator pads, which would have allowed immediate safe de®brillation, may have obviated the need for thoracotomy'. The implication of this is that de®brillation was not carried out due to absence of these pads. As the authors state, prompt de®brillation may have restored cardiac output straight away. Both the Paediatric Advanced Life Support and Advanced Paediatric Life Support manuals [1, 2] stress the importance of immediate de®brillation in ventricular ®brillation. The pads only serve to reduce the electrical resistance between the paddles and the chest wall; in their absence, de®brillation can still be used with the use of aqueous lubricating jelly found in all operating theatres, as this will serve the same purpose. Even if this was not available, I would suggest that de®brillation

All correspondence should be addressed to Professor M. Harmer, Editor of Anaesthesia, Department of Anaesthetics, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK. Letters (two copies) must be typewritten on one side of the paper only and double spaced with wide margins. Copy should be prepared in the usual style and format of the Correspondence section. Authors must follow the advice about references and other matters contained in the Notice to Contributors to Anaesthesia printed at the back of each issue. The degree and diplomas of each author must be given in a covering letter personally signed by all the authors. Correspondence presented in any other style or format may be the subject of considerable delay and may be returned to the author for revision. If the letter comments on a published article in Anaesthesia, please send three copies; otherwise two copies of your letter will suf®ce.

Q 1999 Blackwell Science Ltd

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Correspondence Anaesthesia, 1999, 54, pages 1007±1024 ................................................................................................................................................................................................................................................

should still have been attempted without any lubricant before performing thoracotomy. Cardiac massage only serves to maintain some perfusion whilst awaiting de®nitive therapy, which is de®brillation in the case of ventricular ®brillation. I would urge all anaesthetists to check that there are de®brillator pads on their resuscitation carts, and to remind them that aqueous lubricating jelly can be used in its absence. R. J. Marcus The Women's and Children's Hospital, North Adelaide, South Australia References

1 Chameides L, Hazinski MF, eds. Pediatric Advanced Life Support. American Heart Association, 1997: 7±11. 2 Mackway-Jones K, Molyneux E, Phillips B, Wieteska S, eds. Advanced Paediatric Life Support: the Practical Approach, 2nd edn. BMJ Books, 1998: 49.

The recent case report by Drs Reid and Appleton (Anaesthesia 1999; 54: 364±7) highlights dif®culties in the management of children with Duchenne's muscular dystrophy presenting for scoliosis surgery. We have, however, concerns with the recommendations they make for the pre- and peroperative management of such cases. Firstly, they state that à standard electrocardiogram is the simplest and most reliable tool for detecting cardiac involvement in DMD'. We would take issue with this statement. The cardiomyopathy which develops in patients with DMD may result in reduced ventricular ejection fraction. Whilst an electrocardiogram will detect conduction defects in the DMD heart, it may be quite normal in the presence of a reduced left ventricular ejection fraction. A resting echocardiographic study may not accurately predict the cardiovascular response to operative stress, as the authors state; however, it is a mandatory pre-operative investigation in these patients. A preoperative reduction in the left ventricular ejection fraction to below 50% in the resting patient is signi®cant and should

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be considered a contra-indication to surgery [1]. Second, the authors state in their summary that Ìf possible, full invasive monitoring should be instituted pre-operatively, especially for operations which can be associated with large ¯uid shifts'. It is our opinion that both invasive arterial monitoring and central venous pressure monitoring again are absolutely mandatory in this group of patients. If access is a problem, as in their case, then we would suggest, as has happened in our centre in the past, that either a surgical cut down is performed to attain an arterial line or, indeed, the femoral vessels are utilised. If invasive arterial monitoring cannot be achieved, it would be reasonable to abandon the procedure until a future date. Fluid shifts during spinal surgery can be enormous, and in our opinion cannot be managed adequately without such monitoring. R. W. M. Walker T. K. Howell Royal Manchester Childrens' Hospital, Manchester M27 4RA, UK Reference

1 Morris P. Duchenne muscular dystrophy: a challenge for the anaesthetist. Paediatric Anaesthesia 1997; 7: 1±4.

We read with interest the case report by Drs Reid and Appleton (Anaesthesia 1999; 54: 364±7). After the ®rst 6 h, during which `the operation was unremarkable except for heavy blood loss', the patient developed T-wave inversion and broad complex tachycardia with a systolic blood pressure of 90 mmHg. Shortly thereafter, the patient developed ventricular ®brillation, and resuscitation was started by means of direct cardiac massage after a left posterior thoracotomy. The cardiac output was restored, the operation was ®nished with a total blood loss of 12 l and the patient was transferred to the ICU where he made a full recovery. The authors pose that an exact cause is uncertain, and after presenting a few intrinsic causes, they postulate that this is the ®rst case of ventricular ®brillation occurring in the prone position secondary to the cardiomyopathy of DMD. The

authors recognised on the ECG a right axis deviation and a tall R wave in lead V1 which is a common ®nding in DMD cardiomyopathy and discuss that an abnormal ECG is the most discriminating test for detecting cardiac involvement in DMD. Since we assume that the authors were well aware of the patient's cardiac vulnerability, we were surprised to learn that they accepted the technical failure of inserting a radial artery catheter and proceeded with a major operation with anticipated heavy blood loss. Despite the lack of immediate arterial access, we suggest that serial determinations of at least haemoglobin and electrolytes would have been possible and useful. Although it is quite possible that DMD cardiomyopathy was actually the primary cause of cardiac arrest in this patient, we feel that more common causes may have contributed signi®cantly. Because of the lack of haemodynamic and laboratory data, the presence of severe hypovolaemia cannot be excluded. In our experience, hypovolaemia is a continuous threat in scoliosis surgery which, apart from heavy blood loss, is also caused by sequestration of large amounts of ¯uid in the `third space'. Another clue to the possible cause of the arrhythmia may lie in the ®rst blood gas analysis, which was sampled from the left ventricle during suf®cient resuscitation. It shows a pH 6.95, PaCO2 3.68 kPa, PaO2 25.36 kPa, bicarbonate 5.8 mmol.lÿ1, base excess ÿ26.9 mmol. lÿ1 which is compatible with a severe metabolic acidosis. It is of relevance to know whether this acidosis was preexisting and superimposed by the cardiac arrest. Acidaemia frequently raises the plasma potassium concentration by a shift of potassium from the intra- to the extracellular space, which will mask the severity of potassium-depletion. Interpreting the potassium of 4.6 mmol.lÿ1 from the perspective of severe acidosis may suggest a relative hypokalaemia. The initial ECG signs in this patient (T-wave inversion with a broad complex tachycardia) may have been caused by hypokalaemia. In a patient with a vulnerable heart, even a mild hypokalaemia can cause arrhythmias [1]. The European Resuscitation Council Guidelines


Anaesthesia, 1999, 54, pages 1007±1024 Correspondence ................................................................................................................................................................................................................................................

for Resuscitation advise to consider supplementing potassium in patients with broad complex tachycardia [2]. It would be interesting to know the quantity and composition of the ¯uids administered up to the cardiac arrest. In our opinion, this case report emphasises the risks of embarking on major surgical procedures in patients with severe coexisting disease without adequate haemodynamic and laboratory monitoring. J. W. Smeets C. J. Kalkman Academisch Medisch Centrum, University of Amsterdam, the Netherlands References

1 Rose BD. Clinical Physiology of AcidBase and Electrolyte Disorders. McGrawHill, Inc., 1994. 2 Bossaert L, ed. The European Resuscitation Council Guideline For Resuscitation. For the European Resuscitation Council. Elsevier, 1998. 3 Halperin ML, Kamel KS. Electrolyte quintet; potassium. Lancet 1998; 352: 135±40.

A reply The comments by Drs Marcus, Walker and Howell highlight some important points. Dr Marcus is quite right that correction of scoliosis surgery is indeed a major undertaking. Surgery of this nature should not be undertaken lightly. The view of Drs Walker and Howell that both invasive arterial and central venous monitoring are mandatory is also valid and I now feel, like them, that if invasive arterial monitoring cannot be attained, the surgery should be postponed. However, I stand by the view that the ECG is the simplest and most reliable tool for detecting cardiac involvement in patients with Duchenne's muscular dystrophy (DMD). It is a view held by Joseph Perloff in his Chapter in Braunwald's Heart Disease as well as other authors [1, 2]. The vast majority of patients with DMD will have an abnormal ECG even early in the disease [2±5]; tall R waves, or increased R/S ratio, in the right precordial leads and


sinus tachycardia being the commonest abnormalities. The tall R waves arise as the cardiomyopathy associated with DMD affects predominantly the posterobasal and lateral left ventricular walls [1]. It would be very rare to have a `quite normal' ECG in combination with an echocardiogram showing signi®cant systolic left ventricular dysfunction in patients with DMD [3±5]. Clearly, other cardiac investigations, such as echocardiography and 24-h Holter monitoring, are also required pre-operatively to try and further assess the degree of cardiac involvement. However, as mentioned in the case report, it is not always possible to predict those who will have anaesthesia-related complications [6]. In response to the point made by Dr Marcus concerning prompt de®brillation, the delay in this case was because of dif®culty with access to apply conventional paddles and jelly pads of the type which were on the de®brillator in theatre. The prone position, drapes, blood and metalwork limited access to the available skin over the lateral chest wall. Two people were required to hold the paddles to deliver a shock. Remote de®brillation using stick-on precordial pads would have allowed one person to perform this task. Things would have been quicker still if they had been applied to the front of the chest pre-operatively. The points made by Drs Smeets and Kalkman are very valid and selfexplanatory. J. M. Reid Jersey General Hospital, St Helier, Jersey JE2 3QS References

1 Perloff JK. Neurological disorders and heart disease. In: Braunwald E, ed. Heart Disease: a Textbook of Cardiovascular Medicine, 5th edn. Philadelphia: W.B. Saunders, 1997: 1865±83. 2 Bhattacharyya KB, Basu N, Ray TN, Maity B. Pro®le of electrocardiographic changes in Duchenne muscular dystrophy. Journal of the Indian Medical Association 1997; 95: 40±2. 3 Danilowicz D, Rutkowski M,

Myung D, Schively D. Echocardiography in Duchenne muscular dystrophy. Muscle Nerve 1980; 3: 298±303. 4 D'Orsogna L, O'Shea JP, Miller G. Cardiomyopathy of Duchenne muscular dystrophy. Pediatric Cardiology 1988; 9: 205±13. 5 Backman E, Nylander E. The heart in Duchenne muscular dystrophy: a noninvasive longitudinal study. European Heart Journal 1992; 13: 1239±44. 6 Reid JM, Appleton PJ. A case of ventricular ®brillation in the prone position during back stabilisation surgery in a boy with Duchenne's muscular dystrophy. Anaesthesia 1999; 54: 364±7. A grading system for direct laryngoscopy

We have followed with interest the recent article by Dr Yentis and Lee [1] and subsequent letter by Dr Cook [2] on laryngeal grading. As each of these authors point out, the Cormack and Lehane grading system has numerous problems; grades are ambiguous between grades 1 and 2, and these grades apply to 95±99% of laryngeal views. Dr Cook correctly explained in his letter the ambiguity of the original de®nitions and discordance between the drawings and descriptions of grades in the original articles [3, 4]. Cohen et al. have pointed out the confusion amongst British anaesthetists at correctly de®ning Cormack/ Lehane (CL) grades [5]. Not only is there ambiguity between grades 1 and 2, but there is also ambiguity within these grades. Benumof, for example, has noted that a grade 1 view includes anywhere from 1 to 100% visualisation of the vocal cords [6]. Numerous authors, including Drs Yentis and Lee, have attempted to subcategorise grades 1 and 2 [1, 7±9]. We believe there is a more critical de®ciency with CL grading and modi®cations of CL grading as proposed by Drs Yentis and Lee. The visual restrictions inherent to laryngoscopy cause laryngeal sighting to occur with only one eye [10]. Therefore, two people cannot simultaneously sight the same

1009


laryngeal view. CL grading has never been validated between observers. Historically, no studies have addressed whether two people seeing the same laryngeal view simultaneously agree with the assignment of CL grades. In the process of testing an imaging system for direct laryngoscopy, we discovered that CL grading was inadequate at categorising the laryngeal images we obtained [11]. As with prior studies, we found that almost all views fell into grades 1 or 2, and distinguishing between these grades was dif®cult. To better describe the laryngeal views recorded with the imaging system we devised the percentage of glottic opening (POGO) score [12]. The POGO score represents the percentage of glottic opening seen, de®ned by the linear span from the anterior commisure to the interarytenoid notch (Fig. 1). A 100% POGO score is a full view of the glottis from the anterior commisure to the interarytenoid notch. A POGO score of 0 means that even the interarytenoid notch is not seen. The POGO score replaces CL grades 1 and 2 with a continuous numerical value. Unlike CL grading, POGO score is not dependent upon visualisation of the vocal cords. We have found that shadowing by the epiglottis frequently causes the vocal cords to be poorly visualised even though the glottic opening is clearly delineated. The descriptive nature of the POGO score is easily understood with minimal explanation, and does not require memorisation of numerical and alphabetical categories. We have recently conducted two studies on the validity of POGO scoring as

Figure 1 The percentage of glottic open-

ing (POGO) score for laryngeal grading. The POGO score represents the linear span from the anterior commissure to the interartytenoid notch.

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compared with CL grading [12, 13]. The participants, anaesthetists and emergency physicians, were asked to grade laryngeal views obtained with the imaging system using both CL grades and POGO scoring. We measured both intra- and inter-observer reliability. CL grading and POGO scoring were found to have good intrareliability. Between observers, however, there was very poor agreement with CL grading and very good agreement with POGO scoring. POGO scoring does not distinguish between CL grades 3 (epiglottis) and 4 (tongue) views, as each would have a score of 0. This could be addressed descriptively, however. We are currently assessing the correlation between POGO scores and ease of intubation, as well as evaluating POGO scoring using dynamic images of laryngoscopy. Although further studies are needed, POGO scoring has numerous advantages over CL grading for laryngoscopy research and clinical application. It is a validated, continuous numerical method that is more sensitive than CL grading, and easy for all to understand and apply. R. M. Levitan J. E. Hollander E. A. Ochroch Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA References

1 Yentis SM, Lee DJH. Evaluation of an improved scoring system for the grading of direct laryngoscopy. Anaesthesia 1998; 53: 1041±4. 2 Cook TM. A grading system for direct laryngoscopy. Anaesthesia 1999; 54: 496±7. 3 Cormack RS, Lehane J. Dif®cult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105±11. 4 Williams KN, Carli F, Cormack RS. Unexpected dif®cult laryngoscopy: a prospective survey in routine general surgery. British Journal of Anaesthesia 1991; 66: 38±44. 5 Cohen AM, Fleming BG, Wace JR. Grading of direct laryngoscopy. A survey of current practice. Anaesthesi 1994; 49: 522±5. 6 Benumof JL. Conventional

7

8

9

10

11

12

13

(laryngoscopic) orotracheal and nasotracheal intubation (single-lumen tube). In: Benumof JL, ed. Airway Management: Principles and Practice. St. Louis: Mosby-Yearbook, 1996: 266. Benumof JL, Cooper SD. Qualitative improvement in laryngoscopic view by optimal external laryngeal manipulation. Journal of Clinical Anesthesia 1996; 8: 136±40. Takahata O, Kubata M, Mamiya K, et al. The ef®cacy of the `BURP' manoeuvre during a dif®culty laryngoscopy. Anesthesia and Analgesia 1997; 84: 419±21. Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting dif®cult intubation. British Journal of Anaesthesia 1988; 61: 211±16. Levitan RM, Ochroch AE, Higgins MS. Contrary to popular belief and traditional instruction, the larynx is sighted one eye at a time during direct laryngoscopy. Academic Emergency Medicine 1998; 5: 844±6. Levitan RM. A new tool for teaching and supervising direct laryngoscopy. Academic Emergency Medicine 1996; 3: 79±81. Ochroch EA, Hollander JE, Kush S, Shofer FS, Levitan RM. An outcome measure to assess glottic visualization: Validation of the percentage of glottic opening (POGO) scale [abstract]. Academic Emergency Medicine 1999; 6: 506. Levitan RM, Ochroch EA, Kush S, Shofer F, Hollander JE. Assessment of airway visualization: validation of the percent of glottic opening (POGO) scale. Academic Emergency Medicine 1998; 5: 919±23.

MRSA contamination of a laryngoscope blade: a potential vector for cross infection

We read with interest the paper by Esler et al. (Anaesthesia 1999; 54: 587±92) regarding their survey of practices for decontamination of laryngoscopes in Great Britain. We recently conducted a study to survey the incidence of contamination of laryngoscope blades in our operating department and to determine whether the cleaning procedures were adequate. In this institution, different Q 1999 Blackwell Science Ltd


methods are employed for cleaning laryngoscope blades between the intensive care unit and the operating department. Methicillin-resistant Staphylococcus aureus (MRSA) infection is a particular problem in our hospital. Following concerns expressed about the risks of cross infection, especially in relation to MRSA, laryngoscope blades on the intensive care unit are routinely sent to the hospital sterilisation and disinfection department (HSDU) for sterilisation after each patient use, as with 22% of institutions reported in Esler et al. In contrast, the operating department has no written policy for cleaning. It is normal practice in the operating theatre that the blade is removed from the handle, scrubbed with a plastic reusable brush and HibiscrubTM and then rinsed under a running tap. The blade is dried with a nonsterile paper hand towel and left on the counter top in the anaesthetic room. The sampling of 20 laryngoscope blades was carried out at the end of a routine day of theatre operating lists. No advanced notice had been given to anaesthetic personnel. Laryngoscope blades were identi®ed as ready for patient use if they were found attached to the laryngoscope handle and left on the intubation tray in the anaesthetic room. All the blades were of a standard Macintosh design with either a conventional bulb or a ®breoptic light. Using a `no touch' technique, the laryngoscope was picked up by the handle and the blade was visually inspected. A `Transwab' was moistened in sterile saline and wiped over the shaft of the blade and around the light source. Sampling was not done around the joint between the blade and the handle. Swabs were cultured on blood agar, aerobically and anaerobically and on MacConkey agar. Selective enrichment culture for MRSA was carried out by incubating swabs in 6% salt broth and subculturing onto mannitol salt agar with added methicillin (4 mg.lÿ1). Upon visual inspection, 10 (50%) blades appeared to be clean. Particulate matter was observed on the 10 remaining blades. Varying degrees of contamination were seen on the blade tip (4), light source (7) and blade shaft (3). Of the 20 samples plated, eight had no


Table 1 Contamination of laryngoscope blades

No growth MRSA Commensal oropharyngeal ¯ora Viridans streptococci Bacillus sp. Total

growth reported, ®ve grew commensal oropharyngeal ¯ora, ®ve grew viridans streptococci, one grew Bacillus sp. and one grew MRSA with low-level resistance to mupirocin. The results of the study are illustrated in Table 1. The results of our study demonstrate that the current procedure for the cleaning of laryngoscope blades in our operating department is not effective. Furthermore, another potential vector for the noscomial spread of MRSA has been identi®ed. Although this study cannot be projected beyond this hospital, the cleaning methods described are not unique to this operating department, as illustrated in the national survey. Heat treatment in an automatic washer is being trialed but damage to the light source is a recurring problem. J. E. R. Beamer R. A. Cox Kettering General Hospital, Kettering, Northants. NNI6 8UZ, UK An unusual complication of tracheostomy

An elective tracheostomy performed in an obtunded patient to avoid consequences of long-term intubation caused an important critical incident in our hospital. A 46-year-old man had an elective tracheostomy using a Ciaglia percutaneous tracheostomy set. A 7.5-mm cuffed PVC Mallinckrodt tracheostomy was sited and the patient was transferred from Intensive Care to the ward selfventilating the following day. Three days later, the on-call anaesthetist was called urgently to the ward. The patient's tracheostomy tube appeared to have broken, the ¯ange detached and the

Clean on visual inspection

Contaminated on visual inspection

3 1 2 3 1 10

5 0 3 2 0 10

body of the tube retained within the trachea. The patient had been repeatedly knocking the tracheostomy but was ventilating well. Traction on the still attached pilot line did not visualise the tube at the stoma. In the operating theatre, aids to intubation and ventilation were prepared including an intubating ®breoptic laryngoscope and a set of tracheostomy instruments. An ENT surgeon attended urgently and with use of headlight and tracheal dilators, the end of the tube was eventually grasped and, with the cuff de¯ated, the tube retrieved through the stoma. A size 7.0-mm Portex cuffed tracheostomy tube was immediately reinserted. The patient settled well returning to the ward on 28% oxygen that night. On examination, the tracheostomy tube was noted to be cleanly separated, rather than fractured, from the ¯ange (®gure overleaf). The problem was reported to the manufacturer the following day. Fracture of tracheostomy tubes at the junction of the body and ¯ange has been described rarely and mostly involves metal tracheostomy tubes. The earliest report in 1960 [1] involved a batch defect of a 14day-old silver±nickel alloy tube. Other reports have involved prolonged use and repeated removal, re-cleaning and reinsertion. Fracture of a nonmetallic tracheostomy tube was ®rst reported in 1973 [2] when two PVC tubes were used alternately over 5 years. Prolonged use in this and following reports was again cited. The only report similar to our case was in 1993 [3]. A fractured PVC cannula had entered the right main bronchus and was removed by ®bre-optic bronchoscopy under local anaesthetic. Fortunately, we were able to retrieve the body of the tracheostomy tube under direct vision

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using topical anaesthesia in a self-ventilating patient. The tube had not been exposed to the problems of prolonged use and a manufacturing fault is a likely cause of failure. The tracheostomy is manufactured in two parts and the body and ¯ange glued together. Samples of each batch are pressure tested at room temperature using weights of 25±30 lb for 4 h. The tracheostomy is subsequently sterilised with ethylene oxide. The adhesive product is thermosensitive and it is possible that the glue may have softened with an increase to body temperature. Repeated knocking of the tracheostomy tube by the patient may have exposed an inherent weakness at this junction. Following noti®cation of the incident, Mallinckrodt have released a product batch recall and the Medical Devices Agency have also issued a safety notice (Reference MDA SN1999 (19)). F. V. Smith The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK References

1 Bossoe HH, Boe J. Broken tracheostomy tube as a foreign body. Lancet 1960; 1: 1006. 2 Sood RK. Fractured tracheostomy tube. Journal of Laryngology and Otology 1973; 87: 1033±4.

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3 Malhotra B, Kallan BM. An unusual foreign body in tracheobronchial tree: removed by ®breoptic bronchoscope. Indian Journal of Chest Disease and Allied Science 1993; 35: 85±8.

Cervical spine movements during laryngoscopy

We read with interest the study on the `Cervical spine movements during laryngoscopy' (Anaesthesia 1999; 54: 413±18). One thing that concerned us was that in the method section it is stated that informed verbal consent was given for the procedure. The procedure involved exposure to X-rays and this carries a potential risk to patients. We think that for all research, written consent is more appropriate with detailed explanation of the potential risks and bene®ts involved. Most ethics committees would demand this before giving approval to a study. It is possible that it could have been a printing error stating that verbal consent was taken instead of a written consent and but we feel that this issue is suf®ciently important not to go unchallenged. K. Gupta C. Frerk Nothampton General Hospital, Northampton NN1 5BD, UK

A reply We thank Drs Gupta and Frerk for their comments on our paper. All our patients were competent adults, and were provided with a full written information sheet at the pre-operative visit, which detailed the purpose, risks and bene®ts of the study. As stated in our methods section, they then gave informed verbal consent which was duly recorded in writing by the investigators. We felt that this was an acceptable level of consent, but are concerned to discover that this was a misinterpretation of our original ethics application. We have since discussed the matter and apologised to our ethics committee who feel that we have been in error, but are satis®ed that we have not acted unethically in our consent procedure. However, we are grateful to Drs Gupta and Frerk for pointing this out, and for raising the dif®cult matter of what actually constitutes valid consent for research. P. A. Macintyre A. D. M. McLeod R. Hurley C. Peacock The Middlesex Hospital, London WIN SAA, UK Tension pneumothorax and pneumomediastinum after nasogastric tube insertion

Insertion of a nasogastric tube can be dif®cult at times and has been associated with pneumothorax [1, 2]. One technique proposed to facilitate insertion in dif®cult cases describes the use of a gastroscope biopsy forceps as a `guidewire' to ease insertion [3]. We report a case where the patient developed both tension pneumothorax and pneumomediastinum when this technique was attempted. The case involved a kyphotic 77year-old woman in the intensive care unit recovering from severe diabetic ketoacidosis and subsequent above knee amputation for left lower limb embolism. She had received intermittent positive pressure ventilation for 3 days and had been extubated. Six hours later, she pulled out the nasogastic tube that had previously been dif®cult to



Figure 1 Chest radiograph showing right-sided pneumothorax (thin arrow) and

pneumomediastinum (thick arrow).

insert. The patient was drowsy (not on any sedation) and on 28% supplemental oxygen. In addition, she was not taking oral ¯uids. Attempts to insert another tube in the conventional manner were unsuccessful. It was decided to attempt the procedure using the technique described by Campbell [3]. Brie¯y, it involves the use of a lubricated gastroscope biopsy forceps of suitable diameter as a `guidewire'. Since the normally ¯exible forceps can be made stiff and straight upon clamping of the jaws, the nasogastric tube also becomes stiff or ¯exible along with it. After lubrication, the assembly is passed into the oropharynx and then the forceps are stiffened. The assembly is then advanced into the oesophagus and the stomach; the forceps are rendered ¯oppy and withdrawn from the nasogastric tube. Without any additional sedation, the nasogastric tube was inserted with some dif®culty using the above procedure. However, aspiration of the tube did not reveal any gastric contents and there was no de®nite `gurgling' sound over the epigastrium on injection of air. The patient then became restless and tachypnoeic. Over the next 3±4 min, the oxygen saturation fell to 60% and auscultation of the chest revealed decreased air entry and wheezing bilaterally. The nasogastric tube was removed and 100% oxygen was given via a bag and mask. Assisted ventilation with a Q 1999 Blackwell Science Ltd

facemask was not effective in restoring oxygen saturation. The heart rate decreased from 130 to 68 beat.minÿ1 and the blood pressure fell from 170/ 92 mmHg to 110/74 mmHg. Oxygen saturation failed to improve above 85%. In view of the patient's poor status, her trachea was intubated with the aid of alfentanil 0.5 mg, etomidate 10 mg and suxamethonium 50 mg intravenously and cricoid pressure. Tracheal suctioning revealed scant frothy secretions. High airway pressures up to 50 cmH2O made positive pressure ventilation dif®cult. Examination revealed bilateral hyperresonance on chest percussion and bilateral pneumothoraces were suspected. Two 14-G intravenous cannulae were inserted bilaterally in the 2nd intercostal space in the midclavicular line. A small quantity of air was released from the right side with improvement in the ventilation, oxygenation and haemodynamic parameters. After about 5 min, the patient deteriorated again. A chest X-ray revealed pneumomediastinum and right-sided pneumothorax (Fig. 1). A right-sided intercostal drain was inserted and a signi®cant amount of air was drained. A persistent air leak was noted on the right side with some loss of tidal volume. Due to the possibility of oesophageal perforation, another chest drain was inserted on the left side prophylactically. Check endoscopy using a ¯exible scope under general anaesthetic revealed no

obvious trauma to the oesophagus. The patient remained on positive pressure ventilation due to the bronchopleural ®stula and the initial high oxygen requirement (90%). By 48 h, the air leak from the ®stula was minimal. The patient was weaned and extubated over the next 3 days. Fibreoptic bronchoscopy was not performed due to poor respiratory status immediately following the event. Since there was no evidence of oesophageal perforation or gastric placement of the tube, it is likely that the nasogastric tube forceps assembly would have entered the trachea. Stiffening the forceps would have led to tracheobronchial injury by the assembly leading to tension pneumothorax, pneumomediastinum and the bronchopleural ®stula. If the nasogastric tube had not been removed, the chest X-ray would have con®rmed its ®nal position. We have used this technique before on two occasions without any complications although both the patients were sedated and ventilated at the time of insertion. Although Campbell [3] had mentioned its successful use in both conscious and unconscious patients, the risk of potential life-threatening complications is probably higher in an unintubated patient where the assembly may enter the trachea. S. Kannan B. Morrow G. Furness Altnagelvin Area Hospital, Londonderry BT47 1SB, UK References

1 Thomas B, Cummin D, Falcone RE. Accidental pneumothorax from a nasogastric tube. New England Journal of Medicine 1996; 335: 1325. 2 Duke GJ, Harding J. Pneumothorax from a nasogastric tube. Anaesthesia and Intensive Care 1990; 18: 265. 3 Campbell B. A novel method of nasogastric tube insertion. Anaesthesia 1997; 52: 1234. No evidence for seeker needles

We were interested to read the recent letter by Dr Latto (Anaesthesia 1999; 54: 400±1) concerning internal jugular vein 1013


cannulation which suggested that `the use of a seeker needle should be an integral part of any technique that is imparted to staff-in-training'. We disagree with this for a number of reasons. Firstly, the author's statement that ìnitial use of a ®ne seeker needle to locate the vein is an important part of an optimum technique and should minimise the incidence of serious complications' is not supported by the reference given [1]. On another page of that book there is the comment that injury and haematoma formation are less likely should the carotid artery be inadvertently punctured. This referred to work published in 1970 when needles were of a larger gauge than they are now and would be the only possible bene®t of using a seeker needle in our view. Second, we feel that the conclusion that the trans®xion of the vessel being less likely with the use of a seeker needle confers an advantage to this technique is unjusti®ed. There will always be at least two holes in the vessel if a seeker is used, compared with only one hole on the majority of occasions where it is not. We conclude that there is no evidence presented which demonstrates an advantage to the use of a seeker needle on those occasions (the majority in experienced hands) when the vessel is cannulated ®rst time. On those occasions when more than one attempt is made, the only advantage would appear to be the initial occurrence of a smaller hole in the carotid artery should it be inadvertently punctured. There is no guarantee that subsequent attempts in this situation would not cause a second carotid puncture, nor indeed does the seeker being in the vein guarantee that the vein will be located on the ®rst attempt with the main needle. In addition, there is no evidence presented to suggest trans®xion is less common with a big needle having got a small one in ®rst. A survey of anaesthetic practice in our department showed that 15 out of 30 anaesthetists used a seeker needle routinely before internal jugular cannulation and 15 did not. We shall continue to train anaesthetists in the use of both techniques (with and without seeker needle) and allow them to choose the

1014

technique that best suits their developing practice. M. W. P. Goodwin C. M. Frerk Northampton General Hospital, Northampton NN1 5BD, UK Reference

1 Rosen M, Latto LP, Ng WS. Handbook of Percutaneous Central Venous Catheterisation, 2nd edn. W.B. Saunders 1992; 118 and 36.

A reply I thank Drs Goodwin and Frerk for their thought-provoking letter. My letter was primarily about avoiding venous trans®xion and not about the use of a seeker needle [1]. They comment that the statement in my letter ìnitial use of a ®ne seeker needle is an important part of an optimum technique and should minimise the incidence of serious complications' is not supported by the reference given [2]. The reference given does, however, include the statement `To avoid unnecessary trauma, the vein can ®rst be located with a ®ne needle using the chosen technique'. This statement would appear to support the proposal if not exactly scienti®cally proving it. The use of a seeker needle is, however, only one of a number of suggested technical considerations set out in the next two pages of the chapter. These, when taken together, should be relevant in maximising the incidence of successful cannulation and at the same time minimising the incidence of complications. The disadvantages of using a seeker needle include: a possible increase in time taken, the expense of the green needle, an extra small hole in the vein and the possibility of venous spasm making insertion of the main needle more dif®cult. The advantages include: avoiding multiple stabs with a larger and often longer needle, thus minimising serious trauma and complications and minimising the chance of hitting the artery with a bigger needle. A seeker needle was used as part of another technique which minimised the incidence of venous trans®xion [1]. Individuals will need to come to their own conclusions

as to the relative importance of these advantages and disadvantages. It is not that uncommon for trainees to puncture the carotid artery with a seeker needle. If the seeker needle is withdrawn and then directed more laterally, the vein is usually entered without dif®culty. It is extremely uncommon in our experience to hit the artery with the main needle when using this technique. Of course, if the seeker needle is in the artery and this is not recognised then there is every likelihood that the artery will also be entered with the main needle. If the seeker needle and the main needle are roughly the same diameter and length, this clearly minimises or even cancels the requirement for using a seeker needle. This is, however, not usually the case. There is usually a signi®cant difference in both length and diameter between the two needles. The greater the difference between the seeker needle and the main needle, the stronger the indication for using a seeker needle. My opinion, gained partly by observing trainees not entering the vein with the ®rst pass of a large needle, is that the use of a seeker needle does result in increased patient safety. Some trainees tend to insert long needles virtually up to the hub when struggling to insert jugular catheters, unless restrained from doing so. The initial use of a 4-cm seeker needle clearly demonstrates that a long needle is unnecessary as the vein can nearly always be located with a 4-cm needle. It could therefore be argued that the main needle should also be no longer than 4 cm in length. The disadvantages of using a seeker needle, as set out above, appear to be minimal. It is certainly true that there is no advantage in using a seeker needle if the main needle enters the vein ®rst time (claimed by Goodwin and Frerk to be the majority in experienced hands). This assertion is self-evident. The reality is that there are always cases where it is not easy to locate the vein and multiple attempts need to be made. Quantitative data on the number of attempts to enter the vein both with the seeker needle and the main needle are available [3]. These data were collected when working with carefully supervised trainees.



What do different people do in the work place in respect of using a seeker needle? Some always use a seeker needle. Some never use one. The experienced clinician, sure of his/her abilities, might attempt venous cannulation without using a seeker needle once or maybe twice. If he/she succeeds, ®ne; if not, then it would be sensible to convert to a technique using a seeker needle. Some clinicians use a technique in which the vein is observed to ®ll after manual compression. If the vein is easily visible, they do not use a seeker needle. A seeker needle is used, however, if the internal jugular vein is not visible after release of manual compression. I was interested to note that 50% of Dr Goodwin's colleagues routinely used a seeker needle before internal jugular vein cannulation. Goodwin and Frerk do appear to have shot themselves either in or at least close to the foot and appear to have injected a note of confusion. On the one hand, they disagree with the statement that `the use of a seeker needle should be an integral part of any technique that is imparted to staff in training'. On the other hand, they continue to teach the technique to their trainees. It goes without saying that trainees will look at all techniques taught to them and, at the end of the day, will make their own minds up as to which technique they use. What experienced consultants do is perhaps another matter. Consultants do, however, in¯uence their trainees, either for the good or for the bad, by the example they set. The incidence of carotid artery puncture with the main needle could be compared in a prospective trial in two groups of patients; in one group (A), a seeker needle would be used while in the other group (B), it would not be used. If, for example, the incidence of carotid artery puncture is assumed to be 5% then in group B the artery would be hit with the main needle in 5% of cases. If it is assumed, for example, that in one in ®ve of the cases where the artery is hit with the seeker needle in group (A), the artery is also hit with the main needle (1% of cases) then for a statistical power of 0.8, the size of each of the two groups required would need to be approximately 350 [4]. Other complications,


associated with internal jugular vein cannulation, are various and much rarer [5]. Scott has described three cases of serious damage resulting from inadvertent arterial cannulation with central catheters [6]. He estimates the costs of settling the three cases will be in the region of £500 000. He also predicts that early in the next millennium, the use of ultrasound will be a prerequisite for any technique of central venous cannulation. There are at present some clear indications for the use of ultrasound-guided venous access [7]. These indications are relevant, however, to only a tiny minority of cases. The vast majority of catheters, in the immediate future, will continue to be inserted without the bene®t of ultrasound technology. Scott (personal communication) does not use a seeker needle when using an ultrasound technique but does use one when using a blind technique. We clearly need to take all possible precautions to minimise the risks associated with central venous catheterisation. I. P. Latto University Hospital of Wales, Cardiff CF14 4XW, UK References

1 Latto IP. Avoid internal jugular vein trans®xion. Anaesthesia 1999; 54: 400±1. 2 Rosen M, Latto LP, Ng WS. Handbook of Percutaneous Central Venous Catheterisation, 2nd edn. W.B. Saunders 1992; 118. 3 Latto IP, Hughes JA, Falconer RJ. An assessment of an alternative method of internal jugular vein catheterisation. Anaesthesia 1992; 47: 1047±50. 4 Miller DK, Holman SM. Graphical aid for determining power of clinical trials involving two groups. British Medical Journal 1988; 297: 672±6. 5 Rosen M, Latto IP, Ng WS. Handbook of Percutaneous Central Venous Catheterisation 2E. W.B. Saunders and Co., 1992; 160±6. 6 Scott DHT. Editorial II Ìn the country of the blind, the one-eyed man is king', Erasmus (1466±1536). British Journal of Anaesthesia 1999; 82: 820±1. 7 Hat®eld A, Bodenham A. Portable

ultrasound for dif®cult venous access. British Journal of Anaesthesia 1999; 82: 822±6. Damage to a central venous catheter

We would like to draw colleagues' attention to an unusual but potentially lifethreatening incident involving damage or failure of a central venous catheter. A 35-year-old man with a history of alcohol abuse was admitted to our hospital as a medical emergency, having presented with coffee-ground haematemesis and an acute confusional state. His symptoms were attributed to bacterial spread from an abscess on his right index ®nger. On admission, he was clearly severely dehydrated and obtaining peripheral venous access proved impossible. For this reason and to monitor his ¯uid resuscitation, a Vygon Multicath triple-lumen central venous catheter was inserted into his right internal jugular vein by an experienced medical SHO using standard aseptic technique. The patient's condition initially improved with ¯uids and intravenous antibiotics. However, increasing confusion and aggression necessitated his prompt transfer to the Intensive Care Unit (ICU) under police escort, where he was commenced on infusions of propofol and chlormethiazole (Heminevrin). All three lumina of the central line were ¯ushed and noted to be patent on admission to the Unit, and his central venous pressure was monitored continuously. Thirty-six hours later, while the patient was lying supine and receiving crystalloid maintenance ¯uid via the central line, his attending nurse noticed a damp patch on his pillow. On closer inspection, clear ¯uid was seen coming from under the transparent dressing covering the catheter. A tear was apparent in the catheter at the junction of the hub and the wings (®gure overleaf). An occlusive dressing was applied to the site, the ICU resident immediately alerted and the catheter removed straightaway. Central venous pressure at the time was 8 cmH2O zeroed to the right atrium, and the patient's cardiorespiratory status

1015


remained stable throughout, with no clinical evidence of air embolism. Venous air embolism via a central venous catheter is a well-described complication. Fortunately, it appears to be a rare occurrence, since it may have potentially lethal consequences. The risk is present whenever a pressure gradient exists between the atmosphere and the venous circulation (e.g. hypovolaemia, head-up position, deep inspiration during spontaneous respiration). Previous work has suggested that between 300 and 500 ml air entering the circulation at 100 ml.sÿ1 is lethal in humans [1]. This can be achieved through a 14G cannula with a pressure gradient of only 5 cmH2O [2]. Damage to a multilumen central catheter due to a patient's razor [3] and disarticulation of a hub from a Te¯on catheter [4] have both been reported, but we are unaware of any previous reports of damage such as we describe. The obvious assumption is that the damage occurred as a result of the patient being physically restrained. However, we think this is unlikely given the position of the cannula and the nature of the damage. In addition, no leakage was apparent until 36 h after his admission to the ICU. Thus a spontaneous rupture needs to be considered. Had our patient not been supine, receiving ¯uid through the affected lumen and under constant nursing surveillance, the outcome of this defect 1016

could have been serious. This case emphasises that all patients with central venous catheters in situ should be closely supervised, and the catheter and its insertion site regularly inspected. I. Godfrey I. Crabb Gloucestershire Royal Hospital, Gloucester GL1 3NN, UK References

1 Orebaugh SL. Venous air embolism clinical and experimental considerations. Critical Care Medicine 1992; 20: 1169±77. 2 Flanagan JP, Gradisar IA, Gross RJ, Kelly TR. Air embolism ÿ a lethal complication of subclavian venepuncture. New England Journal of Medicine 1969; 281: 488±9. 3 Bailey AR. A close shave: air embolism following laceration of central venous catheter. Anaesthesia 1996; 51: 294. 4 Kolano JW, Chibber A, Johnson PF. Intraoperative disarticulation of a triple lumen central catheter. Anesthesiology 1996; 85: 434±5. The spread and side-effects of intrathecally administered bupivacaine

We should like to comment on the study by Critchley et al. (Anaesthesia 1999; 54:

469±74) comparing the spread and sideeffects of intrathecally administered bupivacaine in 36 male patients undergoing transurethral surgery. In this study, three groups of 12 patients received 3 ml of bupivacaine 0.5% with each group receiving intrathecal bupivacaine in either a dextrose-free form, or solutions containing 4% or 8% dextrose. Although various differences were noted in the onset of sensory block and the incidence of hypotension between the three groups, there remain several unanswered questions: 1 Was a prior power calculation performed to determine the minimum number of patients required for each group before the study commenced, since 12 patients per group would at ®rst glance appear to be an inadequate number to determine small differences in sensory block and cardiovascular changes? 2 Previous work by Richardson and Wissler [1] has demonstrated that adult male CSF has a mean density of 1.0064 (6 0.00012) g.mlÿl. It is unclear in their paper how the density measurements of their bupivacaine solutions were performed. If the authors' density measurements were indeed measured with a high degree of accuracy, then their dextrosefree bupivacaine solution would lie 24 standard deviations (SD) below the mean adult male CSF density, whereas the densities of their 4% dextrose and the 8% dextrose solutions would lie 60 SD and 157 SD, respectively, above that of adult male CSF. In other words, the 4% dextrose solution would be expected to behave more like the 8% dextrose solution, since they are both signi®cantly hyperbaric relative to adult male CSF whereas the dextrose-free solution is signi®cantly hypobaric. When one considers the results in such a context, it becomes dif®cult to interpret the authors' data and conclusions. S. Hallworth R. Fernando Royal Free Hospital, London NW3 2QG, UK Reference

1 Richardson MG, Wissler RN. Density of lumbar cerebrospinal ¯uid in pregnant and non-pregnant humans. Anesthesiology 1996; 85: 326±30. Q 1999 Blackwell Science Ltd


A reply We agree that the size of our study was small. However, our patient numbers were no different to that used previously in similar studies and were suf®cient to make valid haemodynamic comparisons during the initial phase of spinal block. A prior power calculation was not performed because of the nature of the data being analysed. Calculation of power requires analysing a single variable that is pertinent to the overall hypothesis of the study. In Drs Hallworth and Fernandos' most recent publication [1] they used the duration of analgesia. However, when multiple variables which are measured on repeated occasions are analysed, such as in our study, it becomes very dif®cult justi®ably to single out a single variable upon which to base a power calculation. Consequently, we are unaware of any published study that used a similar methodology to ours in which a valid power calculation was performed. Therefore, we based our choice of sample size on prior experience. To answer Drs Hallworth and Fernandos' second query. In our paper, we quoted densities for plain, mixed and heavy bupivacaine 0.5% measured at 37 8C of 0.9977, 1.0079 and 1.0195 g.mlÿ1, respectively. These densities were measured on two separate occasions as 100-ml volumes on a standard laboratory balance accurate to four decimal places (grams). The quoted density [2] for adult male cerebrospinal ¯uid (CSF) at 37 8C is 1.00064 g.mlÿ1, which implies that our plain solution was mildly hypobaric and our mixed and heavy solutions were both hyperbaric. We ponder over Drs Hallworth and Fernandos' ®nal remark concerning the effects of these densities on our results. Presumably, density is not the sole factor in¯uencing the spread of bupivacaine in the CSF and the onset of neural blockade. However, the important message from our study was that heavy spinal bupivacaine precipitates a more rapid onset of cardiovascular effects. L. A. H. Critchley A. P. Morley J. Derrick Prince of Wales Hospital, Shatin, N.T., Hong Kong Q 1999 Blackwell Science Ltd

References

1 Hallworth SP, Fernando R, et al. Comparison of intrathecal and epidural diamorphine for elective Caesarean section using combined spinal-epidural technique. British Journal of Anaesthesia 1999; 82: 228±32. 2 Richardson MG, Wissler RN. Density of lumbar cerebrospinal ¯uid in pregnant and non-pregnant humans. Anesthesiology 1996; 85: 326±30. Ethics and suxamethoniuminduced myalgia

I read with interest the study by Manataki and colleagues which concluded that propofol infusion can reduce the incidence of suxamethonium-induced postoperative myalgia (Anaeslhesia 1999; 54: 419±22). What were the authors' reasons for choosing to study a group of patients in whom there appears to be no indication for the use of suxamethonium in terms of a full stomach, anticipated dif®cult intubation or short surgical procedure? The authors report that myalgia occurred in 19 of 25 control subjects, including four in whom symptoms were de®ned as `severe inability to get out of bed or cough without distress, or turn the head'. This was a group of patients undergoing elective laparoscopic cholecystectomy, for whom a discharge on the ®rst postoperative day was planned. If the authors' routine practice is to use suxamethonium for all such patients, what is their rationale for doing so and how often is discharge delayed as a result of myalgia? If this is not the authors' routine practice, is it ethical to unnecessarily induce myalgia in order to study how best to reduce its severity? I would suggest that although the results of this study are undoubtedly interesting, it might have been better performed in a more appropriate population, in whom the advantages of using suxamethonium more clearly outweighed the potential side-effects. R. Walpole Royal In®rmary of Edinburgh, Edinburgh EH3 9YW, UK

A reply Thank you for the opportunity to reply to Dr Walpole's letter. Suxamethonium maintains an important role in clinical practice due to its effectiveness in providing safe intubation conditions and, in this respect, probably constitutes the gold standard. There have been many publications dealing with suxamethonium and possible alternative medication for safe and rapid intubation conditions with various success. In most of these, suxamethonium has been used as a comparator in similar groups to ours. One of the major problems with the use of suxamethonium, and a reason for the search for an acceptable alternative, is the incidence of myalgia. Our study was performed to see if that myalgia could be reduced. We routinely use suxamethonium when it is indicated and our study has shown that a propofol infusion helps to reduce troublesome myalgia. This is our simple message. We do not believe that it was unethical to investigate how one might limit myalgia. A. D. Manataki `G. Hatzikosta' General Hospital, Ioannina 45001, Greece Eating in labour

We read with interest the article by Scrutton et al. [1] on the effects of feeding in labour on gastric volume, metabolic pro®le and labour outcome and would like to raise a number of points. Firstly, the authors quoted two references [2, 3] in support of their statement that standard low-dose epidural infusions containing 2 mg.mlÿ1 of fentanyl `have been shown to have no signi®cant effect on gastric emptying'. We would contend that the situation is not as clear as that. Zimmermann et al. [2] showed no delay in gastric emptying 2 h after a 50-mg fentanyl epidural bolus followed by 20 mg.hÿ1 infusion. They suggested that the delays observed in previous studies [4±6] may have been only temporary and perhaps that any effect was dose dependent. Porter et al.'s study [3] showed no delay at 2.5 h but delay at 4.5 h, after total epidural infusion doses of 75 mg and 100±125 mg fentanyl, 1017


respectively, and they concluded that the observed effect on gastric emptying may occur in a dose-dependent manner. It is not possible to say from the details in Dr Scrutton's paper how much fentanyl was given, but might it be that some of the women who received epidural fentanyl fell within the group identi®ed by Porter et al. who showed delayed gastric emptying. If so, should these women not have been excluded from the study along with those who received pethidine? Second, the authors noted that dextrose-containing infusions were used in the 1970s and 1980s to decrease the degree of ketosis with its suggested detrimental effects on the progress of labour. They noted why the use of these solutions had fallen out of favour. However, they made no comment on the type or quantity of any intravenous ¯uids used in the women studied and what effects may have ensued on the metabolic parameters measured. There is evidence from Evans et al. [7] of the effects on b-hydroxybutyrate of the infusion of Hartmann's solution for women with epidurals. Might the use of Hartmann's or other `hydrating' ¯uids have in¯uenced their results? Third, no comment is made on the duration of starvation prior to recruitment and what effect that may have had on metabolic parameters measured or on gastric volume at the time ultrasound assessment was made. Finally, the authors noted the comparison between labouring women and exercising athletes. On this basis, the authors should have had an epidural and a nonepidural group. After all, are not the nonepidural women èxercising' more than those with epidurals as they are experiencing more pain? Shnider et al. [8] showed how epidural analgesia reduces the catecholamine response to the stress of labour and Pearson et al. [9] showed that epidural analgesia was associated with less metabolic acidosis. P. D. Barnardo M. Patel The Royal Women's Hospital, Melbourne, Australia References

1 Scrutton MJL, Metcalfe GA, Lowy C, Seed PT, O'Sullivan G. Eating in labour. Anaesthesia 1999; 54: 329±34. 1018

2 Zimmerman DL, Breen TW, Fick G. Adding fentanyl 0.0002% to epidural bupivacaine 0.125% does not delay gastric emptying in labouring parturients. Anesthesia and Analgesia 1996; 82: 612±6. 3 Porter JS, Bonello E, Reynolds F. The in¯uence of epidural administration of fentanyl infusion on gastric emptying in labour. Anaesthesia 1997; 52: 1151±6. 4 Geddes SM, Thorburn J, Logan RW. Gastric emptying following caesarean section and the effect of epidural fentanyl. Anaesthesia 1991; 46: 1016±18. 5 Wright PMC, Allen RW, Moore J, Donnelly JP. Gastric emptying during lumbar extradural analgesia in labour: effect of fentanyl supplementation. British Journal of Anaesthesia 1992; 68: 248±51. 6 Ewah B, Yau K, King M, Reynolds F, Carson RJ, Morgan B. Effect of epidural opioids on gastric emptying in labour. International Journal of Obstetric Anesthesia 1993; 2: 125±8. 7 Evans SE, Crawford JS, Stevens ID, Durbin GM, Daya H. Fluid therapy for induced labour under epidural analgesia: biochemical consequences for mother and infant. British Journal of Obstetrics and Gynaecology 1986; 93: 329±33. 8 Shnider SM, Abboud T, Artal R, Henriksen EH, Stefani SJ, Levinson G. Maternal catecholamines decrease during labor after lumbar epidural anesthesia. American Journal of Obstetrics and Gynecology 1983; 147: 13±15. 9 Pearson JF, Davies P. The effect of continuous lumbar epidural analgesia on the acidbase status of maternal arterial blood during the ®rst stage of labour. Journal of Obstetrics and Gynaecology of the British Commonwealth 1973; 80: 218±24.

A reply Thank you for the opportunity to reply to the letter from Drs Barnardo and Patel, who raised a number of important points. Firstly, the majority of labouring women in our study received epidural analgesia. In all cases these were the standard for our unit and contained

fentanyl 2 mg.mlÿ1. The loading bolus contained 30 mg of fentanyl, a little less than that used by Zimmermann et al., followed by an infusion of 20 mg.hÿ1 [1]. The total doses of fentanyl were similar in both groups. While there may remain some debate about the in¯uence that this regimen has on gastric emptying, the effect would have been similar in both eating and starved groups. With regard to their second point, it is clear that intravenous infusion of Hartmann's solution has an impact on both b-hydroxybutyrate levels and the other metabolic variables measured in our study. We standardised and recorded all intravenous ¯uids given to women receiving epidurals and/or syntocinon infusions. Total volumes and rate of administration were similar in both eating and starved groups. With regard to their third point, we deliberately recruited women presenting in early labour to our delivery unit between 08.00 hours and 12.00 hours. This to some extent standardised their nutritional starting point ÿ most women having fasted overnight, and having had little or no breakfast before entry into the study. We recorded oral intake for the 12 h prior to recruitment and this was similar for both groups. The baseline metabolic data concur with this observation as there were no differences at the point of entry to the study [2]. Finally, Drs Barnardo and Patel suggest that we should have had epidural and nonepidural arms to our study. While we are aware that epidurals have an impact on the parturients' metabolic pro®les, we pointed out in our study that those parturients in active labour without epidurals ate very little. As a result, we feel that an attempt to compare these two groups in a study such as ours would almost certainly have been confounded by a signi®cant reduction in the calori®c intake of the nonepidural group. M. J. L. Scrutton St Michael's Hospital, Bristol BS2 8EG, UK References

1 Zimmerman DL, Breen TW, Fick G. Adding fentanyl 0.0002% to epidural bupivacaine 0.125% does not delay Q 1999 Blackwell Science Ltd


gastric emptying in labouring parturients. Anesthesia and Analgesia 1996; 82: 612±6. 2 Scrutton MJL, Metcalfe GA, Lowy C, Seed PT, O'Sullivan G. Eating in labour. Anaesthesia 1999; 54: 329±34. Cephalad spread of epidural blockade in a 15-degree headdown position

A ®t ASA grade 1 82-year-old woman presented for an ultra low anterior resection. She had no signi®cant premorbid conditions and was ®t for elective surgery. She was premedicated with temazepam 10 mg. On arrival in the operating theatre, she had a 16-gauge intravenous cannula sited in her right forearm and, in the sitting position, had an epidural catheter sited at the T9/10 level. The depth to the epidural space was 4 cm and 5 cm of catheter was left in the space. Anaesthesia was induced with a combination of fentanyl 100 mg, midazolam 2 mg and propofol 80 mg. She was then given vecuronium 8 mg and intubated with an 8.0-mm tracheal tube after 2 min. Right internal jugular and radial arterial lines were then sited. A test dose of 3 ml of bupivacaine 0.25% plus 1 : 200 000 epinephrine was given and, 10 min later, epidural block was established with 10 ml of bupivacaine 0.25%. In the operating theatre, she was placed in the Lloyd Davis position and tilted 15 degrees head down at the request of the surgeon. Anaesthesia was maintained with 0.5± 1% iso¯urane in 70% nitrous oxide/30% oxygen. She was ventilated to maintain an end-tidal carbon dioxide of 4± 4.5 kPa. Body temperature was maintained with a forced air warming system and monitored with a nasopharyngeal temperature probe. The operation lasted 4.5 h. After 1.5 h, an infusion of bupivacaine 0.1% with fentanyl 2 mg.mlÿ1 was started at a rate of 10 ml.hÿ1. The patient remained stable throughout the operation and received no further opioids or neuromuscular blocking agents. At the end of the operation, she was ventilated with 100% oxygen and


allowed to wake up. Despite being responsive and obviously awake, her respiratory effort was poor and her tidal volumes were 100±150 ml as measured with a Wright's respirometer. Neuromuscular blockade was assessed with double burst stimulation and there was no signi®cant block detected. Her core temperature was 36.2 8C. Her respiratory effort appeared inadequate and a blood gas revealed a PaCO2 of 10.1 kPa. She was given doxapram 50 mg with no effect and so was ventilated in recovery and reassessed. It became apparent that she was fully awake and aware but had poor respiratory effort. She was also noted to have grade 3/5 power in her legs but only grade 1/5 power in her arms. She was well analgesed but it was dif®cult to assess the height of the sensory block as she was still intubated. The presumed diagnosis of a high epidural block was made. The epidural infusion was stopped and she was sedated with sevo¯urane and ventilated for a further 2 h, after which the sevo¯urane was stopped and she was reassessed. At this stage, she had grade 4/5 power in her arms and her legs and had tidal volumes of 300±400 ml. Blood gases at this stage showed PaCO2 of 6.1 kPa and PaO2 of 16.2 kPa on 40% oxygen. She was extubated and the epidural infusion was restarted. After a further 4 h in recovery, she was sent back to the ward. The rest of her recovery was uneventful. One can only assume that the cause for her respiratory failure was cephalad spread of the epidural block caused by the infusion running in a 15 degree head-down position. I have used this technique in other patients without problems and would be interested to hear if anyone else has experienced a similar problem as I can ®nd no cases reported in the literature. There have been many studies trying to establish the effect of gravity and posture on spread of epidural anaesthesia. Grundy reported that epidural anaesthesia induced in the lateral position appeared 2 min earlier, spread two segments higher and lasted 75 min longer [1]. Hodgkinson documented that keeping patients in the sitting position for 5 min after injection of 20 ml of bupivacaine 0.75% limited

cephalad spread but only in obese patients [2]. Apostolou demonstrated slightly higher and slightly longer block on the dependent side when epidural anaesthesia was induced in the lateral position, although he felt these differences were of only minor signi®cance [3]. In 1993, Ponhold documented a decrease in maximum cephalad spread of L1 vs. T10 when epidural anaesthesia was induced with patients who had 30 degrees trunk elevation [4]. However, other investigators [5±8] have reported no signi®cant difference in the eventual spread and distribution of block regardless of position. I can ®nd no studies documenting the effects of infusions in the epidural space in various positions. It may well be that with bolus injections of local anaesthetic, the pressure generated by the injection is such that the effect of posture is relatively small. However, one could suppose that with an infusion running at a low rate, the pressure generated at the tip of the epidural catheter is lower and hence the relative effects of posture and gravity would be much more. I am not sure how this problem could be avoided. Siting the epidural lower would mean that cephalad spread would be less likely to affect respiratory function although cephalad spread is probably not predictable and postoperatively a higher infusion rate may be required to achieve adequate analgesia. Alternatively, giving boluses of local anaesthetic via the epidural catheter rather than an infusion may encourage more even spread around the tip of the catheter as discussed above. This would appear to be a rare but important complication of epidural use in the head-down position and should be considered if such a patient presents with respiratory dif®culty postoperatively. N. White North Hampshire Hospital, Basingstoke RG24 9NA, UK References

1 Grundy EM, Rao LN, Winnie AP. Epidural anaesthesia in the lateral position. Anesthesia and Analgesia 1978; 57: 95±7. 2 Hodgkinson R, Husain FJ. Obesity, gravity and spread of epidural

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3

4

5

6

7

8

anaesthesia. Anesthesia and Analgesia 1981; 60: 421±4. Apostoulou GA, Zarmakoupis PK, Mastrokostopoulos GT. Spread of epidural anesthesia in the lateral position. Anesthesia and Analgesia 1981; 60: 584±6. Ponhold H, Kulier AH, Rehak PK. 30 degree trunk elevation of the patient and quality of epidural anesthesia. Effects of elevation in operations on the lower extremities. Anaesthesist 1993; 42: 788±92. Norris MC, Dewan DM. Effect of gravity on the spread of extradural anaesthesia for caesarean section. British Journal of Anaesthesia 1987; 59: 338±41. Merry AF, Cross JA, Mayadeo SV, Wild CJ. Posture and the spread of extradural analgesia in labour. British Journal of Anaesthesia 1983; 55: 303±6. Ackerman WE III, Herold JA, Junenja MM, Sweeney NJ. Effect of position on the spread of buffered 2% chloroprocaine administered epidurally for the second stage of labour. Southern Medical Journal 1990; 83: 277±9. Whalley DG, et al. The effect of posture on the induction of epidural anesthesia for peripheral vascular surgery. Regional Anesthesia 1995; 20: 407±11.

Spinal haematoma following epidural anaesthesia in a patient with eclampsia

I read with interest the case report of spinal haematoma following epidural anaesthesia in a patient with eclampsia (Anaesthesia 1999; 54: 350±4). From the description of events given, is it not likely that the persistence of paralysis was of pharmacological origin rather than compression by an epidural haematoma? Only 4 ml of blood was removed at surgery yet, during performance of epidural blood patch, it is common to inject as much as 20 ml of blood without symptoms of spinal cord compression. Vakharia et al. [1] examined MRI images of the tamponade effect of blood patches used in the treatment of postdural puncture headache. It was shown that the blood formed a large extradural collection with anterior displacement of the

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thecal sac and the mean spread being 4.6 intervertebral spaces. In spite of the pressure caused by the blood, these patients did not experience any weakness of lower limbs As the authors point out, the presence of air in the ventricular system suggests that there had been an inadvertent dural puncture and it is possible that some of the local anaesthetic given epidurally had spread into the intrathecal space. Is it not likely that the prolonged paralysis seen was in fact due to an inadvertent subarachnoid block, which may persist for many hours on occasion? I. Wijesurendra Kent & Canterbury Hospital, Canterbury CT1 3NG, UK References

1 Vakharia SB, Thomas PS, Rosebaum AE, Wasenko JJ, Fellows DG. Magnetic resonance imaging of cerebrospinal ¯uid leak and tamponade effect of blood patch in postdural puncture headache. Anesthesia and Analgesia 1997; 84: 585±90.

A reply Thank you for the opportunity to reply to Dr Wijesurendra's question. Indeed, we were just as baf¯ed as to why 4 ml of clot, removed at surgery, would cause cord compression. Even if one assumed 8 ml of blood was present before clot formation, this is still much less than the amount of blood used for epidural blood patch. We could not offer any better explanation other than what we have stated in our article. In our case, the important issue was time constraint. Even if it was an inadvertent subarachnoid block, we expected the block to regress with time. However, this was not the case as the block persisted at L2 up to the time of laminectomy, i.e. 6 h following epidural anaesthesia. With an epidural haematoma, we would be jeopardising the patient's chance of recovery from an iatrogenic mishap if we chose to `sit and wait'. We therefore consulted the neurosurgical team and discussed the situation with the patient in detail; she opted for surgery. In fact, it took a

few days after the laminectomy for the patient to recover her lower limb function, which made pharmacological paralysis less likely. In conclusion, we think that laminectomy was justi®ed in our case. T. S. T. Yuen J. S. W. Kua I. K. S. Tan Pamela Youde Nethersole Eastern Hospital, Chai Wan, Hong Kong Spinal anaesthesia for Caesarean section in a patient with systemic sclerosis

We read with interest the case report by Bailey and colleagues demonstrating the successful use of spinal anaesthesia for Caesarean section in a patient with systemic sclerosis and thrombocytopenia as a manifestation of pre-eclampsia (Anaesthesia 1999; 54: 355±8). Patients with systemic sclerosis present special challenges to the anaesthetist. Because of the low prevalence of the condition, much of our knowledge regarding the anaesthetic management is based upon case reports and personal opinion rather than controlled trials. We wish to make the following comments. Microstomia as a result of ®brosis of the skin and subcutaneous tissues and limited mouth opening secondary to induration of the temporomandibular joint may result in dif®cult tracheal intubation in patients with systemic sclerosis. Furthermore, progressive oesophageal ®brosis often induces gastro-oesophageal re¯ux. In spite of this, a regional technique is by no means always preferable to general anaesthesia in patients with systemic sclerosis. We have demonstrated that a meticulous anaesthetic technique and the combined administration of prokinetic and antacid drugs before general anaesthesia in patients with systemic sclerosis reduces the incidence of regurgitation to levels near or below that of a general surgical population, even when using a laryngeal mask [1]. Systemic sclerosis is a condition that may affect a multitude of organs.



Haemostatic or haemopoietic mechanisms are not normally affected. The development of thrombocytopenia as a manifestation of pre-ecclampsia has made this case report especially interesting. In their patient, the authors used a spinal in preference to an epidural technique because it was thought less likely to be a risk factor for the development of an epidural haematoma in a thrombocytopenic patient. It should not be assumed, however, that spinal anaesthesia is safe with respect to the development of a vertebral canal haematoma in a patient with a clotting disorder. In a meta-analysis including 850 000 patients undergoing central nervous blockade, the incidence of vertebral canal haematoma following epidural anaesthesia has been estimated to be 1 in 150 000 compared with 1 in 220 000 after spinal anaesthesia [2]. This difference in relative risk is not suf®cient to exonerate spinal anaesthesia completely. The authors suggest the use of thrombelastography to assess haemostatic function and estimate the risk of epidural haematoma formation. Indeed, thrombelastography has been shown to be a highly sensitive indicator of platelet function and platelet numbers. Both thrombocytopenia and functional impairment of platelets result in reductions of the alpha angle and the maximum amplitude [3]. New instruments have been developed recently, such as a novel platelet function analyser (Dade PFA-100TM), which we are currently evaluating [4]. Case reports are valuable in highlighting the anaesthetic dif®culties associated with certain conditions and their successful management, but eventually only randomised controlled trials will determine the best possible strategies for dealing with rare and challenging conditions such as systemic sclerosis. N. J. Wilkes T. Peachey C. Beard Royal Free Hospital, London NW3 2QG, UK References

1 Wilkes NJ, Beard C, Peachey T. Anaesthetic airway management in 54 Q 1999 Blackwell Science Ltd

cases of systemic sclerosis or scleroderma. British Journal of Anaesthesia 1999; 82 (Suppl. 1): A13. 2 Tryba M. Epidural regional anaesthesia and low molecular heparin: Pro. Anasthesiol Intensivmed Notfallmed Schmerzther 1993; 28: 179±81. 3 Mallett SV, Cox DJA. Thrombelastography. British Journal of Anaesthesia 1992; 69: 307±13. 4 Mammen EF, Comp PC, Gosselin R et al. PFA-100TM System: a new method for assessment of platelet dysfunction. Seminars in Thrombosis and Hemostasis 1998; 24: 195±202.

Nausea and vomiting during Caesarean section

We read with interest the article by Abouleish et al. concerning ondansetron vs. placebo for the control of nausea and vomiting during Caesarean section under spinal anaesthesia (Anaesthesia 1999; 54: 479±83). We note that prior to delivery, despite the use of a 1-L crystalloid preload and a prophylactic ephedrine infusion, hypotension occurred in 69% of the population, nausea in 48% and vomiting in 39%. We wish to suggest a more likely explanation for the nausea than those proposed by the authors. In our hospital, prospective data on the incidence of hypotension, nausea and vomiting at Caesarean section are collected on all patients as part of routine audit. In the 12-month period April 1998 ÿ March 1999, 724 Caesarean sections were performed under spinal anaesthesia, 709 receiving intrathecal opioids. Following preloading with 750±1500 ml crystalloid, a prophylactic infusion of 30 mg ephedrine is started. We routinely measure blood pressure every minute and use further boluses of 3±6 mg ephedrine if the blood pressure is diminishing. Our incidence of hypotension (using the same de®nition as the authors) is 23% (95% CI 20±26%). Intra-operative nausea occurs in 5.4% (95% CI 3.7±7.0%) and vomiting in 1.7%. (95% CI 0.7±2.6%). It is well recognised that nausea and vomiting is closely related to maternal

hypotension following spinal anaesthesia [1]. It is our observation that nausea, in the absence of hypotension, is effectively treated by an anticholinergic drug. In our series, nausea was precipitated by hypotension in 59% (95% CI 43±75%). However, only 13% (95% CI 8±18%) of women with hypotension experienced nausea. We ®nd that if hypotension is corrected rapidly enough it is rare for nausea to occur. If the blood pressure does drop, simply increasing the speed of the ephedrine infusion acts too slowly, and we need to use ephedrine boluses from a syringe as well. In the study by Abouleish et al., blood pressure was measured at 5-min intervals. It is likely that measuring the blood pressure at this frequency and relying on the ephedrine infusion alone led to delayed detection and treatment of hypotension. This is a more plausible explanation for the high incidence of nausea and vomiting than that suggested in their study. The authors suggest that the ondansetron might be more effective if given prophylactically before the spinal is performed. Our data do not support the routine use of prophylactic anti-emetics at this time. More emphasis should be placed on the rapid recognition and treatment of intra-operative hypotension. Postoperatively, many women have nausea precipitated by movement and we do use prophylactic cyclizine at the end of surgery in women receiving intrathecal diamorphine. At present, the British National Formulary [2] advises the avoidance of ondansetron in pregnancy and breast feeding women due to a lack of data. No such restriction is placed on cyclizine. Furthermore, if all of our 724 women received prophylactic ondansetron, the cost to our hospital would be £3785 compared with £447 for cyclizine. We feel that before using the more expensive drug it should be proven to be more effective than the alternatives. G. S. Kar S. M. Ali R. G. W. Stacey G. Samsoon Kingston Hospital, Kingston upon Thames, Surrey KT2 7QB, UK 1021


References

1 Kang YG, Abouleish E, Caritis S. Prophylactic intravenous ephedrine infusion during spinal anesthesia for cesarean section. Anesthesia and Analgesia 1982; 61: 839±42. 2 British National Formulary. Number 37 March 1999 British Medical Association and Royal Pharmaceutical Society of Great Britain.

A reply We are grateful to Dr Kar and associates for their interest in our article. We stated in the Methods section of our article [1] `To prevent hypotension, ephedrine was infused continuously (50 mg in 250 ml saline) [2] When it (hypotension) occurred, it was treated by additional ¯uids and intravenous increments (5± 10 mg) of ephedrine'. Thus, we attempted to treat hypotension in a similar manner to the suggestion of Dr Kar. In fact, we initiated this method of therapy in 1982 [2]. Although we recorded the blood pressure every 5 min, it was measured every 30 s using an automatic noninvasive machine (Vitalert 3200 by Driger Co.) until the fetus was delivered. This is our routine. The reason is that the signi®cant and rapid changes in blood pressure following spinal anaesthesia and ephedrine administration have important impacts on the fetal outcome. Following delivery, the frequency of blood pressure measurement depended on the haemodynamic stability of the patient, but was performed at least every 2± 3 min. We do not have a clear or de®nite answer to the reason/s for the higher incidence of nausea and vomiting in this study [1] compared with our previous study [2] or to those of Dr Kar. It may have been due to the fact that we were looking for and recording every short episode or minor incident of nausea, vomiting or retching. The lower socioeconomic condition and the heavier weight of the present population could have contributed to the higher incidence. In fact, when we tested the data we have on ®le for this study, there was a signi®cant correlation between vomiting and body weight (p 0.0026). Regarding the cost of anti-emetics, 1022

although important, it was not the purpose of our study. However, this brings important philosophical questions. Do we deny an expensive drug the right to be investigated? Do we have to ask the manufacturer to let us know their intention of pricing a drug before we study it? We feel the answer to both questions is no. The pharmacological effects and clinical use of drugs should not be overshadowed by cost. Initially, a patented drug has a high price, but it substantially decreases after the expiration of this privilege. E. I. Abouleish A. Z. Chuang The University of Texas-Houston Medical School, Houston, TX 77030, USA References

1 Abouleish EI, Rashid S, Haque S, Giezentanner A, Joynton P, Chuang AZ. Ondansetron versus placebo for the control of nausea and vomiting during Caesarean section under spinal anaesthesia. Anaesthesia 1999; 54: 466±82. 2 Kang YG, Abouleish E, Caritis S. Prophylactic intravenous ephedrine infusion during spinal anesthesia for cesarean section. Anesthesia and Analgesia 1982; 61: 839±42.

A long 17-G Vygon epidural needle

We wish to report a fault in the Vygon epidural needle that was discovered during siting of an epidural for pain relief during labour. The Vygon epidural needle is well known for its quality. However, recently we found an epidural needle which was 9 cm long instead of 8 cm (®gure above). This could lead to wrong calculation of depth of epidural space from skin and short length of epidural catheter in the epidural space. This incident acts once more to reiterate the importance of checking even new disposable equipment before use. The incidence has been reported to the company. J. Shah M. Mariappan I. Jeyapalan Leicester General Hospital, Leicester LE5 4PW, UK A reply Thank you very much for giving us the opportunity to reply to the letter from Dr Shah and colleagues. As noted, we were aware of the problem, thanks to the vigilance of Dr Jeyapalan who noticed and advised us of the situation. We have clearly made an error during the packaging of the epidural needle into the pack, the European 9-cm model being inadvertently substituted Q 1999 Blackwell Science Ltd


for the 8-cm UK version. We made arrangements for the stock to be isolated, identi®ed other recipients of that Lot number and checked our own stock; two Lot numbers were affected. We identi®ed 200 units had been despatched to ®ve separate hospitals. We talked to the other four hospitals concerned and arranged to isolate all of their stock. We sent out replacement stock the same day and also reported the incident to the MDA under the requirements of the Medical Devices Directive. We arranged uplift of the problem devices that day and all of the stock at the hospitals has now been accounted for. Our manufacturing unit in France is undertaking a comprehensive review of how this packaging error occurred and is initiating a review to eliminate any recurrence of this particular problem. We do strive for perfection in all of our products, from the simplest of bungs to the most complex of procedure packs and believe that we are always getting closer to that goal, but every now and then, we do make a mistake such as this one. We would very much like to apologise to anyone that has been inconvenienced in any way at each of the hospitals by this, fortunately, very rare problem. Vygon (UK) Ltd, Cirencester GL7 1PT, UK Time to recheck the checklist?

We should like to highlight a potential problem we encountered recently with a Blease Frontline anaesthetic machine that would have been missed using the current Association of Anaesthetists' checklist. While checking the machine using a pipeline disconnect test it was noticed that, despite having a full oxygen cylinder attached to the machine as evidenced by the reading on the pressure gauge, there was no ¯ow of oxygen through the ¯ow meter. The service engineer identi®ed a defective valve that normally allows oxygen to ¯ow from the cylinder into the anaesthetic machine, but prevents retrograde ¯ow of oxygen from the pipeline supply through Q 1999 Blackwell Science Ltd

the cylinder port. In this situation the valve did not allow oxygen to ¯ow from the cylinder into the ¯ow meter. The current Association of Anaesthetists' checklist for anaesthetic apparatus [1] recommends a tug test to con®rm a secure connection of the oxygen pipeline and no longer recommends a disconnection test because of potential damage to the Schraeder valve. It therefore relies only on the cylinder pressure gauge to check the cylinder. The previous guidelines made it quite clear that the pipeline supply had to be disconnected whilst the cylinder was being checked [2]. We recommend disconnection of the pipeline supply in order to con®rm oxygen ¯ow from the standby cylinder. S. Ravi Shankar R. G. W. Stacey A. Ravalia Kingston Hospital, Kingston Upon Thames KT2 7QB, UK References

1 Association of Anaesthetists of Great Britain and Ireland. Checklist for anaesthetic machines. 1997. 2 Association of Anaesthetists of Great Britain and Ireland. Checklist for anaesthetic apparatus. 1990. Yet another ®nger and catheter saving tip for the tunnelled epidural catheter

There have been several techniques described to help reduce the risk of epidural catheter trauma during the tunnelling process [1±4]. The use of the Tuohy needle passed from a distant skin site to the site of successful catheter placement can be unpopular because of the potential catheter damage. A simple variation to the technique can reduce the risk of damage to both the catheter and, just as importantly, the operator's ®nger. The epidural is sited in the usual manner. The Tuohy needle is passed from the distal skin site back towards the site of catheter insertion. Just before the needle emerges from the

subcutaneous tissue into the skin incision, the tip of a pair of sponge-holding forceps is placed over the catheter (so as to protect it from the emerging Huber tip). The Tuohy needle is pushed through the èye' at the end of the sponge forceps thus avoiding any needle contact with the epidural catheter and operator's ®ngers. R. C. E. Bates Queens Medical Centre, Nottingham, UK References

1 Murray DM. Tunnelling of epidural catheters. Anaesthesia 1999; 54: 201. 2 Pavy TJG. Tunnelled epidural catheters for routine use. Anaesthesia and Intensive Care 1994; 22: 703±5. 3 Bailey CR. Tunnelling in the opposite direction. Anaesthesia 1996; 51: 797±8. 4 Thompson HM. Tunnelling of epidural catheters. Anaesthesia 1997; 52: 508.

One-lung anaesthesia: response to questions on the ambient pressure oxygen reservoir

Following our report (Anaesthesia 1999; 54: 454±8) describing the use of an ambient pressure oxygen reservoir attached to the nonventilated lung, several centres have sought details of the make of inlet valve and side-line that are incorporated in the àpparatus'. Just as the report states, an inlet valve must be included wherever there is a possibility that surgical suctioning may be performed in a closed chest situation. However, if the surgical/anaesthetic team can guarantee that this is NOT a possibility, then the inlet valve can be omitted. On those occasions where there is no such guarantee, we use a locally fabricated valve incorporating an Àmbu-type' valve lea¯et. Any oneway valve that allows free gas ¯ow into the system will be suitable, provided it does not allow low-pressure gas leakage in the opposite direction. Such gas leakage will result in a progressive emptying of the reservoir bag, independent of ongoing gaseous uptake. 1023


The clamped-off side-line can certainly be omitted if desired. A reservoir bag that becomes fully distended (by gas venting from the nonventilated lung as it collapses down after the thoracic cavity is opened, or by the leakage of ventilating gases past the bronchial cuff) can be returned to a half-®lled state simply by squeezing it gently while the connection to the double-lumen tube is momentarily loosened. A reservoir bag that becomes empty (as a consequence of ongoing gaseous uptake in situations where lung collapse is delayed) can be replaced with a second `half-®lled' oxygen reservoir instead of being replenished via a side-line.

J. P®tzner H. D. Carne E. C. Taylor The Queen Elizabeth Hospital, Adelaide, Australia The left-handed laryngoscope

Your correspondence on the left-handed laryngoscope has reminded me of something that has puzzled me for years. Given that the secret of successful intubation is to get a good view of the larynx, why do right-handed people insist on using their

left hands for the skilful part of the procedure? As a left hander, it is perfectly natural to me to hold the laryngoscope in my left hand. I cannot do joined-up writing with my right hand, but I can push a tube into a hole with it once I can see clearly, and I have done the clever bit with my left hand. Perhaps all you right-handers should routinely use the `left-handed' laryngoscope; you might ®nd it easier. T. J. Hawkins Willoughby on the Wolds, Loughborough LE12 6SY, UK

S A F E T Y N OT I C E S

Safety Notice MDA HN1999(02) Vickers 165 Resuscitaire, NonReturn Valve

by Hill-Rom may be contaminated with oil. This is a signi®cant ®re risk.

Manufacturer Vickers Medical

Immediate action X Ensure that users and servicing personnel are aware of Hill-Rom's recall letter X If any Resuscitaire 165 has not been used since it was last repaired or serviced, check with your servicing agent

Non-return valve supplier Hill-Rom Problem Replacement non-return valves supplied

whether the repair or service included replacement of the non-return valve with a valve of part No. VS165-11-006 supplied by Hill-Rom. If one of these valves has been ®tted then do not use the Resuscitaire X Identify and isolate all unused nonreturn valves, part No. VS165-11-006 and return to the supplier Hill-Rom for replacement

Safety Notice MDA SN1999(26) Surgical Tourniquet Cuffs

Manufacturer/supplier Various Problem There have been several incidents reported to the MDA where `burns'

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have been noted under a tourniquet cuff employed during surgery. These have been so severe in some instances that corrective surgery has been required.

Action X For conventional tourniquets, ensure

that the tourniquet cuff is always applied ®rst, followed by the use of a U-drape or similar device as a drape prior to skin preparation X For roll-on-cuff tourniquets, ensure that the cuff and wedge have had suf®cient time to cool following autoclaving, prior to being used on a patient
