data using laptop computer by surgeon to calculate ... Processing of the CT data is done with the help ... at sites without anaesthetic machine, rapid recovery and.
BHADE, DAVE, SHAH : STEREOTACTIC BRAIN BIOPSY AND ANAESTHESIA Indian J.SHAH, Anaesth. 2002; 46 (2) : 111-114
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RUKMINI PANDIT AWARD WINNING ARTICLE : ISACON - 2001
ANAESTHETIC ASPECTS OF STEREOTACTIC BRAIN BIOPSY Dr. M. A. Bhade 1 Dr. Bhavna Shah 2 Dr. C. R. Dave 3 Dr. R. A. Shah 4 SUMMARY Stereotactic or ‘keyhole’ neurosurgery poses number of anaesthetic challenges. Stereotactic brain enables biopsy of deep seated brain lesions with minimal brain tissue damage. Apart from inherent problems of neuroanaesthesia, there is an additional challenge due to compromised airway arising out of application of stereotactic frame The study presents the various anaesthetic aspects right from the application of frame outside OT, transport of sedated patient to radiology department for CT scan, computerised analysis of radiological information to finally the actual neurosurgical procedure. Modern drugs like propofol and midazolam help in maintaining conscious sedation analgesia during its various stages. Elective intubation before frame application is beneficial in paediatric patients and in difficult intubation cases.With the applicability of stereotactic neurosurgery, anaesthesiologist needs to be familiar with its various clinical and technical aspects.
Keywords : Stereotactic frame, Airway Maintenance, Sedation, Intubation. Introduction The term ‘Stereotactic is a composite of the Greek word ‘Stereos’ which refers to the geometry of solid bodies and the Latin ‘Tactus’ which signifies the sense of touch. Progress in noninvasive imaging technologies like CT scan, MRI, DSA and key concepts by Dr. Ruseel Brown of university of Utah has enabled the transformation of two dimensional CT scan information into three dimensional stereotactic frame co-ordinates (Fig-1). The combined efforts of Cosman, Roberts and Wells have resulted in the present popularly used CRW ARC SYSTEM1.
Aim With the help of this extracranial reference system the surgeon can guide instruments accurately to deep seated 1. 2. 3. 4.
M.D., Junior Lecturer M.D., Associate Professor M.D., Professor M.D., Professor & Head Department Of Anaesthesiology Gujarat Cancer & Research Institute B J Medical College, Admedabad - 380 016 Correspond to : Dr. Madhuri A Bhade 16/B, Janvishram Society, B/H, Sahjanand College Ambawadi, Ahmedabad - 380 015
brain lesions causing minimal iatrogenic brain trauma and hence its importance. Application of the frame gives extremely limited airway access creating problems during maintenance of ‘conscious sedation analgesia’ or intubation; due to restricted movement of head and neck apart from other procedure related problems. Thus, the aim of our study was to observe the difficulties encountered by anesthesiologist, find their solution and observe the related clinical and technical aspects. Material and Method The study consists of 25 patients with age ranging from 7yrs to 75yrs under either general anesthesia or sedation with local anaesthesia. GA was given in children, in patients with brain stem lesions (vital areas of brain), unco-operative adults or for transnasal procedure. Stereotactic biopsy can be done under sedation in cooperative adults. Routine preanaesthetic checkup along with neurological assessment was done one day prior and the procedure explained to adults to allay anxiety. Premedication in the form of Inj. Glycopyrrolate 2-4 mcg/kg-1 IV & Inj. Pentazocine 0.3-0.6 mg/kg-1 IV was given. General anaesthesia was administered in five patients taking all neuroanaesthetic precautions of smooth induction using IV Pentothal (2.5%) 5-7mg/kg-1, Inj. Suxamethonium 1-2mg/kg-1 & maintained with Inj. Vencuronium bromide + gas + O2 + trace of halothane. For sedation, the patients were divided in two groups Group I : Inj. Pentazocine 0.3-0.6 mg/kg-1 IV with Inj. Midazolam 0.05-0.1 mg/kg-1 IV. Top up supplements with Inj. Midazolam.
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Group II : Inj. Pentazocine 0.3-0.6 mg/kg-1 IV with inj. Propofol 2mg/kg -1 IV bolus. Top up supplements with Inj. Propofol. 0.375% bupivacaine was used for local infiltration for application of frame prior to actual surgical procedure. The patients were well monitored, both clinically and by using pulse oximeter, ECG, NIBP & Capnography Extension tubing was attached to IV access where necessary, as patients get fully draped with very limited access.
3. CRW Arc: The base of CRW arc is a square structure fitted over the headring. The arc system has 3 translational slides that move the centre of the arc to the anatomical target. These slides are designated by AP, lateral and vertical coordinates and the mllimetre scales are engraved on the arc for easy visibility by the surgeon during the surgery. (Photo-2).
Indications Following were the indications for brain biopsy in the study: - Secondaries in brain from lung/breast/pancreas. - Brainstem SOL. - Tuberculoma. - Pyogenic abscess. - SOL with or without hydrocephalus. ABOUT THE FRAME AND THE PROCEDURE The CRW are system (Stereotactic frame) has 3 parts: 1. Basic CRW Intubation Headring Assembly This ring has a rotatable intubation hoop in front that helps anesthesiologist in maintaining airway access. (Photo – 1)
2. CT Localiser It enables the stereotactic coordinates (X,Y,Z) to be determined relative to the headring independent of scanner position. (Fig. 2)
The procedure of stereotactic brain biopsy involves 4 steps:-
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Application of base ring of stereotactic frame outside OT.
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Transport of sedated/intubated patient to radiology department for CT Scan.
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Transport back to OT and processing of CT Scan data using laptop computer by surgeon to calculate the cartesian coordinates.
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Biopsy Surgical procedure.
Average duration of the procedure ranges from 1hr to 2hr 30min. Observations Applications of the base ring are done outside OT in either supine or sitting position depending on the age and neurological status of the patient. Head frame is applied by local infiltration at four different sites on the scalp over which head posts of the base ring are screwed. Sedation helps to minimize the ring discomfort. Paediatric patients were intubated electively before application of frame for complete control of airway. Spontaneous
BHADE, SHAH, DAVE, SHAH : STEREOTACTIC BRAIN BIOPSY AND ANAESTHESIA
breathing was maintained & supplemented with oxygen and titrated dose of sedatives. The patients were monitored with pulse oximetry during transport to radiology department, along with all the resuscitative measures kept ready. Most important is that the head wrench should be carried along with the patient so that in case of an emergency, the frame can be removed1 Placing a thin sand bag or rolled towel helped to extend the head as frame limited its extension. Sedative drugs need to be titrated carefully to avoid tongue fall and excessive respiratory depression with adverse effect on ICP. The CT localiser frame with N shaped carbon fibre rods is applied over the base ring in radiology dept. Radiocontrast dye is injected intravenously. Thus here the anesthetist faces the problems of outside OT anaesthesiologist and airway maintenance whilst being remoter from the patient apart from allergy to contrast medium and radiation exposure. After CT scanning the patient is transported back to OT. Spontaneous breathing technique proves beneficial as anesthetist may face problems like elevator failure during transport. Processing of the CT data is done with the help of laptop computer. Thus, some time elapses before the procedure begins, as coordinates need to be adjusted over the CRW arc. Localisation of the target is checked by placing CRW arc on rectilinear phantom frame before applying head (Photo–2) The patients head gets fully draped with extremely limited access to airway after application of CRW arc. In sedation group attaching right angle bar with OT table helps as in other head & neck surgery, as it gives some access below the drapes. Use of nasopharyngeal airway was found to be extremely helpful for oxygenation & airway maintenance. Breathing circuit with gas analyzer cable and capnograph module should be attached to it
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with the help of portex endotracheal tube connector, so that throughout the procedure spo2 caphograpy and breathing movement could be observed over the bag (Photo – 3) Anaesthesiologist has to be always aware of the possibility of convulsions with the frame in situ. Anticonvulsant medication Inj. Phenytoin sodium was gives IV when procedure was converted from biopsy to craniotomy or excision biopsy as the duration of surgery increases. While administering general anesthesia it was difficult to achieve tight fitting of mask for ventilating the patient due to frame. Though the intubation hoop is rotated downward there is hinderance for mask fitting & laryngoscopy2 Sniffing morning air’ position is not possible for intubation due to limited extension, so ‘pseudo-anterior’ larynx is visualized. A well trained assistant proves helpful who can show the larynx by means of external pressure. Dr. Neil Bradburn advocated the use of one smaller ID tube to overcome this difficulty1. Again, this being a closed procedure, surgeon does not have access for cauterization. Therefore, excellent perioperative haemodynamic and ICP control is essential. All neuroanesthetic precautions for smooth induction were taken and muscle relaxant was used for maintenance. Positioning of the patient is done on OT table with Mayfield skull clamp. It needs to be applied carefully in paediatric patient as skull is thin and it can increase ICP3 In lateral position, the edge of the basering can forcefully encroach on patient’s neck and shoulder, conceivably resulting in neuropraxia of the brachial plexus especially in obese patients2 (Photograph-4).
After the procedure, patients were observed in NICU for 4-6 hrs and CT scan was done postoperatively in cases where biopsy was taken from vital areas of brain to rule out haematoma formation.
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Discussion There are various anaesthetic options for the procedure. The whole of it can be done under GA but that increase the cost and adds problems of transporting the anaesthetized patient, as radiology department and surgical theatre may not be on the same floor. In paediatric patients and in difficult intubation cases elective endotracheal intubation help as it abolishes the problems of airway after head ring application. In adult patients, stereotactic biopsy can be done under sedation with local anaesthesia because the skull can be drilled with minimal discomfort. Unexpected pain may occur when the tip of drill impinges on the dura. Scalp though being vascular does not give rise to systemic toxicity of local anaesthetic drugs compared to their subcutaneous infiltration at other sites4. Xylocaine 2% with adrenaline could not be used in all the patients as most of them had associated problems like HT/IHD. 0.375% bupivacaine was found to be satisfactory as it provided longer analgesia. Amongst the sedative drugs, propofol was found to offer advantages like ability to rapidly tirate level of anaesthesia, easy maintenance during patient transfer and at sites without anaesthetic machine, rapid recovery and antiemetic property5,6. Midazolam was used due to rapid recovery over diazepam and favourable effect on ICP. For GA, relaxant technique is ideal in neurosurgical patients for good haemodynamic and ICP control in a closed procedure like stereotactic brain biopsy. Complications Stereotactic brain biopsy is universally described as low risk procedure with complication rate of 0 to 4%1. Bleeding and haematoma formation is possible as there is no direct access for cauterization of bleeding sites. Patients were also observed for complications related to head frame application like haematoma/perforation. None of these were observed. In one of the patient there was air embolism in whom biopsy was taken in sitting position. The ETCO2 had dropped from 28 to 13 along with multiple VPC’s and hypotension (Systolic 60 mmHg). The surgical field was immediately flooded with saline and patient turned supine.
INDIAN JOURNAL OF ANAESTHESIA, APRIL 2002
Patient responded well to resuscitative measures (Ventilation with 100% oxygen + Inj Atropine 0.5 mg IV fast + Inj. Xylocard 2%, 2 mg /kg-1 IV slowly) and there was no untoward complication. This emphasizes the importance of central line in case of biopsy in sitting position2. Conclusion In paediatric patients and those with difficult airway, elective intubation before frame application helps in maintaining complete control of airway. All precautions as for neuroanesthesia like smooth perioperative ICP and haemodynamic control and precautions while positioning the patient including the aspects of sitting position need to be taken into account. Modern drugs like propofol and midazolam with favourable effect on ICP and rapid recovery help in maintaining Total Intravenous Anaesthesia (TIVA) throughout the procedure. Future Scope The field of stereotactic surgery is very vast in the form of functional stereotaxy for treatment of extrapytamidal movement disorders, management of neurogenic central pain syndromes and as stereotactic radiosurgery for treatment of brain tumours and vascular lesions. The study was a step towards understanding its various challenging anaesthetic aspects. References 1. Malcolm F Pell, Eric R. Cosman, David Thomas : Handbook of stereotaxy using CRW apparatus. 2. Roy F. Cucchiara, Susan black, John D Michenfelder : Clinical Neuroanaesthesia, 1998, 2nd edition, 477 - 493. 3. William DM, Baerts, JAAPJDE LANGE et al : Complications of the Mayfield skull clamp, Anaesthesiology, 1984, 61, 460. 4. Blood level of bupivacaine after injection into the scalp with and without adrenaline, Anaesthesiology, 1981, vol. 54, 81. 5. K.C.Baker and P.R.I.Sert: Anesthetic considerations for childen undergoing stereitactic radiosurgery, Anaesthesia and Intensive care 1997, Vol.25, 691-695. 6. Bone M.E., Bristow A : Total IV Anesthesia in stereotactic surgery-One years clinical experience. Eur.J.Anaesthesiol 1991, 8, 47-54.
