ORIGINAL ARTICLE
JOURNAL
OF
THE ROYAL
SOCIETY OF
MEDICINE
93
July 2000
Urgency of caesarean section: a new classi®cation D N Lucas FRCA S M Yentis MD FRCA M Wee FRCA 4 P N Robinson FRCA 5
S M Kinsella FFARCSI 1
A Holdcroft MD FRCA 2
A E May FRCA 3
J R Soc Med 2000;93:346±350
SUMMARY A new classi®cation for caesarean section was developed in a two-part study conducted at six hospitals. Initially, 90 anaesthetists and obstetricians graded ten clinical scenarios according to ®ve different classi®cation methodsÐ visual analogue scale; suitable anaesthetic technique; maximum time to delivery; clinical de®nitions; and a 1±5 rating scale. Clinical de®nitions was the most consistent and useful, and this method was then applied prospectively to 407 caesarean sections at the same six hospitals. There was close agreement (86%) between anaesthetists and obstetricians for the ®ve-point scale (weighted kappa 0.89), increasing to 90% if two categories were combined (weighted kappa 0.91). We suggest that the resultant four-grade classi®cation systemÐ(i) immediate threat to life of woman or fetus; (ii) maternal or fetal compromise which is not immediately life-threatening; (iii) needing early delivery but no maternal or fetal compromise; (iv) at a time to suit the patient and maternity teamÐshould be adopted by multidisciplinary groups with an interest in maternity data collection.
INTRODUCTION
The conventional classi®cation of caesarean section categorizes planned operations as `elective' whilst all others are `emergencies'. These de®nitions are inadequate1 because all non-elective cases are classed as emergencies, although some are clearly more urgent than others. The continued use of this classi®cation limits the comparability, and thus usefulness, of information collected on obstetric and anaesthetic activity at both local2 and national3 levels. Furthermore, this classi®cation differs from that used for surgical procedures by the National Con®dential Enquiry into Perioperative Deaths (NCEPOD), which is emergency/ urgent/scheduled/elective4. Our aim was to develop and evaluate an improved classi®cation of urgency of caesarean section that could be used nationally in obstetric, anaesthetic and other data collection systems. METHODS
The study was conducted at six maternity units, of which four were in teaching hospitals and two were in district Magill Department of Anaesthesia, Intensive Care and Pain Management, Chelsea & Westminster Hospital, London SW10 9NH, UK; 1Anaesthetic Department, St Michael's Hospital, Southwell Street, Bristol BS2 8EG; 2
Department of Anaesthetics, Division of Surgery, Anaesthetics and Intensive
Care, Imperial College School of Medicine, Hammersmith Hospital, London W12 0HS; 3Anaesthetic Department, Leicester Royal In®rmary, Leicester LE1 5WW; 4
Anaesthetic Department, Poole Hospital, Poole BH15 2JB; 5Anaesthetic
Department, Northwick Park Hospital, Watford Road, Harrow HA1 3JU, UK Correspondence to: Dr S M Yentis, Magill Department of Anaesthesia, Chelsea &
346
Volume
Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK E-mail:
[email protected]
general hospitals. In the ®rst phase, anaesthetists and obstetricians were asked to classify ten theoretical obstetric clinical scenarios (Box 1) according to each of ®ve different classi®cations numbered 1±5 as in Box 2. Performance of the ®ve classi®cations was assessed by their ability to discriminate between the ten scenarios (i.e. the distribution of the scenarios between the categories) and the consistency of the scoring between the subjects (i.e. the scatter of responses for each scenario). In the second phase, the most useful classi®cation as judged by the above criteria was applied prospectively to caesarean sections at the same six hospitals. Anaesthetists and obstetricians were shown the classi®cation system and were asked to score consecutive caesarean sections. The clinicians were blinded to their colleagues' assessments. Agreement was assessed by the weighted kappa statistic.
RESULTS
60 anaesthetists and 30 obstetricians responded in the ®rst part of the study. The classi®cation that performed best was number 4 (clinical de®nitions) followed in order by 5, 1, 3 and 2 (Figure 1). In the second part of the study, classi®cation 4 was applied to 407 caesarean sections classi®ed by the anaesthetists and obstetricians associated with each case. The anaesthetists' and obstetricians' gradings of the cases are shown in Table 1(a). There was good agreement (86%) among anaesthetists and obstetricians for the ®ve grades (weighted kappa 0.89); this rose to 90% agreement and a
JOURNAL
OF
THE
ROYAL
Box 1 Clinical scenarios Scenario No. Details
1
A 25-year-old primiparous woman whose cervix has been 6 cm dilated for 8 hours despite maximal oxytocin. The CTG is entirely normal
2
A primiparous woman presents to labour ward at 5 cm cervical dilatation with an undiagnosed breech presentation. The CTG shows a fetal heart rate of 180/min with no decelerations
3
A primiparous woman at 35 weeks' gestation has pre-eclampsia. She is on a hydralazine infusion. Proteinuria is 43 g/day. The fetus has severe IUGR and absent end-diastolic ¯ows. On routine monitoring the CTG is found to be abnormal
4
The CTG of a multiparous woman at 2 cm cervical dilatation shows persistent late decelerations on the CTG. The liquor is heavily stained with meconium
5
A primiparous woman in labour has a prolapsed cord. The CTG is entirely normal
6
The CTG of a multiparous woman shows a severe fetal bradycardia for 2 min
7
A woman who does not speak any English and who has not received any antenatal care presents to the labour ward with an antepartum haemorrhage. On examination she is not tachycardic, has a blood pressure of 120/70 mmHg and is estimated to be of 38 weeks' gestation. The CTG is normal. The bleeding is continuous
8
The CTG of a primiparous woman in labour shows variable decelerations. Fetal blood pH is 7.17. The cervix is 3 cm dilated
9
A woman at 39 weeks' gestation presents to labour ward with an abruption. The CTG shows persistent late decelerations
10
A woman who is booked for elective caesarean section, having had a previous caesarean section for cephalopelvic disproportion, presents in active labour. On examination her cervix is 4 cm dilated and the CTG is normal
CTG=cardiotocograph; IUGR=intrauterine growth retardation
weighted kappa of 0.91 if grades (ii) and (iii) were combined to give a 4-point classi®cation (Table 1(b). DISCUSSION
The ideal method of classi®cation should be simple, applicable to a wide variety of clinical cases, reliable and valid. In the ®rst part of this study we found the classi®cation based on clinical de®nitions (number 4) to perform best, and in the second part of the study it proved to be useful and reliable in clinical practice. Classi®cations 1±3 did not perform as well as expected. Although doctors are accustomed to using visual analogue scales (classi®cation 1) in clinical practice and research, this method seemed too non-speci®c to classify the urgency of caesarean section. Anaesthetic technique (classi®cation 2) is
SOCIETY
OF MEDICINE
Volume
93
July 2000
a popular colloquial way to classify caesarean section (for example, `is there time for a spinal?') but the inadequacies of this method are obvious. The speed with which a technique such as spinal anaesthesia can be performed undoubtedly depends on factors such as the experience of the anaesthetist. Also, is it reasonable to expect obstetricians to classify the urgency of a caesarean section by suggesting techniques in which they have no training? Time to delivery (classi®cation 3) is another commonly used informal method of classi®cation. A time of 30 minutes from decision to delivery is often quoted5, although this is based largely on animal studies from several years ago, in which the endpoints were gross histological changes resulting from fetal hypoxia6. The maximum safe (in terms of fetal outcome) time to delivery in the presence of fetal distress is not known, and probably varies greatly with the severity and nature of the disorder and the fetal `reserve'. When classi®cation 3 (time) was investigated in the ®rst part of our study, the ®gure of 5 minutes was a frequently selected category, illustrating the poor performance of this classi®cation. Although delivery within 5 minutes might be highly desirable, it is unlikely to be achieved in most labour wards. We had hoped that classi®cation 5 (5-point rating scale) would be the best performer, since it would remove the need for de®ning the various categories. However, perhaps because of this absence of precision, this classi®cation too performed badly. We should point out that we did not assess clinicians' opinions of the classi®cation systems, which might have yielded different results from those we found. Classi®cation 4, based on clinical de®nitions, performed well in both phases of the study. It was improved further by combining categories (ii) and (iii) since most of the disagreements between anaesthetists and obstetricians arose from these categories. Use of a 4-point classi®cation would also be compatible with the NCEPOD 4-grade system4. Consequently this re®nement is the classi®cation we wish to promote (Box 3). It seemed to be applicable to a representative sample of caesarean sections in our study, although we did not examine whether the few disagreements that did occur were associated with particular indications for surgery. Reliability, the consistency of measurements between different observers, is assessed in terms of the kappa statistic, and in general a value between 0.8 and 1 signi®es very good agreement. Thus our classi®cation is simple, applicable and reliable. What we cannot be certain of is its validityÐthe ability of a device or system actually to measure what it is supposed to measure. If the purpose of such a classi®cation is to predict poor outcome, then much larger studies are needed with assessment of fetal and maternal wellbeing. However, with the large number of factors that may affect outcome, any antepartum classi®cation is likely to perform poorly as a
347
JOURNAL
OF
THE ROYAL
SOCIETY OF
MEDICINE
Volume
93
July 2000
Box 2 Classi®cations of caesarean section investigated Classi®cation No.
Details
1
10 cm visual analogue scale (0=elective, 10=immediate caesarean section required)
2
According to anaesthetic technique: (i) (ii) (iii) (iv) (v)
3
have a general anaesthetic for a `quick' spinal to top up an existing epidural to insert an epidural from scratch for the anaesthetist to ®nish putting an epidural in another patient
Maximum time to delivery: (i) (ii) (iii) (kv) (v) (vi) (vii)
348
Must Time Time Time Time
55 min 520 min 540 min 560 min 56±8 h 524 h 424 h
4
Clinical de®nition: (i) Immediate threat to life of mother or fetus (ii) Severe fetal or maternal compromise but not immediately life-threatening (iii) Compromise which responds to therapy although underlying problem still exists (iv) Needing delivery but no compromise (v) Can be booked on next elective list
5
5-point verbal rating scale (1=elective, 5=immediate caesarean section required)
Figure 1 Responses of obstetricians and anaesthetists applying ®ve classi®cations of caesarean section to ten hypothetical scenarios. (1) 10 cm visual analogue scale; (2) suitable anaesthetic technique; (3) maximum time to delivery; (4) clinical de®nitions; (5) 5-point verbal rating scale
JOURNAL
OF
THE
ROYAL
SOCIETY
OF MEDICINE
Volume
93
July 2000
Table 1 Assessments of 407 consecutive caesarean sections by anaesthetists and obstetricians using a classi®cation based on clinical de®nitions Score allocated by anaesthetists Score allocated by obstetricians
(i)
(ii)
(iii)
(ii)+(iii)
(iv)
(v)
(a) Original 5-point classi®cation (i)
21
8
3
0
0
(ii)
3
37
7
2
0
(iii)
0
10
40
6
0
(iv)
0
3
9
102
4
(v)
0
0
0
1
151
0
0 0
(b) With categories (ii) and (iii) combined (i)
21
11
(II)+(III)
3
94
8
(IV)
0
12
102
4
(V)
0
0
1
151
predictor, especially since factors affecting maternal and fetal outcome would have to be separated out. If, on the other hand, the purpose of a classi®cation of caesarean section is to divide cases by urgency for audit, training or risk-management purposes1, then a classi®cation such as that presented in Box 3 must perform well, since it relies for its categories on the clinical situation which in turn dictates the degree of urgency. We argue that this aim alone is important enough a reason for adopting or promoting a national classi®cation. A classi®cation of urgency would complement classi®cations based on indication or on stage of pregnancy/labour, and it is not our intention to promote our classi®cation to the exclusion of others. In particular, we would see the role of such a classi®cation as facilitating audit, not in¯uencing clinical practice. Classi®cation of caesarean section has relevance to many different groups involved in maternity care. From the anaesthetic perspective, it is important because of the common view that, especially in non-elective cases, general anaesthesia should be avoided if possible, regional anaesthesia being safer. Audit of anaesthetic techniques used for caesarean section would be much more effective with an improved classi®cation1; it is this which has driven us, as anaesthetists, to pursue this project, although we have received strong support from obstetricians in the process. There is increasing need to standardize de®nitions and terms used in maternity data collection to allow comparison of local, regional and national ®gures2,7±9. The task of standardizing de®nitions in obstetric anaesthesia is one of
Box 3 Proposed classi®cation for urgency of caesarean section Grade
De®nition*
(1) Emergency
Immediate threat to life of woman or fetus
(2) Urgent
Maternal or fetal compromise which is not immediately life-threatening
(3) Scheduled
Needing early delivery but no maternal or fetal compromise
(4) Elective
At a time to suit the woman and maternity team
*Applies to the time of decision to operate; e.g. an episode of fetal compromise caused by aortocaval compression responding to therapy, followed some hours later by caesarean section for failure to progress, would be graded as 3, not 2. Similarly, a case booked as an elective procedure for malpresentation could eventually be classi®ed as grade 3 if the mother goes into labour before the chosen date of surgery. Also applies whether or not the woman is in labour
the aims of the National Obstetric Anaesthetic Database (NOAD) project7, which has the support of the Obstetric Anaesthetists' Association and Royal College of Anaesthetists and has representation from these bodies and also the Royal College of Obstetricians and Gynaecologists, Royal College of Midwives, NHS Executive and patient groups. The study presented here was conducted independently of NOAD but with full support from the NOAD Steering Group. We hope that the new classi®cation will help the various groups involved in maternity data collection to coordinate their efforts. Apart from the bodies named above, an improved classi®cation of caesarean section would also have advantages for the Clinical Negligence Scheme for
349
JOURNAL
OF
THE ROYAL
SOCIETY OF
MEDICINE
Trusts, the Con®dential Enquiry into Stillbirths and Deaths in Infancy, the Con®dential Enquiries into Maternal Deaths and the National Maternity Record project, especially if it were adopted universally by these projects and groups. REFERENCES
1 Lucas N, Nel MR, Robinson PN. The anaesthetic classi®cation of caesarean sections. Anaesthesia 1996;51:791±2 2 Holdcroft A, Verma R, Chapple J, et al. Towards effective obstetric anaesthetic audit in the UK. Int J Obstet Anesth 1999;8:37±42 3 Department of Health. NHS Maternity Statistics, England: 1989±90 and 1994±95. London: Stationery Of®ce, 1997
350
Volume
93
July 2000
4 Campling EA, Devlin HB, Hoile RW, Lunn JN. The Report of the National Con®dential Enquiry into Perioperative Deaths, 1992±1993, London: NCEPOD, 1995 5 Association of Anaesthetists of Great Britain & Ireland/Obstetric Anaesthetists' Association. Guidelines for Obstetric Anaesthesia Services. London: AAGBI, 1998 6 Myers RE. Experimental models of perinatal brain damage: relevance to human pathology. In: Gluck L, ed. Intrauterine Asphyxia and the Developing Fetal Brain. Chicago: Yearbook Medical, 1977:37±97 7 Yentis SM. National obstetric anaesthetic database (NOAD). Obstet Anaesth Assoc Newsletter December 1998:4 8 NHS Executive. Maternity Care Data ProjectÐOverview, IMG-ref C3237. Leeds: NHS, February 1999 9 Yentis SM, Robinson PN. De®nitions in obstetric anaesthesia: how should we measure anaesthetic workload and what is epidural rate? Anaesthesia 1999;54:958±62
