Sobering success rates in trainee epidural competence
ESRA Academy. Dr W Harrop-Griffiths D. Nov 28, 2016; 164422
Dr T Alexander Dr W Harrop-Griffiths
Dr T Alexander Dr W Harrop-Griffiths
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The prospect of a junior anaesthetic trainee covering a labour ward out-of-hours is daunting not only for the trainee but also for those responsible for their training and clinical performance. In addition to the dreaded Category 1 Caesarean section, the task of inserting a lumbar epidural for labour analgesia is one that many novice obstetric anaesthetic trainees will never have attempted before their obstetric training rotation. Determining the point at which a trainee is deemed capable of working independently on the labour ward is challenging, and a robust method of evaluating competence would be highly desirable. In the UK and in other countries, competence is currently often determined by direct observation of the trainee performing the technique in what is called ‘workplace-based assessments’. While there is undoubtedly a place for trainers directly observing practical clinical procedures to ensure the trainee’s technique is appropriate, these provide only a snapshot of the trainee’s performance. In the case of inserting a labour epidural, competence is not necessarily achieved after one successful, directly observed attempt, but when the trainee is able to place an epidural consistently and successfully on multiple occasions.

Drake et al have applied CUSUM analysis to a large, retrospective database of novice anaesthetists and their first 100 attempts at obstetric epidural analgesia. The value of the use of this database is that the success or failure of the epidural analgesia was judged objectively by the midwife caring for the patient rather than being judged by the trainees themselves. We can therefore assume a large degree of candour and accuracy in the assessment. One problem with which the authors were confronted was determining the success rates at which competence was defined. They chose to set a success rate of 65% as an acceptable success rate (and 55% as being unacceptable), arguing that with this threshold, some 95% of the trainees completing the block of training would have been judged competent, and that if a higher success rate of 80% were set as equalling competence, only 57% of trainees would have been judged competent.

This is undoubtedly a pragmatic approach to the definition of competency but is perhaps one that would be greeted with little enthusiasm by obstetric patients. Even with this relatively low hurdle to jump, four out of the cohort of 81 trainees studied were not deemed competent. Other interesting results were that after the performance of their first 10 epidurals, there was little improvement in epidural success rates, and that it took a mean (range) of 46 (19-114) epidural attempts to reach competence as set by the 65% threshold. The overall obstetric epidural success rate calculated from the database of novice trainees was 77%.

This study provides evidence of the value of using CUSUM analysis to guide the delivery of training. One conclusion that we draw is that trainees should be supervised for at least their first 10 epidural attempts, given that their chances of improving their success rates after this appear low. It is tempting to draw the additional conclusion that they should achieve competence after 50 epidurals, but the wide range of the number of attempts before competence was achieved argues against this: somewhere between 19 and 114 attempts. It may be that trainees whose success rate is low in their first 10 attempts should continue to be supervised until their success rates matches those of their peers, i.e. about 77% overall. It is noteworthy that a small number of trainees (four) never achieved competence, which supports a view long held by the more senior author of this review that although obstetric epidural analgesia is fundamentally a simple technique, there remains a small number of anaesthetists who should never be allowed to wield an epidural needle in a clinical setting.

We have only two adverse comments to make about this otherwise laudable and valuable study. First, the crude success rate ignores the context in which the epidurals were placed, e.g. the stage of labour, the anatomy of the patients and the extent with which they were able to cooperate with attempts at their epidurals by novices. Although such factors would most likely equal themselves out in such a large study, it is possible to theorise that the confidence and thereby future success rate of a trainee might be affected adversely if they were confronted with several difficult clinical situations in their first 10 epidurals. Secondly, the reviewers see a difference between the successful placement of a catheter into the anatomic epidural space and the successful management of a correctly placed epidural catheter thereafter. In their experience, the placement of the catheter is often by far the easier of these two challenges, and a methodology that crudely determines epidural to be a success or a failure ignores the value of training in the management of epidural analgesia in labour.

The reviewers are left with one nagging doubt. Should we accept a success rate of 65% for the sake of expedience – or should we set higher success rates that promote excellence, even if by doing so places a greater burden on those charged with training the anaesthetists of tomorrow? If as parturients we were told by our impending epiduralists that they were competent and that their success rate was 65%, we would most likely ask them to leave the room and find an anaesthetist whose success rate was rather higher.

Background: Cumulative sum (CUSUM) analysis has been used for assessing competence of trainees learning new technical skills. One of its disadvantages is the required definition of acceptable and unacceptable success rates. We therefore monitored the development of competence amongst trainees new to obstetric epidural anaesthesia in a large public hospital.

Methods: Obstetric epidural data were collected prospectively between January 1996 and December 2011. Success rates for inexperienced trainees were calculated retrospectively for (1) the whole database, (2) for each consecutive attempt and (3) each trainee’s individual overall success rate. Acceptable and unacceptable success rates were defined and CUSUM graphs were generated for each trainee. Competence was assessed for each trainee and the number of attempts to reach competence was recorded.

Results: Mean (SD) success rate for all inexperienced trainees was 76.8 (0.1%), range 63–90%. Consecutive attempt success rate produced a learning curve with a mean success rate commencing at 58% on the first attempt. After the 10th attempt the attempt number had no effect on subsequent success rates. From these results, the acceptable and unacceptable success rates were set at 65% and 55% respectively. CUSUM graphs demonstrated that 76 out of 81 trainees were competent after a mean of 46 (22) attempts.

Conclusions: CUSUM is useful for assessing trainee epidural competence. Trainees require approximately 50 attempts, as defined by CUSUM, to attain competence. Reviewed by Dr T Alexander & Dr W Harrop-Griffiths, Department of Anaesthesia, St Mary’s Hospital, Imperial College Healthcare NHS Trust, London, UK

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