Failed Obstetric Spinal Anesthesia in a Nigerian Teaching Hospital: Incidence and Risk Factors

BACKGROUND: In a retrospective survey, we found 1% cases with complete and partial failure of spinal anesthesia for cesarean delivery between 2008 and 2010, which we attributed to underreporting because of the study design. In this prospective study, we determined the incidence of failed spinal anesthesia and identified the factors that increased its risk. METHODS: This prospective, observational study consisted of all spinal anesthetics administered for cesarean delivery surgery from January 2011 to December 2013. Our definition of failure covered complete (preoperative) failure to achieve a pain-free operative condition and pain during surgery (intraoperative failure). RESULTS: Of a total of 3568 cesarean deliveries, there were 3239 (90.8%) spinal blocks, and the overall failure was 294 (9.1%). These were rescued by conversion to general anesthesia (22.8%) and repeating spinal (23.1%) and IV analgesic supplementation (54.1%). Analysis by logistic regression model indicated that factors associated with failure were the level of experience of the anesthesia provider as shown by senior registrar (adjusted risk ratio [RR], 1.4; 95% confidence interval [CI], 1.0-1.9), >1 lumbar puncture attempt (adjusted RR, 1.5; 95% CI, 1.1-1.9), and use of the L4/L5 interspace (adjusted RR, 1.7; 95% CI, 1.4-2.0). CONCLUSIONS: The rate of failed spinal anesthesia from this study was high. The independent predictors of failure were multiple lumbar puncture attempts, use of the L4/L5 interspace, and the level of experience of the anesthesia provider. It is imperative to develop clear guidelines to standardize our obstetric spinal anesthetic practice as well as the management of failures.