Total failure of spinal anesthesia for cesarean delivery, associated factors, and outcomes: A retrospective case–control study

Spinal anesthesia is the anesthetic technique of choice for patients undergoing cesarean delivery. In the present study, total spinal anesthesia failure was defined as a case when an absent blockade or inadequate surgery required general anesthesia administration with an endotracheal tube. This study aimed to investigate factors related to this condition and report its maternal and neonatal outcomes. This retrospective matched case-control study was conducted by recruiting 110 patients with failed spinal anesthesia and 330 control patients from September 1, 2016, to April 30, 2020, in the largest university hospital, Thailand. Of 12,914 cesarean deliveries, 12,001 patients received single-shot spinal anesthesia (92.9%) during the study period. Total spinal anesthesia failure was experienced by 110/12,001 patients, giving an incidence of 0.9%. Factors related to the failures were a patient body mass index (BMI) ≤29.5 kg/m2 (adjusted odds ratio 1.9; 95% confidence interval 1.2-3.1; P = .010) and a third-year resident (the most senior trainee) performing the spinal block (adjusted odds ratio 2.4; 95% confidence interval 1.5-3.7; P < .001). In the group with failed spinal anesthesia, neonatal Apgar scores at 1 and 5 minutes were lower than those of the control group (both P < .001). Two patients in the failed spinal anesthesia group (2/110; 1.8%) had difficult airways and desaturation. Independent factors associated with total spinal anesthesia failure were a BMI of ≤29.5 kg/m2 and a third-year resident performing the spinal block. Although the incidence of total failure was infrequent, there were negative consequences for the mothers and neonates. Adjusting the dose of bupivacaine according to the weight and height of a patient is recommended, with a higher dose appropriate for patients with a lower BMI.