Incidence of conversion to general anaesthesia and need for intravenous supplementation in parturients undergoing caesarean section under spinal anaesthesia: A retrospective observational study

Background: Conversion from spinal anaesthesia to general anaesthesia (GA) was shown to be associated with more complications. It has been postulated that spinal injection of a low dose of local anaesthetic is a risk factor. We aimed to discover the rate of conversion from spinal anaesthesia to GA in women who received at least 10 mg heavy bupivacaine and opioids and assess its risk factors. Methods: All women that underwent spinal anaesthesia for caesarean section from 1 January 2017 to 31 December 2020 were included in this analysis. Spinal anaesthesia was performed according to department protocol using heavy bupivacaine 0.5% 10–13 mg, fentanyl 20 μg, and morphine 0.1 mg. We examined rate of conversion from spinal anaesthesia to GA and rate of need for analgesia/sedation. Results: There were 1.7% of women that required conversion to GA. Bupivacaine dose (OR 0.54 [95% CI 0.38 to 0.75], p < 0.001), surgery time (OR 1.03 [95% CI 1.02 to 1.04], p < 0.001), emergency caesarean section (OR 1.06 [95% CI 1.16 to 3.76], p = 0.015), and postpartum haemorrhage (OR 5.96 [95% CI 1.09 to 25.18], p = 0.025) were independent predictors of need for conversion to GA. Of the women who had CS under spinal anaesthesia, 4.1% of parturients required intraoperative analgesics/sedatives and 9.1% required anxiolysis. Conclusions: A small proportion of women required conversion to GA. This conversion occurred especially with emergency caesarean section and when low spinal bupivacaine doses were used.