Hypnotic agents for induction of general anesthesia in cesarean section patients: A systematic review and meta-analysis of randomized controlled trials

Study objective: An ideal induction drug for cesarean section (CS) must have quick action, with minimum side effects such as awareness, hemodynamic compromise, and neonatal depression. Thiopentone is frequently used; however, no reliable evidence is available to support its use as a dedicated hypnotic agent in this setting. Design: A systematic review and meta-analysis, using PRISMA methodology, of randomized controlled trials (RCTs), comparing women undergoing CS using thiopentone with those undergoing CS with propofol, ketamine, or benzodiazepines as hypnotic agents. Data sources: Comprehensive search without language restrictions of MEDLINE, EMBASE, and the Cochrane Controlled Trials Registers until May 2015, with an update in January 2017. Included trials must have reported at least one of the following variables: neonatal arterial or venous umbilical blood gas, maternal systolic blood pressure pre- and post-intubation, or Apgar score. Main results: A total of 911 patients from 18 RCTs were eligible for quantitative analysis. The increase in maternal systolic blood pressure was smaller in patients administered propofol, compared with those administered thiopentone (weighted mean difference [WMD]: -11.52 [-17.60, -5.45]; p = 0.0002). Induction with propofol also resulted in a significantly lower umbilical arterial pO(2) (WMD: -0.12 [-0.20, -0.04]; p = 0.004) than induction with thiopentone. A comparison between propofol and thiopentone revealed no significant differences in other umbilical blood gas parameters or in Apgar scores. In contrast, when comparing ketamine with thiopentone, the number of neonates with a lower Apgar score (< 7) at 1 and 5 min was significantly higher in the ketamine group than in the thiopentone group (p = 0.004). Conclusion: The evidence, based on sparse and relatively old trials, indicates that propofol and thiopentone are equally suited for CS. After 1 and 5 min, ketamine yields lower Apgar scores than thiopentone. Additional well designed trials are needed to reach firmer conclusions.