Induction opioids for caesarean section under general anaesthesia: a systematic review and meta-analysis of randomised controlled trials

Introduction The adverse effects of induction opioids on the neonate are poorly characterised. The study aim was to investigate whether induction opioids can be used in caesarean section without adversely affecting the neonate. Methods Six databases were systematically searched from inception until January 2019. Included studies compared induction opioids and placebo in caesarean section. Results were presented as odds ratios (95% confidence intervals) for dichotomous outcomes and weighted mean difference for continuous outcomes. An I2 statistic of >50% was significant for heterogeneity. The primary outcome was Apgar score (1 and 5 min). Secondary outcomes included neonatal adverse events, cord blood gas analyses, maternal haemodynamic parameters (systolic blood pressure (SBP), mean arterial pressure (MAP), heart rate (HR) and catecholamine concentrations. Results Seventeen studies (n=987) were included in the meta-analysis. Remifentanil 0.5–1 μg/kg or 2–3 μg/kg/h, alfentanil 7.5–10 μg/kg and fentanyl 0.5–1 μg/kg were compared to placebo. There was no significant difference in Apgar scores at 1 min (P=0.25, 0.58 and 0.89 respectively) for all three opioids or at 5 min for remifentanil and alfentanil (P=0.08 and 0.21 respectively). Fentanyl significantly reduced 5 min Apgar scores (P=0.002). There was no difference in neonatal airway interventions with remifentanil or alfentanil (P <0.05). All three induction opioids caused a significant reduction in maximum SBP (P <0.0001), MAP (P <0.00001) and HR (P <0.00001). Conclusion Induction opioids are effective sympatholytic agents. Remifentanil and alfentanil appear to be safe, with no significant effect on Apgar scores or neonatal airway intervention, but a well-powered trial is required to confirm these findings.