Discussion
This study compared postpartum cardiovascular events and neonatal outcomes in parturients with CHD by anaesthetic technique (generalversus neuraxial anaesthesia). We showed that general anaesthesia is not significantly associated with composite postpartum cardiovascular events but is significantly associated with a higher rate of composite neonatal outcomes based on mixed-effects logistic regression.
Our main results are not consistent with a prior systematic review of case reports that suggest higher maternal mortality with general anaesthesia and improved outcomes with neuraxial anaesthesia, but this systematic review could not exclude selection bias due to sicker parturients receiving general anesthesia.13 The mixed-effects logistic regression models which adjusted for major confounders make the present study more reliable. During the 25 years of this study, the overall safety of general anaesthesia for caesarean section has improved dramatically in parturients without CHD, as outlined in a recent review.24 In addition, gestational age at delivery is a known confounder due to the larger impact of pregnancy on hemodynamic during the second or third trimester than during the first trimester.3 Therefore, we conducted sensitivity analyses that included date of caesarean delivery or gestational age at delivery as confounders and propensity score analysis using the IPTW approach. Results of the sensitivity analyses showed the robustness of the primary results.
Regarding neonatal outcomes, the OR for the association between general anaesthesia and adverse composite neonatal outcomes was high. Sensitivity analyses that considered date of caesarean delivery and other possible confounders resulted in higher ORs, thus supporting the primary results. These results were not consistent with a previous systematic review that showed no significant difference between 2 anaesthetic techniques in terms of neonatal outcomes.25 The differences may be attributed to the manner of general anaesthesia induction in parturients with CHD. Induction of general anaesthesia in parturients with high cardiac risk took longer than in the general population. Blunting the hemodynamic response at intubation and during surgery is crucial for maintaining hemodynamic stability in parturients with cardiac disease. Especially during induction, titration of anaesthetics and analgesics can achieve hemodynamic stability more easily than rapid sequence induction. Adequate doses of anaesthetics and analgesics to prevent noxious responses to intubation in parturients often cause neonatal depression. Therefore, neonatal outcomes were worse in the general anaesthesia group. However, an adequate dose for a parturient might outweigh the risk of neonatal depression, because fetal well-being depends on the maintenance of maternal hemodynamic stability and the effects of anaesthetics and opioid analgesics on the fetus could be reversible.26
The choice of neuraxial or general anaesthesia should be tailored for each individual parturient in order to maintain hemodynamic stability after considering the risks and benefits of both anaesthetic techniques.27 Since we did not find significant associations between increased maternal risk and anaesthetic technique, both anaesthetic techniques may be acceptable, especially general anaesthesia when there are contraindications to neuraxial anaesthesia, emergency surgery, or need for invasive monitoring. Moreover, the choice of anaesthetic technique should be made with consideration that general anaesthesia is associated with a higher risk of neonatal intubation or lower Apgar scores based on our results.
This study had the following limitations. First, because this study was retrospective in design, there might be residual confounding. However, most previous studies investigating the association between anaesthetic technique and postpartum and neonatal outcomes were case series. Due to the limited population of pregnant women with CHD, it is not feasible to perform randomized controlled trials to evaluate the superiority of the anaesthetic techniques. Therefore, we performed a retrospective chart review. Second, information about dose and type of drugs used, hemodynamic data, and type of invasive monitoring used during the perioperative period were not included as potential confounders due to lack of data. Third, due to the low rate of maternal and neonatal events, we could not avoid evaluating composite outcomes, which might make the results difficult to interpret.