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.