CLINICAL CONTEXT
Delivery by emergency cesarean delivery is in widespread use in situations of fetal distress or compromise. Urgent cesarean delivery is termed category 1. More than half of all category 1 cesarean deliveries performed in the United Kingdom involve general anesthesia (GA), as it allows faster delivery.


However, the effect of GA vs regional anesthesia (RA) on neonatal outcomes has not been well studied. The objective of this retrospective cohort study was to determine whether the mode of anesthesia significantly affects short-term neonatal respiratory morbidity when there is a presumed fetal compromise and a need to deliver a term baby by category 1 cesarean delivery.


STUDY SYNOPSIS AND PERSPECTIVE
Babies exposed to GA during urgent delivery by cesarean delivery are more likely to experience adverse outcomes than those exposed only to RA, according to a studypublished online June 8 in the Australian and New Zealand Journal of Obstetrics and Gynaecology.


In particular, they are almost 7 times more likely to have a low Apgar score, and twice as likely to require ventilation and admission to intensive care.


Studies have had conflicting results concerning the relative safety of GA and RA for elective cesarean delivery. Data are sparse, however, for category 1 cesarean delivery births performed under urgent or emergency situations, such as when the life of the mother or infant is under immediate threat.


Michael Beckmann, MD, and Susan Calderbank, MD, from the Department of Anaesthesia, Mater Health Services, South Brisbane, Australia, conducted a retrospective cohort study to compare association of GA and RA with neonatal respiratory morbidity under category 1 situations. The researchers compared outcomes for 81 infants exposed to GA to 452 infants exposed to RA between February 2008 and June 2011. RA included spinal anesthesia, additional spinal-epidural anesthesia, and top-up epidural anesthesia. Fetuses exposed to GA experienced a decision-to-deliver interval nearly 8 minutes shorter than the others (24.7 vs 32.6 minutes; P < .001).


One previous study found that GA is riskier than RA for category 1 cesarean delivery, but did not account for important confounders. The present study controls for cord blood gas results, birth weight, and gestational age.


Babies exposed to GA faced more serious outcomes than babies born under RA. Specifically, the GA babies were more likely to have an Apgar score lower than 7 at 5 minutes (adjusted odds ratio [aOR], 6.89; 95% confidence interval [CI], 1.79 - 26.55; P = .005), to require ventilation assistance for more than a minute (aOR, 2.34; 95% CI 1.13 - 4.84; P = .022), and to require admission to the neonatal intensive care unit (aOR, 2.24; 95% CI, 1.16 - 4.31; P = .016). In contrast, babies born by GA were no more or less likely to require intubation (aOR, 1.86; 95% CI 0.52 - 6.71; P = .341).


Past studies have indicated that RA is safer for the mother than GA, but anesthesiologists must consider the benefit of GA in shortening labor, the authors write. This study indicates that RA is associated with better outcomes for the neonate, and therefore may be less risky than GA for this reason. The researchers conclude, "for term babies born by category 1 [cesarean delivery] for presumed fetal compromise, these data suggest an association between general anaesthesia and short-term neonatal respiratory morbidity," independent of cofounders. The results, they add, suggest that it is the GA itself, and not the "urgent clinical scenario," that raises the risk.


Limitations of the study, the investigators write, include entry errors by the midwives collecting the data, lack of control of all possible confounders, selection bias, and the discovery of association, not cause.


The authors have disclosed no relevant financial relationships.


Aust N Z J Obstet Gynaecol. Published online June 8, 2012. Abstract


STUDY HIGHLIGHTS
• This retrospective cohort study from Mater Health Services in Brisbane, Australia, used de-identified data routinely collected by midwives.
• The cohort consisted of 533 term babies born by category 1 cesarean delivery for presumed fetal compromise between 2008 and 2011.
• Using bivariate and multivariate analyses, the investigators compared the outcomes of 81 babies delivered by cesarean delivery under GA (GA-CS) with 452 babies delivered by cesarean delivery under RA (RA-CS).
• The decision-to-delivery interval was almost 8 minutes faster for GA-CS than for RA-CS (24.7 vs 32.6 minutes; P < .001).
• Compared with babies born by RA-CS, those born by GA-CS had worse neonatal outcomes after adjustment for confounders.
• Babies born by GA-CS were significantly more likely to have an Apgar score lower than 7 at 5 minutes (aOR, 6.89; 95% CI, 1.79 - 26.55; P = .005).
• Babies born by GA-CS were also significantly more likely to require a gas-powered resuscitator or bag/mask ventilation for more than 60 seconds (aOR, 2.34; 95% CI, 1.13 - 4.84; P = .022) and to be admitted to a neonatal intensive care nursery (aOR, 2.24; 95% CI, 1.16 - 4.31; P = .016).
• On the basis of these findings, the investigators concluded that despite allowing a more rapid delivery of the baby, GA was associated with short-term neonatal morbidity of term babies born by category 1 CS for presumed fetal compromise.
• The investigators suggest that their data should help the anesthesiologist and obstetrician balance the risks and benefits of the mode of anesthesia.
• Limitations of this study include possible entry error because of data collection by midwives, that the retrospective design was subject to selection bias and possible confounding, and the inability to determine causality.
CLINICAL IMPLICATIONS
• In a retrospective Australian cohort study of term pregnancies in which category 1 cesarean delivery was indicated for presumed fetal compromise, GA allowed more rapid delivery of the baby compared with RA.
• Despite faster delivery, GA vs RA was associated with greater short-term neonatal morbidity of term babies born by category 1 cesarean delivery. The investigators suggest that their data should help the anesthesiologist and obstetrician balance the risks and benefits of the mode of anesthesia.