This was a 5-year retrospective study performed at an academic medical center in the United Kingdom between January 1, 2010 and December 31, 2014. All women who delivered via CD with a singleton pregnancy were included in the study unless necessary data, such as anesthesia technique, were missing. Patients were identified and data obtained from the hospital birth register and procedure logs from the anesthesia department and operating room. They determined the median time for ORII for categories 1 to 4 CDs. Further evaluation of category 1 cases was then performed using time-to-event analysis and a Cox proportional hazards regression model. Covariates included in the regression model were anesthetic technique, body mass index, age, parity, time of delivery, and gestational age. Binary logistic regression was used to analyze associations with neonatal outcome in category 1 CDs.
There were a total of 9486 women included in the initial analysis of ORII and CD category. The unadjusted median [interquartile range (IQR)] ORII for the various categories were: 11 minutes (IQR, 6 to 18) for category 1, 21 minutes (IQR, 15 to 29) for category 2, 28 minutes (IQR, 20 to 37) for category 3, and 33 minutes (IQR, 24 to 43) for category 4.
Among all these CDs, 832 (8.6%) were classified as category 1 with 677 of those meeting entry criteria for the study. When comparing the various anesthetic techniques for category 1 CDs, epidural top-up of an existing labor epidural was considered the reference group to which general anesthesia, spinal anesthesia, and combined spinal-epidural (CSE) anesthesia were compared. The unadjusted median (IQR) ORIIs for anesthetic techniques were: epidural top-up (n=317) 11 minutes (7 to 17), general anesthesia (n=147) 6 minutes (4 to 11), spinal (n=167) 13 minutes (10 to 20), and CSE (n=46) 24 minutes (13 to 35). General anesthesia was the fastest anesthetic technique for category 1 CD with a hazard ratio (HR) of 1.97 [95% confidence interval (CI), 1.60-2.44; P<0.0001], compared with epidural top-up. In contrast, spinal anesthesia and CSE anesthesia both had significantly longer ORIIs with HRs of 0.79 (95% CI, 0.65-0.96; P=0.02) and 0.48 (95% CI, 0.35-0.67; P<0.0001), respectively. For neonatal outcomes, an association was found between the use of general anesthesia for a category 1 CD and a lower likelihood of having a 5-minute Apgar score ≥7 with an odds ratio of 0.28 (95% CI, 0.11-0.68; P<0.01). However, no relationship was found between the ORII and the risk of a 5-minute Apgar score <7 when controlling for confounders, including anesthetic technique.
In conclusion, this single-center retrospective study reported that general anesthesia was associated with the fastest ORII for category-1 CDs, but this did not lead to evidence of improved neonatal outcome. The use of general anesthesia was associated with worsened short term neonatal outcome as measured by 5 minutes. Apgar score <7. In addition, no association was found between the duration of ORII and neonatal outcome.
The rise in the global rate of CDs continues to draw significant attention. Meanwhile, in many western countries, the increase in the number of unplanned or emergency cases appears to exceed the increase in elective cases.1–3 While this is likely secondary to advances in peripartum monitoring it may also reflect a lower threshold for surgical intervention as decided by the attending obstetric team who are perhaps more likely to adopt a more cautious approach. However, the degree of urgency of the delivery has significant implications for the anesthesiologist, and the choice of anesthetic technique for emergency CD has long been a topic for discourse. In the United Kingdom, a system for grading the urgency of CD and recommendations as to the decision-delivery interval (DDI) depending on the degree of urgency was published by the National Institute for Health and Care Excellence (NICE) and endorsed by the Royal College of Obstetricians and Gynaecologists.4,5 Category 1 describes compromise that is an immediate threat to the life of the mother or fetus and a DDI of <30 minutes is recommended. Category 2 describes maternal or fetal compromise, which is not, however, life threatening and a delivery within 75 minutes is recommended. Category 3 describes a need for early delivery but with no evidence of fetal or maternal compromise (such as ruptured membranes in a parturient who is awaiting an elective CD) and category 4 describes all elective deliveries which are timed to suit the mother and the delivery suite team.
A decision to proceed with a general anesthetic (GA) is largely influenced by the perceived degree of urgency and may be requested by the “distressed” obstetrician who is under the impression that a GA is faster and that simply a speedier delivery of the fetus is the safest option. This may sometimes overshadow any due consideration of the anesthetic risks associated with an obstetric GA, including aspiration, failed intubation and maternal awareness, as well as the possible negative impact on neonatal outcome. While a GA is unavoidable in many cases, it may be that sometimes it is used when a neuraxial technique would have sufficed. Choosing the “right” method of anesthesia may have significant implications for the mother, child and clinical team members involved in the case. Despite this, there remains a paucity of clear guidance as to the choice of anesthesia technique for CD as well as evidence as to which type of anesthetic has more favorable outcomes for the parturient and, in particular, the neonate. The cohort study by Palmer and colleagues in the United Kingdom has helped to further tease out the often complex relationships between method of anesthesia, time to delivery and neonatal outcome in emergency CDs.6
General anesthesia was associated with a shorter ORII but was independently associated with a worse short-term neonatal outcome as measured by depressed 5-minute Apgar scores. One cannot, however, exclude the possibility that this reflects the degree of fetal compromise dictating the urgency of delivery in the first place. Other studies have attempted to correct for this and found that, when controlling for confounders, general anesthesia remains a significant risk factor for neonatal Apgar score depression.7 Similarly, one might argue that a depressed 5-minute Apgar score is simply a result of fetal exposure to general anesthesia, but no differences have been found when comparing the effects of neuraxial and general anesthesia on neonatal outcomes following elective CDs.8 The use of depressed Apgar scores as a surrogate for poor neonatal outcome is not without its limitations, and the prognostic value has been questioned. Low Apgar scores do not predict individual neonatal mortality or neurological morbidity and cannot be used as evidence of asphyxia.9,10 Perhaps by focusing on other fetal clinical outcomes such as neonatal intensive care admissions or laboratory measures of fetal stress (serum cortisol or cardiac enzymes) more meaningful and significant differences between anesthetic techniques might emerge.
The management of emergency CDs remains a challenge for the anesthesiologist; allowing additional time to perform a spinal anesthetic or top-up an epidural versus administering a GA is a familiar dilemma especially within the 30-minute DDI target, a time constraint which may preclude neuraxial anesthesia. While there remains little doubt that declaring a category 1 CD implies that the fetus should be delivered as quickly as possible, the evidence supporting a benefit of delivery within 30 minutes remains unclear yet it is a standard that is accepted in the United Kingdom and more widely across many western countries.11,12 The question remains, however, should the choice of anesthetic technique be influenced by the need to meet a target of delivering the fetus within 30 minutes when this standard has no firm evidence base to support a better outcome for mother and neonate? Opportunities to reassess the patient and fetus should not be overlooked once the decision for delivery has been made; due consideration for deescalation of the degree of urgency once maternal and fetal resuscitative measures (uterine displacement, intravenous fluids, oxygen supplementation) have been commenced may defuse an otherwise charged atmosphere in the operating room allowing time to make a more informed decision as to the most appropriate anesthetic technique. Palmer and colleagues have demonstrated that while general anesthesia facilitates a faster time to the start of surgery when compared with neuraxial techniques the results suggest that this may be at the expense of a better neonatal outcome in the short term with neuraxial techniques. Although one should be cautious as to how this may translate to longer term outcomes, the results of this study further support the choice of neuraxial anesthesia for emergency CD in keeping with NICE recommendations.4
Comment by Stephen Ramage, BSc, MBBS, FRCA, Sarah Armstrong, MA, MBBS, FRCA, and Roshan Fernando, MB ChB, FRCA
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