30-minute Rule Research Articles

Cord Gas Analysis, Decision-to-Delivery Interval, and the 30-Minute Rule for Emergency Cesareans

The so-called 30-minute rule is that hospitals having obstetric facilities should be equipped to perform an emergency cesarean delivery starting within 30 minutes of the decision to operate. This study examined the relationship between the results of umbilical arterial blood gas analysis and the decision-to-delivery interval in emergency cases with nonreassuring fetal status. Improved outcomes with an interval less than 30 minutes would presumably validate the rule. A retrospective cohort study included all cesarean deliveries done for this reason during a 16-month period in the years 2001 to 2003. Three specialists in maternal-fetal medicine, masked to the outcome, received a synopsis of clinical information that would have been available at the time of delivery as well as the last hour of the electronic fetal heart rate tracing. Emergent deliveries were done as soon as possible and deliveries within 30 minutes of the decision to operate. The series included 117 women, 34 classified as emergent and 83 as urgent. General anesthesia was given significantly more often in emergent cases and epidural anesthesia in urgent cases. The decision-to-delivery time was nearly 14 minutes less in the emergent group. There were no differences in 1- or 5-minute Apgar scores, but both the umbilical arterial pH and base excess were significantly worse in emergent cases. The decision-to-delivery interval was nearly 15 minutes shorter for general than for spinal anesthesia and 13 minutes less than with epidural anesthesia. Apgar scores recorded at 5 minutes (but not at 1 minute) were significantly increased with general anesthesia. Umbilical artery pH values did not differ significantly between groups, but base excess was significantly less favorable with general anesthesia. An increased decision-to-delivery interval correlated with improved umbilical arterial pH and base excess. This correlation did not help to predict when the fetus would develop metabolic acidosis severe enough to increase the risk of long-term neurologic morbidity. A very large majority of fetuses had normal values even after 30 minutes. Seven premature infants had intraventricular hemorrhage; 6 of them survived. Only fair to moderate agreement was found between the 3 specialists. Metabolic acidosis is not sensitively predicted by electronic fetal monitoring. In this study, blood gas values remained normal even when birth took place more than 30 minutes after the decision to operate. In the presence of nonreassuring fetal monitoring, the 30-minute rule is a compromise that does not precisely predict how much time will pass before severe metabolic acidosis develops.

Cord Gas Analysis, Decision-to-Delivery Interval and the 30-Minute Rule for Emergency Cesareans

Cord Gas Analysis, Decision-to-Delivery Interval and the 30-Minute Rule for Emergency Cesareans

Cord Gas Analysis, Decision-to-Delivery Interval, and the 30-Minute Rule for Emergency Cesareans

Our primary objective was to examine the relationship between umbilical arterial gas analysis and decision-to-delivery interval for emergency cesareans performed for nonreassuring fetal status to determine if this would validate the 30-minute rule. For this retrospective cohort study, all cesarean deliveries performed for nonreassuring fetal status from September 2001 to January 2003 were reviewed. A synopsis of clinical information that would have been available to the clinician at the time of delivery and the last hour of the electronic fetal heart rate tracing prior to delivery were reviewed by three different maternal-fetal medicine specialists masked to outcome, who classified each delivery as either emergent (delivery as soon as possible) or urgent (willing to wait up to 30 minutes for delivery) since immediacy of the fetal condition is the key factor affecting the type of anesthesia used. Of 145 cesareans performed for nonreassuring fetal status during this period, 117 patients met criteria for entry, of which 34 were classified as emergent and 83 as urgent. Kappa correlation was 0.35, showing only fair/moderate agreement between reviewers. In the emergent group, general anesthesia was more common (35.3%, 10.8%, p=0.003), and the decision-to-delivery interval was 14 minutes shorter (23.0+/-15.3, 36.7+/-14.9 minutes, p<0.001). Linear regression showed a statistically significant relationship between increasing decision-to-delivery interval and umbilical arterial pH (r=0.22, p=0.02) and base excess (r=0.33, p<0.001) showing that delivery proceeded sooner for most of those with the worst cord gases, with a gradual improvement over time. For the 13 (11%) neonates with cord gases placing them at increased risk for long-term neurologic sequelae, the decision-to-delivery interval was 24.7+/-14.6 minutes (range 6 to 50 minutes), and 3/13 (23%) were classified as urgent rather than emergent. Electronic fetal monitoring shows considerable variation in interpretation among maternal-fetal medicine specialists and is not a sensitive predictor of the fetus developing metabolic acidosis. There is no deterioration in cord gas results after 30 minutes, and most neonates delivered emergently or urgently for nonreassuring fetal status even when born after 30 minutes have normal cord gases. The 30-minute rule is a compromise that reflects the time it takes the fetus to develop severe metabolic acidosis, our imprecision in its identification, and its rarity in the presence of nonreassuring fetal monitoring.