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Uterine relaxation for preterm cesarean delivery: comparison between nitroglycerin under spinal anesthesia and general anesthesia with sevoflurane
Abstract Number: T-78
Abstract Type: Original Research
Delivery of fragile preterm fetus during cesarean delivery(CD) can be problematic due to relatively thick myometrium. Some obstetricians in Japan advocate uterine relaxation with sevoflurane. However, general anesthesia carries higher risk to the mothers. Alternatively, nitroglycerin (NTG) is a known relaxant for pregnant uterus, and we have reported its benefit under spinal anesthesia in preterm fetuses less than 26 weeks gestation. In this study, we aimed to compare the effects of NTG under spinal anesthesia and sevoflurane during general anesthesia (GA) for uterine relaxation to facilitate delivery of preterm fetuses.
After IRB approval, retrospective review of medical and anesthesia records were conducted on CDs for fetuses less than 26 weeks gestation from 2002 to 2014. We abstracted cases when either NTG or sevoflurane was used during CD, then compared uterine incision to delivery interval (UI-D interval), type of uterine incision, Apgar scores, umbilical artery pH, NICU survival discharge rate. NTG 50-100mcg bolus was administered upon obstetrician’s request at the time of CD, 45 seconds prior to uterine incision, and repeated as needed until delivery of the infant. Data were compared by Chi-square or unpaired t-test whichever appropriate.
There were 157 CDs less than 26 weeks. The number of cases in gestational weeks 22, 23, 24, 25 was 15, 27, 52, and 62 cases, respectively. NTG was used in 95 cases (73%) of spinal anesthetic, and sevoflurane was used without NTG in 18 cases (64%) under GA, which comprise 2 comparison groups. 10 GA cases used both sevoflurane and NTG. Median NTG dose was 100μg, range:50-350μg. Sevoflurane concentration was 3% in all cases until delivery of the infant. UI-D intervals and UA pH were 1.83 min vs. 2.06 min, 7.378 ± 0.08 vs. 7.254 ± 0.22 in NTG group and sevoflurane group, respectively. Uterine incision other than transverse incision was 54.7% vs. 72.2%, Apgar score less than 7 at 1 minute was 84.2% and 94.4% in NTG and sevoflurane group, respectively. These results and NICU survival discharge rates were not statistically different between the groups.
In this study, we failed to show the benefit of NTG spinal anesthesia compared to sevoflurane GA to facilitate delivery of preterm fetuses during CD, even though the results tended to be better in NTG gruop. This may be partly due to the practice that NTG was administered at the discretion of anesthesiologists based on the obstetrician’s request for uterine relaxation. Thus NTG groups could have been more difficult cases with regard to fetal extraction during CS. On the other hand, GA was chosen in fetal compromise more often than spinal anesthesia, which may have affected Apgar score and pH.
In order to facilitate delivery of preterm fetuses during CS, uterine relaxation with NTG under spinal anesthesia may be a good option to the mother and neonate when compared to sevoflurane during general anesthesia.