Amyl Nitrite: Use as a Smooth Muscle Relaxant in Difficult Preterm Cesarean Section

ABSTRACT

Amyl nitrite is a smooth muscle relaxant that has been used clinically to facilitate uterine relaxation in difficult deliveries. In this retrospective study, we evaluate the safety of amyl nitrite use during preterm cesarean deliveries, and we assess possible advantageous effects on surgical incision choice. Women who received amyl nitrite cesarean section were compared to a control group matched for gestational age, fetal presentation, and mode of delivery who did not receive amyl nitrite. There were no statistical differences between the groups in the independent variables (maternal age, parity, medical or obstetric history, type of anesthesia, anesthesia or obstetric attending physician, antepartum hematocrit, or neonatal weight). Outcome (dependent) variables (estimated blood loss, Apgar scores, postpartum hematocrit, cord gases, or postpartum complications) were assessed, and there were no significant differences between the groups. Low transverse cesarean section was performed more frequently in the amyl nitrite group (58 of 64) than in the comparison group (48 of 64) (p <0.03). Considering the 128 women with and without amyl nitrite together, the decrease in hematocrit observed postpartum was greater after classic section (7%) than after low transverse section (4%) (p <0.002). We conclude that the use of amyl nitrite during preterm cesarean section poses no threat to mother or fetus and may facilitate delivery by allowing the performance of a low transverse rather than a classic cesarean section without maternal or neonatal complications.