Effects of methylergometrine and oxytocin on thoracic epidural pressure during cesarean section

The effects of oxytocics on thoracic epidural pressure during cesarean section were studied in 60 parturients, (American Society of Anesthesiologist physical status, class I or II) after obtaining informed consent.

The subjects were randomized to either a ergometrine (n = 30) or oxytocin treatment group (n = 30). The subjects were anesthetized with 11-12 mg of intrathecal isobaric bupivacaine (0.5%), and an epidural catheter was placed at Th 11/12, and was connected to a pressure transducer to continuously monitor thoracic epidural pressure. We analyzed epidural pressure, blood pressure, and heart rate 5 min after administering intrathecal bupivacaine (SAB5m), immediately before skin incision (pre-incision), immediately after delivery of the placenta (placenta-del), and 5 min after delivery of the fetus (CS5m).

In both groups, epidural pressures were found to be elevated after delivery compared with their levels before the skin incisions were made, (P < 0.0001). Epidural pressures at placenta-del (P = 0.0055) and CS5m (P < 0.0001) were higher than at SAB5m in the ergometrine group. Epidural pressures at placenta-del were also higher than at SAB5m in the oxytocin group (P < 0.0001). Epidural pressures at placenta-del were lower in the ergometrine group compared with the oxytocin group (P = 0.0122), but epidural pressures at CS5m were higher in the ergometrine group compared with the oxytocin group (P < 0.0001).

We conclude that there is an increase in thoracic epidural pressure after fetal delivery, which appears to be associated with uterine contraction.