BACKGROUND: In this study, we investigated the inhibitory effects of desflurane and sevoflurane on oxytocin-induced contractions of isolated human myometrium.
METHODS: Following delivery of the infant and placenta, a small segment of myometrium was excised from the upper incisional surface of the lower uterine segment and 20 strips, randomly assigned into two groups (n = 10), were obtained from 20 non-laboring term parturients. The study protocol consisted of a 60-min period of spontaneous contractions, control recording with oxytocin 2 x 10(9) m (10-min period), washout interval of 10 min, volatile administration (three times per 15-min period) of 0.5, 1 and 2 minimum alveolar concentration (MAC), response to oxytocin (10-min period), a further washout interval (10-min period) and subsequent control recording with oxytocin without anesthetics.
RESULTS: After oxytocin administration, the frequency and amplitude of contractions increased (P < 0.05) and the duration decreased (P < 0.05). The frequency and amplitude of contractions induced with oxytocin decreased significantly at 0.5, 1 and 2 MAC of desflurane and sevoflurane (P < 0.05). The amplitude of contractions was significantly different at 1 MAC between the two groups (P < 0.05). The duration of contractions at 2 MAC decreased in both groups (P < 0.05).
CONCLUSIONS: Desflurane and sevoflurane at 0.5, 1 and 2 MAC inhibit the frequency and amplitude of myometrial contractions induced with oxytocin in a dose-dependent manner. However, desflurane inhibits the amplitude less than sevoflurane at 1 MAC. We suggest that 0.5 MAC of both agents and 1 MAC of desflurane may be safely used in the presence of oxytocin following delivery of the infant and placenta during Cesarean section without fear of uterine atony and hemorrhage.
