Efficacy of dexmedetomidine in suppressing cardiovascular and hormonal responses to general anaesthesia for caesarean delivery: a dose-response study.

ABSTRACT

BACKGROUND: Preoperative dexmedetomidine administration blunts haemodynamic and hormonal responses to tracheal intubation and reduces anaesthetic requirements. We hypothesized that dexmedetomidine would reduce the maternal haemodynamic and hormonal responses to elective caesarean delivery without harmful neonatal effects. METHODS: After ethical approval, 68 parturients scheduled for elective caesarean delivery under general anaesthesia were randomly allocated to receive either placebo, or 0.2, 0.4 or 0.6 µg/kg/h intravenous dexmedetomidine (n=17 per group) 20 min before induction. Anaesthesia was induced using a rapid-sequence technique with propofol and suxamethonium, and was maintained with 0.5-0.75 minimum alveolar concentration sevoflurane. Changes in maternal heart rate, mean blood pressure, minimum alveolar concentration sevoflurane, uterine tone, serum cortisol level, and Apgar scores, Neurologic Adaptive Capacity Scores and acid-base status were recorded. RESULTS: After induction, patients receiving dexmedetomidine had smaller increases in heart rate (P<0.001) than those in the placebo group. Patients who received 0.4 and 0.6 µg/kg/h infusions of dexmedetomidine showed slower heart rates (-21.5% and -36%, respectively; P<0.001), lower mean blood pressures (-17% and -25%, respectively; P<0.001), sevoflurane minimum alveolar concentrations (-40% and -44.5%, respectively; P<0.001) and serum cortisol levels (-27% and -34.6%, respectively; P<0.001) and higher sedation scores for the first 15 min after extubation and greater uterine tone (P<0.002). Apgar scores, NACS and acid-base status were similar in the four groups. CONCLUSION: Preoperative administration of dexmedetomidine 0.4 and 0.6 µg/kg/h is effective in attenuating the maternal haemodynamic and hormonal responses to caesarean delivery under sevoflurane anaesthesia without adverse neonatal effects.