Norepinephrine for the prevention of spinal-induced hypotension during caesarean delivery under combined spinal-epidural anaesthesia: Randomised, double-blind, dose-finding study.

Background: During caesarean delivery under spinal anaesthesia hypotension may be managed by norepinephrine in preference to phenylephrine due a perception of less bradycardia and fewer reductions in cardiac output.

Objective: As the optimum prophylactic dose of norepinephrine is unclear, we aimed to investigate its dose-response for preventing postspinal hypotension in caesarean delivery.

Design: A randomised, double-blinded, dose-finding study.

Setting: Jiaxing University affiliated Women and Children Hospital, Jiaxing, China.

Patients: Ninety-nine patients undergoing elective caesarean delivery from 1 February to 5 August: excluding patients with ASA III or above, preeclampsia or hypertension, pre-existing or gestational diabetes, BMI more than 35 kg m, height less than 150 cm or with more than 175 cm, or with contraindications to local anaesthesia.

Interventions: Patients received 0, 0.04, 0.05, 0.06 or 0.07 μg kg min preventive norepinephrine infusions immediately after intrathecal injection of 10 mg bupivacaine with 5 μg sufentanil.

Main Outcome Measures: The norepinephrine (Median effective dose) or (95% effective dose) ED50 and ED95, which were estimated using Probit analysis to compare haemodynamic changes associated with the different doses.

Results: The incidence of hypotension was 70, 47.4, 40, 20 and 15% in the 0, 0.04, 0.05, 0.06 and 0.07 μg kg min groups, respectively. The ED50, ED80 and ED95 values were 0.029 (95% CI 0.008 to 0.042 μg kg min), 0.068 (95% CI 0.055 to 0.099 μg kg min) and 0.105 μg kg min (95% CI 0.082 to 0.172 μg kg min), respectively. Apgar scores or umbilical arterial pH were similar among groups.

Conclusion: The ED50, ED80 and ED95 were 0.029, 0.068 and 0.105 μg kg min respectively. A 0.07 μg kg min norepinephrine infusion may be optimum for preventing postspinal hypotension after intrathecal injection of 10 mg bupivacaine combined with 5 μg sufentanil.

Trial Registration: Chinese Clinical Trial Registry (identifier: ChiCTR-TRC-1800014614).