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).