Dose-related attenuation of cardiovascular responses to tracheal intubation by intravenous remifentanil bolus in severe pre-eclamptic patients undergoing Caesarean delivery

Abstract

Background: The optimal dose of remifentanil to attenuate the cardiovascular responses to tracheal intubation in pre-eclamptic patients undergoing Caesarean delivery under general anaesthesia has not been established. We compared the effects of two low doses of remifentanil on the cardiovascular responses to tracheal intubation and neonatal outcomes.

Methods: Forty-eight women with severe pre-eclampsia were randomly assigned to receive either remifentanil 0.5 µg kg⁻¹ (R0.5 group, n=24) or 1 µg kg⁻¹ (R1.0 group, n=24) over 30 s before induction of anaesthesia using thiopental 5 mg kg⁻¹ and succinylcholine 1.5 mg kg⁻¹. Systolic arterial pressure (SAP), heart rate (HR), and plasma catecholamine concentrations were measured. Neonatal effects were assessed using Apgar scores and umbilical cord blood gas analysis.

Results: SAP was decreased by induction of anaesthesia and increased by tracheal intubation in both groups. The peak SAP after intubation was greater in the R0.5 group than in the R1.0 group, whereas it did not exceed baseline values in either group. HR increased significantly above baseline in both groups with no significant differences between the groups. Three subjects in the R1.0 group received ephedrine due to hypotension (SAP < 90 mm Hg). Norepinephrine concentrations remained unaltered after intubation and increased significantly at delivery with no significant differences between the groups. Neonatal Apgar scores and umbilical arterial and venous pH and blood gas values were comparable between the groups.

Conclusions: Both doses of remifentanil effectively attenuated haemodynamic responses to tracheal intubation with transient neonatal respiratory depression in pre-eclamptic patients undergoing Caesarean delivery under general anaesthesia. The 1.0 µg kg⁻¹ dose was associated with hypotension in three of 24 subjects.