Effect-site concentration of remifentanil for attenuating QTc interval prolongation following intubation in hypertensive female patients.

Abstract

Haemodynamic changes after sympathetic stimuli like tracheal intubation are more pronounced in hypertensive patients than in normotensive patients. Heart rate (HR)-corrected QT (QTc) interval changes related to intubation may also be more prominent in hypertensive patients. We hypothesised that there would be a difference in the effect-site concentration (Ce) of remifentanil to attenuate QTc interval prolongation in normotensive and hypertensive patients following intubation. Twenty-two normotensive and 22 hypertensive female patients (≥ 50year) were enrolled and anaesthesised with remifentanil and propofol using a target-controlled infusion. All hypertensive patients received oral antihypertensive medications for > 6months and took the medications in the morning of the surgery. The effective concentration of remifentanil Ce in 50% (EC50 ) and 95% of the population (EC95 ) required to maintain QTc interval prolongation < 15ms following intubation was calculated using the isotonic regression and a bootstrapping approach following the Dixon's up-and-down method. Median duration of hypertension was 6years. Isotonic regression revealed that the EC50 (83% confidence interval) of remifentanil Ce for reducing QTc interval prolongation following intubation was 3.8 (3.5-4.1) ng/ml in normotensive and 6.1 (5.8-6.2) ng/ml in hypertensive female patients. The EC95 (95% confidence interval) of remifentanil Ce was 4.4 (4.3-4.5) ng/ml in normotensive and 6.5 (6.4-6.5) ng/ml in hypertensive female patients. The Ce of remifentanil required to attenuate QTc interval prolongation following intubation was significantly higher in hypertensive patients than it was in normotensive patients. Thus, more caution should be taken related to QTc interval prolongation when intubating hypertensive patients.