Remifentanil Effect-site Concentration Blunting Cardiovascular Responses to Tracheal Intubation for Different Sex during Propofol Infusion

Abstract

Background: Tracheal intubation induces clinically adverse hemodynamic changes. Various pharmacological strategies for controlling these reponses have been suggested with opioids being widely used. The purpose of this study was to determine the effect site concentration of remifentanil in blunting the cardiovascular responses to tracheal intubation according to gender. Methods: Eighty ASA physical status I or II patients, aged 20－40 years undergoing elective surgery, were classified into a male group (n = 40) and a female group (n = 40). Anesthesia was induced using a propofol target controlled infusion (TCI: Marsh model). A propofol target effect-site concentration of 4μg/ml was chosen. Rocuronium 0.6 mg/kg was administered after the patients lost consciousness. Remifentanil TCI (Minto model) was started 1 min after the propofol injection. Initially, an effect-site concentration of 3 ng/ml was chosen. The next concentration was chosen using the up-and-down method reported by Dixon. The non-invasive blood pressure and heart rate were recorded before induction (baseline), after the remifentanil injection, immediately after intubation as well as 1 and, 3 minutes after intubation. Results: Probit analysis revealed a remifentanil effect-site EC50 and EC95 in the male group to be 1.94 ng/ml (95% CI, 1.60－2.27 ng/ml ), 3.07 ng/ml (95% CI, 2.65－4.06 ng/ml), respectively. The EC50 and EC95 in the female group were 1.69 ng/ml (95% CI, 1.35－2.01 ng/ml), 2.81 ng/ml (95% CI, 2.39－3.81 ng/ml), respectively. There were no significant differences between the two groups. Conclusions: The effect-site concentration of remifentanil blunting the cardiovascular responses to tracheal intubation during propofol TCI anesthesia was between 2 and 3 ng/ml. There were no gender differences.