An analysis of correlation between remifentanil effect site concentration and age blunting hemodynamic response to endotracheal intubation

ABSTRACT

BACKGROUND: There are many studies using propofol-remifentanil target controlled infusion (TCI) for the prevention of adverse hemodynamic changes during tracheal intubation. Most of these studies suggested optimal remifentanil target concentration without considering age. The purpose of this study is to analyze the correlation between concentration of remifentanil and age to blunting adverse hemodynamic responses during tracheal intubation. METHODS: We enrolled ASA physical state I or II 55 patients, aged 12-75 years undergoing elective surgery. Anesthesia was induced using a propofol TCI (Marsh model). A 4micro/ml effect-site concentration of propofol was chosen. Rocuronium 0.6 mg/kg was administered after the patients lost consciousness. Remifentanil TCI (Minto model) was started 1 minute after the propofol injection. Initially, a 3 ng/ml effect-site concentration was chosen. The next concentration was chosen using Dixon's up-and-down method. The non-invasive blood pressure and heart rate were recorded before induction (baseline), after the remifentanil infusion, immediately after intubation as well as 1 and 3 minutes after intubation. RESULTS: Probit analysis revealed a remifentanil effect site EC50 and EC95 in all patients to be 1.768 ng/ml (S.E. +/-0.136) and 2.912 ng/ml (S.E. +/-0.307). Final probit equation was as following consisted with age and remifentanil effect site concentration. Probit = -2.588 + 1.886 remifentanil effect site concentration -0.022 x Age. CONCLUSIONS: The probability of success rate of blunting adverse hemodynamic response is related to the concentration of remifentanil directly and age inversely.