RESUMEN
This clinical trial was conducted to evaluate optimal time of injection of a small dose of fentanyl during anesthetic induction to attenuate circulatory responses to laryngoscopy and tracheal intubation. 120 patients who had enrolled in this clinical trial, with ASA physical status of I or II scheduled for the elective surgery. The patients were randomly allocated to five groups. In groups II, III, IV, and V, patients received fentanyl [2 mcg/kg] 1, 3, 5, or 10 min respectively before tracheal intubation. In group I patients did not receive fentanyl and served as the control group. After induction with thiopental and atracorium, an oral tracheal intubation was accomplished in each patient. Changes in each circulatory variable after tracheal intubation were based on the differences between baseline values and values obtained 1 min after intubation. Increase in postintubation heart rate, diastolic and mean arterial pressure compared with preinduction values in group III was less than the other groups. Increased systolic pressure in group IV was less compared with other groups; but there was not a significant difference between groups III and IV. The results of our study revealed that the optimal injection time of fentanyl in blunting the circulatory responses to tracheal intubation is 3 min before intubation