RESUMEN
Transient increases in blood pressure and heart rate(HR) at the end of anesthesia and during extubation are common. Tomori and Widdicombe observed that mechanical stimulation of four areas of the upper respiratory tract (nose, epipharynx, laryngopharynx, tracheobnchial tree) induced reflex cardiovascular responses associated with enhanced neuronal activity in the cervical sympathetic efferent fibers. In susceptible patients, even this short period of hypertension and tachycardia can result in myocardial ischemia or increased intracranial pressure. The purpose of present study was to evaluate the effect of esmolol in attenuating cardiovascular responses to extubation under general anesthesia with endotracheal intubation. A sixty healthy patients who underwent elective noncardiac operation under general anesthesia (N2O-O2-enflurane) with endotracheal intubation were randomly divided into two groups : one was placebo group that received intravenous injection of 0.1 cc/kg normal saline, the other was esmolol group that received intravenous injection of 1 mg/kg esmolol. Extubation was performed when the patients could breathe spontaneously and open their eyes on command. In practice extubation was done between 2 and 4 minutes after drug(esmolol or saline) injection. The measurement of systolic blood pressure and heart rate was obtained one minute before extubation and every minute for 5 minutes after extubation, then rate-pressure product was calculated. The results were as follows; 1) When compared to pre-extubation systolic blood pressure, systolic blood pressure for 2 minutes after extubation in both groups increased significantly but systolic blood pressure was more rapidly returned to pre-extubation level in the esmolol group than in the placebo group. When compared to pre-extubation systolic blood pressure, after extubation the number of patients in whom systolic blood pressure increased more than 20% was significantly fewer in the esmolol group than in the saline group. 2) When compared to pre-extubation heart rate, heart rate at 1 minute after extubation in the placebo group increased significantly but heart rate after extubation in the esmolol group did not change significantly. 3) When compared to pre-extubation rate-pressure product, rate-pressure product for 2 minutes after extubation in both group increased significantly. At 4 minutes after extubation, rate-pressure product in the saline group increased significantly when compared to rate-pressure product in the esmolol group. These results suggest that intravenous injection of 1 mg/kg esmolol before extubation blocks heart rate elevation following extubation under general anesthesia and is effective for rapid return to the pre-extubation level of systolic blood pressure.