Effect of Preinduction Intravenous Labetalol on Cardiovascular Responses to Tracheal Intubation

Lee, Il Ok

Abstract

This study was designed to evaluate the effectiveness of preinduction intravenous bolus injection of labetalol in attenuating the hemodynamic response to tracheal intubation following induction of general anesthesia. Forty patients, ASA Physical Status I, scheduled for elective surgery were selected randomly. They were divided into four groups(Group 1:control group with saline, Group 2:labetalol 1.0 mg/Kg, Group 3:labetalol 1.25 mg/Kg, Group 4:labetalol 1.5 mg/Kg, n 10 in each group) giving as a bolus 5 minutes before induction with thiopental sodium(5 mg/Kg) and succinylcholine(1 mg/Kg). After tracheal intubation, vecuronium 0.1 mg/Kg was injected, 50% nitrous oxide in oxygen and 2% enflurane were inhaled. We measured the blood pressure and heart rate with noninvasive method at one minute intervals for 10 minutes. Preinduction labetalol alone, prior to thiopental /succinylcholine, did not produce significant changes in hemodynamics. Dose of labetalol 1.5 mg/Kg produced significant ablation of systolic blood pressure (146.6+/-8.6 mmHg comparing with 165.5+/-17.6 mmHg, 162.0+/-19.7 mmHg, and 158.4+/- 17.6 mmHg in Group 1, 2, and 3, respectively) after tracheal intubation. All labetalol groups produced less changes in heart rate ( 97.3+/-7.5 beats per minute, 97.5+/-12.7 beats per minute, 97.5+/-11.8 beats per minute, and 107.7+/-14.0 beats per minute in Group 2, 3, 4, and 1, respectively) after tracheal intubation, but were not significantly different in all groups. We suggested that the pressure responses to tracheal intubation were sufficiently controlled by labetalol 1.5 mg/Kg bolus injection prior induction, and simultaneously, we had to give attention to the side effects until postoperative period. We also suggested that labetalol bolus injection prior induction blunted heart rate changes caused by tracheal intubation.