Transient increases in blood pressure and heart rate following laryngoscopy and endotracheal intubation are common. These stress responses are greatly exaggerated in patients with hypertension and cardiovascular diseases and can lead to cardiac
arrhythmia, pulmonary edema, and cerebral hemorrhage.
Many approaches have been tried to attenuate these potentially adverse circulatory responses but none has been satisfactory.
This study was made to evaluate the hemodynamic responses to tracheal intubation using combined α-and β-adrenoreceptor blocking agent, labetalol.
We intravenously administered labetalol or placebo prior to laryngoscopy and tracheal intubation in adult patients with ASA class 1, or 2. Sixty patients were randomly assigned to one of three treatment groups. Group 1 patients (control group,
n=20)
received normal saline 3ml, Group 2 patients (n=20) received labetalol 0.3mg/kg, and Group 3 patients (n=20) received labetalol 0.6mg/kg intravenously.
These drugs were injected 3 minutes before induction with thiopental sodium (5mg/kg). Succinylcholine chloride 1.0mg/kg i.v. was used to facilitate endotracheal intubation. After the completion of intubation, nitrous oxide/oxygen with enflurane
or
isoflurane was administered.
The blood pressure and heart rate weremeasured upon arrival in the operating room (baseline), immediately before intubation, immediately after intubation, 1 minutes after intubation and at 2, 3, 5, 7, 10 minutes after intubation.
There were no significant differences in preinduction values of blood pressure and heart rate.
A significant reduction in heart rate was observed in the group 3, group 2 in that order compared with the group 1. Similarly, systolic, diastolic and mean arterial pressure decreased in labetalol groups. But was not significantly different in
all
groups.
None of the patients experienced any untoward side effects, such as hypotension, significant bradycardia, bronchospasm or electrocardiographic changes.
In conclusion, in patients with no history of hypertension or significant cardiac disease, labetalol 0.3 or 0.6mg/kg i.v. is better suited to blunting tachycardia than to blunting hypertension to laryngoscopy and intubation.
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