Labetalol as a hypotensive agent for middle ear microsurgery.

Area of Science:

• Anesthesiology
• Pharmacology
• Cardiovascular Physiology

Background:

• Controlled hypotension is crucial for microsurgery to optimize visualization and minimize blood loss.
• Alpha- and beta-adrenergic blockade offers a potential method for achieving intraoperative hypotension.

Purpose of the Study:

• To evaluate labetalol as a hypotensive agent during halothane-based anesthesia for middle ear microsurgery.
• To assess the safety and efficacy of labetalol in achieving and maintaining a hypotensive state.

Main Methods:

• 41 patients undergoing middle ear microsurgery received labetalol during halothane-N2O-fentanyl-d-tubocurarine anesthesia with a 5-degree head-up tilt.
• Labetalol dosage was initiated at 0.3 mg/kg, with subsequent doses of 0.05-0.07 mg/kg administered at 30-minute intervals.
• Hemodynamic parameters (mean arterial pressure, heart rate, cardiac output), oxygenation (PaO2), and surgical hemostasis were monitored.

Main Results:

• Labetalol induced a mean hypotensive period of 102 minutes with average mean arterial pressure between 59-62 mmHg and heart rate of 61-66 bpm.
• Maximum decrease in cardiac output was 7%, and PaO2 remained adequate (145-149 mmHg) with 40% FiO2.
• Excellent hemostasis (91/100 mm) was achieved, with rapid eye opening (8-9 min) and stable recovery post-extubation.
• Peroperative ECG changes (junctional rhythm, bradycardia) occurred in 10%; postoperative nausea (39%) and nausea with vomiting (20%) were most common.

Conclusions:

• Labetalol is an effective hypotensive agent for middle ear microsurgery, facilitating excellent surgical conditions.
• The drug demonstrates a favorable safety profile with minimal impact on cardiac output and adequate oxygenation.
• Rapid recovery and acceptable postoperative side effect profile support the use of labetalol in this surgical context.