Preliminary experience of using fixed dose of intravenous labetalol in surgical resection of pheochromocytoma.

Seven patients scheduled for resection of pheochromocytoma with loose preoperative control of their blood pressure were selected in our study. All the cases are impressed of pheochromocytoma that predominantly excrete norepinephrine. Anesthesia was induced with fentanyl, 2.5% sodium thiopental, valium and atracurium. Labetalol was used as antihypertensive agent and was given in repeated bolus (up to total dose of 2 mg/kg) intravenously before skin incision and no supplemental dosage was given later on. The anesthesia was maintained with nitrous oxide, oxygen, isoflurane and atracurium. Blood pressure, heart rate and arterial blood gas analysis were recorded. After giving intravenous labetalol, mean systolic blood pressure and heart rate declined by 26.2% and 29.76% respectively when compared to preanesthetic values. Although bradycardia was noted after administration of labetalol, it seemed acceptable except for one patient who needed atropine right after receiving labetalol and another patient who needed levophed infusion after tumor removal. During tumor removal, the blood pressure of all patients was stable except one patient who needed sodium nitroprusside infusion together with labetalol to help control the elevated blood pressure. All the patients in our study had no sequela postoperatively. We concluded that total dose of labetalol (2 mg/kg) administered intravenously at the beginning of anesthesia was possible to control blood pressure during the resection of pheochromocytoma under general anesthesia even in the case of poor preoperative blood pressure control.