Pretreatment with phenoxybenzamine improves short-term survival and hemodynamic stability in dogs undergoing adrenalectomy for pheochromocytoma

Objective: To evaluate indices of hemodynamic instability (HDI) in dogs and evaluate the effects of phenoxybenzamine (PBZ) on HDI and short-term survival in dogs undergoing adrenalectomy for pheochromocytoma. Methods: A retrospective medical record review of all dogs that underwent adrenalectomy at a single institution between 1996 and 2024. Dogs were included if the mass was confirmed to be a pheochromocytoma on histopathology and excluded if they received α antagonists other than PBZ, had incomplete medical or anesthetic records, or were treated with laparoscopy. Results: 52 dogs met the inclusion criteria. Thirty-five dogs that did not receive PBZ were entered in the NPBZ group, and 17 that received PBZ were entered in the PBZ group. The mean dosage of PBZ was 1.1 mg/kg/d (0.4 to 1.7 mg/kg/d) administered for a mean length of time of 13.4 days (9.3 to 17.4 days) before surgery. Indices of HDI including systolic blood pressure > 200 mm Hg seemed to be more appropriate for dogs with pheochromocytoma. Six of the 22 dogs in the NPBZ group that required cavotomy experienced HDI compared to 0 of 17 in the PBZ group. The 14-day survival rate was 94.1% in the PBZ group and 62.9% in the NPBZ group. Conclusions: Pharmacologic α-adrenergic blockade with PBZ prior to adrenalectomy improved short-term patient survival. Indices of HDI that include systolic arterial pressure above 200 mm Hg seem to be more appropriate for dogs. Clinical Relevance: PBZ should be considered as an effective pretreatment strategy to reduce the effects of HDI during adrenalectomy in dogs undergoing adrenalectomy for pheochromocytoma.