Retrospective evaluation of the influence of phenoxybenzamine pretreatment on intraoperative cardiovascular variables in dogs with pheochromocytoma.

Abstract

OBJECTIVE: To compare cardiovascular outcomes in dogs undergoing adrenalectomy for pheochromocytoma with and without phenoxybenzamine pretreatment. ANIMALS: A total of 65 medical records from dogs at 5 veterinary hospitals. PROCEDURE: Records from January 2004 to December 2021 were evaluated for systolic, mean, and diastolic arterial pressures; numbers of hypertensive and hypotensive episodes; highest and lowest systolic arterial pressure differences; dose and duration of phenoxybenzamine; and presence of intraoperative arrhythmias. Phenoxybenzamine-pretreated dogs (Group PT,= 33) and dogs not receiving phenoxybenzamine (Group N,= 31) were compared. The Shapiro-Wilk test was used to test for normality, Student's-test was used for normally distributed data, and Fisher's exact test was used for ordinal and categorical data. Multivariable logistic regression was used to assess effect of pretreatment with phenoxybenzamine on occurrence of hypotension and hypertension, allowing for adjustment for confounding variables (< 0.05). RESULTS: Median (range) phenoxybenzamine dose was 0.46 (0.08 to 2.0) mg/kg, PO, q12h. Peak systolic and mean arterial pressures, lowest systolic and mean arterial pressures, duration of hypertension, duration of sinus tachycardia, number of hypotensive episodes, and duration of hypotension were not different between groups. More hypertensive episodes (= 0.01) and anesthetic events involving hypertension (= 0.02) were recorded in Group PT than in Group N. CONCLUSION: In dogs undergoing adrenalectomy for pheochromocytoma, phenoxybenzamine pretreatment as administered did not offer any cardiovascular benefits based on the measured variables, and may be associated with more intraoperative hypertensive episodes. CLINICAL RELEVANCE: Intraoperative changes in cardiovascular variables are prevalent in dogs with pheochromocytoma undergoing adrenalectomy. Further evaluation of pretreatment with phenoxybenzamine is needed to determine its role in these cases.