Predictive Factors and the Effect of Phenoxybenzamine on Outcome in Dogs Undergoing Adrenalectomy for Pheochromocytoma

Abstract

Background: Some studies in dogs undergoing adrenalectomy for pheochromocytoma suggest that anesthetic complications and perioperative mortality are common. In humans, surgical outcome has improved with the use of phenoxybenzamine (PBZ) before adrenalectomy.Hypothesis: Dogs treated with PBZ before adrenalectomy have increased survival compared with untreated dogs. Animals: Forty-eight dogs that underwent adrenalectomy for pheochromocytoma. Methods: A retrospective medical record review for dogs that underwent adrenalectomy for pheochromocytoma at a veterinary medical teaching hospital over the period from January 1986 through December 2005.Results: Twenty-three of 48 dogs were pretreated with PBZ (median dosage: 0.6 mg/kg PO q12h) for a median duration of 20 days before adrenalectomy. Duration of anesthesia and surgery, percentage of dogs with pheochromocytoma involving the right versus left adrenal gland, size of tumor, and presence of vascular invasion were similar for PBZ-treated and untreated dogs. Thirty-three (69%) of 48 dogs survived adrenalectomy in the perioperative period. PBZ-treated dogs had a significantly (P 5 .014) decreased mortality rate compared with untreated dogs (13 versus 48%, respectively). Additional significant prognostic factors for improved survival included younger age (P 5 .028), lack of intraoperative arrhythmias (P 5 .0075), and decreased surgical time (P 5 .0089).Conclusions and Clinical Importance: Results from this retrospective study support treatment with PBZ before surgical removal of pheochromocytoma in dogs.

Clinical features, outcome and prognostic factors in dogs diagnosed with non‐cortisol‐secreting adrenal tumours without adrenalectomy: 20 cases (1994–2009)

“…As it is described, adrenal adenomas usually are slow growing tumours (Capen 2002), so dogs with hypertension could be more likely to have a carcinoma. It could also be possible, that animals with a higher diastolic blood pressure could have been those with clinically unapparent pheocromocytomas, or even aldosteronoma, as hypertension is one of the common clinical signs of animals with these types of tumours (Herrera and others 2008, Quante and others 2010, Melián 2012). As mentioned before, sometimes the diagnosis of these tumours is difficult, and when pheocromocytomas or primary hyperaldosteronism cannot be ruled out, diastolic pressure could be used as a tool for predicting tumour growth and for making the decision whether to perform adrenalectomy or not.…”

Management of life‐threatening hypertension in a 12‐year‐old bichon frise undergoing an adrenalectomy for phaeochromocytoma excision

“…The decision to commence PBZ in the present case was based upon previous literature reporting a decrease mortality in dogs administered PBZ before adrenalectomy compared with untreated dogs (Herrera and others 2008). PBZ non-competitively binds to α-adrenergic receptors, which undergo irreversible alkylation and inhibition.…”

Anaesthetic management of a unilateral adrenalectomy of an adrenocortical tumour in a dog

“…This case provides an http: //www.openveterinaryjournal.com I.K. Wise and S. Boveri Open Veterinary Journal, (2016) (Herrera et al, 2008). In our patient, the presence of many clinical signs of hyperadrenocorticism without evidence of hypertensive episodes or local tumour invasion lead to a preoperative presumptive diagnosis of an adrenocortical tumour producing excess cortisol.…”

“…Phenoxybenzamine, an α-adrenergic antagonist, irreversibly binds to α1 and α2 adrenergic receptors to block the response to circulating catecholamines (Herrera et al, 2008). Preoperative treatment of human patients is for at least two weeks (Kyles et al, 2003), while the literature for dogs reports time frames between 7 and 120 days (Herrera et al, 2008).…”

“…In patients suspected to have a phaeochromoytoma due to documented hypertensive episodes, preoperative stabilisation with phenoxybenzamine has been advocated to decrease perioperative mortality (Kyles et al, 2003;Herrera et al, 2008;Massari et al, 2011). Phenoxybenzamine, an α-adrenergic antagonist, irreversibly binds to α1 and α2 adrenergic receptors to block the response to circulating catecholamines (Herrera et al, 2008).…”