Endocrine Abstracts

Phaeochromocytomas are rare catecholamine secreting tumours with an incidence of 1:4500–1:1700 in the United States. Doxazosin and Phenoxybenzamine are alpha-1 selective and non-selective alpha blockers respectively which are commonly used to treat this condition peri-operatively. There are no randomized controlled studies comparing the effectiveness of these two medications. However, there are retrospective studies comparing these two medications; some favouring alpha-1 selective blockade and some showing no difference.

Aim: To compare and contrast the effectiveness of Phenoxybenzamine and Doxazosin in treating phaeochromocytomas at our centre.

Methods: Retrospective data collection of phaeochromocytomas, identified from elevated urinary metanephrines from the laboratory and coding for adrenalectomies over a five year period.

Results: 12 out of 171 patients with elevated urinary metanephrines had confirmed, 11 phaeochromocytomas and 1 paraganglioma. 11 out of 31 adrenalectomies performed were for phaeochromocytomas. Mean age of our cohort was 54 years, with 7 (58.3%) Males and 11 (91.6%) Caucasians. All patients were on beta blockers peri-operatively. In the Doxazosin group: n=8(66.7%), Mean pre-operative blood pressure (BP)=128/80 mmHg, Mean intra-operative BP=122/72 mmHg, Mean highest systolic and diastolic BP intra-operatively was 159 and 90 mmHg respectively, Mean length of surgery was 4 hours 15 minutes, Mean intra-operative fluids prescribed=3.6 L, 4 patients(50%) were given other agents to control the BP intra-operatively ranging from 1 to 3 different agents. In the Phenoxybenzamine group: n=4(33.3%), Mean pre-operative BP=121/73 mmHg, Mean intra-operative BP=125/69 mmHg, Mean highest systolic and diastolic BP intra-operatively was 164 and 92 mmHg respectively, Mean length of surgery was 4 hours 40 minutes, Mean intra-operative fluids prescribed=3.17 L, 1 patient(25%) was given 3 agents to control the BP intra-operatively.

Conclusion: Doxazosin seems to be as effective as Phenoxybenzamine in the peri-operative management of this condition. Even though there were more patients in the Doxazosin group requiring other intra-operative agents to control the BP, it was not statistically significant (χ=0.6857, P=0.408). Ideally, we need a bigger cohort to have the power to demonstrate the true significance of the differences between the two medications. There are a number of limitations in this audit, in particular, the sample size and the rarity of this condition. The experience of the anaesthetist could also be a contributing factor for the use of other agents intra-operatively.