Preoperative Alpha Blockade for Pheochromocytoma

Overview

Pheochromocytoma is a rare, catecholamine (ex. adrenaline) secreting tumor that requires preoperative alpha blockade to minimize intraoperative hemodynamic instability, thereby reducing intra- and postoperative morbidity and mortality. Phenoxybenzamine is a non-selective alpha blocker that is significantly more expensive and is associated with increased adverse effects in comparison with selective alpha blockers such as doxazosin. Retrospective studies show minimal differences in hemodynamic instability and no differences in postoperative morbidity and mortality between selective vs. non-selective alpha blockers. This study is a randomized controlled trial that will compare hemodynamic instability, morbidity, mortality, cost, and quality of life between patients blocked with phenoxybenzamine vs. doxazosin.

Pheochromocytoma is a catecholamine (ex. adrenaline) secreting tumor for which the primary treatment is surgical resection. Due to the hormones secreted by the tumor, alpha receptors on peripheral blood vessels are activated, causing constriction of these blood vessels and dangerously high blood pressure. During resection of the tumor, the source of excess hormone secretion is abruptly removed, which can lead to life-threatening blood pressure fluctuations during surgery. Alpha blockers are a class of medication that blocks the alpha receptor on blood vessels. Given preoperatively over a few weeks, these medications negate the effects of the excess hormones secreted by the pheochromocytoma, reducing the frequency and severity of dangerous blood pressure fluctuations intraoperatively and postoperatively. Preoperative alpha blockade is therefore critical to safely perform surgery to resect pheochromocytoma. Phenoxybenzamine, a non-selective alpha blocker, is the most common medication used to alpha block patients prior to pheochromocytoma resection. However, due to increasing drug costs and increased side effects in comparison with selective alpha blockers, there is a renewed interest in studying alternatives to phenoxybenzamine. Selective alpha blockers such as doxazosin are also commonly used to alpha block patients prior to pheochromocytoma resection. Selective alpha blockers are significantly less expensive and are associated with fewer side effects than phenoxybenzamine. Most retrospective studies comparing phenoxybenzamine with selective alpha blockers show no difference in intraoperative blood pressure fluctuations, morbidity, or mortality in pheochromocytoma resection. However, no prospective, randomized controlled trials comparing phenoxybenzamine to selective alpha blockers have been performed. The purpose of our study is to analyze preoperative, intraoperative, and postoperative outcomes in patients randomized to receive phenoxybenzamine (non-selective) or doxazosin (selective) for alpha blockade prior to pheochromocytoma resection. Outcomes will include postoperative morbidity and mortality, intraoperative hemodynamic instability, quality of life, and cost.