ODP032 Case Series: Prazosin in the Preoperative Management of Pheochromocytoma and Paraganglioma
Authors: Barreiro Margarita , Arafah Baha 
Published: November 2022

Abstract

Background
Prazosin is a competitive alpha-1 adrenoreceptor antagonist. It is an ideal agent for preoperative blockade in neuroendocrine tumors compared to more commonly used agents such as phenoxybenzamine, a non-selective alpha blocker or doxazosin a longer acting alpha-1 blocker. Its affinity for alpha-1 receptors lessens the risk for systemic side effects while its short half-life and a relatively short duration of action of about 10-24 hours decreases the risk for intra and post-operative hypotension.

Case 1
38 year old male was found to have resistant hypertension during routine follow up visit. Work up for secondary causes of hypertension revealed plasma metanephrines 5.1nmol/L, normetanephrine 6.7nmol/L, epinephrine 5990pg/mL, norepinephrine 15318 pg/mL, with 24 hour urine epinephrine 1329ug/24hr and norepinephrine 3115ug/24hr. Imaging findings shows 4.8cm right adrenal mass consistent with Pheochromocytoma. He was started on Prazosin titrated up to a dose of 5mg TID and labetalol 200mg TID to a goal systolic BP &lt;130 mmHg. A right laparoscopic adrenalectomy was done and intraoperatively, he remained hemodynamically stable with no vasopressor or antihypertensive requirement. His blood pressure normalized immediately post op and did not require further antihypertensives for the rest of his hospitalization.

Case 2
62 year old female was found to have an incidental 4.7cm left adrenal mass after a routine surveillance for pulmonary nodule. Biochemical data showed plasma metanephrines 14nmol/L, normetanephrine 3nmol/L, epinephrine 2719pg/mL, norepinephrine 701pg/mL, and chromogranin A 3507ng/m with a 24 hour urine epinephrine 938uh/24hr, consistent with Pheochromocytoma. The patient was started on Prazosin, titrated up to a maximum tolerated dose of 2mg TID before symptomatic hypotension occurred. Labetalol 100mg BID was later added. She underwent a left laparoscopic adrenalectomy but required Clevidipine drip and IV pushes of norepinephrine PRN intraoperatively for low blood pressure. However, she was taken off antihypertensives immediately post-op, and did not have any hypotensive episodes events thereafter.

Case 3
50 year old female presented for left sided chest pain where a CT angiogram was done and incidentally found a para-aortic mass measuring 2.7×1.6×2.3cm in the organ of Zuckerlandl. Biochemical findings showed plasma normetanephrine 5.6nmol/L, norepinephrine 4564pg/mL, and chromogranin A 440ng/mL, consistent with a Paraganglioma. She was started on Prazosin titrated up to 6mg TID, labetalol 100mg TID and amlodipine 10mg daily to reach goal systolic blood pressure and heart rate. She underwent an open resection where there were no hypotensive events intraoperatively but did require Clevidipine drip for hypertension. Immediately post-op her BP normalized, the drip was discontinued, and she did not have any post-op hypotensive events.

Conclusion
This case series highlights the advantages of short acting alpha-1 blockade in the preoperative management of neuroendocrine tumors. All three patients did not have any post-operative hypotension and had an uncomplicated post-op course.
Presentation: No date and time listed