This USMLE® Step 2 Question of the Day focuses on sinus tachycardia and its association with conditions like pheochromocytoma and hypertensive emergencies. Understand the role of alpha-blockers in management.
A 54-year-old woman presents to the emergency department with the abrupt onset of severe headache, palpitations, and diaphoresis. She reports similar episodes over the past two months. Past medical history includes uncontrolled hypertension despite adherence to a three-medication antihypertensive regimen, including a diuretic, calcium channel blocker, and ACE inhibitor. The patient’s sister was diagnosed with a paraganglioma two years ago. Temperature is 37.2°C (99°F), blood pressure is 210/125 mmHg, pulse is 130/min, respiratory rate is 22/min, and O2 saturation is 97% on room air. Physical examination reveals an anxious-appearing woman. Her skin is cool and clammy. A cardiac exam reveals tachycardia without murmurs. Neurologic examination shows no focal abnormalities. Laboratory results are significant for a creatinine of 2.2 mg/dL. An ECG is significant for sinus tachycardia. Which of the following is the best next step in management?
A. Intravenous phentolamineB. Intravenous labetalol
C. Oral ramipril
D. MRI of the abdomen and pelvis
E. CT scan of the head
Scroll down for the correct answer!
The correct answer to today’s USMLE® Step 2 CK Question is…
A. Intravenous phentolamine
Before we get to the Main Explanation, let’s see why the answer wasn’t B, C, D, or E. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
Today’s incorrect answers are…
B. Intravenous labetalol
Incorrect: Labetalol is a combined alpha- and beta-blocker used in the management of hypertensive emergencies. However, in patients with suspected pheochromocytomas, alpha-blockade must be established before beta-blockade. Starting a beta-blocker before an alpha-blocker can lead to worsened hypertension due to unopposed alpha-adrenergic stimulation.
C. Oral ramipril
Incorrect: ACE inhibitors like ramipril are often used for chronic management of hypertension, but they are not appropriate for the management of hypertensive emergencies.
D. MRI of the abdomen and pelvis
Incorrect: An MRI of the abdomen and pelvis can assist in tumor localization once the diagnosis of pheochromocytoma has been biochemically confirmed. It is not the first step in management for a patient with a hypertensive emergency.
E. CT scan of the head
Incorrect: CT scan of the head would be useful for evaluating the cause of a headache if there was suspicion of CNS pathology. This patient has no focal neurologic findings and other symptoms and signs suggestive of a pheochromocytoma.
Main Explanation
This patient is presenting with an abrupt and severe headache, palpitations, diaphoresis, severe hypertension, elevated creatinine, and a history of uncontrolled hypertension and familial history of paraganglioma; he likely has a pheochromocytoma presenting as a hypertensive emergency. An alpha-adrenergic receptor blocker, like intravenous phentolamine, can be used as an initial treatment. It decreases blood pressure by counteracting the vasoconstrictive effects of the catecholamines secreted by the pheochromocytoma.
Pheochromocytomas are catecholamine-secreting tumors that can cause paroxysmal hypertension and precipitate hypertensive emergencies. The immediate goal of treatment is to control blood pressure and reduce the risk of serious complications, such as stroke, myocardial infarction, and aortic dissection. An alpha-adrenergic receptor blocker such as phentolamine can be used to lower blood pressure quickly in a hypertensive emergency caused by a pheochromocytoma. Alpha-blockade must be initiated before beta-blockade to prevent a paradoxical hypertensive crisis from unopposed alpha stimulation. Nitroprusside, which is a vasodilator, can also be used, as well as nicardipine.
Following the acute management of hypertension, the next step in management is to confirm the diagnosis with biochemical testing, typically with a plasma-free metanephrines test or a 24-hour urine collection for catecholamines, metanephrines, and creatinine. Once the diagnosis of pheochromocytoma is confirmed, definitive treatment is surgical removal of the tumor. Before surgery can be performed, the patient must undergo a period of preoperative alpha-blockade (and then possibly beta-blockade) to prevent intraoperative hypertensive crises.
Major Takeaway
Acute management of a hypertensive crisis secondary to a pheochromocytoma involves rapid blood pressure reduction with intravenous alpha-blockers like phentolamine or with other agents like nitroprusside or nicardipine. Treatment with alpha-blockers should precede treatment with beta-blockers to prevent worsening hypertension.
References
- Lenders JW, Duh QY, Eisenhofer G, et al. Pheochromocytoma and paraganglioma: an endocrine society clinical practice guideline [published correction appears in J Clin Endocrinol Metab. 2023 Apr 13;108(5):e200]. J Clin Endocrinol Metab. 2014;99(6):1915-1942. doi:10.1210/jc.2014-1498
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