A 38-year-old African American man comes to the emergency department after experiencing severe back pain for the past 2 days. He has a history of hypertension for the last 5 years. His current medications include hydrochlorothiazide, amlodipine, and valsartan. The patient has a 15-pack-year history and drinks 4-5 bottles of beer daily. His temperature is 36.7 C (98 F), blood pressure is 230/112 mm Hg, and pulse is 84/min. Funduscopic examination shows arteriolar wall thickening and occasional cotton-wool spots. The rest of the examination is within normal limits. Initial laboratory studies show serum blood urea nitrogen of 28 mg/dL, potassium of 5.1 mEq/L, and serum creatinine of 2.3 mg/dL. Transesophageal echocardiogram is consistent with dissection in the descending aorta. The patient is admitted to the coronary care unit and started on intravenous labetalol and nitroprusside infusion. The next morning, the nurse finds him confused and agitated. He then has a generalized tonic-clonic seizure. His temperature is 36.7 C (98 F), blood pressure is 176/99 mm Hg, and pulse is 102/min. Physical examination remains otherwise unchanged. Which of the following is the most likely diagnosis?

Question

A 38-year-old African American man comes to the emergency department after experiencing severe back pain for the past 2 days.  He has a history of hypertension for the last 5 years.  His current medications include hydrochlorothiazide, amlodipine, and valsartan.  The patient has a 15-pack-year history and drinks 4-5 bottles of beer daily.  His temperature is 36.7 C (98 F), blood pressure is 230/112 mm Hg, and pulse is 84/min.  Funduscopic examination shows arteriolar wall thickening and occasional cotton-wool spots.  The rest of the examination is within normal limits.  Initial laboratory studies show serum blood urea nitrogen of 28 mg/dL, potassium of 5.1 mEq/L, and serum creatinine of 2.3 mg/dL.  Transesophageal echocardiogram is consistent with dissection in the descending aorta.  The patient is admitted to the coronary care unit and started on intravenous labetalol and nitroprusside infusion.  The next morning, the nurse finds him confused and agitated.  He then has a generalized tonic-clonic seizure.  His temperature is 36.7 C (98 F), blood pressure is 176/99 mm Hg, and pulse is 102/min.  Physical examination remains otherwise unchanged. Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c116_f3d4_8f63_b37be2940852_MD0005_00 This patient's symptoms suggest acute cyanide toxicity in the setting of renal failure and nitroprusside use. Nitroprusside is a potent vasodilator that works on both arterial and venous circulation and is used for hypertensive emergency management. It has rapid onset and offset of action. The most important side effect is cyanide accumulation and toxicity. Patients with chronic renal failure or those receiving a high-dose or prolonged infusion of sodium nitroprusside are at increased risk for cyanide toxicity. As a result, low infusion rates (<2 µg/kg/min), short-term usage, and close monitoring are recommended. Treatment involves cessation of nitroprusside and administration of sodium thiosulfate. (Choice B) The initial goal in hypertensive emergencies is to rapidly lower diastolic pressure to 100-105 mm Hg over 2-6 hours, with the total drop in blood pressure being no more than 25% of the initial value. Excessive hypotensive therapy with sudden drop in blood pressure can lead to ischemic events (eg, cerebral ischemia, myocardial infarction), altered mental status, or generalized seizures. However, this patient's blood pressure drop is not excessive enough to cause cerebral ischemia. (Choice C) Extension of dissection to the aortic arch and/or carotid arteries can cause symptoms and signs suggestive of a stroke (aphasia with associated motor or sensory abnormalities). It would not be expected to cause altered mental status or seizures. (Choice D) Rapid and severe rise in blood pressure causes increased cerebral perfusion pressure, which results in cerebral edema and hypertensive encephalopathy. Patients typically complain of insidious onset of headaches, nausea, and vomiting; this can progress to restlessness, confusion, agitation, seizures, and coma. This patient's blood pressure has actually improved with treatment, which is not suggestive of hypertensive encephalopathy. (Choice E) Patients with intracerebral hemorrhage typically develop headache and/or vomiting. Seizures may occur and are more common in lobar hemorrhages than other types of intracerebral hemorrhage. Patients typically have focal neurologic deficits such as hemiplegia or paresis and hemianopsia. Educational objective: Nitroprusside is frequently used in the management of acute hypertensive emergency. It is metabolized to cyanide, which may accumulate and can be toxic in patients with chronic renal failure or those receiving a high-dose or prolonged infusion. Toxicity should be suspected in all patients on nitroprusside infusion who have unexplained metabolic acidosis and altered mental status.

A 38-Year-Old African American Man Comes to the Emergency Department