A 35-year-old man comes to the emergency department with shortness of breath that started 2 days ago and worsened last night. He also has a dry cough. The patient has a history of hypertension, and his medications include chlorthalidone, amlodipine, and labetalol. He ran out of his medications about 3-4 days ago. The patient smokes a pack of cigarettes and drinks 4-5 beers on the weekends. His last drink was 4 days ago. The patient's temperature is 36.7 C (98 F), blood pressure is 220/120 mm Hg, pulse is 105/min, and respirations are 20/min. Oxygen saturation is 96% on 2 liters of oxygen via nasal cannula. Chest auscultation shows bibasilar crackles and fourth heart sound. Funduscopic examination shows normal optic discs and occasional cotton-wool spots. His serum potassium is 5.0 mEq/L, and creatinine is 2.1 mg/dL. The patient is admitted to the coronary care unit and started on intravenous furosemide and nitroprusside infusion with improvement of his symptoms. The next morning, the nurse finds him confused and agitated, and he has a generalized tonic-clonic seizure. His temperature is 36.7 C (98 F), blood pressure is 176/95 mm Hg, and pulse is 102/min. Physical examination shows normal breath sounds bilaterally and no focal muscle weakness. Which of the following is the most likely cause of this patient's new neurologic findings?

Question

A 35-year-old man comes to the emergency department with shortness of breath that started 2 days ago and worsened last night.  He also has a dry cough.  The patient has a history of hypertension, and his medications include chlorthalidone, amlodipine, and labetalol.  He ran out of his medications about 3-4 days ago.  The patient smokes a pack of cigarettes and drinks 4-5 beers on the weekends.  His last drink was 4 days ago.  The patient's temperature is 36.7 C (98 F), blood pressure is 220/120 mm Hg, pulse is 105/min, and respirations are 20/min.  Oxygen saturation is 96% on 2 liters of oxygen via nasal cannula.  Chest auscultation shows bibasilar crackles and fourth heart sound.  Funduscopic examination shows normal optic discs and occasional cotton-wool spots.  His serum potassium is 5.0 mEq/L, and creatinine is 2.1 mg/dL.  The patient is admitted to the coronary care unit and started on intravenous furosemide and nitroprusside infusion with improvement of his symptoms.  The next morning, the nurse finds him confused and agitated, and he has a generalized tonic-clonic seizure.  His temperature is 36.7 C (98 F), blood pressure is 176/95 mm Hg, and pulse is 102/min.  Physical examination shows normal breath sounds bilaterally and no focal muscle weakness.  Which of the following is the most likely cause of this patient's new neurologic findings?

Quizplus · Accepted Answer

This patient presents with severe hypertension and associated acute end-organ complications (renal failure and signs of congestive heart failure). These findings are suggestive of hypertensive emergency. Nitroprusside is a parenteral vasodilator with quick onset and offset of action and is commonly used for rapid blood pressure control in patients with hypertensive emergency. Metabolism of nitroprusside releases nitric oxide and cyanide ions. Nitric oxide induces arteriolar and venous vasodilation. Cyanide toxicity can occur in patients receiving prolonged infusions or higher doses of nitroprusside, and is most common in patients with renal insufficiency. It is characterized by altered mental status, lactic acidosis, seizures, and coma. This patient had initial improvement in his symptoms, followed by acute neurologic change. This is most likely due to cyanide toxicity following prolonged nitroprusside infusion in the setting of renal insufficiency. (Choice A) Alcohol withdrawal typically peaks during the second day following cessation, and seizures are most likely to occur at 12-48 hours. This patient's last alcohol use was 4 days ago, making alcohol withdrawal seizures less likely. Alcohol withdrawal (Choice B) Acute aortic dissection can occur in the setting of severe uncontrolled hypertension and presents with a sudden onset of severe, tearing chest or back pain. This patient has no symptoms or signs suggestive of an aortic dissection. (Choice D) In hypertensive emergencies, mean arterial pressure should be lowered by 10%-20% in the 1st hour and by another 5%-15% over the next 23 hours. An excessive drop in blood pressure can lead to cerebral ischemia, with altered mental status and/or generalized seizures. But this patient's blood pressure drop was not excessive. (Choice E) Hypertensive encephalopathy is characterized by a marked increase in blood pressure associated with signs and symptoms of cerebral edema. Patients present with headaches, nausea, and vomiting, nonlocalizing neurologic symptoms, restlessness, confusion, agitation, seizures, and coma. (Choice F) This patient has no focal muscle weakness or other localizing signs suggestive of an ischemic stroke. (Choice G) Severe hyperkalemia (>7.0 mEq/L) can cause muscle weakness or paralysis, cardiac conduction abnormalities, and/or life-threatening arrhythmias. It is typically not associated with mental status changes and/or generalized tonic-clonic seizures. Educational objective: Cyanide toxicity can occur in patients treated with nitroprusside who receive prolonged infusions, higher doses, or have underlying renal insufficiency. It presents with altered mental status, lactic acidosis, seizures, and coma. References: Cyanides. (http://www.ncbi.nlm.nih.gov/pubmed/16168309) Cyanide poisoning caused by ingestion of apricot seeds. (http://www.ncbi.nlm.nih.gov/pubmed/20196932)

A 35-Year-Old Man Comes to the Emergency Department with Shortness