What toxicity monitoring is essential when using sodium nitroprusside in hypertensive emergencies?

• A. Monitor for cyanide toxicity
• B. Monitor for hypokalemia
• C. Monitor for hepatic failure
• D. Monitor for hypoglycemia

Answer: (A)

Sodium nitroprusside can release cyanide as it is metabolized, so the essential toxicity to monitor is cyanide toxicity. The risk rises with high infusion doses, prolonged use, and in patients with renal or hepatic dysfunction. Cyanide disrupts cellular respiration, leading to tissue hypoxia and lactic acidosis, so watch for neurologic changes (confusion, agitation, delirium), dyspnea, tachycardia, and signs of metabolic acidosis. Practical monitoring includes frequent blood gases with lactate measurements; cyanide or thiocyanate levels can be checked if available. If toxicity is suspected, stop the drug and provide antidotal therapy (such as hydroxocobalamin or sodium thiosulfate) and supportive care. Other listed toxicities are not the primary concerns with this agent.