A 58-year-old woman receiving intravenous sodium nitroprusside for three days at a dose of 8 micrograms/kg/min develops progressive confusion, a rising anion gap metabolic acidosis and elevated serum lactate. What is the most appropriate next step?

• A Increase the nitroprusside infusion rate to control blood pressure
• B Stop the infusion and administer hydroxocobalamin ✓
• C Add oral captopril and continue the current infusion
• D Switch to intravenous furosemide

Explanation

Nitroprusside releases cyanide ions during metabolism, and toxicity occurs with prolonged infusions above roughly 2 micrograms/kg/min, especially beyond 48 hours and in hepatic or renal impairment. It presents with refractory metabolic acidosis, rising lactate, confusion and arrhythmias because tissues cannot utilize oxygen. Treatment is immediate discontinuation plus hydroxocobalamin (with sodium thiosulfate as alternative). Raising the dose accelerates cyanide generation and worsens the acidosis.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.