Cyanide toxicity following nitroprusside induced hypotension

Area of Science:

• Anesthesiology
• Clinical Toxicology
• Pharmacology

Background:

• Sodium nitroprusside is a potent vasodilator used during surgery.
• Recent deaths linked to sodium nitroprusside have raised concerns about cyanide toxicity.
• Cyanide accumulation from nitroprusside metabolism is a significant clinical concern.

Purpose of the Study:

• To investigate cyanide levels and toxicity following short-term sodium nitroprusside infusions during intracranial surgery.
• To determine if current recommended doses of sodium nitroprusside pose a risk of cyanide accumulation.
• To assess the clinical manifestations of cyanide toxicity in patients receiving nitroprusside.

Main Methods:

• Administered brief sodium nitroprusside infusions (mean 36 minutes) at recommended doses during intracranial surgery.
• Monitored blood cyanide levels post-infusion in 13 patients.
• Assessed for metabolic acidosis and blood Adenosine Triphosphate (ATP) levels in patients with high cyanide concentrations.

Main Results:

• Peak blood cyanide levels reached 65.2 +/- 17.5 microgram per cent within 45 minutes post-infusion.
• The highest detected cyanide level was 205 microgram per cent, within the lethal range.
• Metabolic acidosis and depressed ATP levels were observed in patients with the highest cyanide levels (90-205 microgram per cent), indicating disturbed aerobic metabolism.

Conclusions:

• Short-term sodium nitroprusside infusions at currently recommended doses can lead to significant cyanide accumulation.
• Evidence of cyanide toxicity, including metabolic acidosis and impaired cellular metabolism, is present.
• A dose limit of 0.5 mg/kg for sodium nitroprusside is recommended for short infusions to mitigate cyanide toxicity risk.