Sodium Nitroprusside

How it works

It releases nitric oxide, which raises cyclic GMP in vascular smooth muscle to produce balanced arterial and venous dilatation, lowering both preload and afterload almost immediately.

Prescribing in practice

• Prolonged or high-rate infusion risks accumulation of cyanide and thiocyanate metabolites causing potentially fatal toxicity, so limit duration and rate, and use cyanide antidotes if toxicity is suspected — risk is greater in hepatic or renal impairment.
• It must be given by titrated infusion with continuous arterial blood pressure monitoring because hypotension is rapid in onset and offset, and the solution and giving set must be protected from light.
• Avoid in compensatory hypertension (such as coarctation), severe vitamin B12 deficiency and Leber's optic atrophy.

Monitoring

Monitor blood pressure continuously, ideally intra-arterially, and watch for metabolic acidosis or rising thiocyanate as markers of cyanide accumulation during prolonged infusion.

Counselling the patient

• Explain this is a short-acting drip used to control blood pressure precisely.
• It is given only with close monitoring and the dose is adjusted minute to minute.

Evidence & guidelines

Its role in hypertensive emergencies and controlled hypotension is long-established and supported by the SPC and critical care references.