💉 Sodium Nitroprusside is a potent, fast-acting vasodilator used for short-term blood pressure control in critical care.
⚠️ Its use is limited by the risk of cyanide accumulation with prolonged infusion → requires expert supervision and careful monitoring.
👉 Always check the BNF link here before prescribing.
🧪 About
- Chemical formula: Na₂Fe(CN)₅NO·2H₂O.
- Highly photosensitive in solution → must be protected from light (wrap infusion bag/tubing).
- Used as an IV infusion only (never bolus).
⚙️ Mode of Action
- Direct relaxation of vascular smooth muscle → balanced arterial & venous dilatation.
- Reduces preload & afterload → rapid fall in BP and reduced cardiac workload.
- Onset within 1–2 minutes, duration short → needs continuous infusion & invasive BP monitoring.
- Tachyphylaxis may occur with prolonged use.
💊 Indications & Dosing
- 🚨 Hypertensive emergencies – immediate BP reduction.
- 💔 Acute LV failure / cardiogenic pulmonary oedema (specialist setting).
- 🔪 Aortic dissection (with beta-blocker e.g. labetalol to prevent reflex tachycardia).
Dosing
- Initial: 0.3–1.5 micrograms/kg/min, titrate slowly.
- Typical range: 0.5–8 micrograms/kg/min.
- Stop if no satisfactory response after 10 minutes.
- Heart failure: often lower fixed doses (10–200 micrograms/minute).
- ⚠️ Must be administered in ITU/CCU with invasive BP monitoring.
- Infusion must be protected from light.
🔗 Interactions
- Refer to BNF for detailed list.
- Other antihypertensives → risk of profound hypotension.
- Nitrates & PDE5 inhibitors → additive vasodilation.
🚫 Contraindications
- Severe aortic stenosis or hypertrophic cardiomyopathy (risk of worsening obstruction).
- Significant renal impairment (CKD, AKI) → impaired cyanide clearance.
- Severe vitamin B12 deficiency or Leber’s optic atrophy (risk of cyanide toxicity).
⚠️ Side Effects
- Excessive hypotension → syncope, organ hypoperfusion.
- Cyanide & thiocyanate toxicity with prolonged/high-dose infusion → confusion, seizures, lactic acidosis, arrhythmias.
- Reflex tachycardia (often countered by concurrent beta-blocker).
💡 Clinical Pearls
✔️ Always use invasive arterial line monitoring when infusing nitroprusside.
✔️ Keep infusion time short (hours, not days) → toxicity risk rises with duration.
✔️ In aortic dissection, combine with a beta-blocker to blunt reflex sympathetic drive.
✔️ Watch for unexplained metabolic acidosis or neurological changes → think cyanide toxicity.
📚 References
- BNF: Sodium Nitroprusside
- Goldman-Cecil Medicine, 26th ed. – Critical Care Pharmacology.
- European Society of Cardiology (ESC) Hypertension Guidelines 2018.
