Classification: vasodilator
  • relaxes arterial and venous smooth muscle to decrease afterload and preload; afterload reduction arterial effect > venous
  • decreases pulmonary artery pressure
  • enhanced renal blood flow
  • enhanced coronary blood flow
  • antihypertensive
  • Infusions:
    • 0.5-8 mcg/kg/min
Administration: IV Infusion:
50mg/250 dextrose 5%, normal saline 0.9% or Ringer's Lactate (maximum concentration 200mg/500mL)
  • protect from light
  • hypovolemia should be corrected concurrently with initiation of therapy
  • drug should be weaned off
Adverse Effects:
  • hypotension
  • hypovolemia
  • Toxicity: 
      • each nitroprusside molecule contains 5 cyanide molecules
      • healthy humans eliminate cyanide as follows:
      • the cyanide contained in 18 mg of nitroprusside will combine with methemoglobin for elimination
      • the cyanide from an additional 50 mg of nitroprusside is bound to thiosulfate to form thiocyanate, which is eliminated in the urine 
      • cyanide toxicity occurs when the total dose of nitroprusside exceeds the ability to eliminate the cyanide (total dose of 68 mg), or if thiosulfate stores are low (e.g. in smokers)
      • thiocyanate toxicity develops if thiocyanate elimination is impaired due to renal failure
    • Cyanide Toxicity (inhibits O2 utilization by tissues):
      • increased HR
      • metabolic acidosis
      • increased lactate despite normal Sp02
      • decreased response to drug
      • increased mixed venous O2 saturation
      • decreased oxygen extraction
      • rapidly progressive tolerance is an important early indication of cyanide toxicity
    • Thiocyanate Toxicity (Increased risk in renal failure):
      • confusion, hallucinations, delerium
      • seizures
      • fatigue, weakness
      • pupillary constriction
      • tinnitus
      • rash
      • hypothyroidism (blocks thyroid uptake and binding of iodine)
  • renal failure, hyponatremia, hypovolemia, hypothyroidism (thiocyanate inhibits uptake and binding of iodine)
  • hepatic failure, Vitamin B12 deficiency, Leber's optic atrophy
  • sodium thiosulfate
Drug Interactions:
  • nitroprusside + dopamine/dobutamine = enhanced hemodynamic effects
Monitoring Therapy:
  • blood pressure
  • continuous heart rate and ECG rhythm
  • urine output
  • central or mixed venous oxygen saturation (increased in cyanide poisoning)
  • lactate (increased with increased central venous oxygen in cyanide poisoning)
  • blood gases
  • continuous oxygen saturation (may worsen shunt)
  • cardiac index if monitored
  • SVRI if monitored
  • urea, creatinine (decreased renal function increase risk for thiocynate toxicity)
  • toxicity correlates with thiocyanate levels > 1.7 uM/L
Adult Critical Care Protocol:
  • May be administered by IV infusion by a nurse in Adult Critical Care.
  • May be titrated by a nurse in Adult Critical Care.
  • Must be administered via central venous access device; in emergency situations may be temporarily infused through a peripheral vasuclar access device until a central venous line can be established.
  • Patient requires placement of an arterial line to monitor BP.
  • Continuous infusions must be administered by infusion device and the pump library must be enabled.
  • Should not be infused via the proximal injectate port (blue) of a pulmonary artery catheter. If this is the only available central venous line, it may be administered through the proximal injectate port but thermodilution cardiac output measurements must not be measured during infusion).

Lynne Kelly, Pharmacist, CCTC
Brenda Morgan, Clinical Nurse Specialist, CCTC
Last Update: September 17, 2018