Nitroprusside

Aka: Nitroprusside, Nipride

1. Indications
   1. Hypertensive Emergency
      1. Nicardipine is now preferred instead for Hypertensive Emergency
      2. Reduces Blood Pressure rapidly
      3. However difficult to titrate due to a wide variation in bloold pressure variation
      4. Well tolerated
      5. Easily reversed by discontinuing infusion
   2. Congestive Heart Failure with pulmonary congestion
      1. Refractory to Diuretics
      2. Often used in combination with Dopamine
         1. Similar net effect to Dobutamine
      3. Nitroglycerin is preferred in Coronary Artery Disease
2. Mechanism: Potent peripheral vasodilation
   1. Effects arterial and venous Smooth Muscle
   2. Reduces arterial Blood Pressure
      1. Reduces peripheral arterial resistance
      2. Increases venous capacitance
   3. Decreases Preload
      1. Risk of reflex Tachycardia
3. Metabolism
   1. Metabolites include Cyanide and Thiocyanate
      1. Hepatic dysfunction can allow Cyanide build-up
   2. Red Blood Cells metabolize to Hydrocyanic acid
   3. Liver converts to thiocyanate
   4. Renal Excretion
4. Pharmacokinetics
   1. Very short Half-Life
      1. Effects are seen almost immediately on infusion
      2. Effects cease as soon as infusion is stopped
5. Dosing
   1. Preparation
      1. Reconstitute 50-100 mg powder in 2-3 ml D5W
      2. Dilute with 250 ml D5W or Normal Saline
      3. Final Concentration: 200-400 ug/ml
   2. Additional Measures
      1. Wrap solution immediately in aluminum foil
         1. Prevents deterioration under light exposure
      2. Use solution immediately after making it
      3. Discard solution if becomes highly colored
         1. Solution with faint brown tint is still usable
   3. Infusion
      1. Start 0.1 ug/kg/min
      2. Titrate 0.5 to 8.0 ug/kg/min
         1. Carefully monitor hemodynamic parameters
      3. Use lower doses in elderly
6. Precautions
   1. Hypotension may precipitate secondary events
      1. Myocardial Ischemia or Myocardial Infarction
      2. Cerebral Vascular accident
   2. Avoid Nitroprusside in Coronary Artery Disease
      1. Use Nitroglycerin instead
   3. Thiocyanate Intoxication
      1. Rarely seen unless:
         1. Nitroprusside doses over 3 ug/kg/min
         2. Prolonged Nitroprusside infusion over 2-3 days
         3. Renal Failure
      2. Monitor blood thiocyanate level
         1. Levels below 10 mg/100 ml are safe
      3. Signs of thiocyanate Intoxication
         1. Tinnitus
         2. Blurred Vision
         3. Altered Level of Consciousness
         4. Nausea
         5. Abdominal Pain
         6. Hyperreflexia
         7. Seizure Disorder