Nitroprusside Sodium

A to Z Drug Facts

 Action Relaxes vascular smooth muscle and dilates peripheral veins and arteries.

 Indications Immediate reduction of blood pressure in hypertensive crisis; production of controlled hypotension to reduce bleeding during surgery; for acute congestive heart failure. unlabeled use(s): Has been used alone or with dopamine in acute myocardial infarction.

 Contraindications Treatment of compensatory hypertension, in which primary hemodynamic lesion is aortic coarctation or arteriovenous shunting; to produce hypotension during surgery in patients with known inadequate cerebral circulation or in moribund patients (A.S.A. Class 5E) coming to emergency surgery; patients with congenital (Leber's) optic atrophy or with tobacco amblyopia; acute CHF associated with reduced peripheral vascular resistance.

 Route/Dosage

Give by IV infusion using infusion pump, preferably volmetric pump. ADULTS & CHILDREN: IV 0.3 mcg/kg/min initially; titrate upward gradually every few minutes to desired effect. Do not exceed 10 mcg/kg/min. Do not use maximum rate for more than 10 min. Average rate of infusion is 3 mcg/kg/min; some patients require much lower doses, especially if other hypotensive agents are used.

 Interactions Antihypertensives, ganglionic blocking agents, volatile anesthetics (eg, enflurane, halothane): Additive hypotensive effects.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: Evidence of rapid blood pressure reduction (eg, abdominal pain; apprehension; diaphoresis; dizziness; headache; muscle twitching; nausea; palpitations; restlessness; retching; retrosternal discomfort); bradycardia; ECG changes; tachycardia. GI: Ileus. HEMA: Methemoglobinemia; decreased platelet aggregation. DERM: Flushing; venous streaking; irritation at infusion site; rash. META: Hypothyroidism. OTHER: Thiocyanate toxicity; cyanide toxicity; increased intracranial pressure.

 Precautions

Pregnancy: Category C. Lactation: Undetermined. Elderly: May be more sensitive to hypotensive effects. Anesthesia: Patient's ability to compensate for anemia and hypovolemia may be diminished during anesthesia. Cyanide toxicity: Infusions faster than 2 mcg/kg/min generate cyanide faster than body can dispose of it. Symptoms of cyanide toxicity include venous hyperoxemia with bright red venous blood, metabolic (lactic) acidosis, air hunger, confusion and death. Excessive hypotension: Precipitous drops in BP can occur. If not properly monitored, decreases can lead to irreversible ischemic injuries or death. Hepatic impairment: Cyanide may accumulate. Intracranial pressure: Use with extreme caution in patients with elevated intracranial pressure; nitroprusside can increase intracranial pressure. Methemoglobinemia: Clinically significant methemoglobinemia is seen rarely, but suspect condition in patients who have received more than 10 mg/kg of nitroprusside and who have signs of impaired oxygen delivery despite adequate cardiac output and arterial Po₂. Blood may be chocolate brown. Severe renal disease, anuria: Thiocyanate may accumulate. Thiocyanate toxicity: Cyanide is eliminated in form of thiocyanate. When cyanide elimination is accelerated by infusion of thiosulfate or when prolonged infusions are used, thiocyanate levels may increase. Thiocyanate is neurotoxic (tinnitus, miosis, hyperreflexia) and toxicity may be life threatening.

 Administration/Storage

• Dilute 50 mg in 2 mL D5W. Add to 250 to 500 mL D5W. Resulting solution is 200 mcg/mL or 100 mcg/mL. Use only D5W; no other diluent should be used. No other medication should be infused with nitroprusside medication. Protect solution from light, usually by wrapping with aluminum foil. However, it is not necessary to protect drip chamber or tubing.
• Avoidance of excessive hypotension: While the average effective rate in adults and children is about 3 mcg/kg/min, some patients will become dangerously hypotensive when they receive nitroprusside at this rate. Start at a very low rate (0.3 mcg/kg/min), with gradual upward titration every few minutes until the desired effect is reached or the maximum recommended infusion rate (10 mcg/kg/min) has been reached.
• Do not use if solution is discolored or if particulate matter is seen.
• Store diluted solution at room temperature for no longer than 24 hr and protect from light.
• Do not give by bolus infusion; infuse slowly using pump or controller to regulate rate.

• CHF: Nitroprusside can be titrated by increasing the infusion rate until measured cardiac output is no longer increasing, systemic blood pressure cannot be further reduced without compromising the perfusion of vital organs or the maximum recommended infusion rate has been reached, whichever comes earliest.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Assess baseline vital signs, ECG, heart sounds, and lung sounds.
• Assess baseline neurological status.
• Place patient in Trendelenburg position to increase venous return.
• Perform continuous ECG monitoring.
• Monitor vital signs every 15 min while on drip and every 5 min while infusion is being titrated.
• Monitor I&O throughout therapy.
• Monitor plasma cyanogen level if used for > 48 hr or with hepatic impairment.
• Monitor thiocyanate level (< 10 mg/dl) if used for > 48 hr or in severe renal dysfunction.
• Monitor for chest pain or flushing.
• Notify physician of severe hypotension, abdominal pain, apprehension, dizziness, headache, vomiting, bradycardia or tachycardia, ECG changes, or syncope.
• Notify physician of signs of cyanide toxicity such as bright red venous blood, metabolic acidosis, air hunger, and mental confusion.
• Monitor for and notify physician of signs of thiocyanate toxicity (ie, tinnitus, miosis, hyperreflexia).

 Patient/Family Education

• Instruct patient to report the following symptoms to physician: Dizziness; retching, nausea, abdominal pain, chest pain, palpitations, tinnitus, or flushing.
• Caution patient to avoid sudden position changes to prevent orthostatic hypotension.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts