Question

What are the nursing implementation considerations for a patient receiving nitroprusside for blood pressure?

Answer 1

Sodium nitroprusside is a common Medication administered in critical care for its arterial and venous vasodilating effects. It is a drug of choice for management of patients with acute hypertensive emergencies and is also used for CHF and in the operating room to reduce bleeding during surgery .

It's use has many implications for the critical care nurse not only in terms of monitoring blood pressure but also it's side effects.

The pharmacological action of nitroprusside is the relaxation of smooth muscles of blood vessels including arteries and veins by the production of nitric oxide. It has more activity in the dilation of veins than on arteries. This selectively results in pooling of blood in the veins with consequential decrease in venous return to the heart. These hemodynamic changes results in decreased left ventricular end diastolic pressure and capillary wedge pressure. The dilatation of arteries reduces systemic vascular resistance, systolic arterial pressure and mean arterial pressure ( after load ). These changes also result in coronary artery vasilodilation . There is variable effect on cardiac output. Metabolism of nitroprusside occurs through conversion to cyanide ions and thiocyanate . It's side effects mainly due to its potent Hypotensive effects and accumulation of cyanide and thiocyanate.

The important nursing implication constructions are,

* The drug has a very profound effect on hemodynamic thus it is recommended that patients on nitroprusside should have an arterial line to monitor blood pressure.

* Always use an IV infusion device to deliver the drug.

The drug may NOT be administered by Direct injection. It must be reconstituted.

Inadvertent bolus administration should be avoided such as flushing the line and accidentally infusing a large amount at one time.

To this end, the line should never be used to give other Medications.

In addition, no other drugs should be administered in the same line as the sodium nitroprusside.

* Exposure to light of the incorporated medicine cause decomposition.

Will show orange, dark brown or blue. A blue discoloration indicates degradation to cyanide.

The IV solution and tubing should be protected from light by wrapping with aluminium foil or any opaque material.

* Erythrocytes usually uptake cyanide and is incorporated into cyanocobalamin and serves as a buffer for the effects of cyanide.

However, if the drug is used for morethan 48 hours, there is a risk for the development of cyanide toxicity, especially if the patient has altered renal function.

In addition, prolonged infusion faster than 2 mcg/kg/min causes cyanide to be generated faster.

Signs of cyanide toxicity includes,

Increased heart rate and metabolic acidosis. Metabolic acidosis is an early sign of cyanide toxicity. Coma and almond smell on the breath may also be observed.

* Thiocyanate toxicity :- cyanide is bound to thiocyanate which is normally eliminated via the kidney. When the patient has impaired renal function, thiocyanate toxicity develops. This condition is manifested by mental status changes such as confusion, hallucinations, and delirium. It may also cause hyper reflexia which may lead to seizure and coma. Monitor thiocyanate blood levels ( less than 0.1 mg/ml) particularly if the patient receives it for morethan 3 days.

* Monitor for methamoglobinemia.

Methamoglobinemia decreases the blood's oxygen carrying capacity. This should suspected if the patient has received morethan 10 mg/ kg of sodium nitroprusside. Methamoglobin levels are measured in the laboratory.

* Monitor for hypothyroidism - thiocyanate interferes with iodine uptake by the thyroid.

* Monitor renal and hepatic function.

* Standard concentration : 200 mcg/ml in D5W ( not compatible in D10W ) .

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