Norepinephrine is a potent sympathomimetic drug. This means it mimics the effects of epinephrine, a natural stimulant produced in the body. Because the effects of norepinephrine work on the cardiovascular system, it is used to treat severe hypotension or low blood pressure. It is also a treatment option during cardiac arrest.
Vasoconstriction
Billie Ann Wilson, Ph.D., Margaret Shannon, Ph.D., and Kelly Shields Pharm.D., authors of the "2010 Pearson Nurse's Drug Guide," explain that norepinephrine is a very powerful vasoconstrictor. This means it causes blood vessels to narrow which increases blood pressure. The vasoconstriction effects of norepinephrine make it an excellent drug for treating severe hypotension, or low blood pressure, in emergency situations.
Hypertension
A less desirable effect of norepinephrine is extreme hypertension or high blood pressure. When treating patients for very low blood pressure, the norepinephrine dose is closely titrated, or adjusted, in order to achieve a stable blood pressure. Unfortunately, because of the very powerful vasoconstriction effects, a rebound hypertension can result. This can be just as devastating to a patient as hypotension can be. Patients are closely monitored throughout drug therapy with continuous electrocardiography, oxygen saturation, and blood pressure readings.
Inotropic Effects
In an article in the October 2008 issue of "Critical Care" the authors praise the superior cardiac stimulation effects of norepinephrine. Norepinephrine has inotropic effects on the heart. This means it can make the heart pump harder delivering a greater volume of blood to the body with every beat. This effect of norepinephrine makes it a good drug choice when a patient is experiencing heart failure or cardiac arrest.
Coronary Dilator
Norepinephrine improves blood flow through the coronary arteries because it is also a coronary dilator; it widens the arteries that bring oxygen rich blood to the heart muscle itself. This improves coronary blood flow, which improves overall heart function so the heart can work harder without tiring so easily.
Fatal Arrhythmia
Because norepinephrine is a cardiac stimulator, it can cause fatal heart arrhythmias. Arrhythmias are irregular heart rates and rhythms. A fatal arrhythmia which can occur is ventricular fibrillation. In this instance, the heart does not beat, it simply quivers. The heart cannot pump blood to the body and the patient will die if the arrhythmia is not corrected immediately. This is why patients receiving norepinephrine are in an acute care setting, such as the emergency room or the intensive care unit.
References
- "Pearson Nurse's Drug Guide 2010"; Wilson, B. A., Shannon, T. M., & Shields, K. M.; 2010
- "Critical Care"; Phenylephrine versus norepinephrine for initial hemodynamic support of patients with septic shock: a randomized, controlled trial; Andrea Morelli, et al.; October 2008
