Norepinephrine, also known as noradrenaline, is a powerful medication that is primarily used for its effect on the heart and blood vessels. It is normally produced in the medulla portion of the adrenal glands, and has been approved by the Food and Drug Administration (FDA) for medicinal use since its synthetic production in 1938.
Method of Action
Norepinephrine acts on a variety of adrenergic receptors in the body, including the alpha and beta receptors. Its action on the alpha receptors causes constriction of blood vessels, instantly increasing systemic blood pressure and blood flow in the coronary arteries. It also acts on beta receptors which can stimulate the heart to beat faster and harder. In small doses, the beta receptor action is dominant; at increasing doses, the alpha receptor effects predominate. Norepinephrine's effects are quite rapid, and also fade quickly when it is not administered; this makes it a favorite of physicians in intensive care and emergency settings where rapid response and stabilization is needed.
Low Blood Pressure
The main use of norepinephrine is in situations where blood pressure is extremely low, such as shock. No matter what the source of the shock may be, the main problem is decreased blood pressure and resulting blood flow to vital organs like the heart, kidney and brain. The effects of norepinephrine to powerfully constrict the blood vessels increase blood pressure to levels that maintain adequate blood to vital organs. Systolic and diastolic blood pressure increase is reported, although decreased blood has been noted to abdominal organs and skeletal muscle. In emergent situations, however, clinicians prefer to protect the heart rather than the biceps, for obvious reasons.
Adjunct Treatment for Heart Attack
Cardiac arrest, or heart attack, can also be treated with norepinephrine in addition to the normal protocol that has been initiated. Since norepinephrine has been shown to increase blood flow in the coronary arteries, and increase the strength and rate at which the heart beats, it makes it a natural fit to help patients who suffer from arrest of cardiac function. This is another way that norepinephrine helps to maintain adequate blood pressure; if the heart isn't pumping out enough blood, there is no pressure to speak of.
References
- "Critical Care Medicine"; Norepinephrine in fluid-refractory catecholamine-resistant cold shock: Are we sure?; Carcillo, J.; July 2009
- "Neurology in Clinical Practice, 5th Edition;" Bradley; 2008
- "Critical Care Medicine"; The effect of increasing doses of norepinephrine on tissue oxygenation and microvascular flow in patients with septic shock; Jhanji, S., Stirling, S., et al.; June 2009
