Norepinephrine is an alpha agonist medication. Activation of alpha receptors causes smooth muscle contraction, leading to constriction of blood vessels and subsequent increase in blood pressure.
Norepinephrine is also a beta-1 agonist, meaning that it stimulates beta-1 receptors in the heart, thereby increasing heart rate.
Norepinephrine is a vasopressor, which causes constriction of blood vessels. In instances of severe hypotension, norepinephrine can be given to produce a dramatic increase in blood pressure, potentially saving a patient’s life.
Because this medication is a potent vasoconstrictor, blood vessels will constrict causing less blood to perfuse the kidneys. Norepinephrine decreases renal blood flow in an attempt to supply blood to more vital organs, such as the brain and the heart, in a severe hypotensive crisis.
Cardiac arrhythmias can occur in patients receiving norepinephrine, related to excessive activation of beta-1 receptors in the heart.
If given in excess, vasoconstriction caused by activation of alpha-1 receptors may cause the patient to become hypertensive. Blood pressure should be monitored carefully in these patients to avoid a hypertensive crisis.
If norepinephrine extravasates or leaves the blood vessel during administration, it can cause tissue necrosis. If extravasation occurs, the antidote, phentolamine (Regitine) can be infused into necrosed area to allow blood vessels to re-expand.
Norepinephrine is a last resort medication and should be used only when other medical and/or pharmaceutical interventions have proven to be ineffective.
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