Vasopressors on the NCLEX
Norepinephrine, epinephrine, dopamine, vasopressin, phenylephrine: receptors, first-line uses, titration, extravasation.
Five drips, five receptor profiles. The receptor logic answers most vasopressor questions before you memorize anything else.
The receptor logic
Alpha-1 squeezes vessels → raises SVR and BP. Beta-1 drives the heart → raises rate and contractility. Beta-2 relaxes bronchioles and some vessels. V1 (vasopressin) constricts vessels through a completely separate, non-adrenergic pathway. Every pressor is just a mix of these.
Norepinephrine (Levophed)
Strong alpha-1 with modest beta-1. First-line for septic shock. Titrate to MAP of at least 65 mmHg. Runs through a central line whenever possible: extravasation causes tissue necrosis. If it infiltrates peripherally, the antidote infiltrated into the site is phentolamine.
Epinephrine
Alpha and beta together, dose-dependent. Cardiac arrest, anaphylaxis, and second-line in septic shock. Expect tachycardia, tremor, and rising glucose and lactate. A climbing lactate on an epi drip may be the drug, not worsening shock.
Dopamine
Receptor effects shift with dose: dopaminergic low, beta-1 mid, alpha-1 high. The tested downside is tachyarrhythmias, which is why norepinephrine displaced it in sepsis. 'Renal-dose' dopamine does not protect kidneys. If a question offers it as a benefit, it is the wrong answer.
Vasopressin
Pure V1 constriction, no adrenergic receptors. Added to norepinephrine in septic shock at a fixed dose that is not titrated. Because it bypasses adrenergic receptors, it still works in severe acidosis when catecholamines lose effect.
Phenylephrine
Pure alpha-1. Raises BP with no direct cardiac stimulation, so expect reflex bradycardia. Useful when tachycardia is the problem; a poor choice when cardiac output is already low, because pure squeeze raises afterload.
Nursing priorities on any pressor
Continuous BP monitoring, arterial line for accuracy at higher doses. Never stop a pressor abruptly; wean as the MAP allows. Check the IV site every hour. Titrate to the ordered MAP target, and chart every rate change.
Frequently asked
Which pressor is first-line for septic shock?
Norepinephrine. Vasopressin is the usual add-on, epinephrine after that.
A norepinephrine line infiltrates. First action?
Stop the infusion, leave the catheter for now, and prepare phentolamine to infiltrate the site. Then restart the pressor through another line: the patient still needs it.
Why does phenylephrine slow the heart?
Baroreceptors sense the alpha-1 pressure rise and answer with reflex bradycardia. There is no beta-1 activity to oppose it.
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