Updated July 2026 · 8 min read

Vasopressin (Vasostrict): The ICU Nurse's Guide

Part of the ICU Pharmacology Hub — browse every related guide in one place.

Vasopressin is the pressor that behaves nothing like the others on your pump. It doesn't titrate to a MAP, it isn't a catecholamine, and in most units it runs at a single fixed rate you set once and rarely touch. Understanding why it sits second-line behind norepinephrine — and what it can quietly do to fingers and gut — is core ICU knowledge that carries straight into anesthesia practice.

What vasopressin is and how it works

Vasopressin is a synthetic form of antidiuretic hormone (ADH), the body's own water-conserving hormone. At the doses used in shock it acts on V1 receptors in vascular smooth muscle to cause potent vasoconstriction, raising systemic vascular resistance and blood pressure. Because that pathway is completely separate from the adrenergic receptors that norepinephrine, phenylephrine, and epinephrine target, vasopressin still works in the acidotic, catecholamine-resistant patient whose other pressors are losing traction.

In septic shock the body's endogenous vasopressin stores become relatively depleted. Replacing a low, physiologic dose restores vascular tone — which is exactly why it's dosed as a hormone replacement, not titrated like a catecholamine.

Dosing in the ICU

The defining feature for the bedside nurse: vasopressin in septic shock is usually a set-and-leave fixed dose, not a titratable drip.

Guidelines suggest adding vasopressin when norepinephrine is climbing (often around 0.25–0.5 mcg/kg/min) and the MAP still isn't at goal. The point is to reduce the catecholamine requirement and its arrhythmia burden while keeping the MAP at 65. When shock resolves, vasopressin is typically weaned or stopped, though many units taper norepinephrine off first.

The side effects that matter at the bedside

Peripheral and digital ischemia. Intense vasoconstriction can compromise perfusion to fingers, toes, and skin. Check distal extremities every shift for mottling, dusky color, or delayed cap refill — especially in patients already on norepinephrine.

Mesenteric ischemia. The same vasoconstriction hits the splanchnic bed. New abdominal pain, rising lactate, or a distended, tender abdomen on a vasopressin patient deserves escalation.

Bradycardia and decreased cardiac output. Unlike catecholamines, vasopressin doesn't provide inotropy and can reflexively slow the heart. Watch for a falling cardiac output in patients who need pump support.

Hyponatremia and antidiuresis. Because it's an ADH analog, it can promote water retention and drop serum sodium on longer runs.

Why it belongs on the pump — the catecholamine-sparing logic

The Surviving Sepsis framework puts norepinephrine first and vasopressin second for a reason: adding a fixed low dose of vasopressin lets you hold or lower the norepinephrine rate, which reduces tachyarrhythmias and the metabolic cost of high catecholamine states. It's a complement, not a replacement. A nurse who understands this reads the two-pressor patient correctly — the vasopressin is the steady floor, the norepinephrine is the dial.

Bottom line

Vasopressin is the quiet second pressor: fixed dose, non-catecholamine, effective when acidosis defeats the adrenergic drugs. Set the rate as ordered, watch fingers and gut for ischemia, don't chase MAP with it, and understand its job is to spare norepinephrine. Get comfortable managing the two-pressor septic patient at the bedside and you'll carry that judgment into every hemodynamically unstable case in the OR.

This article is general educational information for licensed clinicians and students, not medical advice or a substitute for your institution's protocols, pharmacy guidance, or a provider's orders. Always follow facility policy and verify doses independently.