Reference — Critical Care
Vasopressors & Inotropes Reference
The vasoactive drips an RT sees running in the ICU, grouped by receptor activity — norepinephrine, epinephrine, vasopressin, phenylephrine, dopamine, dobutamine, and milrinone — with the primary effect, the clinical use, and the monitoring notes that matter at the bedside.
Written by Apex Respiratory Editorial Team
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Overview
Respiratory therapists do not order or titrate these drugs, but they work alongside them constantly — managing the airway and ventilator of the same critically ill patient whose hemodynamics are being supported by a vasoactive infusion. Knowing what each agent does to the receptors, the blood pressure, and the heart explains the patient’s vital-sign trends and the rationale behind the plan. The table groups the common agents by receptor activity with the effect, the typical use, and the monitoring caution.
Vasoactive Agents
| Drug | Receptors / Class | Primary Effect | Clinical Use | RT / Monitoring Notes |
|---|---|---|---|---|
| Norepinephrine | α1 > β1 | Vasoconstriction with modest inotropy | First-line in septic and most distributive/undifferentiated shock | Titrate to MAP ≥65; central line preferred; extravasation causes tissue necrosis. |
| Epinephrine | α1, β1, β2 | Inotropy plus vasoconstriction; bronchodilation | Anaphylaxis (first-line), cardiac arrest, refractory shock | Raises lactate; tachyarrhythmias; bronchodilates in anaphylaxis. |
| Vasopressin | V1 receptors (non-adrenergic) | Vasoconstriction | Add-on to norepinephrine in septic shock | Given at a fixed dose, not titrated; risk of digital/splanchnic ischemia. |
| Phenylephrine | Pure α1 | Vasoconstriction, no inotropy | Hypotension with tachyarrhythmia; peri-procedural | Can lower cardiac output by raising afterload; reflex bradycardia. |
| Dopamine | Dose-dependent (dopaminergic, β1, α1) | Variable by dose | Limited use today; more arrhythmias than norepinephrine | Largely superseded; arrhythmogenic. |
| Dobutamine | β1 > β2 | Inotropy with vasodilation (inodilator) | Cardiogenic shock, low cardiac output, septic myocardial dysfunction | May drop blood pressure via β2 vasodilation; tachycardia. |
| Milrinone | PDE-3 inhibitor | Inotropy with vasodilation (inodilator) | Decompensated heart failure; RV failure / pulmonary hypertension | Hypotension; renally cleared with a longer half-life. |
Vasopressor vs Inotrope
The two categories solve different problems. Vasopressors raise blood pressure mainly by vasoconstriction — increasing afterload and systemic vascular resistance. Inotropes increase the heart’s contractility and therefore cardiac output. Inodilators — dobutamine and milrinone — do both: they add inotropy while causing vasodilation, which is why they can support a failing pump but may also drop the blood pressure.
Clinical Notes
- Central access is preferred. Vasopressors are given through a central line whenever possible because extravasation from a peripheral IV can cause tissue necrosis.
- Titrate to a perfusion target, not pressure alone. The goal is a MAP of at least 65 alongside improving markers of perfusion — lactate, urine output, mentation — rather than a blood-pressure number in isolation.
- Norepinephrine is first-line in septic shock. It is the initial vasopressor of choice in septic shock, with vasopressin added on when norepinephrine alone is insufficient.
- Reach for an inotrope when the problem is the pump. Choose an inotrope when the issue is low cardiac output rather than low systemic vascular resistance — the failing heart, not the dilated vasculature.
Related Resources
Sources
- Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Crit Care Med. 2021;49(11):e1063-e1143.
- Gardenhire DS. Rau's Respiratory Care Pharmacology. 10th ed. Elsevier; 2019.
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021.