Guide — Critical Care
Vasopressors and Inotropes Explained
How vasoactive medications work, which drug fits which shock state, MAP targets, and what ICU nurses monitor when these infusions are running.
14 min read · Critical Care
Educational use only. Vasoactive medications are high-alert drugs requiring intensive clinical monitoring. This content is for learning purposes and does not constitute prescribing guidance. Follow your institution's protocols for all patient care decisions. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Vasopressor vs. Inotrope
Vasopressors work by constricting blood vessels, increasing systemic vascular resistance (SVR) and raising mean arterial pressure. They are used when the primary problem is vasodilation — distributive shock states such as septic, anaphylactic, or neurogenic shock.
Inotropes work by increasing myocardial contractility and cardiac output (CO). They are used when the heart itself is failing — cardiogenic shock — and the problem is pump function rather than vascular tone.
In practice, most vasoactive drugs have overlapping effects. Understanding receptor profiles is the key to matching the right drug to the hemodynamic problem.
Receptor Basics
| Receptor | Location | Effect When Stimulated |
|---|---|---|
| Alpha-1 (α1) | Vascular smooth muscle | Vasoconstriction → ↑SVR, ↑BP |
| Beta-1 (β1) | Heart (SA node, myocardium) | ↑Heart rate (chronotropy), ↑Contractility (inotropy) |
| Beta-2 (β2) | Bronchi, peripheral vasculature | Bronchodilation, mild peripheral vasodilation |
| Dopaminergic (DA) | Renal and mesenteric vasculature | Local vasodilation of renal and splanchnic beds |
| V1 (Vasopressin) | Vascular smooth muscle | Vasoconstriction via non-adrenergic pathway |
Drug-by-Drug Breakdown
Norepinephrine (Levophed)
Receptors: Alpha-1 (dominant) + Beta-1 (moderate)
Dose Range: 0.01–3 mcg/kg/min IV infusion
Hemodynamic Effects: Strong vasoconstriction ↑SVR, moderate ↑HR, moderate ↑contractility
Primary Indication: First-line for septic shock and most distributive shock states
Nursing Monitoring: Arterial line BP, urine output, peripheral perfusion, extravasation risk at peripheral sites
Key Point: Norepinephrine is the Surviving Sepsis Campaign first-line vasopressor for septic shock. The outdated "leave 'em dead" nickname is not evidence-based — it is the preferred agent.
Epinephrine (Adrenalin)
Receptors: Alpha-1 + Beta-1 + Beta-2 (all three)
Dose Range: 0.01–1+ mcg/kg/min infusion; 1 mg IV bolus per ACLS in cardiac arrest
Hemodynamic Effects: Potent ↑HR, ↑contractility, ↑SVR; Beta-2 causes mild vasodilation at low doses
Primary Indication: Anaphylaxis (IM first-line), cardiac arrest (ACLS), refractory septic shock
Nursing Monitoring: Serial lactate (epinephrine elevates lactate directly), HR, blood glucose, BP
Key Point: Epinephrine stimulates glycogenolysis, raising serum lactate independent of tissue hypoxia. Do not use lactate alone to assess perfusion adequacy in patients receiving epinephrine.
Dopamine
Receptors: Dose-dependent: Dopaminergic (low) → Beta-1 (mid) → Alpha-1 (high)
Dose Range: 2–20 mcg/kg/min IV infusion (dose tiers shift receptor profile)
Hemodynamic Effects: Low dose: renal/mesenteric vasodilation. Mid dose: ↑HR and ↑contractility. High dose: ↑SVR
Primary Indication: Cardiogenic shock with bradycardia; less commonly used due to dysrhythmia risk
Nursing Monitoring: Continuous cardiac monitoring (tachycardia, new atrial fibrillation), BP, HR
Key Point: The 'renal-protective' low-dose dopamine strategy has been disproven. Dopamine now has a limited ICU role due to a higher dysrhythmia incidence compared to norepinephrine.
Dobutamine
Receptors: Beta-1 (dominant) + Beta-2 (moderate); minimal alpha activity
Dose Range: 2–20 mcg/kg/min IV infusion
Hemodynamic Effects: ↑Contractility, ↑cardiac output, mild ↓SVR (vasodilation); primarily inotropic
Primary Indication: Cardiogenic shock with low CO and elevated SVR; acute decompensated heart failure
Nursing Monitoring: BP closely (may drop from vasodilation), HR, signs of ↑cardiac output (improved perfusion, UO)
Key Point: Dobutamine is an inotrope, not a vasopressor. It increases CO but may drop BP if the vasodilatory effect exceeds the CO benefit. It is often paired with a vasopressor in cardiogenic shock.
Vasopressin (ADH)
Receptors: V1 vascular receptors (smooth muscle); not adrenergic
Dose Range: Fixed rate 0.03–0.04 units/min IV infusion — not titrated
Hemodynamic Effects: Vasoconstriction via V1 receptor stimulation; no direct cardiac chronotropy or inotropy
Primary Indication: Adjunct vasopressor in refractory septic shock; vasodilatory shock; catecholamine sparing
Nursing Monitoring: Skin perfusion (ischemia risk), urine output, serum sodium, extremity warmth
Key Point: Vasopressin is always run at a fixed rate and is not titrated like catecholamines. Its mechanism is completely independent of adrenergic receptors, making it useful when catecholamine responsiveness is reduced.
Phenylephrine (Neo-Synephrine)
Receptors: Pure Alpha-1; no beta-1 or beta-2 activity
Dose Range: 0.4–9.1 mcg/kg/min IV infusion
Hemodynamic Effects: Strong ↑SVR via vasoconstriction; reflex ↓HR (baroreceptor-mediated); no direct ↑CO
Primary Indication: Hypotension when tachycardia is hemodynamically harmful; neurogenic shock
Nursing Monitoring: HR (reflex bradycardia), peripheral perfusion, cardiac output if monitored
Key Point: Phenylephrine is the only pure alpha-1 vasopressor. It raises MAP without increasing heart rate — useful when tachycardia is a problem, but it does not improve cardiac output and should be avoided in cardiogenic shock.
MAP Goals in Critical Care
Mean arterial pressure (MAP) is calculated as: MAP = (SBP + 2 × DBP) ÷ 3. It represents the average driving pressure for organ perfusion throughout the cardiac cycle.
| Clinical Context | MAP Target | Rationale |
|---|---|---|
| Septic shock (standard) | ≥65 mmHg | Surviving Sepsis Campaign minimum; adequate for most organ perfusion |
| Chronic hypertension history | ≥70–80 mmHg | Autoregulatory curve is shifted right; organs need higher baseline pressure |
| Traumatic brain injury (TBI) | ≥80 mmHg | Cerebral perfusion pressure = MAP − ICP; adequate MAP protects injured brain |
| Post-cardiac arrest (ROSC) | 65–100 mmHg | Avoid both hypotension and severe hypertension during cerebral reperfusion |
| Cardiogenic shock | ≥65 mmHg | Balance organ perfusion against the added myocardial oxygen demand of higher pressure |
Matching the Drug to the Shock State
| Shock State | Core Problem | First-Line Agent | Escalation |
|---|---|---|---|
| Septic | ↓SVR, distributive vasodilation | Norepinephrine | Add vasopressin 0.03 units/min, then epinephrine if refractory |
| Anaphylactic | ↓SVR, histamine-mediated | Epinephrine IM (0.3–0.5 mg) | Norepinephrine infusion if hypotension persists |
| Cardiogenic | ↓CO, pump failure, ↑SVR | Dobutamine (↑CO) | Norepinephrine if MAP inadequate; avoid if tachycardia present |
| Neurogenic | ↓SVR + bradycardia (loss of sympathetic tone) | Phenylephrine or norepinephrine | Atropine or pacing if bradycardia is dominant |
| Hypovolemic | ↓Preload, ↓CO from volume loss | Fluid resuscitation (primary treatment) | Norepinephrine as bridge only if MAP critically low during resuscitation |
Nursing Monitoring Priorities
Arterial LineContinuous invasive BP monitoring is standard for patients on vasopressors. Non-invasive cuffs are inadequate for real-time titration and may be inaccurate in severe vasoconstriction.
Urine OutputTarget ≥0.5 mL/kg/hr. Declining UO despite adequate MAP indicates inadequate renal perfusion, renal vasoconstriction, or evolving AKI.
Peripheral PerfusionAssess skin color, temperature, capillary refill, and mottling. Livedo reticularis or cool, mottled extremities indicate excessive vasoconstriction.
Central Access VerificationVasopressors must infuse through a confirmed central venous catheter whenever possible. Peripheral extravasation causes tissue necrosis — know your institution's peripheral vasopressor protocol.
Lactate TrendingSerial lactate reflects tissue oxygen debt. Clearance of ≥10% per 2 hours suggests improving perfusion. Epinephrine directly elevates lactate — do not interpret this as worsening without full clinical context.
Titration DocumentationDocument the time, dose change, clinical reason, and hemodynamic response for every titration. These infusions change frequently; accurate records are essential for safe handoff.
NCLEX / CCRN Pearls
- ›Norepinephrine is the first-line vasopressor for septic shock — not dopamine.
- ›Dobutamine is an inotrope that increases CO but may drop BP — monitor closely in cardiogenic shock.
- ›Vasopressin is run at a fixed rate (0.03–0.04 units/min) and is never titrated like catecholamines.
- ›Phenylephrine is the only pure alpha-1 agent — it raises MAP without increasing heart rate.
- ›Epinephrine directly raises serum lactate through glycogenolysis — this is not equivalent to worsening perfusion.
- ›All vasopressors should infuse through central access whenever possible; peripheral extravasation causes tissue necrosis.
- ›MAP ≥65 mmHg is the standard septic shock target; patients with chronic hypertension or TBI may need higher targets.
Related Resources
Vasopressor Quick ReferenceDrug, dose, receptor, indication, and monitoring at a glance
Open →Vasopressor Comparison ChartSide-by-side receptor profiles, hemodynamic effects, and clinical use
Open →Shock Hemodynamics ReferenceHemodynamic parameters by shock type for rapid clinical lookup
Open →Shock Type Hemodynamic ComparisonCO, SVR, PCWP, CVP, and treatment options by shock classification
Open →Shock States OverviewPathophysiology of hypovolemic, distributive, cardiogenic, and obstructive shock
Open →Vasoactive Medications ReferenceVasopressors, inotropes, and vasodilators quick reference
Open →Inotropes for NursesDobutamine, milrinone, and the contractility side of the equation
Open →Sedation Scales ReferenceRASS and SAS scoring for the sedated patient on pressors
Open →SOFA Score ChartOrgan-dysfunction scoring across all six systems, plus bedside qSOFA
Open →Standards & sources
Fact-checked Jun 20, 2026This page is written to align with Society of Critical Care Medicine (SCCM) · Surviving Sepsis Campaign · American Association of Critical-Care Nurses (AACN). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →