Improve Cardiac Output

Vasopressors

Using Vasopressors: A Clinical Guide

Vasopressors are medications that cause vasoconstriction to increase blood pressure. Here's a practical overview of their use:

When to Use Vasopressors

Vasopressors are indicated when you have:

Hypotension that persists despite adequate fluid resuscitation
Distributive shock (septic, anaphylactic, neurogenic)
Cardiogenic shock (sometimes, often combined with inotropes)
Need to maintain adequate perfusion pressure to vital organs

Key Principles

Initial steps before vasopressors:

Ensure adequate fluid resuscitation (unless contraindicated)
Identify and treat the underlying cause
Establish appropriate monitoring (continuous BP monitoring, ideally arterial line)

Target blood pressure: Generally aim for mean arterial pressure (MAP) ≥65 mmHg, though this may be individualized based on the patient's baseline BP and comorbidities.

Common Vasopressors

Norepinephrine (first-line for most shock states)

Dose: Start 0.05-0.1 mcg/kg/min, titrate up to 2+ mcg/kg/min
Primarily alpha-adrenergic (vasoconstriction) with some beta effects
Preferred agent for septic shock

Vasopressin

Dose: Fixed at 0.03-0.04 units/min (not titrated)
Often added as second agent to norepinephrine
Works through non-adrenergic mechanism

Epinephrine

Dose: 0.05-2 mcg/kg/min
Both alpha and beta effects (vasoconstriction + increased cardiac output)
Used in anaphylaxis or as rescue therapy

Dopamine (less commonly used now)

Dose: 5-20 mcg/kg/min
Higher risk of arrhythmias than norepinephrine

Phenylephrine

Dose: 0.5-3 mcg/kg/min
Pure alpha agonist
May be preferred when tachycardia is concerning

Practical Administration

Access: Requires central venous access for most agents (especially at higher doses), though peripheral access can be used temporarily in emergencies
Monitoring: Continuous BP monitoring, urine output, lactate, end-organ perfusion markers
Titration: Start low, titrate to MAP goal, reassess frequently
Weaning: Gradually reduce as patient stabilizes and underlying condition improves

Important Considerations

Vasopressors are supportive therapy—always treat the underlying cause
Monitor for complications: tissue ischemia, arrhythmias, extravasation injury
Don't delay vasopressors if needed while pursuing additional fluid resuscitation
Combination therapy (typically norepinephrine + vasopressin) is common in refractory shock

[Is there a specific clinical scenario or aspect of vasopressor use you'd like me to elaborate on?]

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Vasopressors are used when there has been an inadequate response to volume resuscitation or if there are contraindications to volume infusion.

Vasopressors are most effective when the vascular space is "full".

Patients with chronic hypertension may be at greater risk of renal injury at lower blood pressures; These patients need to be with a higher MAP calculated from their currrent high systolic and diastolic pressures.

In others, there appears to be no mortality benefit in raising MAP above the 65 to 70 mm Hg range.

Vasopressor agents have variable effects on the α-adrenergic, β-adrenergic, vasopressin, and dopaminergic receptors.

Although vasopressors improve perfusion pressure in the large vessels, they may decrease capillary blood flow in certain tissue beds, especially the GI tract and peripheral vasculature.

If multiple vasopressors are used, they should be simplified as soon as the best therapeutic agent is identified.

In addition to a vasopressor, an inotrope may be needed to directly increase CO by increasing contractility and stroke volume.

All vasopressors increase myocardial oxygen demand; most should be titrated to desired effect

Dobutamine
Dopamine
Epinephrine
Isoproterenol
Norepinephrine
Phenylephrine
Vasopressin

Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
2.0–20.0 micrograms/kg/min	β1, some β2 and α1 in large dosages	++++	+	++	Increases

Side effects and comments

Inotrope only; Causes tachydysrhythmias, occasional GI distress, hypotension in volume-depleted patients; has less peripheral vasoconstriction than dopamine; can cause fewer arrhythmias than isoproterenol

Note: 0 = no effect; + = mild effect; ++ = moderate effect; +++ = marked effect; ++++ = very marked effect.

Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
0.5–20 micrograms/kg/min	α, β, and dopaminergic	++ at 2.5–5 micrograms/kg/min	++ at 5–20 micrograms/kg/min	+ at 0.5–2.0 micrograms/kg/min	Usually increases

Side effects and comments

Tachydysrhythmias; a cerebral, mesenteric, coronary, and renal vasodilator at low doses; Surviving Sepsis Campaign second line, lot of overlap with α/β/dopaminergic receptors and dose; can be given through a peripheral IV

Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
2–10 micrograms/min	α and β	++++ at 0.5–8 micrograms/kg/min	++++ at >8 micrograms/kg/min	+++	Increases

Side effects and comments

Causes tachydysrhythmia, leukocytosis; increases myocardial oxygen consumption; may increase lactate; no real maximum dose

Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
0.01–0.05 micrograms/kg/min	β1 and some β2	++++	0	++++	Increases

Side effects and comments

Inotrope; causes tachydysrhythmia, facial flushing, hypotension in hypovolemic patients; increases myocardial oxygen consumption; never use alone in shock

Drug	Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
	0.5–50 micrograms/min	Primarily α1, some β1	++	++++	0	Slightly increases
Side effects and comments	Useful when loss of venous tone predominates; first-line agent for most situations; should be given through a central line

	Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
	10–200 micrograms/min	Pure α	0	++++	0	Decreases
Side effects and comments	Reflex bradycardia, headache, restlessness, excitability, rarely arrhythmias; can be used on patients in shock with tachycardia or supraventricular arrhythmias; not good comparatively for septic shock

Drug	Dose	Action	Cardiac Contractility	Vasoconstriction	Vasodilation	Cardiac Output
	0.01–0.04 units/min	Directly stimulates V1 receptor on smooth muscle	0	++++	0	0
Side effects and comments	Primarily vasoconstriction; usually started at max dose and not titrated

Improve cardiac output
Improve Tissue Perfusio

Determine oxygen delivery (Do2).

(DO2) is the volume of oxygen delivered to the systemic vascular bed per minute and is the product of cardiac output (CO) and arterial oxygen concentration (CaO2): DO2 = CO x CaO2.

Oxygen uptake is the amount of oxygen that diffuses from capillaries to mitochondria.

cardiac rhythm monitoring

Adequate central venous pressure

Adequate mean arterial pressure

Adequate central venous oxyhemoglobin saturation

A comprehensive assessment of the adequacy of perfusion is useful to guide resuscitation, rather than merely aiming for an arbitrary mean arterial pressure.