What are the recommended vasopressors for managing shock or severe hypotension?

Recommended Vasopressors for Managing Shock or Severe Hypotension

Norepinephrine is the first-line vasopressor for managing shock, particularly distributive shock, with vasopressin recommended as a second-line agent when additional blood pressure support is needed. 1, 2

Types of Shock and First-Line Vasopressors

Distributive Shock (e.g., Septic Shock)

• First-line: Norepinephrine at 0.05-0.1 μg/kg/min, titrated to maintain MAP ≥65 mmHg 1, 2
• Second-line options:
  • Vasopressin (up to 0.03 U/min) to raise MAP or decrease norepinephrine dosage 1, 2
  • Epinephrine (0.05-2 μg/kg/min) when additional agent is needed 1, 3

Cardiogenic Shock

• First-line: Inotropes (dobutamine, dopamine, phosphodiesterase III inhibitors) 1
• For persistent hypotension with tachycardia: Norepinephrine 1
• For bradycardia: Dopamine may be considered 1
• For afterload-dependent states (aortic stenosis, mitral stenosis): Phenylephrine or vasopressin 1

Vasopressor Administration Guidelines

Timing of Initiation

• Initiate vasopressors early in profound hypotension while continuing fluid resuscitation 2, 4
• Early norepinephrine administration improves cardiac output, enhances microcirculation, and prevents fluid overload 4

Target Blood Pressure

• Target MAP of 65 mmHg for most patients 1, 2
• Consider higher MAP targets in patients with chronic hypertension 1, 4
• Monitor tissue perfusion markers (lactate clearance, urine output, skin perfusion, mental status) 1, 2

Refractory Hypotension Management

1. Add vasopressin (up to 0.03 U/min) to norepinephrine 1, 2, 5
2. Consider epinephrine as an alternative second agent 1, 6
3. Phenylephrine only in specific circumstances:
   • When norepinephrine causes serious arrhythmias
   • When cardiac output is high but blood pressure remains low
   • As salvage therapy when other agents have failed 1

Specific Vasopressor Considerations

Norepinephrine

• Mechanism: α1-adrenergic agonist causing vasoconstriction 7
• Benefits: Increases MAP with less tachycardia than epinephrine 1
• Caution: High doses may increase pulmonary vascular resistance and right ventricular afterload 2

Vasopressin

• FDA-approved indication: To increase blood pressure in adults with vasodilatory shock who remain hypotensive despite fluids and catecholamines 5
• Dosing: 0.01-0.04 units/minute 2
• Benefits: Norepinephrine-sparing effect, potential benefits for renal function 6
• Adverse effects: Decreased cardiac output, bradycardia, ischemia (coronary, mesenteric, skin, digital) 2

Dopamine

• Only recommended in highly selected patients with low risk of tachyarrhythmias and bradycardia 1
• Not recommended for general use in septic shock due to higher rates of cardiac arrhythmias 6

Epinephrine

• Dosing: 0.05-2 μg/kg/min, titrated to achieve desired MAP 3
• Considerations: Causes more tachycardia than norepinephrine and may have metabolic effects (lactate elevation) 6
• May be useful in settings where norepinephrine is unavailable or in refractory shock with myocardial dysfunction 6

Common Pitfalls and Caveats

1. Inadequate fluid resuscitation: Ensure adequate volume status before or during vasopressor therapy 2
2. Delayed vasopressor initiation: Early administration of norepinephrine is beneficial for restoring organ perfusion 4
3. Fixed vasopressor dosing: Always titrate to effect rather than using fixed doses 1
4. Failure to individualize MAP targets: Consider patient factors such as age and history of hypertension 1
5. Delayed weaning: Begin weaning vasopressors as soon as hemodynamic stabilization is achieved 1

For refractory shock, always consider underlying causes such as pericardial effusion, pneumothorax, hypoadrenalism, hypothyroidism, ongoing blood loss, increased intra-abdominal pressure, or inadequate source control of infection 1.