Norepinephrine Dosing in Cardiogenic Shock
Norepinephrine should only be added to cardiogenic shock management when inotropic therapy (dobutamine or dopamine) combined with fluid resuscitation fails to restore systolic blood pressure >90 mmHg with persistent signs of inadequate organ perfusion—it is not a first-line agent. 1, 2
Algorithmic Approach to Vasopressor Use
Step 1: Initial Management
- Start with inotropes first (dobutamine 2.5-10 μg/kg/min is preferred, or dopamine in bradycardic patients) after assessing volume status with a fluid challenge of 250 mL over 10 minutes if clinically indicated. 1, 2
- Target systolic blood pressure >90 mmHg and mean arterial pressure ≥65 mmHg. 2, 3
Step 2: When to Add Norepinephrine
- Add norepinephrine only when the combination of inotropic agent and fluid challenge fails to restore adequate blood pressure despite improvement in cardiac output. 1, 2
- This represents a second-line intervention after optimizing volume status and inotropic support. 2
Step 3: Norepinephrine Administration
- Administer through a central line ideally to minimize risk of tissue necrosis from extravasation. 1, 3
- Titrate to achieve mean arterial pressure ≥65 mmHg (or up to 85 mmHg based on recent research showing improved cardiac performance and tissue oxygenation at higher MAP targets). 2, 3, 4
- Use with extreme caution as cardiogenic shock typically involves high systemic vascular resistance. 1
Specific Dosing Considerations
No specific initial dose is provided in guidelines—the emphasis is on titration to hemodynamic targets rather than fixed dosing. 1 Research studies have used:
- Starting doses ranging from 0.28-0.6 μg/kg/min, titrated up to 0.76-2.6 μg/kg/min to achieve target MAP. 5, 4
- The dose should be the minimum necessary to achieve hemodynamic goals. 1
Critical Monitoring Parameters
Monitor these markers serially to assess adequacy of perfusion: 2, 3
- Hemodynamic targets: Systolic BP >90 mmHg, MAP ≥65 mmHg, cardiac index >2 L/min/m²
- Perfusion markers: Urine output, serum lactate clearance, mixed or central venous oxygen saturation, mental status, skin perfusion
Important Caveats and Pitfalls
Do Not Use as First-Line
- Vasopressors are explicitly not recommended as first-line agents in cardiogenic shock—this is a critical distinction from septic shock management. 1, 2
- The diseased heart in cardiogenic shock may not tolerate the increased afterload from vasopressors without adequate inotropic support first. 1
Discontinue as Soon as Possible
- All vasopressors should be discontinued as soon as hemodynamically feasible due to increased myocardial oxygen demand and arrhythmia risk. 1, 2
- Short-term norepinephrine up-titration appears well-tolerated when combined with inotropes, but prolonged use is associated with increased 30-day mortality. 5, 6
Combination Therapy Considerations
- Exercise caution when combining norepinephrine with dopamine as dopamine already exerts vasopressor effects. 1
- The combination of norepinephrine-dobutamine is superior to epinephrine alone, as epinephrine causes more tachycardia, arrhythmias, lactic acidosis, and impaired splanchnic perfusion. 7
- Epinephrine is not recommended as an inotrope or vasopressor in cardiogenic shock and should be restricted to cardiac arrest scenarios. 1
Blood Pressure Monitoring
- Non-invasive blood pressure measurements become unreliable at very high norepinephrine doses, necessitating arterial line placement for accurate monitoring. 8