Management of Cardiogenic Shock with Milrinone and Norepinephrine

Definition and Pathophysiology

Cardiogenic shock is defined as hypotension with signs of hypoperfusion, including low urine output, cold extremities, altered mental status, elevated lactate levels, and low mixed venous oxygen saturation, and represents a state of low cardiac output leading to tissue hypoperfusion and organ dysfunction, most commonly caused by acute myocardial infarction 2

Immediate comprehensive assessment, including ECG and echocardiography, is required in all patients with suspected cardiogenic shock, and invasive monitoring with an arterial line is recommended for continuous blood pressure monitoring 2
Fluid challenge should be administered as first-line treatment if there are no signs of overt fluid overload, and all patients with cardiogenic shock should be rapidly transferred to a tertiary care center with 24/7 cardiac catheterization capabilities and dedicated ICU with availability of mechanical circulatory support 2, 4

Milrinone is a phosphodiesterase-3 inhibitor that increases cardiac output and stroke volume while reducing pulmonary artery pressure, pulmonary wedge pressure, and systemic and pulmonary vascular resistance, and is particularly valuable in patients on beta-blocker therapy or with right ventricular dysfunction 1, 5
The American College of Cardiology recommends milrinone as a treatment option for patients with cardiogenic shock, especially those with right ventricular failure or pulmonary hypertension, due to its pulmonary vasodilatory effects 1, 6

Norepinephrine is recommended as the preferred vasopressor when mean arterial pressure needs pharmacologic support, and is indicated when the combination of an inotropic agent and fluid challenge fails to restore SBP >90 mmHg with inadequate organ perfusion 1, 4
The European Society of Cardiology recommends norepinephrine as a first-line vasopressor in cardiogenic shock, with a starting dose of 2-3 mL/minute (8-12 mcg/minute) and adjustment to maintain systolic blood pressure 80-100 mmHg 4, 7

The combination of milrinone and norepinephrine may be beneficial in patients with cardiogenic shock, as milrinone improves cardiac output by reducing afterload, while norepinephrine maintains coronary and systemic perfusion pressure 6
In patients with right ventricular failure, the combination of milrinone and norepinephrine is particularly beneficial, as milrinone reduces RV afterload while norepinephrine maintains RV perfusion pressure 6

Continuous blood pressure monitoring, cardiac output, and cardiac index should be monitored, with targets of SBP >90 mmHg and cardiac index >2 L/min/m², and signs of improved organ perfusion, such as urine output, mental status, and lactate clearance, should be closely monitored 1, 4, 8

All inotropes should be used at the lowest possible doses for the shortest duration due to their propensity to increase myocardial oxygen demand, ischemic burden, and risk of arrhythmias, and vasopressors should be used with caution and discontinued as soon as possible 1, 4