From the FDA Drug Label
In studies in congestive heart failure patients, milrinone when administered as a loading injection followed by a maintenance infusion produced significant mean initial increases in cardiac index of 25 percent, 38 percent, and 42 percent at dose regimens of 37.5 mcg/kg/0.375 mcg/kg/min, 50 mcg/kg/0.5 mcg/kg/min, and 75 mcg/kg/0.75 mcg/kg/min, respectively.
The target range for cardiac index is not explicitly stated in the provided drug labels. However, the labels do provide information on the increases in cardiac index achieved with different dose regimens of milrinone.
- A low cardiac index can be managed with milrinone, which has been shown to increase cardiac index by 25-42% in congestive heart failure patients, depending on the dose regimen used 1.
- The management of low cardiac index should be guided by the patient's hemodynamic and clinical response to milrinone therapy, with adjustments made to the infusion rate as needed to achieve the desired effect 1.
From the Research
The normal target range for cardiac index is 2.5 to 4.0 L/min/m², with values below 2.2 L/min/m² generally considered low and requiring intervention. Management of a low cardiac index focuses on identifying and treating the underlying cause while optimizing cardiac function. Initial interventions include fluid resuscitation with crystalloids (typically 500-1000 mL boluses) if hypovolemia is suspected, followed by inotropic support if fluid administration is insufficient or contraindicated.
Key Interventions
- First-line inotropes include dobutamine (starting at 2-5 mcg/kg/min, titrating up to 20 mcg/kg/min) or milrinone (loading dose of 50 mcg/kg over 10 minutes, followed by 0.375-0.75 mcg/kg/min) 2.
- Vasopressors such as norepinephrine (starting at 0.01-0.03 mcg/kg/min) may be added if hypotension persists despite inotropic support.
- Mechanical circulatory support devices like intra-aortic balloon pumps or ventricular assist devices may be necessary in severe cases unresponsive to pharmacological therapy.
Monitoring and Goals
- Continuous hemodynamic monitoring is essential during treatment, with assessment of blood pressure, heart rate, urine output, lactate levels, and mixed venous oxygen saturation to guide therapy.
- The goal is to improve tissue perfusion by enhancing cardiac contractility, optimizing preload and afterload, and ensuring adequate oxygen delivery to tissues.
Evidence Basis
Studies have shown that milrinone and dobutamine can effectively increase cardiac index in patients with heart failure, with milrinone having additional benefits of reducing pulmonary artery pressure and improving right ventricular systolic function 3, 4. The choice of inotrope and vasopressor should be individualized based on the patient's specific hemodynamic profile and clinical response.