What are Inotropes and What Do They Do?
Inotropes are drugs that change the strength or force of each heartbeat. Some inotropes, called positive inotropes, increase the force of each heartbeat, while others (negative inotropes) decrease it.
When are inotropes used? In cardiogenic shock, positive inotropes are often used to boost the force of heart contractions and increase blood pressure. Commonly used positive inotropes are dobutamine (Dobutrex) or milrinone (Primacor).
Why does the force of each heartbeat matter? The greater the strength of each heartbeat, the more blood flows through the heart. Maintaining adequate blood flow through the heart is needed to provide the body with oxygen and nutrients and remove cellular waste. When the heart is diseased or damaged it may not be able to pump adequate amounts of blood throughout the body. The body cannot live without oxygen and reduced blood flow can cause organ damage and death.
To prevent inadequate blood flow to the vital organs, a condition called cardiogenic shock, patients may be given inotropes to increase the force of contraction of the heart muscle and stabilize blood pressure. Once blood flow is stabilized, clinicians can provide further treatment, such as PCI, to address the underlying medical condition(s).
Inotropes are used to treat cardiogenic shock. When a patient does not respond to one inotrope, common practice has been to increase the dose of medication or use another inotrope. The use of multiple inotropes or the prolonged use of a single inotrope increases the risk of death from 3% for one low-dose inotrope to 7.5% for one moderate-dose inotrope to 42% for two high-dose inotropes and to 80% for three high-dose inotropes (Samuels, et al., 1999).
This increased risk may be due to the fact that while inotropes increase the force of heart contractions they also require the heart to use more oxygen and do more work. Both of these may not be good for a damaged or diseased heart.
Best practices for use of inotropes recommend using one inotropic drug at the lowest dose for the shortest amount of time to stabilize blood flow. Once blood flow has been stabilized, it is important for clinicians to wean the patient off inotropes. If the patient is presenting within 48 hours of acute myocardial infarction cardiogenic shock (AMICS), and the heart needs additional support, use of a heart pump like the Impella® will help maintain blood flow, allow the heart to rest and recover to avoid further heart damage.