Managing cardiogenic shock

Cardiogenic shock, due to low cardiac output, may occur as a result of low stroke volume or bradycardia. In this video, from our ICU Masterclass: Inotropes and Vasopressors course, we'll cover the reversible and irreversible causes of low cardiac output, as well as how to be selective when choosing agents to manage these effectively.

Providing hemodynamic support for unstable patients can be a daunting process. In our ICU Masterclass: Inotropes and Vasopressors course, you’ll learn a systematic, hands-on approach for using vasopressors and inotropes. You’ll discover why one size does not fit all and the underlying mechanisms of action of these agents so that you can safely and effectively use the appropriate agent for each unique patient.

Cardiogenic shock is inadequate perfusion originating from failure of the heart to pump blood effectively. Cardiac output produced by the heart is equal to the stroke volume times the heart rate. Low heart rate may be a cause of decreased cardiac output, or a contributing factor if a compensatory tachycardia is blunted. Chronotropic agents may be useful if there's a reversible cause for the bradycardia.

These include isoproterenol, dobutamine, milrinone, epinephrine, glucagon, calcium, or dopamine. These agents would not be expected to work, however, in the case of an irreversible cause, like infarction of the conducting system. The preferred agent depends on whether there is alternate pathology present, like ischemia, hyperkalemia, or a nodal-blocking toxin. Isoproterenol is likely the most effective agent from the standpoint of purely increasing the heart rate.

While increasing heart rate may improve cardiac output, increasing stroke volume may also be beneficial. A low stroke volume may also be the result of a variety of different conditions, including ischemia, cardiomyopathy, hypocalcemia, or the presence of a toxin. Mechanical considerations like hypovolemia or obstruction may also decrease the stroke volume.

The options for inotropic medicines for improving stroke volume are essentially the same as for increasing heart rate. Dobutamine is likely the first agent for inotropy for most providers. For patients with high blood pressure, pulmonary hypertension, or those taking beta-blockers or beta-agonists, milrinone may be a more effective agent.

For patients with the low blood pressure, an agent with combined inopressor effects like epininephrine may be preferred. Low cardiac output as a result of hypercalcemia, adrenal insufficiency, hypovolemia, obstruction, or toxic ingestion could obviously have the underlying cause addressed in addition to the consideration of inotropes.