Inotropes increase cardiac output by enhancing cardiac contractility through different mechanisms of action, but they also bear variable vasodilatory or vasoconstrictive effects depending on agent and dosage. They constitute an important tool for the treatment of patients with AHF or AdvHF, as they are often effective in improving hemodynamics and symptoms. However, their administration has been associated with increased short and long-term mortality due to frequent adverse effects, but also due to their improper use. The classes of inotropes currently used in HF are the β-adrenergic receptor agonists including dopamine, dobutamine and the catecholamines norepinephrine and epinephrine, the…
When I left my first spell in neonatal training, I thought there were just two inotropes – dopamine and dobutamine. There was a myth of another agent called adrenaline and the even more elusive noradrenaline, but no one seemed to survive after these drugs. Later, in ICU training, I came across strange agents that I could not even spell, before working out the simple and the basic principles that have helped me and my patients ever since. Fundamentally, inotropes are properly dangerous drugs, and should only be used if you and the rest of the team know what they are doing, and the patient is properly monitored.
Clinical pitfall: giving an ionotrope before initiating a vasopressor may decrease BP further as they are vasodilators, which may lead to cardiovascular collapse; our experts suggest initiating norepinephrine prior to giving an ionotrope in heart failure patients with cardiogenic shock
Inotrope use in critically ill patients is quite heterogeneous as self-reported by individual caregivers. Eleven strong recommendations on the indications, choice, triggers and targets for the use of inotropes are given by international experts. Future studies should focus on consistent indications for inotrope use and implementation into a guideline for circulatory shock that encompasses individualized targets and outcomes.
The currently available inotropic agents in clinical practice fall into three main categories: beta-agonists, phosphodiesterase III inhibitors and calcium sensitisers. However, due to the well-documented potential for adverse events and their association with increased long-term mortality, physicians should be aware of the indications and dosing strategies suitable for different types of patients. Novel inotropes that use alternative intracellular pathways are under investigation, in an effort to minimise the drawbacks that conventional inotropes exhibit.
inotropes are agents that increase myocardial contractility (inotropy)
— e.g. adrenaline, dobutamine, isoprenaline, ephedrine.
vasopressors are agents that cause vasoconstriction leading to increased systemic and/or pulmonary vascular resistance (SVR, PVR)
— e.g. noradrenaline, vasopressin, metaraminol, vasopressin, methylene blue.
inodilators are agents with inotropic effects that also cause vasodilation leading to decreased systemic and/or pulmonary vascular resistance (SVR, PVR).
Inotropes are used for cardiogenic shock patients, specifically when volume status is elevated and the cardiac output is low.
Dobutamine acts on beta-1 and beta-2 adrenergic receptors, increasing contractility and blood pressure. It also causes vasodilation – for patients with a systolic blood pressure less than 80 caution is advised. It could be beneficial to have levophed hanging in the case of a hypotensive episode.
Milrinone is a phosphodiesterase-3 inhibitor that blocks breakdown of cyclic AMP.
Dobutamine has a half life of minutes, whereas milrinone has a half life of hours.
Condensing all of “inotropes and vasopressors” into a single 5 minute podcast is of course doomed to fail but that’s never stopped me before. Next let’s look at the phosphodiesterase inhibitors. Milrinone, enoxamone and levosimendan are all in this bucket. They work by non-receptor mediated inhibition of PDE, ultimately resulting in increased cAMP. They are thought to be unique in that they may improve lusitropy (ability of heart to relax). All come with potent vasodilation so expect to have to crank up your pressor to compensate.
The management of cardiogenic shock is complex, often requiring tandem use of vasopressors and inotropes to stabilize hemodynamics. But what inotrope is more effective, dobutamine or milrinone?
Inotropes aim at increasing cardiac output by enhancing cardiac contractility. They constitute the third pharmacological pillar in the treatment of patients with decompensated heart failure, the other two being diuretics and vasodilators. Three classes of parenterally administered inotropes are currently indicated for decompensated heart failure, (i) the beta adrenergic agonists, including dopamine and dobutamine and also the catecholamines epinephrine and norepinephrine, (ii) the phosphodiesterase III inhibitor milrinone and (iii) the calcium sensitizer levosimendan. These three families of drugs share some pharmacologic traits, but differ profoundly in many of their pleiotropic effects. Identifying the patients in need of inotropic support and selecting the proper inotrope in each case remain challenging.