Dobutamine is another inotropic agent we use in the ICU. It’s referred to as a catecholamine—our word for an organic compound that is released by the adrenal medulla during the fight-or-flight response—but dobutamine is synthetic. It’s actually a structural analogue of isoprenaline (Isuprel), and is administered as a racemic mixture (*important fact*).
This medication is administered primarily for patients in cardiogenic shock, but is also utilized heavily in the advanced heart failure population. It can be a home infusion for those patients. It’s also used for stress testing, interestingly enough. Make sure you hold the beta-blocker that morning.
Dobutamine acts on three different receptor sites on the surface of the myocardial cell. It directly stimulates the beta-1 receptors, the beta-2 receptors, and the alpha receptors. The fact it’s a racemic mixture ensures that the alpha activity of dobutamine is balanced. Because dobutamine (unlike dopamine) does not act on dopamine receptors, it doesn’t promote the release of norepinephrine. This means it won’t increase afterload despite its action on the sympathetic nervous system.
- Beta-1 activity: agonist, increases contractility and heart rate
- Beta-2 activity: agonist, resulting in vasodilation of blood vessels in skeletal muscle tissue, as well as dilating bronchioles
- Alpha-1 activity: balanced agonist and antagonist activity via the (+) and (-) isomers
The effects of dobutamine are dose-dependent. The primary hemodynamic factor followed for titration of the drip is cardiac index. Standard dose range is 2.5-20 mcg/kg/min, and may be titrated by 2.5 mcgs every 15 minutes or so. Increase in heart rate is more marked starting around 12 mcg/kg/min.
Dobutamine increases myocardial metabolism and oxygen consumption. This mechanism results in worsened myocardial ischemia and angina may occur. Hence its use during stress testing…
Effects on other systems
Nausea and vomiting can be quite pronounced, as activation of the beta-2 receptor sites slows gastric motility. This effect can be worse in patients who are diabetic, as well as those who have received anesthetic medications.
Dobutamine stimulates glycogenolysis in skeletal muscle and gluconeogenesis in the liver, which raises blood sugar, as well as insulin secretion in the pancreas, to drive said serum glucose into the cell. If your patient is a diabetic, however…
It increases renin secretion from the kidney. This results in activation of the RAAS, which is a mechanism for hypertension.
It inhibits histamine release.
PRIMARY CONSIDERATIONS: Administration of dobutamine can contribute to down-regulation of the beta-receptors. It’s also proarrythmogenic, and can precipitate ventricular and supraventricular arrhythmias, as well as cause chest pain from angina.