DOBUTAMINE

Dobutamine is a synthetic catecholamine that is generally considered the inotropic drug of choice for the acute management of severe (systolic) heart failure. It is primarily a b1-receptor agonist (cardiac stimulation), but it also has mild b-2 effects (vasodilation).

ACTIONS

As demonstrated in Figure 18.1, dobutamine causes a dose-dependent increase in stroke volume (upper graph) accompanied by a decrease in cardiac filling pressures (lower graph). The increase in stroke output is usually accompanied by a proportional decrease in systemic vascular resistance (baroreceptor-mediated), and thus the arterial blood pressure usually remains unchanged. The drug is effective in both right- and left-sided heart failure.

The inotropic and chronotropic effects of dobutamine can vary widely in critically ill patients. This is partly due to variable pharmacokinetics and partly due to variable end-organ responsiveness. Elderly patients are relatively resistant to dobutamine and can have only half the inotropic responsiveness seen in younger patients. The variable response to dobutamine in critically ill patients emphasizes the need to guide dobutamine therapy by preselected hemodynamic end-points, not by preselected dose rates.

Indications

As mentioned, dobutamine is the preferred inotropic agent for the acute management of low output states due to systolic heart failure. Because dobutamine does not usually raise the arterial blood pressure, it is not indicated as monotherapy in patients with cardiogenic shock.

Dobutamine is also used in patients with septic shock and multiple organ failure who may have a normal cardiac output. These conditions are often accompanied by hypermetabolism, and in this situation, a normal cardiac output may be not be adequate for the increased oxygen requirements of hypermetabolism. The goal of dobutamine therapy in these conditions is to drive the cardiac output to supranormal levels (e.g., > 4.5 L/min/m2) to meet the increased oxygen consumption of the hypermetabolic state. The use of dobutamine to achieve a hyperdynamic state has had an inconsistent effect on survival, and thus is not universally accepted.

DRUG ADMINISTRATION

The drug is available in 250-mg vials and is infused in a concentration of 1 mg/mL. The usual dose range is 5 to 15 ug/kg/min, but doses as high as 200 ug/kg/min have been used to achieve a hyperdynamic state in patients with septic shock and multiple organ failure.

Incompatibilities

An alkaline pH inactivates catecholamines such as dobutamine, and thus sodium bicarbonate or other alkaline solutions should not be administered through intravenous tubing used for dobutamine infusions.

ADVERSE EFFECTS

Dobutamine has few serious side effects. As mentioned, tachycardia can develop in some patients. However, malignant tachyarrhythmias are uncommon.

Contraindications

Dobutamine is not indicated for the management of heart failure due to diastolic dysfunction and is contraindicated in patients with hypertrophic cardiomyopathy.

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