This chapter discusses the actions, indications, pharmacokinetics,
dosing, and adverse effect profiles of vasopressor drugs that are
pertinent to emergency medicine practice. Specific medications also
are discussed. Please also see Chapter 25, Approach to the Patient in Shock.
Dobutamine (Dobutrex) is a synthetic sympathomimetic drug that
exerts potent inotropic and mild chronotropic activities. Dobutamine
is formulated as a racemic mixture with β1- and β2-adrenergic and α-adrenergic
agonist activities that are offset by α-adrenergic
antagonist activity (Table 24-1). The net
result is an increase in myocardial contractility and systemic vasodilation,
with minimal changes in heart rate. Doses of up to 20 micrograms/kg/min
will increase cardiac output, decrease peripheral vascular resistance,
and decrease pulmonary occlusive pressures. Conversely, doses >20
micrograms/kg/min will increase the heart rate
and induce arrhythmias.
24-1 Ability of Commonly Used Sympathomimetic Agents to
Stimulate Adrenergic Receptors
| Save Table
The onset of action of dobutamine is 1 to 2 minutes, and the peak
response occurs within 10 minutes after IV administration. The apparent
volume of distribution (Vd) is 0.2 L/kg, and the drug is
metabolized primarily in tissue and the liver to inactive metabolites.
The elimination half-life is 1 to 2 minutes, with the majority of
the drug being eliminated within 48 hours in the urine as inactive
Dobutamine is indicated for short-term positive inotropic support
for the treatment of cardiovascular decompensation secondary to ventricular
dysfunction or low-output heart failure. It is the preferred agent
in septic shock with depressed cardiac output despite adequate left
ventricular filling pressures. Dobutamine is also usually the preferred
agent in the management of cardiogenic shock. It increases
cardiac output and renal and mesenteric blood flow without direct stimulation
of the heart rate and decreases systemic vascular resistance.
Dosing and Administration
Dobutamine is administered only as a continuous IV infusion.
The dosage range is 2 to 20 micrograms/kg/min; however,
most patients can be maintained on 10 micrograms/kg/min. Doses
larger than 20 micrograms/kg/min increase the
risk of tachyarrhythmia. To assess effectiveness of the dose administered,
patients should be monitored with a central venous pressure or pulmonary
artery catheter. Unlike many pressor agents, dobutamine may safely
be given peripherally.
The primary adverse effects of dobutamine are modest increases
in heart rate (increases >5 to 15 beats/min are uncommon),
blood pressure ...