In the treatment of postoperative low cardiac output syndrome (LOS), isoproterenol (ISP) hasbeen frequently utilized clinically to improve capdiac performance. However, ISP may produce undesirable results on arterial pressure (AP), heart rate (HR) as well as on cardiac rhythm. Dobutamine, a new synthetic inotropic agent has less significant positive chronotropic and/or arrhythmogenic effects and less peripheral vasocons. trictive effect than other currently used cardiac stimulants.
Dobutamine was administered by intravenous infusion to 17 patients whe developed various degrees of low cardiac output syndrome following the open heart surgery. The dosage of Dobutamine ranged from 2 to 8 mcg/kg/min with stepwise increase of its dosage (2,4,6 and 8 mcg/kg/min). Dobutamine was repeated in four of these 17 patients on the followingday of initial treatment.
Cardiac index (CI) rose from 2.52 to 3.01 and 3.38L/min/M²/with 4 and 8 mcg/kg/min of Dobutamine, respectively. Heart rate increased from 89 to 97 and 110 beat/min with 4 and 8 mcg/kg/min of Dobutamine, respectively. Systolic AP and systolic pulmonary arterial pressure (PAP) rose significantly from 129 to 147 mmHg and from 31 to 35 mmHg with 8 mcg/kg/min of Dobutamine. While mean AP, diastolic AP, mean PAP and diastolic PAP were unchanged. Mean left atrial pressure (MLAP) lowered slightly but significantly from 16 to 14 mmHg. Stroke volume index, stroke work index and left ventricular work also increased. As compared to the cardiac effects of ISP, slopes of the dose-response curves on the above-mentioned parameters obtained from the same pts were greater in Dobutamine than in ISP. No arrhythmias or other side-effects were observed.
We concluded that Dobutamine is a potent inotropic agent which increases cardiac output without developing a significant tachycardia or arrhythmias in pts with reduced cardiac output.

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