Pharmacological management of low cardiac output syndrome after cardio-pulmonary bypass surgery

ABSTRACT

Low cardiac output syndrome is a pathophysiological state in which the cardiac output is not sufficient to maintain blood flow to meet the metabolic needs of the body. After coronary artery bypass surgery, therapeutic intervention of low cardiac output syndrome should ideally provide positive inotropy without increasing myocardial oxygen consumption, after load reduction, antiarrhythmic activity and selective renal vasodilatation. Therefore this study was carried out to compare the efficacy and safety of adrenaline/tridil with dopamine and dobutamine in the treatment of low cardiac output syndrome after weaning from extracorporeal circulation, Thirty patients, scheduled for coronary artery bypass surgery, were enrolled. Usual hemodynamic monitoring was carried out using arterial and percutaneous heparin coated multiflex thermodilution catheter. Immediately after separation from CPB, and after confirmation of low cardiac output syndrome, patients [10/group] were randomized to receive one of the following inotropes dopamine 2 micro g/kg/min [Dopamine group], or dobutamine 5 micro g/kg/min [Dobutamine group], or adrenaline 0.1 micro g/kg/min/tridil 0.5-1 micro g/kg/min [adrenaline/tridil group]. The dose of the drug was titrated in order to attain a CI>3L min/m[2]. The following baseline hemodynamic variables and derived hemodynamic indices were taken HR, MAP, CVP, PCWP, CI, SVI, SVRI and PVRL These variables were measured prior to the drug administration [TI], 30 minutes [T2], I-[T3], 3-[T4], 6-[15], 12-[T6], and 24-[T7] hours after initiation of the drug administration. There were no significant differences in the operative procedures or hemodynamics at entry into the study [T1]. Infusion of dobutamine or adrenaline tridil resulted in a significant increase of HR, MAP, CL and SVI. associated with reduction of CVP and PCWP compared to baseline values at all assessment times. On the other hand, infusion of dopamine increased HR, MAP, and SVL but did not affect CVP. Compared to the baseline values, both SVRI and PVRI values were significantly increased after dopamine, decreased after adrenaline/tridil whereas dobutamine did not affect both variables. Immediately after CPB [TI], mean CI values were less than 2L/min/m[2] [1.54, 1.57 and 1.66 L/min/m[2] at TI, for dopamine, dobutamine and groups; respectively]. At the end of the study time [17], mean CI values were 2.95, 3.08 and 3.22 L/min/m[2]. During the entire study period, no adrenaline/tridil between-group differences in HR, CI or SVI were found. Compared to other groups, significant increases in MAP, PCWP, SVRI and PVRI were noticed in dopamine group, whereas CP was significantly lower in the adrenaline/tridil group. Although the mean 24-hrs volumes of fluids given to the patients were comparable, the mean 24-hrs mm volume was significantly higher in the adrenaline/tridil group than in dopamine and dobutamine groups. None of patients receiving adrenaline/tridil developed PVC's or ST-segment depression in contrast to the other 2 groups. Administration of adrenaline/tridil to patients with low cardiac output syndrome following cardiac surgery proved an effective way to stabilize the circulation in the immediate postoperative period. The combination of adrenergic activity and vasodilator activity, could give adrenaline/tridil favorable and unique application