Comparison of Hemodynamic and Oxygen Transport Effects of Dopamine and Dobutamine in Critically Ill Surgical Patients: Discussion
Data in the Subsequent Postoperative Period and in Those with Complications
In the subset of nine patients who were studied more than three days after surgery, dopamine increased Cl by 0.71 ±0.45 (SD) from a baseline of 3.4 ±0.98 L/min/sq m, while dobutamine increased Cl by 0.79 ±0.67 from a baseline of 3.44 ±0.87 L/ min/sq m. There were appreciable changes in other variables which were not statistically significant, in part because of the small numbers in each group. Similarly, the responses to both agents were appreciable but not statistically significant in patients with sepsis, patients with respiratory or renal failure, patients who were over the age of 65 years, and hyperdynamic patients who had baseline cardiac indices greater than 4.5 L/min/sq m. Moreover, in these subsets, the responses to dobutamine were not significantly different from those to dopamine. comments
The hemodynamic effects of dopamine have been well described in various types of hypotensive shock; similarly, the effects of dobutamine in cardiac patients with low flow are well documented. Circulatory problems usually have been focused on hemodynamics, including blood pressure, cardiac output, stroke work, dP/dt, and other functions appropriate to the cardiac patient. The present report compared hemodynamic and oxygen transport responses to both agents in the same series of critically ill general surgical patients. Although both agents increased cardiac output, the PAWP was maintained by dopamine but reduced by dobutamine. The reduced venous pressure and reduced PVRI after dobutamine is consistent with its p2-adrenergic peripheral effect, as well as its (^-adrenergic cardiac inotropic effect.
In either case, the reduced wedge pressures may permit subsequent fluid administration to be given safely. It should be noted that these patients had essentially normal MAP and were not in shock; when dopamine increased MAP inappropriately, it was discontinued. Values for MAP would have been higher if the full dosage schedule of dopamine had been given in all patients.
Recently, we described effects of dobutamine on oxygen transport in postoperative patients. Although cardiac effects of catecholamines have been the main focus of previous reports, the action of dobutamine on peripheral perfusion may be of greater importance. Tissue perfusion may be evaluated by Do2 and Vo2. Evidence for improved tissue perfusion is suggested when increased Do2 improves Vo2. Increased Vo2 does not occur with increased Cl and Do2in the normal person before surgery because there is no oxygen debt, or in the late-stage and terminal patient whose peripheral microcirculatory defect is irreversible.