Hemodynamic and Renal Effects of Dopexamine and Dobutamine in Patients With Reduced Cardiac Output Following Coronary Artery Bypass Grafting: Appendix

Hemodynamic and Renal Effects of Dopexamine and Dobutamine in Patients With Reduced Cardiac Output Following Coronary Artery Bypass Grafting: AppendixThe hemodynamic effects of dopexamine in healthy volunteers include dose-dependent increases in HR and cardiac output, reductions in systemic vascular resistance, increased oxygen delivery and consumption, and increased splanchnic blood flow.” The renal effects of dopexamine include an increased glomerular filtration rate and increased sodium and water excretion, with variable effects on potassium excretion and renovascular resistance.” These effects are most pronounced in the setting of established heart failure, but recent studies also indicate the potential benefits of this drug in septic shock Hakim et al earlier demonstrated the safety of dopexamine in cardiac surgical patients, with increases in Cl from 2.58 to 3.64 L/min/m2 in detail asthma medications inhalers. However, this group also noted a pronounced increase in HR from 85 to 119 beats/min with kg/min doses of dopexamine.
The original protocol for this study called for ten patients in each treatment group; however, the study was terminated prior to its conclusion by the sponsor because of concerns for patient safety due to the high incidence of tachycardia requiring intervention (eg, esmolol) plus the occurrence of ECG changes suggestive of possible myocardial injury. As both drugs were dosed to cause an increase in Cl, no direct inferences can be made to differences in hemodynamic effects between the two drugs. Certainly, larger studies are needed to better define the side effect profile of dopexamine. Given the similarity of diuresis and natriuresis between the two drugs, Wilcoxon rank sum test power analyses were performed to determine the sample sizes per patient group required to show a significant (a=0.05) difference between drugs on urine output and sodium excretion. Tables 1 and 2 show the results of these power analyses. To show a 50-mEq difference in sodium excretion between dopexamine and dobutamine over the 24-h study period with 90 percent certainty, a study would have to have more than 800 patients in each group. While both dopexamine and dobutamine produce increased Cl, the incidence of tachycardia will probably limit the use of either of these drugs in patients in the post-CABG period.
In conclusion, although dopexamine and dobutamine both increase Cl in the immediate post-CABG period, both agents cause significant increases in HR that limit their utility in this patient group. We have demonstrated that dopexamine has hemodynamic effects similar to those of dobutamine in the first 24 h after cardiac surgery. In addition, there were no significant differences in indices of renal function (natriuresis and diuresis) comparing these two agents. Further studies are needed with dopexamine to identify the patients who will benefit most from this novel agent. These studies should include patients with congestive heart failure and peripheral vascular disease compromising mesenteric and renal blood flow.

This entry was posted in Pulmonary Function and tagged Cardiac surgery (CABG), dobutamine, dopexamine, inotropic support (inotropy).