Study objectives: We hypothesized that lowering blood viscosity with acute normovolemic hemodilution (ANH) would confer additional cardioprotection in patients undergoing coronary artery bypass surgery (CABG) with aortic cross-clamping.
Design: In a prospective, randomized controlled trial, we studied the efficacy of ANH in anesthetized patients prior to cardiopulmonary bypass for the prevention of myocardial injuries.
Setting: Cardiac surgical center in a university hospital.
Patients and methods: Patients scheduled to undergo elective CABG entered the study protocol and were randomly allocated to one of two groups: ANH (n = 43 patients) or standard care management (n = 41 patients). In the ANH group, the whole-blood/colloid exchange was aimed to achieve a hematocrit value of 28%. All patients were managed with standard myocardial preservation techniques including cold-blood cardioplegia and anesthetic preconditioning. The outcome measures included the release of myocardial enzymes (plasma troponin I and creatinine phosphokinase), perioperative hemodynamic changes, need for pharmacologic cardiovascular support, and cardiac complications.
Results: In the hemodilution group, the postoperative release of troponin I (mean peak plasma concentration, 1.4 ng/mL; 95% confidence interval, 1.0 to 1.8) and myocardial fraction of creatine kinase (mean, 29 U/L; 95% confidence interval, 23 to 35) were significantly lower than in the control group (mean, 3.8 ng/mL; 95% confidence interval, 3.2 to 4.5; and 71 U/L; 95% confidence interval, 53 to 89). Requirement for inotropic support was significantly lower in the protocol patients (7 of 41 patients vs 15 of 39 patients), and fewer patients presented with either atrial fibrillation, atrioventricular conduction blockade, or combined disorders (12 of 41 patients vs 26 of 39 patients, p < 0.05).
Conclusions: In addition to conventional myocardial preservation techniques, preoperative ANH achieved further cardiac protection in patients undergoing on-pump myocardial revascularization.