The effects of propofol compared to high-dose fentanyl anesthesia on rheologic parameters in coronary artery surgery

Abstract

Propofol has previously been found to decrease hematocrit values. Because hematocrit is an important determinant of blood viscosity, lower hematocrits may cause a decrease in blood viscosity, improving blood flow and oxygen delivery. This phenomenon may be beneficial in certain intraoperative situations. To study the influence of two anesthetic techniques on a variety of rheologic parameters, 32 patients scheduled for coronary artery bypass grafting (CABG) were divided into two groups. Group I (n = 18) was induced with high-dose fentanyl anesthesia (100 μg/kg), and group II (n = 16) with a combination of propofol and fentanyl anesthesia (1 to 1.5 mg/kg and 35 to 50 μg/kg, respectively). Maintenance anesthesia continued with infusions of the same drugs. Blood and plasma viscosity, hematocrit, erythrocyte aggregation factor, and erythrocyte deformability were measured preoperatively, intraoperatively, and up to 48 hours postoperatively. Whole blood viscosity was corrected to a standard hematocrit of 0.45. The two groups were comparable with respect to age, bypass duration, blood loss, urine output, transfusions, and fluid management. Erythrocyte deformability did not decrease during or after cardiopulmonary bypass (CPB). In both groups, hematocrit and blood and plasma viscosity were decreased significantly during and after CPB ( P < 0.01) and returned to baseline levels 48 hours after surgery. After induction and before CPB, blood viscosity was only decreased in group 11. However, the corrected blood viscosity was significantly elevated at all shear rates in group II compared to group I at 24 and 48 hours postoperatively ( P < 0.01). In group II at these sampling times, this parameter was also significantly elevated compared to preoperative values. The results show that in group II the postanesthetic, preoperative decrease in hematocrit was accompanied by the expected decrease in whole blood viscosity. On the other hand, the late postoperative viscosity was shown to be too high for the accompanying hematocrit. This could compromise oxygen delivery to the myocardial muscle. Thus, propofol, with its known negative circulatory effects, may not be the drug of choice for CABG.