Background: Acute normovolemic hemodilution (ANH) includes the removal of blood from a patient either immediately before or shortly after the induction of anesthesia and the simultaneous replacement with an appropriate volume of plasma substitute to maintain normovolemia. Thromboelastography (TEG) is a non-invasive diagnostic approach designed to monitor and analyze the coagulability state of a blood sample in order to assist clinical assessment of the haemostatic condition of the patient. The aim of this study was to use the ANH technique in patients requiring coronary artery bypass graft (CABG) surgery and to confirm the advantages of the ANH technique along with TEG.
Method: A controlled randomized clinical trial was conducted in 130 patients (32 females, mean age 57±9.0 years, range 38 to 79 years) who were scheduled for CABG surgery with cardiopulmonary bypass (CPB). They were equally divided into two equal-sized ANH and control groups (n=65). Patients in group A underwent ANH with an average of 500 ml whole blood removal after the induction of anesthesia and their removed blood was replaced with crystalloid solution; blood was not removed in the subjects of the control group. Serum levels of hemoglobin and platelets, TEG parameters analysis, homodynamic changes before and after the operation, and the amount of blood transfused during surgery and in the ICU were checked in both groups. Statistical analysis was performed using repeated measures ANOVA models.
Results: After the surgery, there were significant decreases in hemoglobin and platelets levels (p<0.005), but the decrease was less in the ANH group. However, no difference was found in the amount of platelets decrease between the two groups. Changes in TEG parameters - K, ANGLE, EPL and CI – in the ANH group were statistically significant before and after the surgery (all p-values<0.05). Also, there were significant differences in MA, EPL, and CI parameters between the ANH and control groups (all p-values<0.05).
Conclusion: Use of ANH in patients undergoing CABG surgery results in greater preservation of coagulation factors and platelets that may reduce the amount of bleeding.