Influence of hemodilution of plasma proteins on erythrocyte aggregability: an in vivo study in patients undergoing cardiopulmonary bypass

Erythrocyte aggregation is known to be affected by a number of factors including the concentration of various plasma proteins. This study was performed to examine the in vivo effect of hemodilution of plasma proteins on erythrocyte aggregation in patients undergoing cardiopulmonary bypass (CPB) surgery. Blood samples were taken before, during, and after operation from 40 coronary artery bypass grafting patients who were operated with CPB and concomitant hemodilution (CPB, n=20) and who without (nonCPB, n=20). Erythrocyte aggregation was determined with a LORCA aggregometer, during which all samples were standardized to a hematocrit level of 40%. Results showed that in the CPB patients the aggregation index (AI) dropped to 44% of its preoperative baseline level 5 minutes after the start of hemodilution (from 47.7+/-10.1 to 26.6+/-11.4, p<0.01). Meanwhile, plasma concentration of fibrinogen (Fb) dropped to 55%, haptoglobin to 85%, ceruloplasmin to 55%, and albumin to 67%. In the nonCPB patients, however, there was only a slight drop in AI and the concentrations of plasma proteins during the similar period of time. On postoperative day 1, AI was rebounded to 37.1+/-12.4 in CPB patients compared with 44.3+/-11.7 in nonCPB patients. At baseline, AI was correlated only with Fb. During CPB and hemodilution, AI was correlated not only with Fb but also with haptoglobin and ceruloplasmin. Postoperatively, significant correlationship was found between AI and Fb, CRP, haptoglobin, ceruloplasmin, as well as albumin. These results indicate that hemodilution of plasma proteins significantly reduces the aggregability of erythrocytes in patients undergoing CPB. Besides Fb, other plasma proteins also contribute to AI during the early postoperative period when patients are recovering from CPB surgery.