In vivo effect of haemodilution with saline on coagulation: a randomized controlled trial

Background. Previous studies have shown that 10–30% haemodilutionwith crystalloid may induce a hypercoagulable state demonstrableby using the Thrombelastograph^® (TEG). While most are invitro studies, the few in vivo studies are limited by confoundingsurgical or ‘environmental’ factors. We conductedthis randomized controlled study to evaluate the coagulationchanges associated with in vivo haemodilution. Methods. Twenty patients undergoing major hepatobiliary surgerywere randomly allocated to one of two study groups. Group H(n=10) had 30% blood volume withdrawn over 30 min and replacedwith saline. Group C (n=10) did not have any blood withdrawn.Blood samples were taken in both groups at 10, 20 and 30 min.Native TEG, complete blood count, coagulation profile, fibrinogen,antithrombin III, protein C and thrombin–antithrombincomplex concentrations were measured. Results. Compared with Group C, Group H patients had significantlygreater shortening of r-time at 30 min (–30% vs +36%),greater shortening of k-time at all time points (–36%vs +17% at 10 min; –37% vs +44% at 20 min; –45%vs +49% at 30 min), and greater widening of