We investigated the coagulation changes that might occur in acute normovolemic hemodilution (ANH) blood over several hours during cardiac surgery requiring cardiopulmonary bypass.

This study was a prospective observational study.

This study took place at a university teaching hospital.

This study included 26 patients, either ASA 3 or 4 and without known coagulation disorders, undergoing cardiac surgery. Patients were included if the use of cardiopulmonary bypass was expected to reach 2.5 h.

ANH blood was collected into CPDA-1 collection bags before systemic heparinization. Samples were taken directly from the bags at time of collection and reinfusion to assess changes in platelet and thrombin generation parameters.

Whole blood from citrated tubes was used immediately for rotational thromboelastometry and platelet aggregometry analyses. Thrombin generation was assessed using calibrated automated thrombography with platelet poor plasma.

Despite no significant change in platelet count over the ANH storage period, there was significant degradation in platelet function as measured by thrombin receptor activating peptide stimulation on Mulltiplate™ analysis and maximum clot formation on ROTEM™ EXTEM. Notably, there was no change in the ability to generate thrombin.

Little data exists regarding the quality of coagulation factors in autologous blood. Our study confirms ANH collection results in decreased platelet aggregation with TRAP stimulation; however, this is not appreciated with ADP stimulation. Thrombin generation capacity remains preserved.