Context: Viscoelastic hemostatic assays (VHA) are commonly used to identify specific cellular and humoral causes for bleeding in cardiac surgery patients. Cardiopulmonary bypass (CPB) alterations to coagulation are observable on VHA. Citrated VHA can approximate fresh whole blood VHA when kaolin is used as the activator in healthy volunteers. Some have suggested that noncitrated blood is more optimal than citrated blood for point-of-care analysis in some populations. 

Aims: To determine if storage of blood samples in citrate after CPB alters kaolin activated VHA results. 

Settings and Design: This was a prospective observational cohort study at a single tertiary care teaching hospital.

 Methods and Material: Blood samples were subjected to VHA immediately after collection and compared to samples drawn at the same time and stored in citrate for 30, 90, and 150 min prior to kaolin activated VHA both before and after CPB. 

Statistical Analysis Used: VHA results were compared using paired T-tests and Bland–Altman analysis. 

Results: Maximum clot strength and time to clot initiation were not considerably different before or after CPB using paired T-tests or Bland–Altman Analysis. 

Conclusions: Citrated samples appear to be a clinically reliable substitute for fresh samples for maximum clot strength and time to VHA clot initiation after CPB. Concerns about the role of citrate in altering the validity of the VHA samples in the cardiac surgery population seem unfounded.