Thromboelastography (TEG), which indicates hemostatic ability, is useful for monitoring coagulation during extracorporeal circulation (ECC). However, the extent to which TEG levels are independently affected by ECC exposure remains unclear. To determine the effects of TEG levels in blood exposed to a membrane oxygenator, we performed in vitro experiments using whole human blood with ECC circuits including a membrane oxygenator.

Blood provided by healthy volunteers was heparinized and circulated in three types of experimental circuits: polymer-coating, heparin-coating (HC), or non-coating (NC) membrane oxygenators (five of each type). Thromboelastography tests using a global hemostasis assay were performed at 3, 6, 12, and 24 h of circulation in each experiment. During TEG, the sampled blood was reversed with 0.05 mg of protamine. One-way analysis of variance (ANOVA) and two-way repeated measures ANOVA were performed to evaluate trends in circulation duration and coating types, respectively.

Citrated kaolin with heparinase reaction times (CKHR) were significantly shortened at 6 and 12 h but prolonged at 24 h. The maximum amplitude for citrated kaolin with heparinase (CKHMA) was magnified from 6 to 12 h. Regarding the coating type, a significant difference was observed between HC and NC in CKHR at 6 h, but significance was not noted in other comparisons of coating types in CKHR and CKHMA.

Thromboelastography data indicated that the hemostatic capability of blood exposed to membrane surfaces was maintained after 12 h of circulation. The effects on TEG data in terms of coating type remain to be determined.