A prospective study of thromboelastography (TEG) and filter life during continuous veno-venous hemofiltration

Anticoagulants are commonly used to prolong circuit life during continuous hemofiltration. However, a clear correlation between routinely performed bl ood coagulability tests and circuit life has not been demonstrated. This la ck of correlation may derive from the limited ability of such tests to desc ribe the likelihood of in vivo clotting. We hypothesized that thromboelasto graphy (TEG), which derives its variables from a closer reproduction of in vivo coagulation, would significantly correlate with filter life. According ly, we conducted a prospective pilot study of the correlation between filte r life and TEG-derived variables in 21 hemofilters used in 6 critically ill patients admitted to a tertiary intensive care unit. It involved the perfo rmance of TEG during steady state anticoagulation, measurement of circuit l ife, and of routine coagulation variables. The results showed that the mean circuit life was 20.7 +/ -4.0 h despite an average aPTT of 67.7 +/- 12.8 s and a mean heparin dose of 472.5 +/- 96.2 IU / h. The mean INR was 1.4 +/- 1 and the mean platelet count was 118 +/- 16 x 10(3) / mm(3). Although sev eral TEG variables correlated with heparin dose (p < 0.03), no correlation was found between ally of the routine coagulation variables or any of the T EG variables and circuit life. In conclusion, no significant correlation be tween TEG derived variables or routinely measured coagulation variables and circuit life could be demonstrated. These findings suggest that such tests are not useful indicators of circuit anticoagulation adequacy and that Fac tors other than blood coagulability may play a role ill circuit failure.