Usefulness of thrombelastography for dosage monitoring of low molecular weight heparin and unfractionated heparin during hemodialysis.

Low molecular weight heparin (LMH) acts as an anticoagulation agent mainly through its anti-activated coagulation factor X (Xa) activity. Thrombelastography (TEG) is expected to be useful to monitor the dosage of LMH during hemodialysis because reaction time on TEG (TEG-r) is considered to reflect blood thromboplastin formation time, which depends on the formation of Xa. To test this possibility, we compared the usefulness of TEG, activated coagulation time (ACT), activated partial thromboplastin time (APTT), and anti-Xa activity in 28 hemodialysis patients using both conventional unfractionated heparin (UFH) and LMH on separate dialysis procedures. Anti-Xa activity of LMH was comparable to that of UFH when it was measured using both LMH and UFH as standards. Anti-Xa activity, which theoretically depended on the heparin concentration in blood samples, did not correlate with the degree of dialyzer clotting. The APTT correlated well with anti-Xa activity in patients using LMH (r = 0.686, p less than 0.01) and UFH (r = 0.906, p less than 0.01), but not with the degree of dialyzer clotting. The TEG-r correlated well with the degree of dialyzer clotting both in patients using LMH and those using UFH (measurements of samples obtained from the venous side of the extracorporeal circuit) and weakly correlated with anti-Xa activity in patients using LMH (r = 0.402, p less than 0.05). The ACT did not correlate with the degree of dialyzer clotting or anti-Xa activity. These results suggest that TEG-r reflects the efficacy of heparin in the extra-corporeal blood circuit, whereas APTT mainly reflects heparin concentration of the blood samples.(ABSTRACT TRUNCATED AT 250 WORDS)