TITLE: MONITORING THE ANTICOAGULATION EFFECTS OF LOW-MOLECULAR-WEIGHT HEPARIN (LMWH) USING THROMBOELASTOGRAPHY (TEG) AND SONOCLOT (SNC)-IN VITRO STUDY

AUTHORS: Alexandru Gottlieb, MD, Juraj Sprung, MD PhD, Mark F. Banoub, Boris Mraovic, MD
AFFILIATION: Cleveland Clinic Foundation, Cleveland, OH.

Low-molecular weight heparin (LMWH) is an alternative to unfractionated heparin to prevent deep venous thrombosis. However, its use may be associated with occurrence of spinal hematoma during regional anesthesia, therefore, anticoagulation must be closely monitored. But, the anticoagulation effect of LMWH can not be monitored by "conventional" methods. Our objectives were to quantify the effect of LMWH in vitro with TEG and SNC. After informed consent, we drew 10ml blood from 18 surgical patients. The samples were mixed with sodium citrate at 9:1 ratio. The LMWH (Lovenox^®) was diluted in 0.9% saline solution and added to each blood sample to obtain final concentrations of 0.1, 0.2, and 0.3 U/ml. Saline 0.9% solution was used as a control. Before each test, the sample was recalcified with of 0.2M CaCl². The TEG markers for measurement of coagulation [r (mm); k (mm); "alpha" (^o) and MA (mm)] and the SNC markers [ACT (Sec) and Clot Rate (^o)], were determined for each of the above LMWH concentrations. Statistical analysis was performed using ANOVA with Bonferroni's adjustment, differences were considered statistically significant at P<0.05. As the LMWH concentration increased, the TEG parameters r and k increased (P<0.0001) and "alpha" decreased significantly (P<0.0001), while the SNC markers; SNC-Act increased and Clot Rate decreased (table). Our results indicate that TEG and SNC reproducibly reflects the anticoagulation effects of LMWH, which may be useful for the assessment of coagulation in patients with neuraxial block. However, because of significant variability in both TEG and SNC among different individuals, additional studies are necessary to perform precise quantification.

anti-Xa activity; ‡P <0.05 vs. control; ^*P <0.05 vs. preceding value; ^**p<0.05 vs. control.