title: Thrombelastography monitoring of resistance to enoxaparin anticoagulation in thrombophilic pregnancy patients.
abstract: The anticoagulant effect of enoxaparin is readily observed by Thrombelastography (TEG), particularly on the reaction time (R) to form a clot, and is completely reversed by heparinase. In this study, recalcified citrated whole blood with heparinase (CNHR) and without (CNR), along with TEG R time, was used to derive a delta R (CNR-CNHR). This delta R (DeltaR) was then used to measure enoxaparin anticoagulation, which was correlated by linear regression (r(2)=0.806) with plasma anti-Xa in 48 thrombophilic pregnancy patients. In a follow up study whole blood from 15 thrombophilic and 15 normal pregnancy subjects was titrated ex vivo with enoxaparin and TEG DeltaR determined. Linear dose responses (all r(2)>0.9) of DeltaR versus plasma enoxaparin concentration were obtained for each subject. A large variation in slope was observed for both thrombophilic (>7 fold, 217 to 1,588 s DeltaR/unit anti-Xa) and normal (>3 fold, 788 to 2,758) pregnancy subjects. The average slope for the thrombophilic group (710 s DeltaR/unit anti-Xa) was significantly (P=0.002) lower than the normal pregnancy group (1,354 s), indicating resistance to enoxaparin anticoagulation in the thrombophilic group. This technique may help gauge the appropriate dose of enoxaparin for each individual, check for residual anticoagulation before invasive procedures, and perhaps help screen for thrombophilic subjects.
authors.affiliation: Department of Anesthesiology, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, TN 37920, United States. RCCarrol@mc.utmck.edu
authors.forename: Roger C
authors.initials: RC
authors.lastname: Carroll
authors.forename: Robert M
authors.initials: RM
authors.lastname: Craft
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Whitaker
authors.forename: Carolyn C
authors.initials: CC
authors.lastname: Snider
authors.forename: Ryan K
authors.initials: RK
authors.lastname: Kirby
authors.forename: Robert F
authors.initials: RF
authors.lastname: Elder
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hennessey
mesh_terms: D000925:Anticoagulants / Q000097:blood / Q000627:therapeutic use*; D001777:Blood Coagulation / Q000187:drug effects*; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D017984:Enoxaparin / Q000097:blood / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D016014:Linear Models; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D013916:Thrombelastography / Q000379:methods*; D013923:Thromboembolism / Q000175:diagnosis / Q000628:therapy
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin