Use of thromboelastography in dogs with immune-mediated hemolytic anemia: 39 cases (2000-2008)

Objective To analyze thromboelastograms (TEGs) of naturally occurring cases of immune-mediated hemolytic anemia (IMHA) in order to identify whether a hypercoagulable state was present and whether its presence was associated with differences in survival. Design Retrospective study spanning January 2000 to June 2008. Medical records of dogs were evaluated. Endpoints were considered death or discharge from the hospital. Setting Academic teaching hospital. Animals Thirty-nine dogs with a diagnosis of IMHA and at least one TEG performed during hospitalization were included. Interventions None. Measurements and Main Results Four values were evaluated from the TEG: the R time (R), K time (K), alpha angle (alpha), and maximum amplitude. From these values, a coagulation index (CI) was calculated to classify patients as normocoagulable, hypercoagulable, or hypocoagulable. Thirty-three of 39 patients were hypercoagulable based on the CI. The 6 remaining dogs were normocoagulable. The patients with a normocoagulable CI had an increased mortality rate (100%) when compared with the hypercoagulable patients using Fisher's exact test (P=0.02). Additionally, prolongation of partial thromboplastin time did not preclude hypercoagulable TEG values. Conclusions The majority of dogs with IMHA were hypercoagulable as measured by TEG. A normal CI was associated with a worse outcome in this patient population. TEG may provide additional and complementary information to prothrombin time and partial thromboplastin time relating to coagulation status in dogs with IMHA and may help predict prognosis and potentially guide clinical decisions to utilize anticoagulant drugs.