Original Article

Coagulation Monitoring During Extracorporeal Membrane Oxygenation: The Role of Thrombelastography

Division of Clinical Perfusion Education, School of Allied Health Professions, University of Nebraska Medical Center, Omaha, NE

^* Address correspondence to: Alfred H. Stammers, MSA, CCP, Division of Clinical Perfusion Education, University of Nebraska Medical Center, 600 South 42nd Street, Swanson Hall, Room 3019, Omaha, NE 68198-5155

Abstract

Patients undergoing extracorporeal membrane oxygenation (ECMO) are at an increased risk for developing coagulopathies due to the adverse effects of extracorporeal circulation on the hemostatic mechanism. Methods of determining causative factors of bleeding diathesis are often inconsistent and non-specific. ECMO patients require aggressive transfusion therapy with autogenic blood products to stabilize and maintain hemostasis. The present study evaluated the coagulation status of newborn patients undergoing ECMO therapy, using a viscoelastic monitor (Thrombelastograph -TEG) that measures functional aspects of clot development and stabilization.

Seventeen neonatal patients undergoing ECMO for severe respiratory dysfunction were entered into this study. Serial blood samples were obtained and routine coagulation assessment including fibrinogen concentration, platelet count and ionized calcium was performed. In addition, fibrin ( ogen) degradation products (FDP), d-Dimers, antithrombin III and plasma free hemoglobin were measured. Transfusion indicators were established and total transfusion requirements recorded. TEG profiles were determined with the use of heparinase, an enzyme that degrades heparin but has little effect on other coagulation factors.

The most commonly encountered complication was hemorrhaging which was diagnosed by laboratory and clinical assessment in 11 of 17 patients. Transfusion requirements (measured in ml/kg/ECMO hour) were the following: packed red blood cells - 1.34±0.5; platelets - 0.71 ±o.57; fresh frozen plasma- 0.09±0.12; cryoprecipitate 0.05 ±o.05. Thrombelastograph profiles reflected hemostatic conditions that ranged from severe coagulopathies (DIC) to hypercoagulability. Interpretation of TEG profiles identified hemostatic abnormalities in 57 of 101 profiles ( 46.5% ), with the most common etiology related to platelet dysfunction. In the non-hemorrhagic group the TEG profiles were normal in 30 of 41 (73.2%) instances, while the hemorrhagic group had 24 of60 (40%) profiles in the normal range (p<.001). d-Dimers and FDP were elevated in all patients during ECMO despite maintenance of activated clotting times greater than 180 seconds.

During ECMO coagulation assessment with the TEG provides useful information for the rapid diagnosis of hemorrhagic conditions, which may help guide transfusion therapy.