Coagulation Monitoring During Extracorporeal Membrane Oxygenation: The Role of Thrombelastography

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.

Comparison of Routine Laboratory Measures of Heparin Anticoagulation for Neonates on Extracorporeal Membrane Oxygenation

“…TEG and ROTEM provide information about anticoagulation, thrombosis, platelet function, and fibrinolysis and can assist in decision-making with respect to both heparin infusion rate and administration of blood products or coagulation factors. This assay is poorly studied in the ECMO population and rarely used with nearly 60% of ECMO programs reporting that they never obtain TEG in their patients (2,19). However, TEG and ROTEM may be useful adjuncts for managing anticoagulation in patients in ECMO and warrant further investigation.…”

Thromboelastography in the Perioperative Period: A Literature Review

“…Also, the TEG flat line reading had no relation to the perioperative bleeding [ 210 ]. However, other studies showed that the conventional TEG parameters were effective to monitor anticoagulation [ 211 ] and to predict coagulopathy in adults on ECMO patients [ 212 ].…”

Hemostatic Management in Extracorporeal Membrane Oxygenation

“…The 2 most common viscoelastic monitoring techniques are TEG and ROTEM. 58,59 These techniques are performed differently but result in similar information that has been most widely used in transfusion medicine.…”

“…The main categories that are most discussed for viscoelastic monitoring are phase 1: time to initial fibrin/clot formation; phase 2: rate of clot formation; phase 3: maximal clot strength; and phase 4: lysis (Table 3). 59,60 Finally, another potential benefit of this monitoring strategy is the addition of enzymes that eliminate heparin (ie, heparinase). This allows the team to simultaneously monitor the effects of heparin on the viscoelastic laboratory test result and the patient's underlying coagulopathy.…”

“…There are some limitations around the sensitivity for these tests to detect depletion of vitamin K-dependent factors, and results can vary depending on the activator used and the existence of citrate in the collection tube. [59][60][61] This monitoring strategy is more expensive, can be less timely than other laboratory monitoring, and more education is required for proper interpretation. This holistic coagulation monitoring strategy is one that with further research could be used more routinely in practice.…”