Rotem sigma

ROTEM Sigma (Werfen UK) is a viscoelastic point of care test with a fully automated system containing a sample handler and cartridge that uses whole blood to measure coagulation [27 (link)]. All tests were analysed for 60 minutes and within 4 hours of sample collection. Reference ranges were obtained from healthy volunteer data (n = 26) previously collected.
Data from three ROTEM channels are presented, FIBTEM, INTEM and EXTEM. FIBTEM uses cytochalasin D to inhibit platelet activity and provide a clot tracing that reflects the presence of fibrinogen. It provides information on fibrin formation and polymerisation without platelet contribution [28 (link)]. In EXTEM tissue factor is used to initiate the extrinsic clotting cascade. The INTEM test uses ellagic acid to initiate clotting via the intrinsic pathway. The EXTEM and INTEM tests provide information on the extrinsic and intrinsic pathways respectively. The viscoelastic characteristics of the clot are measured from clot formation to lysis and include clotting time (CT), clot formation time (CFT), maximum clot firmess (MCF), A5-A30 (measure of clot firmess from 5–30 minutes) and maximum lysis (ML) which is the degree of fibrinolysis relative to MCF achieved during measurement and is reported as percentage of clot firmness lost [29 (link)]. A shortened CFT with an increased MCF is indicative of a hypercoagulable state.

Transfusion management was the same at both institutions and was in concordance with Extracorporeal Life Support Organisation (ELSO) guidelines. The transfusion thresholds were haemoglobin ≤ 70 g/L, platelet < 50 × 10⁹/L and fibrinogen < 1 g/L⁹. If there was no clinically significant bleeding, lower platelet counts and fibrinogen levels were accepted by treating intensivists. Viscoelastic coagulation testing (ROTEM Sigma, Werfen, Barcelona, Spain, in Cambridge; TEG 6, Haemonetics, Boston, MA, USA, in Manchester) was used alongside laboratory values to guide transfusion requirements.