Viscoelastic haemostatic assay

Conventional coagulation tests were not developed to be used as overall markers of hemostasis, and only provide information on the time for clot initiation in plasma and NOT on dynamics and strength in whole blood.

Evidence in trauma, PPH, liver transplant, cardiac surgery

ROTEM

Rotational thromboelastometry (ROTEM, TEM International, Munich, Germany) utilizes a fixed cuvette and a rotating pin to initiate clotting

The ROTEM sigma device is fully automated, while the delta device requires trained operators to pipette blood samples

The EXTEM test activates the extrinsic pathway using tissue thromboplastin with the clot time (CT) reflecting the time taken for clot formation to begin, and therefore the velocity of thrombin generation

The amplitude of the EXTEM trace is dependent on both platelets and fibrinogen and is reported at 5 and 10 minutes, as well as at maximum firmness

The addition of cytochalasin D, a potent platelet inhibitor, to the FIBTEM test isolates the contribution of fibrinogen to clot strength

The INTEM test utilizes ellagic acid and phospholipids to initiate clot formation and reflects the intrinsic pathway

The APTEM assay incorporates a plasmin inhibitor to allow evaluation of fibrinolytic activity

TEG

The manually operated TEG 5000 initiates clot formation with an oscillating cup around pin

automated TEG6S device utilizes pre-filled cartridges and a resonance technique, vibrating the sample and measuring clot formation with an LED system

Tissue factor and kaolin stimulate the intrinsic and extrinsic pathway in the Rapid TEG assay with the kaolin assay alone reflecting the intrinsic pathway

The addition of abciximab (a platelet inhibitor) allows isolation of fibrinogen contribution to clot strength

References

Point-of-Care Viscoelastic Testing

Viscoelastic testing: an illustrated review of technology and clinical applications - PMC