Point-of-Care Viscoelastic Testing
- Author: M. Wells
- Full Title: Point-of-Care Viscoelastic Testing
- Category: #books
Highlights
- Activation of coagulation in vivo occurs on cells that express tissue factor and involves a dynamic, interactive network of processes. This model has four stages; initiation, amplification, propagation and stabilisation (Page 1)
- Clinically relevant deviations of ‘normal clotting’ can affect the time taken to form a clot, the dynamics and maximal strength of the clot, and finally its appropriate and controlled dissolution (Page 1)
- Standard VETs are generally insensitive to most antiplatelet drugs. However, the TEG platelet mapping (TEGPM) assay provides a method for testing the degree of platelet inhibition (Page 4)
- Small-scale studies have suggested that VETs can be used to identify the presence of DOACs and guide their reversal.5 Findings include prolonged clot formation, with higher permeability and susceptibility to lysis.6 However, findings are non-specific and cannot differentiate the type of DOAC. (Page 5)
- Normal VET results confer a high negative predictive value for transfusion need.16 Reduced clot strength with lysis >3% on TEG can be used as an indicator of increased risk of transfusion. (Page 6)
- During acute bleeding, VETs can facilitate timely, individualised use of blood products; enable real-time assessment of response to therapy; differentiate between surgical bleeding and coagulopathy, most commonly hypofibrinogenaemia; and avoid overcorrection with clotting products. (Page 6)
- At term, the coagulation system is in a procoagulant state: normal ranges for TEG and ROTEM variables differ from non-pregnant values (Page 6)
- Viscoelastic testing is increasingly being used as part of the treatment algorithms for the management of PPH. Hypofibrinogenaemia is the most common abnormality, and there is evidence to suggest that a FIBTEM A5 <12 mm (ROTEM) with ongoing bleeding or FIBTEM A5 <7 mm may warrant fibrinogen replacement.20 Conversely, a patient with a FIBTEM A5 >12 mm is unlikely to benefit from this therapy (Page 6)
- Viscoelastic tests are insensitive to mildemoderate fibrinolysis; thus they should not be used to withhold antifibrinolytic therapy (Page 7)
- Viscoelastic testing remains inferior to the gold standard test of light transmission aggregometry for platelet function analysis, and are insensitive to the nuances of platelet function defects. They are also insensitive for vWF and the anticoagulant protein C system (Page 7)