Table 2 Conventional anticoagulation monitoring methods
From: Current and future strategies to monitor and manage coagulation in ECMO patients
Method | Sample type | Advantages | Disadvantages | Purpose | Desired range | Ref |
|---|---|---|---|---|---|---|
aPTT | Plasma | ● Widely available ● Well known method ● Easy to interpret ● Not affected by platelet count | ● Nonspecific to heparin ● Time-consuming and user-dependent ● Can be affected by various parameters, such as drugs, hematocrit, abnormalities in coagulation factors, fibrinogen, high C-reactive protein ● Extended clotting time in the presence of lupus anticoagulant | To monitor anticoagulant effect | 25–90 s or 1.5–2.5 times baseline (depending on the device, anticoagulant, and utilized method) | [70] |
Anti-factor Xa assay | Plasma | ● Sensitive to UFH ● Independent of coagulopathy, thrombocytopenia, or dilution ● Correlates better than ACT and aPTT with heparin concentration | ● Affected by hyperlipidemia and hyperbilirubinemia, haemolysis, lipaemia, AT, and high plasma-free haemoglobin ● Not easily accessible ● Costly ● Time-consuming ● Only measures inhibition while not showing the amount of fibrin and thrombin generated | To monitor anticoagulant effect | 0.3–0.7 IU/mL | [71] |
ACT | Whole blood | ● Point-of-care test ● Low cost and fast ● Simple operation ● Better correlate with high concentrations of heparin Small sample volume | ● User and instrument dependent results ● Lack of specificity Sensitive to various parameters including platelet dysfunction, platelet inhibitors (e.g., GP IIb/IIIa), temperature, haematocrit, blood thrombocyte activity, haemodilution, anemia, hypothermia, coagulation factors deficiencies, hypofibrinogenemia, fibrinogen, thrombocytopenia, AT level, oral coagulants, and activator type | To assess anticoagulant effect | 180–220 s | [72] |
D-dimer | Whole blood or plasma | ● Prognostic value for oxygenator failure ● High sensitivity | ● Time-consuming ● Relatively expensive ● Moderate specificity | To monitor fibrin formation and fibrinolysis in the circuit and patient’s body | 0.28–1 mg/L | [73] |
PT/INR | Plasma | ● Indicator of various factors including factors I, II, V, VII, and X | ● Interfere with DTIs ● Deficits in common factors I, II, V, and X can prolong PT | To assess underlying coagulability and to monitor Vitamin K antagonists | < 1.5 for heparin-treated patients, > 2–3 for other anticoagulants | [74] |
ECT | Plasma | ● Simple operation ● Not sensitive to heparin | ● Rely on both prothrombin and fibrinogen ● Lack of standardization and uniformity ● Results affected by DTIs | To monitor the effect of DTIs | 300–500 s | [75] |
Viscoelastic tests (ROTEM/TEG) | Whole blood | ● Point-of-care test ● Distinguishing clotting factor deficiency, platelet dysfunction, and hyperfibrinolysis | ● Poor specificity ● Low sensitivity to hyperfibrinolysis ● Sensitive to vibration ● Extended clotting time in the presence of lupus anticoagulant ● Lack of standardization and uniformity | To assess clotting time (anticoagulant effect), thrombocytopenia, hypofibrinogenemia, and fibrinolysis | Not established |