Monitoring of unfractionated heparin in antiphospholipid syndrome patients
| Regular laboratory monitoring of IV UFH is essential due to pharmacokinetic unpredictability. | |||||
Platelet count monitoring is indicated in all patients receiving UFH due to the increased risk of HIT:
| |||||
| Monitoring test . | Dose . | Target range . | Points to note . | ||
|---|---|---|---|---|---|
| Chromogenic anti-Xa assay | IV bolus of UFH 5000 units/75 units/kg (10 000 units for severe PE), then 15-25 units/kg/hour, by continuous IV infusion, dose adjusted | 0.3-0.7 IU/mL36 | • Use anti-Xa assay when baseline aPTT prolonged (eg, due to LA effect) • Anti-Xa preferred as first line assay for UFH monitoring in APS patients, as it is unaffected by LA or acute phase reactants (unlike aPTT) • In CAPS patients in the acute situation, anti-Xa is appropriate for UFH monitoring and may aid interpretation of concomitant aPTT • The anti-Xa assay should be standardized versus the international standard for UFH • Limitations of anti-Xa assays include: not universally available, suboptimal reproducibility and interlaboratory variation | ||
| aPTT | aPTT therapeutic range corresponding to UFH levels of 0.3 to 0.7 IU/mL anti-Xa activity36 | • For UFH monitoring by aPTT, a relatively LA-insensitive aPTT reagent is required • Avoid use of aPTT for monitoring UFH if baseline aPTT is prolonged • The aPTT may be unreliable in the acute phase situation (eg, CAPS: factor VIII may shorten aPTT; CRP may prolong aPTT; anti-Xa assay is uninfluenced by these factors) • aPTT therapeutic range should be locally adapted to the responsiveness of the reagent and coagulometer used | |||
| ACT | In non-APS patients undergoing CPB, generally a dose of UFH of ~300-400 IU/kg is administered prior to CPB with additional boluses given as required | • In non-APS patients: ACT in a non-anticoagulated patient is ~107 s ± 13 s • During CPB, UFH is titrated to maintain an ACT of 400-600 s | • The ACT is widely used to monitor UFH during CPB • The ACT is a phospholipid-dependent test and may be prolonged by LA • Reported modifications for use in patients with APS: ○ target clotting time twice the baseline ACT ○ measure heparin concentrations by automated protamine titration device ○ use patient-specific heparin-ACT titration curves (preoperative in vitro derived) ○ ACT coupled with thromboelastography | ||
| Regular laboratory monitoring of IV UFH is essential due to pharmacokinetic unpredictability. | |||||
Platelet count monitoring is indicated in all patients receiving UFH due to the increased risk of HIT:
| |||||
| Monitoring test . | Dose . | Target range . | Points to note . | ||
|---|---|---|---|---|---|
| Chromogenic anti-Xa assay | IV bolus of UFH 5000 units/75 units/kg (10 000 units for severe PE), then 15-25 units/kg/hour, by continuous IV infusion, dose adjusted | 0.3-0.7 IU/mL36 | • Use anti-Xa assay when baseline aPTT prolonged (eg, due to LA effect) • Anti-Xa preferred as first line assay for UFH monitoring in APS patients, as it is unaffected by LA or acute phase reactants (unlike aPTT) • In CAPS patients in the acute situation, anti-Xa is appropriate for UFH monitoring and may aid interpretation of concomitant aPTT • The anti-Xa assay should be standardized versus the international standard for UFH • Limitations of anti-Xa assays include: not universally available, suboptimal reproducibility and interlaboratory variation | ||
| aPTT | aPTT therapeutic range corresponding to UFH levels of 0.3 to 0.7 IU/mL anti-Xa activity36 | • For UFH monitoring by aPTT, a relatively LA-insensitive aPTT reagent is required • Avoid use of aPTT for monitoring UFH if baseline aPTT is prolonged • The aPTT may be unreliable in the acute phase situation (eg, CAPS: factor VIII may shorten aPTT; CRP may prolong aPTT; anti-Xa assay is uninfluenced by these factors) • aPTT therapeutic range should be locally adapted to the responsiveness of the reagent and coagulometer used | |||
| ACT | In non-APS patients undergoing CPB, generally a dose of UFH of ~300-400 IU/kg is administered prior to CPB with additional boluses given as required | • In non-APS patients: ACT in a non-anticoagulated patient is ~107 s ± 13 s • During CPB, UFH is titrated to maintain an ACT of 400-600 s | • The ACT is widely used to monitor UFH during CPB • The ACT is a phospholipid-dependent test and may be prolonged by LA • Reported modifications for use in patients with APS: ○ target clotting time twice the baseline ACT ○ measure heparin concentrations by automated protamine titration device ○ use patient-specific heparin-ACT titration curves (preoperative in vitro derived) ○ ACT coupled with thromboelastography | ||
Adapted from Table 3 in Cohen et al.52