Related Experiment Videos
Establishing an institution-specific therapeutic range for heparin
D F Volles1, C J Ancell, K A Michael
1Department of Pharmacy Services, University of Virginia Health System, Charlottesville 22906-0002, USA.
Summary
Pooled plasma spiked with heparin does not accurately reflect patient activated partial thromboplastin time (aPTT) ranges. Establishing institution-specific therapeutic aPTT ranges using patient samples is crucial for safe heparin monitoring.
Area of Science:
- Clinical Chemistry
- Pharmacology
- Hematology
Background:
- Accurate monitoring of unfractionated heparin (UFH) therapy is essential for patient safety.
- Activated partial thromboplastin time (aPTT) is commonly used to monitor UFH, but its correlation with heparin concentration can vary.
- The use of heparin-spiked pooled plasma for establishing therapeutic aPTT ranges is a common practice but its validity requires assessment.
Purpose of the Study:
- To compare the relationship between heparin concentration and aPTT in pooled plasma versus patient samples.
- To evaluate the feasibility of using heparin-spiked pooled plasma for determining therapeutic aPTT ranges.
- To establish accurate therapeutic aPTT ranges for intravenous UFH administration.
Main Methods:
- Blood samples were collected from 32 patients receiving intravenous UFH.
- Pooled normal plasma was spiked with UFH to achieve known concentrations (0-0.5 U/mL).
- Heparin concentrations (anti-Xa assay) and aPTT values were measured for both patient and pooled samples.
Main Results:
- Patient (ex vivo) samples showed a therapeutic aPTT range of 64-106 seconds (2.3-3.9 times normal) for heparin concentrations of 0.3-0.7 U/mL.
- Pooled (in vitro) samples yielded a significantly wider aPTT range of 121-256 seconds (4.4-9.4 times normal) for the same heparin concentrations.
- The traditional therapeutic range (1.5-2.5 times normal) was found to be inadequate based on patient data.
Conclusions:
- Heparin-spiked pooled plasma is not a reliable substitute for patient samples in establishing therapeutic aPTT ranges.
- Significant discrepancies exist between in vitro and ex vivo aPTT values, highlighting the need for patient-specific calibration.
- Each institution must establish its own therapeutic aPTT range by correlating aPTT values with measured heparin concentrations from actual patient samples.