A practical heparin reduction algorithm: execution and operational characteristics.

A limited pilot study has been made of a newly devised heparin reduction algorithm (HRA). This formulation is a derivative of the alternative surveillance plan known as the activated partial thromboplastin time after heparin removal (aPTT/HR) scheme. Unlike the traditional plan, the HRA is the first approach to provide information about the individual and collective pharmacological effects of heparin and coumarins when the drugs are administered simultaneously. In this feasibility study the HRA was used without incident in six patients every 24 h to calculate the trend of the evolving anticoagulant effect of coumarin. The computations provided by a laboratory based data management group permitted the clinician to titrate precisely the withdrawal of heparin in response to the daily fluctuations in coumarin effect. In this way, the activated partial thromboplastin time could always be maintained within the desired therapeutic interval. Three divergent patient experiences are presented to demonstrate the operational characteristics and responsiveness of the new HRA plan.

Trials of commercial reagents in anion-exchange coagulation procedures: ortho diagnostics.

The suitability of Ortho Diagnostics one-stage prothrombin time (PT) reagent (Ortho Brain Thromboplastin) and activated partial thromboplastin (aPTT) reagent (Activated Thrombofax) has been evaluated for use in conjunction with the anion-exchange heparin removal maneuver. The PT/HR and aPTT/HR are tests used to follow the anticoagulant influence of coumarins when heparin also is being administered. After establishing a coumarin therapeutic range for Activated Thrombofax, a parallel trial was conducted with Ortho Brain Thromboplastin on coumarin-treated patient plasmas. Determinations also were made after heparin (0.2 mu/mL) was added and then removed by ECTEOLA microchromatography columns. Ortho Brain Thromboplastin was found to induce a shortening bias associated with a spurious improvement in the precision of tests run on anion-exchange treated plasmas that potentially could result in coumarin overdosage. The systematic error did not appear to result either from protracted incubation or the activation of prekallikrein, high molecular weight kininogen, Factor XI or XII. This reagent was found to perform appropriately with plasma not exposed to ECTEOLA. Activated Thrombofax gave reliable and reproducible results before and after heparin removal. This aPTT reagent could be used in the aPTT/HR anticoagulant surveillance scheme.