MONITORING OF HIGH-DOSE INTRAVENOUS HEPARIN-THERAPY - A CONTRIBUTION TO THE SAFETY OF HEPARIN MONITORING

Whenever unfractionated heparin (UFH) is administered i.v. in therapeu tic doses, therapeutic drug monitoring of the anticoagulant response s hould be mandatory and the dose should be adjusted accordingly. UFH th erapy is usually monitored by the activated partial thromboplastin tim e (APTT). A 1.5- to 2.5-fold prolongation of APTT has become generally accepted as an indicator of effective i.v. anticoagulation, but it ha s become common to recommend this ratio without testing the APTT reage nts used for their heparin sensitivity and for their actual therapeuti c APTT ratio (actual APTT: normal control APTT). Internal heparin sens itivity testing of APTT reagents is managed using heparin sensitivity curves obtained from heparin-spiked normal plasma pool. The most commo n APTT reagents in Austria and a newly developed double activated APTT reagent were tested for their heparin sensitivity and therapeutic rat ios on different automated analyzers, depending on their optical and c hemical conditions. Also, newly developed, commercially prepared hepar in standards (0.19, 0.52, 0.86 IU heparin/ml plasma) were tested. APTT reagents differ in their heparin sensitivity and therapeutic ratio; v ariations in heparin sensitivity are also seen between different analy zers. Therefore, therapeutic ratio should regularly be checked and the literature should always state which APTT reagent was used on which i nstrument.