ABSTRACT
In addition to heparin, the standard medication for prophylaxis and therapy of thromboembolism,
several other substances have been developed and tested for clinical use with the
aim of decreasing or eliminating side effects. Most of all, hirudin, a direct antithrombin
(AT), has proved to be effective. To define the therapeutic range and to avoid underdosage
or overdosage, clinical monitoring is necessary. For monitoring of hirudin, thrombin
time (TT) is not suited because of the missing linearity of the standard curve. Activated
partial thromboplastin time (aPTT) can be used only in the lower hirudin level range,
where the standard curve is quite linear. However, high and toxic hirudin levels cannot
be determined using aPTT. Another drawback is a high variation in single measurements
and in the normal value of patients. Methods using chromogenic substrates are suited
for determination of hirudin in plasma but cannot be used at bedside. Especially for
monitoring of hirudin, the ecarin clotting time (ECT) was developed. The standard
curve is linear over the entire concentration range. There are no influences by other
coagulation parameters or anticoagulants. For both acute clinical situations and long-term
monitoring, this method capable of point-of-care therapy (POCT) will be the method
of choice.
KEYWORD
Hirudin - ecarin clotting time - aPTT - thromboembolism