Summary
Bolus injections of beef-lung heparin at doses of 50, 100 and 200 u/kg body weight
were administered to mongrel dogs. Neutralization of the anticoagulant effect was
evaluated using sequential samples withdrawn from the animals (in vivo samples) and aliquots from a 100 ml sample withdrawn from the dog at 30 minutes post-injection
(in vitro samples). Tests of the activated partial thromboplastin time (APTT) and prothrombin
time (PT) did not indicate the degree of anticoagulation. Tests of the whole blood
clotting time (WBCT), celite- activated whole blood clotting time (ACT), and celite-activated
thromboelastography (ATEG) indicated pronounced hypocoagulability immediately after
the injection, followed by a fairly rapid decay in anticoagulability, and a slight
Ziype/coagulability at three to four hours post injection. The results from the in vitro ATEG samples were essentially identical to those on the in vivo samples, whereas
the in vitro WBCT and ACT generally indicated higher degrees of anticoagulation. Calculated half-lives
of the anticoagulant effect are significantly shorter than previously reported, being
18 to 36 minutes, and slightly dose dependent. The decay of the effects, however,
does not appear to follow a single exponential curve, dropping very rapidly immediately
post-injection and at a somewhat slower rate 60 or more minutes post-injection.
