Monitoring of the heparinization in the rabbit animal model during endovascular interventions.

INTRODUCTION: The purpose of this study was to monitor and to optimize heparinization during endovascular procedures in the New Zealand White Rabbit (NZWR) model.
METHODS: Right common carotid artery aneurysms were surgically created in 43 NZWR, with an average weight of 4,330 g (range 3,500-5,430 g). The activated partial thromboplastin time (aPTT) was measured during different stages of the interventional procedures. Blood samples were taken before and 10 min after administration of heparin and at the end of each endovascular procedure. We compared three different experimental groups: 100 U heparin, 500 U heparin and 100 U heparin plus pretreatment with aspirin and clopidogrel. The individual aPTT values were measured using a ball coagulometer.
RESULTS: The average baseline aPTT in the rabbit is 75.2 ± 18.9 s compared to a mean of 33 s (range 26-40 s) in humans. The dosages of heparin used achieved anticoagulation in all cases. Five hundred units of heparin increased the aPTT significantly more than 100 U. No difference was found between the aPTT obtained from the 100 U and the 100 U plus pretreatment group, as aspirin and clopidogrel do not affect the coagulation cascade.
CONCLUSION: One hundred units of heparin can achieve anticoagulation in a similar magnitude as needed in interventional procedures in humans. This fact enhances suitability of the rabbit animal model for the testing of intravascular devices.