Effects of two injectable anesthetic agents on coagulation assays in the rat.

The rat is commonly used as an animal model to test the efficacy of new anticoagulant and antithrombotic drugs. Many of the protocols require the use of anesthetics for surgical procedures. Three common coagulation assays used to monitor the effects of new anticoagulant and antithrombotic drugs are thrombin time, activated partial thromboplastin time, and prothrombin time. We examined the effects of either urethane- or ketamine/xylazine-induced anesthesia on variables in the three coagulation assays with blood samples obtained from the rats before the induction of anesthesia, compared with samples obtained at 15 or 60 min after anesthesia induction. Statistically significant differences were observed in the ketamine/xylazine group for thrombin time at 60 min (compared with control values) and in the urethane group for activated partial thromboplastin time at 60 min (compared with control values). In both instances a prolongation of times was the effect seen. These results indicate that the choice of anesthetic affects the data in certain coagulation assays in the rat and must be taken into account when one is planning studies and analyzing results.