WHOLE-BLOOD PLATELET-AGGREGATION, BUCCAL MUCOSA BLEEDING-TIME, AND SERUM CEPHALOTHIN CONCENTRATION IN DOGS RECEIVING A PRESURGICAL ANTIBIOTIC PROTOCOL

Whole-blood platelet aggregation (using the impedance method) and aden osine triphosphate (ATP) release, buccal mucosal bleeding time (BT), a nd serum cephalothin concentration were measured in 21 adult female Be agles before (PRE) and 1 hour (1 HR) after IV administration of cephal othin (22 mg/kg). A second injection of cephalothin (22 mg/kg) was giv en 3 hours after the first, and blood samples were obtained 1 hour (4 HR, 4 hours after the first injection) and 3 hours (6 HR, 6 hours afte r the first injection) after the second injection. Samples of jugular blood were obtained from each dog, using citrate as an anticoagulant. A platelet count was obtained for each sample. Platelet aggregation an d Am released from the aggregating platelets were measured within 1 ho ur of sample collection, using a whole-blood aggregometer. Adenosine d iphosphate (ADP) and collagen were used as aggregating agents. Aggrega tion was measured over 6 minutes for each aggregating agent; Am releas e in response to collagen, but not to ADP, was measured over the same period. For 1 HR samples, there was a significant (P < 0.01) reduction from PRE values in the ability of platelets to aggregate in response to ADP. Bleeding time was determined, using a published procedure, wit h each dog as its own control. Bleeding time during the same period wa s found to be significantly increased over PRE values for 1 HR (P < 0. 01) and 6 HR (P < 0.02) samples. There was no significant difference b etween BT for 1 HR and 4 HR samples. Median serum cephalothin concentr ations in PRE, 1 HR, 4 HR, and 6 HR samples did not correlate signific antly to platelet aggregation, An release, platelet count, or BT at an y time during the study. Because serum cephalothin concentration was s o low, and because there are few reports of the kinetics of cephalothi n after IV administration, serum cephalothin was measured in 2 dogs ov er 2 hours after single IV administration of cephalothin. Values reach ed a peak at 2 minutes after drug administration, then decreased rapid ly over 10 to 15 minutes, and were low by 2 hours.