Whole-blood platelet aggregation, buccal mucosa bleeding time, and serum cephalothin concentration in dogs receiving a presurgical antibiotic protocol

Abstract

Summary Whole-blood platelet aggregation (using the impedance method) and adenosine triphosphate (atp) release, buccal mucosal bleeding time (bt), and serum cephalothin concentration were measured in 21 adult female Beagles before (pre) and 1 hour (1hr) after iv administration of cephalothin (22 mg/kg). A second injection of cephalothin (22 mg/kg) was given 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 after 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 and atp released from the aggregating platelets were measured within 1 hour of sample collection, using a whole-blood aggregometer. Adenosine diphosphate (ADP) and collagen were used as aggregating agents. Aggregation was measured over 6 minutes for each aggregating agent; atp release 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, with each dog as its own control. Bleeding time during the same period was 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 between bt for 1 hr and 4 hr samples. Median serum cephalothin concentrations in pre, 1 hr,4hr, and 6 hr samples did not correlate significantly to platelet aggregation, atp release, platelet count, or bt at any time during the study. Because serum cephalothin concentration was so low, and because there are few reports of the kinetics of cephalothin after iv administration, serum cephalothin was measured in 2 dogs over 2 hours after single iv administration of cephalothin. Values reached a peak at 2 minutes after drug administration, then decreased rapidly over 10 to 15 minutes, and were low by 2 hours.