Pharmacokinetics of ketamine following a short intravenous infusion to isoflurane-anesthetized New Zealand White rabbits (Oryctolagus cuniculus).

OBJECTIVE: To describe the pharmacokinetics of ketamine following a short intravenous (IV) infusion to isoflurane-anesthetized rabbits. STUDY DESIGN: Prospective experimental study. ANIMALS: A total of six adult healthy female New Zealand White rabbits. METHODS: Anesthesia was induced with isoflurane in oxygen. Following determination of isoflurane minimum alveolar concentration (MAC), the isoflurane concentration was reduced to 0.75 MAC and ketamine hydrochloride (5 mg kg-1) was administered IV over 5 minutes. Blood samples were collected before and at 2, 5, 6, 7, 8, 9, 13, 17, 21, 35, 65, 125, 215 and 305 minutes after initiating the ketamine infusion. Samples were processed immediately and the plasma separated and stored at -80 °C until analyzed for ketamine and norketamine concentrations using liquid chromatography-mass spectrometry. Compartment models were fitted to the concentration-time data for ketamine and for ketamine plus norketamine using nonlinear mixed-effects (population) modeling. RESULTS: A three- and five-compartment model best fitted the plasma concentration-time data for ketamine and for ketamine plus norketamine, respectively. For the ketamine only model, the volume of distribution at steady state (Vss) was 3217 mL kg-1, metabolic clearance was 88 mL minute-1 kg-1 and the terminal half-life was 59 minutes. For the model including both ketamine and norketamine, Vss were 3224 and 2073 mL kg-1, total metabolic clearance was 107 and 52 mL minute-1 kg-1 and terminal half-lives were 52 and 55 minutes for the parent drug and its metabolite, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: This study characterized the pharmacokinetics of ketamine and norketamine in isoflurane-anesthetized New Zealand White rabbits following short IV infusion. The results obtained herein will be useful to determine ketamine infusion regimens in isoflurane-anesthetized rabbits.

A retrospective study of anesthesia for subcutaneous ureteral bypass placement in cats: 27 cases.

The goals of this retrospective clinical case series study were to describe the management of anesthesia, and to report perioperative complications in cats undergoing subcutaneous ureteral bypass (SUB) placement due to ureteral obstruction. Medical records of client-owned cats with ureteral obstruction and anesthetized for SUB placement between 2012 and 2015 in a veterinary teaching hospital were reviewed. Twenty-seven cases were identified. Duration of anesthesia and surgery (mean ± standard deviation) were 215 ± 42 min and 148 ± 36 min, respectively. Hypothermia was the most common intraoperative complication. Hypotension, hypocapnia, hypertension and bradycardia were also frequently observed. Out of 22 cats who experienced intraoperative hypotension, 17 received inotropes and vasopressors. There was a significant decrease in creatinine (P=0.008) and total solids (P=0.007) after SUB placement when compared with baseline values. Postoperative complications included pain, anorexia, nausea, hypertension, and urinary tract-related problems. No death occurred in the postoperative period. Successful management of anesthesia for SUB placement involves rigorous anesthetic monitoring and immediate treatment of complications. Perioperative complications appear to be common. This study could not identify risk factors associated with this procedure.