Comparison of Intrarenal and Intravenous Injections of Sodium Pentobarbital for Euthanasia in New Zealand White Rabbits (Oryctolagus cuniculus)

Peripheral venous access in rabbits can be difficult to obtain. When failure occurs, there is a dire need for alternative vascular access routes to be available. The AVMA categorizes intrarenal injection of pentobarbital as acceptable with conditions for euthanasia. Animals must be in an unconscious state, and only minimal studies using intrarenal administration have been reported. A total of 53 rabbits were used to conduct 3 separate analyses to assess and measure the efficacy, efficiency, and validity of the intrarenal route for euthanasia in New Zealand White rabbits by assessing the time to cardiopulmonary arrest (TCPA). Animals were sedated with 40 mg/kg ketamine and 50 μg/kg dexmedetomidine intramuscularly into the lumbar muscles, and timing started at the beginning of the injection and ended when cardiac and respiratory arrest were observed. Cardiac and respiratory arrest following intravenous injection of pentobarbital was significantly quicker (cardiac, 6 to 24 s, median 9 s; respiratory, 6 to 19 s, median 9 s; P < 0.001) than for the intrarenal route (cardiac, 40 to 900 s, median 411 s; respiratory, 23 to 900 s, median 120 s; P < 0.001), with no negative animal reactions observed during euthanasia injection performance. Four animals did not achieve TCPA within 15 min after administration. Although TCPA was longer with intrarenal compared with intravenous euthanasia (P < 0.001), this study demonstrates that the intrarenal approach under anesthesia is a feasible alternative to the intravenous approach, as it can be reliably performed without observed animal distress or alterations in organ pathology. The overall information from this study can help guide both laboratory and practicing clinicians considering this technique. Still, factors such as variable times to cardiopulmonary arrest and technical skill should be considered.