Evaluation of two combinations of Domitor, Zoletil 100, and Euthatal to obtain long-term nonrecovery anesthesia in Sprague-Dawley rats.

We sought to evaluate a new protocol designed to maintain long-term, nonrecovery, surgical anesthesia in Sprague-Dawley rats. In the first phase, two groups of rats were anesthetized with two different dose combinations of Domitor (medetomidine) and Zoletil 100 (tiletamine-zolazepam) to investigate their efficacy in induction of anesthesia. One combination comprised Domitor at 35 microg/kg and Zoletil 100 at 40 mg/kg, whereas the other comprised Domitor at 50 microg/kg and Zoletil 100 at 20 mg/kg. Both combinations effectively induced deep anesthesia and caused no mortality, but the duration of anesthesia differed statistically. In the second phase, we induced anesthesia with both Domitor-Zoletil 100 dose combinations then investigated the possibility of maintaining anesthesia for 5 h by administering Euthatal (pentobarbitone) intra-arterially at 10 mg/kg hourly. Depth of anesthesia, mortality, physiological parameters, blood gas analysis, hematology, clinical chemistry, and postmortem histopathology were recorded. Euthatal provided stable long-term anesthesia with both dose combinations of Domitor-Zoletil 100. Seven of 8 (88%) animals anesthetized with Domitor at 50 microg/kg and Zoletil 100 at 20 mg/kg successfully were maintained under deep anesthesia for 5 h. Higher mortality (36% versus 12%) occurred in group of animals treated with Domitor at 35 microg/kg and Zoletil 100 at 40 mg/kg. This difference may be linked to dose-related respiratory depression, as alterations of arterial gas levels were noted. Our findings suggest that, when long-term nonrecovery anesthesia is required, doses of 50 microg/kg Domitor and 20 mg/kg Zoletil 100 are preferable when given with Euthatal to maintain physiological conditions in animals.