Anaesthesia of laboratory rabbits using etorphine/methotrimeprazine and midazolam

The use of etorphine (a potent mu-opioid), methotrimeprazine (a phenothiazine tranquilizer) and midazolam (a benzodiazepine) in laboratory rabbits is described. The central ear artery was cannulated under local anaesthesia using lignocaine/prilocaine cream, enabling cardiovascular monitoring in conscious animals. Anaesthesia was characterized by respiratory arrest, profound analgesia and a stable cardiovascular system (after commencing intermittent positive pressure ventilation). Reversal of anaesthesia with buprenorphine (a partial mu agonist) did not reduce the degree of post-operative respiratory depression, but shortened the period of unconsciousness considerably. This anesthetic regimen can only be recommended for rabbits that are free of respiratory disease and if facilities for IPPV are available.