Abstract

Urethane is a long-acting anesthetic used in laboratory animals to undertake procedures where the preservation of neural transmission and autonomic reflexes is essential. There is little information about the quality of anesthesia induced by urethane in ducks. This study aimed to investigate the quality of urethane anesthesia in Pekin ducks. Urethane was administered IV bolus (1.25g/kg) to 9 ducks followed by continuous rate infusion (CRI, 0.5-2g/kg/hr) to attempt to achieve anesthesia for up to two hours. Time and duration to a defined depth of anesthesia as quantified by measurements of muscle relaxation, antinociception (toe pinch), cardiorespiratory, and eye reflexes were assessed every 5 minutes during the urethane CRI maintenance. In addition, air sac cannulation was attempted to assess a possible surgical plane of anesthesia. The time to the defined depth of anesthesia was 7.67±4.74 minutes. Paradoxical muscle movements with or without rigidity were observed before complete muscle relaxation and periodically after muscle relaxation had been achieved. Inconsistent absence of palpebral reflex and antinociception occurred in most of the ducks during the anesthesia period. Only 2 ducks reached the depth of anesthesia for air sac cannulation with one duck moving during the procedure. Three of the 9 tested ducks died before the study ended. We concluded that urethane at the dosages tested induced a reasonable immobilization for non-invasive procedures in Pekin ducks but was inadequate in producing a surgical plane of anesthesia for air sac cannulation surgery. Furthermore, it had a narrow margin of safety for producing the defined depth of anesthesia in the current study.

Keywords:Anesthesia; Urethane; Duck; Analgesia

Abbreviations:CRI: Constant Rate Infusion; TAS: Total Anesthesia Score