Abstract

The anesthetic and cardiopulmonary effects of pre- vs. postoperative intramuscular butorphanol were determined and compared in eleven, adult sevoflurane-anesthetized Hispaniolan Amazon parrots (Amazona ventralis) undergoing coelomic endoscopy for gonadal evaluation. In two trials, 21 days apart, birds were randomly assigned to receive either pre-operative (n=11) butorphanol tartrate (Torbugesic®, Fort Dodge Animal Health, Fort Dodge, IA, USA) (2 mg/kg, IM) 20 minutes prior to induction of anesthesia with sevoflurane (SevoFlo™, Abbott Laboratories, North Chicago, IL, USA) or immediately post-sevoflurane (n=11) anesthesia. Baseline heart and respiratory rates were recorded in all birds prior to each study. Following induction of anesthesia with sevoflurane in 100% oxygen via face mask, each bird was intubated and anesthesia was maintained with sevoflurane for 40 minutes. Heart rate (HR), respiratory rate (RR), relative arterial oxygen saturation (SpO₂), and end-tidal CO₂ concentration (EtCO₂) were measured every minute for the first 5 minutes and every 5 minutes thereafter. No differences were seen in time to induction of anesthesia between birds administered butorphanol (40±8 seconds) and those induced with sevoflurane alone (38±8 sec). In pre-operative butorphanol treated birds, heart rates were significantly higher at 25 and 30 minutes (399±37 beats/minutes) when compared to baseline values and to birds anesthetized with sevoflurane alone (334±53 beats/minutes). Amazons anesthetized with sevoflurane alone had significantly lower heart rates at 15, 20, 25, and 40 minutes of anesthesia when compared to baseline values. Respiratory rates were significantly lower in both groups throughout the anesthetic event when compared to baseline values. Birds receiving butorphanol prior to anesthesia had significantly lower respiratory rates at 5 and 40 minutes (18±6 breath/minutes) of anesthesia compared to Amazons under sevoflurane (26±3 breath/minutes) anesthesia alone. SpO₂ values were >90% throughout the anesthetic event in both groups, and no differences were noted over time or between groups. EtCO₂ values were significantly higher in butorphanol-sevoflurane anesthetized birds at 2 and 3 minutes compared to sevoflurane-anesthetized birds. For the remainder of the anesthetic event, EtCO₂ values did not change significantly over time, and no significant changes were present between groups. In both groups, EtCO₂ values were within clinically acceptable limits for 35 minutes of anesthesia, however, at 40 minutes mild hypercapnia (>45 mm Hg) was noted in all birds. Recoveries in both groups were rapid and smooth, and no differences in recovery time were seen between birds receiving pre-operative butorphanol (3.8±1.4 minutes) and birds receiving postoperative butorphanol (4.6±1.5 minutes). Administration of pre-operative butorphanol (2 mg/kg, IM) as part of a preemptive analgesic regimen appears to be safe and effective and will not cause significant changes in anesthetic and cardiopulmonary parameters in sevoflurane anesthetized Hispaniolan Amazons parrots.