Psittacine Sedation and Anesthesia

Hypothermia and rewarming times during general anesthesia in Hispaniolan Amazon parrots (Amazona ventralis): A comparative study between isoflurane, sevoflurane and desflurane

OBJECTIVE

To evaluate induced hypothermia and rewarming times in Hispaniolan Amazon parrots (HAP; Amazona ventralis) anesthetized using isoflurane, sevoflurane or desflurane, and to describe selected cardiovascular and respiratory effects.

STUDY DESIGN

Randomized, balanced, crossover experimental study.

ANIMALS

A group of 12 adult HAP.

METHODS

Parrots were premedicated with intramuscular butorphanol (0.5 mg kg-1) and anesthetized with the three inhalants with a 7 day washout period between events. Anesthesia was induced using isoflurane at 4 vol%, sevoflurane at 6 vol% or desflurane 12 vol% carried in oxygen, delivered via face mask. After orotracheal intubation, anesthesia maintenance was with end-tidal concentrations of 1.4-2% (Fe'Iso), 2.4-3% (Fe'Sevo) and 8.5-9.2% (Fe'Des). Hypothermia was defined as an esophageal temperature (BT) below 37.8 °C. External heat support was provided when BT dropped to 37.5 °C. Time for temperature decrease from 38.9 °C to 37.5 °C (T1), time to first increase in BT above 37.5 °C (T2) and time from external heat support to achieving 38.9 °C (T3) were recorded and compared via Friedman tests with post hoc Dunn's test. Heart rate, respiratory rate and end-tidal carbon dioxide, amongst other variables, were evaluated.

RESULTS

All inhalants caused hypothermia (T1): isoflurane, 12 (2-37) minutes [median (range)]; sevoflurane, 12 (4-18) minutes; desflurane, 11.5 (6-24) minutes, with no significant differences between treatments (p > 0.05). T2 was significantly (p = 0.042) longer for sevoflurane than for desflurane but not isoflurane. Transient apnea was observed with all inhalants, including 25% of birds anesthetized with sevoflurane. Second-degree atrioventricular block and ventricular escape beats occurred with all inhalants with hypothermia potentially exacerbating cardiac arrhythmias.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypothermia rapidly developed in butorphanol-sedated HAP anesthetized using isoflurane, sevoflurane or desflurane. Sevoflurane prolonged warming time. Hypothermia may be associated with an increased likelihood of bradyarrhythmia in parrots anesthetized with inhalants.

Effective Dose of Dexmedetomidine with Nalbuphine Hydrochloride or Butorphanol Tartrate for Sedation in Buff Orpington Hens (Gallus gallus domesticus)

Chickens (Gallus gallus domesticus) are commonly used for research, food production, show, and companionship. Sedation is often necessary for sample collection, imaging, or treatment. Dexmedetomidine has been previously used to sedate birds, often with other sedatives. Butorphanol tartrate, a Schedule IV controlled substance, is commonly used but presents regulatory challenges. Nalbuphine hydrochloride, an opioid with similar receptor affinity to butorphanol, has potential as a noncontrolled alternative. Although information regarding nalbuphine use in birds is limited, its noncontrolled status makes it more accessible. The purpose of this study was to determine the effective dose to produce sedation in 50% (ED50) of patients and to estimate the calculated effective dose of dexmedetomidine in combination with either butorphanol (DexBut) or nalbuphine (DexNal) in domestic hens to sedate 99% of patients (ED99). Eighteen 33-week-old laying Buff Orpington hens were divided into 2 groups: one receiving DexBut (n = 9) and the second receiving DexNal (n = 9). Each hen was sedated with varying doses of intramuscular dexmedetomidine with a constant dose of either 2 mg/kg IM butorphanol or 12.5 mg/kg IM nalbuphine by an up-and-down design. Sedation was determined using a clinically applicable scoring system. The ED50 values of dexmedetomidine with 2 mg/kg IM of butorphanol, calculated by both the up-and-down method and logistic regression, were 38 and 49 µg/kg, respectively, while the ED50 values of dexmedetomidine in combination with 12.5 mg/kg IM of nalbuphine were 19 and 18 µg/kg, respectively. The estimated dexmedetomidine ED99 values with butorphanol or nalbuphine were 51 and 19 µg/kg, respectively. Multiple chickens in both groups exhibited open-mouth breathing and comb pallor but no lasting morbidity or mortality occurred. Combinations of DexBut or DexNal should be considered for sedation of domestic chickens.

COMPARISON OF THREE MIDAZOLAM-BASED SEDATION PROTOCOLS IN BUDGERIGARS (MELOPSITTACUS UNDULATUS) AND BLACK-CHEEKED LOVEBIRDS (AGAPORNIS NIGRIGENIS)

This randomized, crossover study evaluated three sedation protocols administered subcutaneously in nine budgerigars (Melopsittacus undulatus) and nine black-cheeked lovebirds (Agapornis nigrigenis). All protocols included midazolam (5 mg/kg), combined with butorphanol (5 mg/kg) (BM), medetomidine (20 lg/kg) (MM), or alfaxalone (13 mg/kg) (AM). Mortalities from suspected cardiorespiratory arrest were observed when AM was used in lovebirds, even after reduction of alfaxalone dosage to 3 mg/kg, and therefore this protocol was excluded from further use in this species. Induction and recovery times were recorded and their quality assessed. Sedation depth and heart and respiratory rates were measured every 5 min and radiographic positioning was attempted at 10 and 20 min. At 30 min, midazolam and medetomidine were reversed with flumazenil (0.05 mg/kg, SC), and atipamezole (0.2 mg/kg, SC), respectively. MM consistently provided deep sedation in both species, with successful radiographic positioning at every attempt. As expected, heart rate was often lower with MM than with other protocols, but no associated complications were noted. In budgerigars, BM had the lowest radiographic positioning success rate (10 min: 5/9, 20 min: 3/9), whereas in lovebirds it provided significantly deeper sedation (P < 0.001), allowing radiographic positioning in all subjects. In both species, BM provided the shortest recovery times. AM resulted in reliable radiographic positioning of all budgerigars at 10 min, but not at 20 min (5/ 9), and provided consistently poor recoveries. This study highlights how differently two psittacine species of similar size may react to the same sedation protocols. AM sedation cannot be fully reversed and produced significant undesirable effects, several of which have been previously reported with alfaxalone administration to avian species. The authors therefore caution against using alfaxalone-midazolam combinations in budgerigars and black-cheeked lovebirds. Both BM and MM provided reliable sedation in these species, and appear to be suitable alternatives to AM.