Sedation and Local Anesthesia as an Alternative to General Anesthesia in 3 Birds

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.

Raptor Sedation and Anesthesia

Sedation and/or anesthesia is routinely and successfully used in raptors for a wide variety of procedures from the routine such as physical examination, radiographs, or venipuncture, to the more complex, such as orthopedic surgeries. Understanding the anatomy and physiology of raptor patients who present for care, and being fully prepared before the start of any procedure, can increase the success of anesthetic procedures. Recent advances in raptor sedation and anesthesia continue to improve the health and welfare of these avian patients.

Local and Regional Anesthesia in Zoological Companion Animal Practice

Local anesthetics provide analgesia and can be incorporated into multimodal anesthetic protocols. They work by blocking the voltage-dependent sodium ion channels along neurons that mediate nociception. Systemically, these drugs can be cardiotoxic in a dose-dependent manner. Lidocaine and bupivacaine are the most commonly used local anesthetics and their use has been reported in all classes of vertebrates. Despite anecdotal reports to the contrary, zoologic companion animals are unlikely to be more susceptible to the cardiotoxic effects of local anesthetics than domestic small animals. Local anesthetics can be clinically useful for analgesia and anesthesia in zoologic companion animal practice.

Avian Sedation

The use of procedural sedation in birds has become a routine practice in veterinary medicine during the past 10 years, with a corresponding increase in avian sedation research. Sedation is most often used in a clinical setting for birds to facilitate examination and/or diagnostic sample collection, splint application, grooming, and minor surgical procedures. Sedation provides several benefits over manual restraint or general anesthesia when performing clinical procedures. This review provides an overview of current studies on avian sedation and discusses common indications, protocols, and adverse effects of sedation in avian patients.

SEDATIVE, CARDIORESPIRATORY, AND THERMOREGULATORY EFFECTS OF ALFAXALONE ON BUDGERIGARS (MELOPSITTACUS UNDULATUS)

Alfaxalone is a neurosteroid anesthetic agent that has been extensively used in both human and veterinary medicine for more than 50 yr. Previous studies involving avian species demonstrated various dose ranges and multiple routes of administration. The aim of this study was to evaluate the short-term sedative, cardiorespiratory, and thermoregulatory effects of an intramuscular injection of alfaxalone on budgerigars (Melopsittacus undulatus). A crossover study was performed with a sample size of 10 male budgerigars, previously determined to be healthy based on physical examination. Alfaxalone was administered intramuscularly at two doses: 15 and 20 mg/kg. The lower dose resulted in mild to moderate sedation for 29 ± 5 min, whereas the higher dose resulted in moderate to profound sedation for 29 ± 7 min. A statistically significant decrease in heart rate was observed 2 min after administration of alfaxalone at 15 mg/kg; however, this finding was noted to be transient. A statistically significant decrease in respiratory rate was observed at 6 and 10 min after injection in both groups. Cloacal temperature measurement with a digital thermometer and eye temperature calculated from thermographic images demonstrated a decrease in body temperature over time but was not found to be statistically significant. Intramuscular use of alfaxalone proved to provide short-term sedation in budgerigars, with statistically significant but clinically mild cardiorespiratory effects. Due to a significant decrease in body temperature, active warming is recommended when using alfaxalone in budgerigars.

Development and evaluation of a technique for spinal anaesthesia in broiler chickens

AIMS

To develop a technique for the injection of local anaesthetic into the spinal canal of broiler chickens by first determining the ideal location for needle placement based on anatomy and histology, and then using the developed technique to assess the onset and duration of action of three doses of lidocaine.

METHODS

Two-month-old Ross broiler chickens (n = 30) were used in this study. Computed tomography imaging followed by anatomical examination of fresh cadavers (n = 6) were used to identify a suitable intervertebral space for injection of local anaesthetic, and landmarks to locate this space. Histological evaluation of the microanatomy of the caudal vertebral column in another six birds was used to examine the position of the spinal cord within the canal. Spinal anaesthesia was attempted using injection of lidocaine at 0.5 mg/kg (n = 6), 1 mg/kg (n = 6), and 2 mg/kg (n = 6) via the selected intervertebral space. Analgesia was tested by pinching the skin of the pericloacal area with thumb forceps to determine the onset and duration of analgesia. Respiratory rate, and cloacal temperature were measured at 0 minutes and every 10 minutes after injection until sensation returned.

RESULTS

The space between synsacrum and first free coccygeal vertebra (synsacrococcygeal space) was selected as the most suitable site for spinal injection. In this region, the dura mater adhered to the internal wall of the spinal canal, and the subarachnoid space was large indicating that injection would be into the subarachnoid rather than the epidural space. The interval to onset of analgesia was similar for all doses of lidocaine (1.5 (SD 0.7), 2 (SD 1) and 1.3 (SD 0.5) minutes for 0.5, 1 and 2 mg/kg, respectively; p = 0.604). Duration of analgesia was longer following injection with 2 than 0.5 or 1 mg/kg lidocaine (21.3 (SD 2.5) vs. 4.5 (SD 3.5) vs. 11.3 (SD 2) minutes, respectively; p = 0.002). Mean cloacal temperature decreased between 0 and 20 minutes after injection with all doses of lidocaine (p = 0.021).

CONCLUSIONS AND CLINICAL RELEVANCE

Spinal anaesthesia in chickens is feasible and is a practical, inexpensive and simple technique for regional anaesthesia of the pericloacal area.

Locoregional Anesthesia in Exotic Pets

Locoregional techniques are used in exotic pets to improve perioperative analgesia as well as decrease the requirement of systemic analgesics during and after invasive surgeries. This article focuses on the techniques that have been described for exotic mammals, birds, and reptiles, focusing on those that rely on ultrasonographic or nerve stimulator guidance.