Comparative studies of the use of some injectable anaesthetic agents in birds

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.

The Safety Profile of the Anesthetic Effect of Alfaxalone and its Interaction with Xylazine and Ketamine in Chick’s Model (Gallus Gallus Domesticus)

The objective of our research was to estimate the therapeutic index and assess the interaction of alfaxalone (IP) with ketamine or xylazine (IM) in chicks by using isobolographic analysis. The up-and-down technique was involved to calculate the median effective anesthetic dosages (ED50) of alfaxalone, xylazine, and ketamine given separately or at the same time in young chicks. Then the up-and-down technique was involved to estimate the median lethal dosage (LD50) of alfaxalone (IP) to determine the safety profile. The ED50 of all anesthetics was evaluated isobolographically to assess the type of interaction between alfaxalone and xylazine or alfaxalone and ketamine. The alfaxalone ED50 was 32.88 mg/kg (IP), whereas the LD50 was 102.40 mg/kg (IP). The ED50 values for alfaxalone, ketamine, and xylazine were 32.88, 12.24, and 2.45 mg/kg, respectively. The ED50 values of alfaxalone with ketamine or xylazine (25:25 ED50 values) were: 7.39+2.35, and 8.61+0.63 mg/kg, respectively. ED50 values were decreased when the combinations of alfaxalone/ketamine or alfaxalone/xylazine were administered by 22-21% and 26-25%, respectively. The anesthesia of chicks with alfaxalone is safe, produces a surgical stage of anesthesia, and can be used for minor surgical procedures. The use of alfaxalone with ketamine or xylazine has been shown to have a synergistic effect and these findings may be of clinical relevance in poultry or may be extended to mammals following further clinical trials.

Evaluation of the anesthetic and cardiorespiratory effects of intramuscular alfaxalone administration and isoflurane in budgerigars (Melopsittacus undulatus) and comparison with manual restraint

OBJECTIVE To evaluate the anesthetic and cardiorespiratory effects of IM alfaxalone and isoflurane administration in budgerigars (Melopsittacus undulatus) and compare use of these agents with use of manual restraint. ANIMALS 42 healthy budgerigars. PROCEDURES For dose comparison, birds received alfaxalone (5 or 10 mg/kg [2.27 or 4.54 mg/lb], IM; groups A5 and A10, respectively; n = 6/group). For treatment comparison, birds received alfaxalone (10 mg/kg, IM) or isoflurane (via face mask) or were manually restrained (groups A, I, and M, respectively; n = 10/group). Data were obtained on onset, degree, and duration of sedation or anesthesia; heart and respiratory rates; and recovery times. Birds in the treatment comparison underwent physical examination and blood gas analysis. RESULTS All group A5 birds became sedate, but not recumbent. In group A10, 5 of 6 birds lost the righting reflex; however, none lost the noxious stimulus response. Median time to initial effects was significantly shorter and mean time to complete recovery was significantly longer in group A10 than in group A5. Heart and respiratory rates in group A10 remained clinically acceptable; however, some birds had signs of excitement during induction and recovery. Times to initial effects, recumbency, and complete recovery were significantly longer, yet clinically practical, in group A than in group I. Plasma lactate concentrations were significantly higher in group M than in groups A and I. CONCLUSIONS AND CLINICAL RELEVANCE Alfaxalone administered IM at 10 mg/kg produced effective sedation in healthy budgerigars and may be a viable alternative to isoflurane and manual restraint for brief, minimally invasive procedures. Brief manual restraint resulted in a significant increase in plasma lactate concentration.

The effects of anesthesia with a combination of intramuscular xylazine-diazepam-ketamine on heart rate, respiratory rate and cloacal temperature in roosters

OBJECTIVE

To examine the anesthetic effects of a xylazine-diazepam-ketamine (XDK) combination in roosters.

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Six healthy white Leghorn roosters weighing 2.03 +/- 0.08 kg.

METHODS

Each rooster was pre-medicated with xylazine (3 mg kg(-1), IM) and after 15 minutes anesthesia was induced with a diazepam (4 mg kg(-1)) and ketamine (25 mg kg(-1)) combination injected into the pectoral muscles. Heart and respiratory rates were recorded before anesthesia and every 15 minutes after induction for 165 minutes. Cloacal temperature was measured before and 15 minutes after pre-medication and every 75 minutes thereafter during anesthesia. Quality of induction and recovery were scored subjectively; duration of loss of righting reflex, abolition of response to a painful stimulus and palpebral reflex were also recorded.

RESULTS

Intramuscular injection of xylazine smoothly induced loss of the righting reflex within 3-4 minutes. Loss of response to a painful stimulus occurred at 13.1 +/- 2.9 minutes (mean +/- SD) after the administration of the D-K combination, and lasted for 63.0 +/- 5.3 minutes. Roosters anesthetized with this combination had a significant decrease in heart and respiratory rates and cloacal temperature. The recovery period lasted for up to 4 hours (227.5 +/- 15.4 minutes). Quality of recovery was satisfactory for four roosters but excitation was noted in two birds.

CONCLUSIONS AND CLINICAL RELEVANCE

The XDK combination was a useful anesthetic technique for typhlectomy in roosters. Nevertheless this drug combination should be used with caution and cardiopulmonary parameters monitored carefully. Under the conditions of this experiment it was associated with a decreased cloacal temperature and prolonged recoveries.

Clinical evaluation of intranasal benzodiazepines, α2-agonists and their antagonists in canaries

OBJECTIVE

To evaluate the effects of intranasal benzodiazepines (midazolam and diazepam), alpha(2)-agonists (xylazine and detomidine) and their antagonists (flumazenil and yohimbine) in canaries.

STUDY DESIGN

Prospective randomized study.

ANIMALS

Twenty-six healthy adult domesticated canaries of both sexes, weighing 18.3 +/- 1.0 g.

METHODS

In Study 1 an attempt was made to determine the dose of each drug that allowed treated canaries to be laid in dorsal recumbency for at least 5 minutes, i.e. its effective dose. This involved the evaluation of various doses, during which equal volumes of the tested drug were administered slowly into each nostril. In study 2 the onset of action, duration and quality of sedation induced by each drug at its effective dose were evaluated. The efficacy of flumazenil and yohimbine in antagonizing the effects of the sedative drugs was also studied.

RESULTS

In study 1 administration of 25 microL per nostril diazepam (5 mg mL(-1) solution) or midazolam (5 mg mL(-1) solution) to each bird caused adequate sedation within 1-2 minutes; birds did not move when placed in dorsal recumbency. After administration of 12 microL per nostril of either xylazine (20 mg mL(-1)) or detomidine (10 mg mL(-1)), birds seemed heavily sedated and assumed sternal recumbency but could not be placed in dorsal recumbency. Higher doses of xylazine (0.5 mg per nostril) or detomidine (0.25 mg per nostril) prolonged sedation but did not produce dorsal recumbency. In study 2 in all treatment groups, onset of action was rapid. Duration of dorsal recumbency was significantly longer (p < 0.05) with diazepam (38.4 +/- 10.5 minutes) than midazolam (17.1 +/- 2.2 minutes). Intranasal flumazenil (2.5 microg per nostril) significantly reduced recumbency time. Duration of sedation was longer with alpha(2)-agonists compared with benzodiazepines. Detomidine had the longest duration of effect (257.5 +/- 1.5 minutes) and midazolam the shortest (36.9 +/- 2.4 minutes). Nasally administered flumazenil significantly reduced the duration of sedation with diazepam and midazolam while yohimbine (120 microg per nostril) effectively antagonized the effects of xylazine and detomidine.

CONCLUSION

Intranasal benzodiazepines produce rapid and effective sedation in canaries. Intranasal alpha(2) agonists produce sedation but not sustained recumbency. Specific antagonists are also effective when used by this route. Clinical relevance Intranasal sedative drug administration is an acceptable alternative method of drug delivery in canaries.

Sedative effects of midazolam and xylazine with or without ketamine and detomidine alone following intranasal administration in Ring-necked Parakeets

OBJECTIVE

To evaluate the effects of intranasal administration of midazolam and xylazine (with or without ketamine) and detomidine and their specific antagonists in parakeets.

DESIGN

Prospective study.

ANIMALS

17 healthy adult Ring-necked Parakeets (Psittacula krameri) of both sexes (mean weight, 128.83+/-10.46 g [0.28+/-0.02 lb]).

PROCEDURE

The dose of each drug or ketamine-drug combination administered intranasally that resulted in adequate sedation (ie, unrestrained dorsal recumbency maintained for >or=5 minutes) was determined; the onset of action, duration of dorsal recumbency, and duration of sedation associated with these treatments were evaluated. The efficacy of the reversal agents flumazenil, yohimbine, and atipamezole was also evaluated.

RESULTS

In parakeets, intranasal administration of midazolam (7.3 mg/kg [3.32 mg/lb]) or detomidine (12 mg/kg [5.45 mg/lb]) caused adequate sedation within 2.7 and 3.5 minutes, respectively. Combinations of midazolam (3.65 mg/kg [1.66 mg/lb]) and xylazine (10 mg/kg [4.55 mg/lb]) with ketamine (40 to 50 mg/kg [18.2 to 22.7 mg/lb]) also achieved adequate sedation. Compared with detomidine, duration of dorsal recumbency was significantly longer with midazolam. Intranasal administration of flumazenil (0.13 mg/kg [0.06 mg/lb]) significantly decreased midazolam-associated recumbency time. Compared with the xylazineketamine combination, duration of dorsal recumbency was longer after midazolam-ketamine administration. Intranasal administration of flumazenil, yohimbine, or atipamezole significantly decreased the duration of sedation induced by midazolam, xylazine, or detomidine, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Intranasal administration of sedative drugs appears to be an acceptable method of drug delivery in Ring-necked Parakeets. Reversal agents are also effective when administered via this route.

Lack of Efficacy of Injectable Ketamine with Xylazine or Diazepam for Anesthesia in Chickens

Compared to other laboratory animals, little is known about the use of anesthetics in birds, potentially resulting in the use of improper dosing regimens. The authors compared two commonly used ketamine combinations with isoflurane and concluded that the injectable doses were ineffective for induction of surgical anesthesia in chickens.

Pharmacokinetics and anesthetic and cardiopulmonary effects of propofol in red-tailed hawks (Buteo jamaicensis) and great horned owls (Bubo virginianus)

OBJECTIVE

To determine induction doses, anesthetic constant rate infusions (CRI), and cardiopulmonary effects of propofol in red-tailed hawks and great horned owls and propofol pharmacokinetics in the owls during CRI.

ANIMALS

6 red-tailed hawks and 6 great horned owls.

PROCEDURE

The CRI dose necessary for a loss of withdrawal reflex was determined via specific stimuli. Anesthesia was induced by IV administration of propofol (1 mg/kg/min) and maintained by CRI at the predetermined dose for 30 minutes. Heart and respiratory rates, arterial blood pressures, and blood gas tensions were obtained in awake birds and at various times after induction. End-tidal CO2 (ETCO2) concentration and esophageal temperature were obtained after induction. Propofol plasma concentrations were obtained after induction and after completion of the CRI in the owls. Recovery times were recorded.

RESULTS

Mean +/- SD doses for induction and CRI were 4.48 +/- 1.09 mg/kg and 0.48 +/- 0.06 mg/kg/min, respectively, for hawks and 3.36 +/- 0.71 mg/kg and 0.56 +/- 0.15 mg/kg/min, respectively, for owls. Significant increases in PaCO2, HCO3, and ETCO2 in hawks and owls and significant decreases in arterial pH in hawks were detected. A 2-compartment model best described the owl pharmacodynamic data. Recovery times after infusion were prolonged and varied widely. Central nervous system excitatory signs were observed during recovery.

CONCLUSIONS AND CLINICAL RELEVANCE

Effects on blood pressure were minimal, but effective ventilation was reduced, suggesting the need for careful monitoring during anesthesia. Prolonged recovery periods with moderate-to-severe excitatory CNS signs may occur in these species at these doses.

Intraosseous cannulation and drug administration for induction of anesthesia in chickens

Twenty-four chickens were randomly assigned to one of three treatments (ketamine, 30 mg/kg; thiopental, 20 mg/kg; saline, 0.8 mL). Baseline data (heart rate, respiratory rate, systolic blood pressure, and cloacal temperature) were recorded before ulnar intraosseous cannulation and administration of drug treatment and for 30 minutes after administration. One investigator, unaware of the treatment administered, assessed the reaction to cannulation, number of attempts per cannulation, reaction to injection, time to induction and recovery, and quality of induction and recovery. Respiratory rate increased significantly (p < .05) from baseline after thiopental. Other parameters did not vary within groups or between groups. Most birds did not react or had a mild reaction to cannulation and injection, and on average fewer than two attempts were necessary. Quality of recovery was significantly (p < .05) better after thiopental. Time to recovery was significantly (p < .05) shorter after thiopental. No major histopathologic changes were noted in bone marrow samples from the injection site. This study demonstrates that the intraosseous route may be used to induce anesthesia in chickens, and that minimal changes in the variables studied were produced by ketamine and thiopental.

Effects of steroid anaesthesia on some liver function tests in goats

The effect of Saffan, a steroid anaesthetic, on the liver function of goats has been studied. Forty healthy animals were divided into 4 equal groups. The first 2 groups were given 2 and 4 mg Saffan/kg b. wt respectively. A mixture of Saffan (1 mg) and Xylazine (0.1 mg)/kg b. wt was given to the third group and Xylazine alone to the fourth group (0.1 mg/kg b. wt). Serum samples from all groups were analysed for glucose, total protein, total and direct bilirubin and the level of activity of transaminases. Administration of Saffan evoked more hyperglycemia than a mixture with Xylazine, or Xylazine alone. The hyperglycemic effect of both doses of Saffan (2 and 4 mg) was equivocal beyond 2 h. The effect then differed and glucose was increased 4-fold by 2 mg and 3-fold by 4 mg Saffan. Serum total protein, conjugated and total bilirubin, and GPT and GOT were not changed in the four experimental groups. This was good evidence of a normally functioning liver during the course of steroid anaesthesia administration in goats.