Basic veterinary care, research sample collection, and husbandry practices are often performed by use of manual restraint in both captive and free-ranging avian species. Although manual restraint is a widely practiced handling technique for brief procedures, the adverse physiologic consequences of manual restraint in birds are well known.1–4 Research has demonstrated that serum concentrations of corticosterone, the major stress hormone in birds, can increase within 10 minutes of handling and may remain high for minutes to hours following the initial restraint.1 Thus, even short periods of manual restraint may have adverse effects in avian species.
Alternatives to manual restraint include both chemical and behavioral means, with the most common chemical restraint technique being general anesthesia with inhalant anesthetics. Although an effective means of restraint, inhalant anesthetics produce dose-dependent cardiorespiratory depression and can result in dangerously deep anesthetic planes if not closely titrated. Additionally, use of manual restraint and a face mask during the initial stages of induction is not only stressful for patients but can result in marked environmental contamination with vaporized anesthetic. Therefore, alternative methods of restraint for avian species have the potential to benefit veterinary patients and personnel.
Neurosteroid anesthetics, including alfaxalone, have long been recognized for their excellent anesthetic properties. Alfaxalone was originally marketed in 1971 for human and veterinary use as a coformulation with a second, less potent neuroactive steroid (alfadolone). Several studies5–7 investigated the use of this drug in various avian species, including the evaluation of IM alfaxalone-alfadolone administration in budgerigars (Melopsittacus undulatus).8 Although alfaxalone-alfadolone was an effective anesthetic in humans and many veterinary species, this formulation was discontinued owing to adverse effects and deaths associated with its use. These effects were largely attributed to one of its carrier vehicles (polyoxyl 35 hydrogenated castor oil).9
Given its otherwise favorable anesthetic properties, a reformulated alfaxalone product that uses a different carrier vehicle (2-hydroxypropyl-β-cyclodextrin) was first released for clinical veterinary use in Australia in 2001, with approval for use in the United States in 2014. Numerous studies in domestic10–17 and nondomestic18–23 animals have investigated the use of this alfaxalone reformulation. However, the only evaluation of its effectiveness in an avian species is a report24 in which safe and effective anesthetic induction in flamingos following alfaxalone administration (2 mg/kg [0.9 mg/lb], IV) is described. Currently, alfaxalone is only FDA approved for anesthesia in dogs and cats by IV administration,25 although alternate routes of administration,12,15,20,21,23 including IM, provide clinically useful, brief anesthetic effects in nonavian species. In light of its favorable effects following IM administration in other species and the need for safe chemical restraint alternatives in birds, particularly in smaller species in which venous access may be challenging, alfaxalone holds promise as a single-agent, short-duration IM anesthetic protocol for avian species, and further investigation is warranted.
One objective of the study reported here was to compare the anesthetic and cardiorespiratory effects of IM administration of 2 doses of alfaxalone. A second objective was to compare the effects of IM administration of alfaxalone, face mask administration of isoflurane, and manual restraint in budgerigars. We hypothesized that IM administration of alfaxalone at 5 and 10 mg/kg (2.27 and 4.54 mg/lb) would produce dose-dependent anesthesia and dose-dependent respiratory depression. Furthermore, we hypothesized that alfaxalone administered IM would be as effective as isoflurane and superior to manual restraint when brief, minimally invasive veterinary procedures (eg, physical examination or venipuncture) were conducted.
Materials and Methods
Animals and husbandry
Forty-two adult male (n = 21) and female (21) budgerigars were obtained from a zoo aviary collection; birds were visually sexed on the basis of cere color. The age and body weight ranged from 11 to 23 months and from 31.81 to 55.91 g (1.12 to 1.97 oz), respectively. Birds had no known history of disease and were considered healthy on the basis of visual examination; testing was performed for Chlamydophila spp, avian bornavirus, avian polyoma virus, Macrorhabdus ornithogaster, and enteric parasites on a subset of birds at the time of acquisition and at subsequent routine intervals. Birds were group housed in 5 wire cages (45.7 × 45.7 × 50.8 cm) with 6 or 10 birds/cage. The lighting cycle was 12 hours of light and 12 hours of darkness, and the room temperature was maintained at 19° to 22°C (66.2° to 71.6°F). An in-house prepared budgerigar diet and fresh water were available in each cage, and food was withheld for approximately 4 hours before data collection. The study was divided into 2 parts: alfaxalone dose comparison (n = 12 birds) and treatment comparison (30 birds); each bird was assigned to only 1 part of the study. The Institutional Animal Care and Use Committee of the Chicago Zoological Society reviewed and approved all study procedures.
Alfaxalone dose comparison
Birds were assigned to receive alfaxalonea in group A5 (5 mg/kg, IM; n = 6) or in group A10 (10 mg/kg, IM; 6) by arbitrary selection of birds from the group housing area until 3 male and 3 female birds/group were attained. Each bird was briefly manually restrained for measurement of baseline HR via auscultation and then transferred to an individual 3.8-L clear, vented containerb to obtain body weight and for baseline measurement (via visual examination) of RR and sedation score (Appendix). Each bird then remained in the container with no stimulation for 5 minutes; during this time, alfaxalone doses were calculated, and the final volume for each bird was rounded to the nearest whole unit on a 0.5-mL insulin syringec attached to a 28-gauge needle. Each bird was then manually restrained, alfaxalone was injected into the pectoral muscles, and the bird was immediately returned to its container.
Time to initial effects, characterized by obvious head droop, muscle relaxation, or eyelid closure, and time to sternal or lateral recumbency (recumbency 1) were recorded. When recumbency 1 was noted, the righting reflex was assessed by manually rotating the bird into dorsal recumbency; if the righting reflex was still present, reassessment was performed every 60 seconds until the righting reflex was lost or the bird recovered from anesthesia. For birds that lost the righting reflex, the response to noxious stimulus was assessed immediately after the loss of this reflex by applying the jaws of a 5-cm mosquito hemostatd on the first digit and closing it to the first ratchet; the response (positive or negative) and time of the response were recorded. All birds in dorsal recumbency were assessed at 5 minutes after alfaxalone administration and at 5-minute intervals thereafter (T5, T10, T15, etc, until return to sternal recumbency); the assessment included evaluation of response to noxious stimulus, auscultation of HR and heart rhythm, and measurement of RR. For assessment of response to noxious stimulus, sequential application of the hemostat to the first digit was performed on alternating limbs to minimize repeated tissue trauma. Any bird with an HR that exceeded the detection limit (> 600 beats/min) was recorded as such. Times to return to sternal recumbency (recumbency 2), standing, and complete recovery were also recorded. Duration of recumbency and time to complete recovery were defined as the time from recumbency 1 to standing and as the time from administration of anesthetic agent to complete recovery, respectively. A maximum sedation score was assigned to each bird on the basis of the highest level of sedation achieved during the observation period. Following complete recovery, all birds were returned to the group housing area and monitored daily for 1 month for evidence of adverse effects or death.
Treatment comparison
Birds were assigned to group A (alfaxalonea at 10 mg/kg, IM; n = 10), group I (isofluranee via face maskf; 10), or group M (manual restraint only; 10) by arbitrary selection of birds from the group housing area until 5 male and 5 female birds/group were attained. Each bird was manually transferred to an individual container, and measurements were obtained as described for the alfaxalone dose comparison. For group A, alfaxalone administration was as described for the alfaxalone dose comparison. For groups A and I, the time to initial effects and time to subsequent anesthetic effects were recorded as described for the alfaxalone dose comparison. Birds in group I were manually restrained, and anesthesia was induced with 5% isoflurane in oxygen (2 L/min flow rate) delivered via face mask attached to a nonrebreathing Mapleson D circuit. At the time that initial effects were noted, characterized by obvious head droop, muscle relaxation, or eyelid closure, the isoflurane vaporizer setting was reduced to 2%. Time to recumbency 1 was recorded, and when noted, birds were positioned in left lateral recumbency and left unstimulated until isoflurane had been continuously delivered for 5 minutes. For the birds in group M, body weight and baseline HR, RR, and sedation score measurements were obtained as described for groups A and I; the birds were then left unstimulated in their individual containers for 5 minutes.
At 5 minutes following treatment administration (groups A and I) and baseline measurements (group M), each bird was manually restrained for blood sample collection from the right jugular vein by use of a 27-gauge needle attached to a 1-mL syringe, with an attempted collection volume of ≤ 1% of body weight. Measurements of blood glucose concentration, Hct, and venous blood gas parametersg and plasma lactate concentrationh were obtained immediately after blood sample collection. For birds in group I, isoflurane delivery was discontinued after venipuncture, with continued delivery of 100% oxygen via face mask. Following venipuncture, a standardized physical examination was performed on each bird from each group; HR, RR, and body condition score (scale, 1 to 5 [1 = emaciated, 3 = optimal, and 5 = overconditioned]) were measured; the eyes, oral cavity, vent, and plumage were examined in the aforementioned order; and the duration of the examination was recorded. Oxygen delivery was discontinued in birds from group I after RR was measured.
Following completion of the physical examination, birds were immediately returned to the group housing area (group M) or to individual containers positioned in dorsal recumbency (groups A and I). On positioning in dorsal recumbency, each bird in groups A and I was assessed for the righting reflex and assigned a sedation score. Time to initial arousal was noted for birds in group I; times to recumbency 2, standing, and complete recovery were noted for birds in groups A and I. Following complete recovery, birds in groups A and I were returned to the group housing area. All birds were monitored daily for 1 month for evidence of adverse effects or death.
Statistical analysis
Alfaxalone dose comparison—All numeric variables (ie, body weight, baseline RR, time to anesthetic effects, maximum sedation score, and duration of recumbency) were assessed for normality with the Shapiro-Wilk test, and descriptive statistics, including mean, median, and SD, were determined. Multinomial logistic regression was performed with sedation score as the dependent variable, sex and dose (ie, groups A5 and A10) as categorical predictor variables (fixed effects), and body weight as a continuous predictor variable. Body weight, baseline RR, time to initial effects, and time to complete recovery were compared between groups A5 and A10 by use of the independent t test and the Mann-Whitney U test for normally and nonnormally distributed continuous variables, respectively. For birds that reached a sedation score ≥ 4, repeated-measures ANOVA was used to evaluate the effect of time on RR. Levene tests were used to assess the homogeneity of variances.
Treatment comparison—All numeric variables (ie, body weight, baseline RR, time to anesthetic effects, sedation score, duration of recumbency, duration of physical examination, collected blood volume, body condition score, physical examination RR, blood gas measurements, blood glucose concentration, Hct, and plasma lactate concentration) were assessed for normality with the Shapiro-Wilk test, and descriptive statistics, including mean, median, and SD, were determined. Multinomial logistic regression was performed with sedation score as the dependent variable, sex and treatment (ie, groups A, M, and I) as categorical predictor variables (fixed effects), and body weight as a continuous predictor variable. Comparisons of body weight, baseline RR, duration of physical examination, collected blood volume, body condition score, physical examination RR, blood gas measurements, blood glucose concentration, Hct, and plasma lactate concentration between treatment groups were performed by use of the 1-way ANOVA and the Kruskal-Wallis test for normally and nonnormally distributed data, respectively; post hoc comparisons were performed with the Tukey and Mann-Whitney U tests, respectively. Levene tests were used to assess the homogeneity of variances. Mean sedation score and time to effects were compared between groups A and I by use of the independent t test and the Mann-Whitney U test for normally and nonnormally distributed data, respectively. For groups A and I, mean RR at baseline and during physical examination (5 to 8 minutes after treatment administration) were compared within each group by use of the paired t test.
Because HR exceeded detectable limits (> 600 beats/min) for most birds at most time points, this variable was excluded from all analyses. All analyses were performed with commercially available statistical software.i Normally distributed data were reported as mean ± SD, and nonnormally distributed data were reported as median (range). Values of P < 0.05 were considered significant.
Results
Alfaxalone dose comparison
The mean ± SD administered alfaxalone dose was 5.36 ± 0.47 mg/kg (2.44 ± 0.21 mg/lb) and 10.50 ± 0.65 mg/kg (4.77 ± 0.30 mg/lb) for groups A5 (target dose, 5 mg/kg) and A10 (target dose, 10 mg/kg), respectively. Mean body weight and baseline RR were not significantly different between groups. After IM alfaxalone administration, all 6 birds in group A5 became minimally sedated (maximum sedation score, 1), and birds in group A10 became moderately (n = 1; maximum sedation score, 3) or heavily (5; maximum sedation score, 4) sedated. In group A10, all 6 birds became laterally or sternally recumbent, and 5 lost the righting reflex; no birds lost the response to noxious stimulus. Times to initial effects and complete recovery (groups A5 and A10); times to recumbency 1 and 2, loss of righting reflex, and standing (group A10); and duration of recumbency (group A10) were summarized (Table 1). In the multinomial logistic regression model that controlled for sex and body weight, birds in group A10 had significantly (P = 0.002) higher sedation scores than those in group A5; sex and body weight were not significantly (P = 0.07 and P = 0.15, respectively) associated with sedation score.
Measurements obtained for 12 budgerigars (Melopsittacus undulatus) following IM administration of alfaxalone at 5 mg/kg (2.27 mg/lb; group A5) or 10 mg/kg (4.54 mg/lb; group A10).
| Variable* | A5 (n = 6) | A10 (n = 6) | P value |
|---|---|---|---|
| Time to initial effects | 1.71 (1.13–1.83) | 0.85 (0.35–1.20) | 0.004 |
| Time to recumbency 1† | — | 2.32 (1.50–5.63) | — |
| Time to loss of righting reflex | — | 2.76 ± 0.49 | — |
| Time to recumbency 2‡ | — | 15.47 ± 3.33 | — |
| Time to standing | — | 15.91 ± 3.53 | — |
| Time to complete recovery§ | 10.92 ± 2.06 | 20.68 ± 4.47 | 0.001 |
| Duration of recumbency‖ | — | 13.86 ± 3.64 | — |
Normally distributed data are reported as mean ± SD and nonnormally distributed data as median (range).
All variables were measured in minutes.
Defined as time to sternal or lateral recumbency after administration of anesthetic agent.
Defined as time to return to sternal recumbency during recovery from anesthesia.
Defined as time from administration of anesthetic agent to complete recovery.
Defined as time from recumbency 1 to standing.
— = Not applicable.
At baseline, all birds from groups A5 and A10 had an HR > 600 beats/min. At T5 (5 minutes after alfaxalone administration), 5 birds in group A10 lost the righting reflex, of which 4 were bradycardic relative to baseline (360, 410, 480, and 520 beats/min) with a concurrent sinus arrhythmia (HR returned to baseline [> 600 beats/min] at T10 and T15 in 3 of 4 and 1 of 4 birds, respectively, with normal sinus rhythm). For the 5 birds from group A10 that had a maximum sedation score of 4, there was no significant (P = 0.41) difference in RR over time; the RR (mean ± SD) at T5 (n = 5), T10 (5), and T15 (3 [not measured in 2 birds that had returned to sternal recumbency]) was 85.6 ± 23.1 breaths/min, 89.8 ± 21.7 breaths/min, and 84.0 ± 4.0 breaths/min, respectively. Apnea was not noted in any bird at any time point.
During the period between alfaxalone administration and recumbency 1 (time to sternal or lateral recumbency), 6 of 12 birds (in groups A5 and A10) displayed increased and uncoordinated activity, including ataxia, stumbling, increased limb and body movements, swaying, and biting at the container wall to varying degrees. In contrast, the other 6 birds within these groups displayed minimal activity during this period (ie, a relaxed, wide-based stance and head droop). The recovery period was also characterized by increased (ie, pacing and flailing) and uncoordinated (ie, stumbling and ataxia) activity among 6 birds (in both groups). The duration of these effects, which resolved in all birds without intervention, was variable within and between groups and ranged from several seconds to several minutes. Transient (< 5 seconds) but aggressive biting at the feet was observed in 3 birds during the following periods: time from administration of anesthetic agent to recumbency 1 (group A10; n = 1), from time of initial effects to complete recovery (group A5; 1), and from time of standing to complete recovery (A10; 1). No adverse effects or deaths were observed in birds from either group during the 1-month monitoring period following recovery.
Treatment comparison
The mean ± SD administered alfaxalone dose was 10.77 ± 0.91 mg/kg (4.89 ± 0.41 mg/lb) for group A; this did not differ significantly (P = 0.56) from the dose used for group A10 in the alfaxalone dose comparison part of the study. Mean body weight and baseline RR were not significantly different among groups A (alfaxalone at 10 mg/kg, IM), I (isoflurane via face mask), and M (manual restraint). At baseline, all birds had an HR > 600 beats/min and a sedation score of 0. The times to initial effects, recumbency 1 and 2, venipuncture, start of physical examination, initial arousal, standing, and complete recovery and durations of physical examination and recumbency were summarized (Table 2). Three of 10 birds in group A had not achieved recumbency 1 at 5 minutes following alfaxalone administration. Duration of recumbency for birds in group A was significantly (P = 0.04) longer than for birds in group A10 that received alfaxalone at the same dose (10 mg/kg, IM) for the alfaxalone dose comparison. In the multinomial regression model that controlled for sex and body weight, only treatment group was significantly (P < 0.001) associated with sedation score; sex and body weight were not significantly (P = 0.61 and P = 0.91, respectively) associated with sedation score. Birds that received chemical restraint had significantly (P < 0.001) higher sedation scores than those that were manually restrained, but there was no significant (P > 0.99) difference in sedation scores between birds in groups A and I.
Measurements obtained for 30 budgerigars following administration of alfaxalone (10 mg/kg, IM; group A), isoflurane via face mask (group I), or manual restraint (group M).
| Variable* | Group A (n = 10) | Group I (n = 10) | Group M (n = 10) | P value |
|---|---|---|---|---|
| Time to initial effects | 1.18 ± 0.52 | 0.32 ± 0.14 | — | < 0.001 |
| Time to recumbency 1† | 2.65 ± 1.02¶ | 0.54 ± 0.14 | — | 0.002 |
| Time to venipuncture | 5.93 (5.63–6.63)a | 5.42 (5.10–7.32)b | 6.13 (5.58–8.77)b | 0.02 |
| Time to start examination | 6.54 (6.00–6.83)a | 5.58 (5.25–7.50)b | 6.53 (5.70–8.83)b | 0.04 |
| Time to initial arousal | — | 7.41 (6.15–11.85) | — | — |
| Time to recumbency 2‡ | 27.03 ± 10.34# | 10.75 ± 2.09 | — | 0.001 |
| Time to standing | 26.60 ± 10.07 | 10.80 ± 2.07 | — | 0.001 |
| Time to complete recovery§ | 30.23 ± 9.87 | 12.22 ± 3.25 | — | < 0.001 |
| Duration of examination | 1.88 ± 0.19 | 1.66 ± 0.20 | 1.63 ± 0.31 | 0.053 |
| Duration of recumbency‖ | 22.93 ± 5.25¶ | 10.26 ± 2.13 | — | < 0.001 |
Times were not obtained for 3 birds that had not achieved recumbency at 5 minutes after alfaxalone administration.
Time was not obtained for 1 bird that had a positive righting reflex at the end of physical examination.
Values with the same superscript letters are significantly (P < 0.05) different.
See Table 1 for remainder of key.
Similar to birds in the alfaxalone dose comparison, several (3) birds in group A displayed transient increased and uncoordinated activity following alfaxalone administration and during the recovery period. Significant differences were identified among groups in physical examination findings (ie, RR and body condition score), blood gas parameters (ie, Pco2 and Po2), and plasma lactate concentration (Table 3). There was a significant difference between the RR at baseline and the RR at physical examination in group A (mean ± SD, 133.8 ± 18.9 breaths/min and 108.0 ± 32.9 breaths/min, respectively; P = 0.045) and group I (122.2 ± 12.9 breaths/min and 64.4 ± 13.9 breaths/min, respectively; P < 0.001). The median RR at physical examination was significantly lower in group I than in group A (P = 0.005) and group M (P < 0.001). Apnea was not noted in any birds at any time point.
Collected blood volume, physical examination findings, blood gas values, and plasma lactate concentrations for the 30 budgerigars in Table 2.
| Variable | Group A (n = 10) | Group I (n = 10) | Group M (n = 10) | P value |
|---|---|---|---|---|
| Collected blood volume (mL) | 0.21 (0.20–0.26)a | 0.20 (0.20–0.22)b | 0.20 (0.20–0.20)a | 0.02 |
| RR (breaths/min) | 110 (60–160)a | 60 (50–100)a,b | 120 (90–130)b | ≤ 0.005 |
| Body condition score (1–5) | 3.5 (3.0–4.0)a | 2.8 (2.0–4.0)a,b | 3.5 (3.0–5.0)b | ≤ 0.02 |
| pH | 7.45 ± 0.04 | 7.43 ± 0.04 | 7.41 ± 0.03 | 0.09 |
| Pco2 (mm Hg) | 36.50 ± 3.99a | 38.13 ± 4.56b | 31.37 ± 3.86ab | ≤ 0.03 |
| Po (mm Hg) | 35 (30–57)a | 51 (42–81)a,b | 36 (28–40)b | ≤ 0.01 |
| Glucose (mg/dL) | 304.8 ± 40.4 | 275.6 ± 22.2 | 288.9 ± 36.3 | 0.17 |
| Hct (%) | 44.9 ± 3.0 | 47.3 ± 4.5 | 44.8 ± 4.1 | 0.28 |
| Plasma lactate (mmol/L) | 1.62 ± 0.47a | 1.58 ± 0.35b | 4.92 ± 1.54ab | < 0.001 |
See Tables 1 and 2 for key.
In group A, 1 of 10 birds was bradycardic relative to baseline (460 beats/min) with a concurrent sinus arrhythmia during physical examination. In group I, 2 of 10 birds were bradycardic relative to baseline (480 and 540 beats/min) with a normal sinus rhythm during physical examination. Apnea was not noted in any of the birds. Heavy sedation (maximum sedation score, 4) was achieved in 9 of 10 and in all 10 birds in groups A and I, respectively. Moderate sedation (maximum sedation score, 3) was achieved in 1 bird in group A; this bird also had the highest plasma lactate value for group A (2.5 mmol/L).
The mean ± SD duration of isoflurane delivery (group I) and manual restraint (group M) was 5.90 ± 0.64 minutes and 3.36 ± 1.09 minutes, respectively. No adverse effects or deaths were observed in birds from any of the groups during the 1-month monitoring period following treatment.
Discussion
Intramuscular alfaxalone administration at 10 mg/kg produced effective sedation of short duration in the budgerigars of the present study, with no clinically appreciable adverse effects. Sedative effects following IM alfaxalone administration at 5 mg/kg were mild and likely not of clinical relevance in healthy budgerigars. However, this dose may be of clinical use for compromised birds, given its short times to initial effects and complete recovery (< 2 minutes and < 15 minutes, respectively) in the birds of the present study. The higher dose (10 mg/kg) produced heavy sedation, recumbency, and loss of the righting reflex, with maintenance of response to noxious stimulation in all tested birds. Thus, the anesthetic effects of IM alfaxalone administration are likely dose dependent in budgerigars, and higher doses (> 10 mg/kg) would presumably result in loss of response to noxious stimulation and anesthesia. Dose-dependent anesthetic effects following IM alfaxalone administration have been described in other species, including dogs,11 cats,10 rabbits,16 and reptiles.22,23 Although a direct comparison cannot be made between the current and former alfaxalone formulations with respect to drug dosing and efficacy, a 1977 study8 investigating IM alfaxalone-alfadolone administration in budgerigars also revealed dose-dependent anesthetic effects, supporting this hypothesis and highlighting the need for future studies of alfaxalone dose effect.
The present study also demonstrated that sedation with IM alfaxalone administration at 10 mg/kg was a viable alternative to general anesthesia with isoflurane for brief procedures in budgerigars. Injection volume in the present study was clinically reasonable (< 0.05 mL); however, greater doses with larger injection volumes could be a clinical impediment in future studies or for larger avian species. Although times to initial effects and recumbency were significantly faster with isoflurane than with alfaxalone, times for both groups were clinically practical. Overall times to initial effects and recumbency of 1 and 2.5 minutes, respectively, following IM alfaxalone administration would be remarkably fast for any species. Furthermore, the significantly faster time to recumbency (< 1 minute) in birds that were administered isoflurane rather than alfaxalone may be too fast, given that anesthetic overdose and severe adverse effects and death could result if inhalant administration is not closely titrated during the induction period. Additionally, use of manual restraint to apply a face mask is arguably more psychologically stressful than brief handling for a single IM injection. Other advantages of alfaxalone over isoflurane or other inhalant anesthetics include its ease of administration, greater patient accessibility for examination and handling, the need for minimal equipment, and improved environmental and personnel safety.
Although not objectively assessed, all birds that received alfaxalone at 10 mg/kg or isoflurane had sufficient muscle relaxation to allow manipulation for successful venipuncture. Time from treatment administration to successful venipuncture was significantly faster with isoflurane than with manual restraint, which would not be unexpected for chemically restrained birds. Time to successful venipuncture did not differ significantly between birds that received alfaxalone and those that were manually restrained. Although blood sample collection was successful in all birds in the manual restraint group, in the authors’ experience, venipuncture may be accomplished more quickly and efficiently by use of chemical restraint, especially for inexperienced avian phlebotomists.
When one is comparing recovery times for birds that received alfaxalone or isoflurane, the differences in route (IM vs inhalation) and method (1 injection vs continuous delivery) of anesthetic administration should be considered. Nevertheless, times from alfaxalone administration to the various stages of recovery (ie, sternal recumbency, standing, and complete recovery) were clinically practical and applicable to brief procedures. No lingering sedative or adverse effects were noted following recovery from the anesthetic agents, and all birds were returned to the group housing area without concern. Although both parts of the study included birds that received alfaxalone at 10 mg/kg, the duration of recumbency was significantly longer for birds in group A (treatment comparison) than for those in group A10 (alfaxalone dose comparison). This was likely attributable to the noxious stimulus applied to birds in group A10 at 5-minute intervals until sternal recumbency was reached. Despite this difference, the duration of recumbency in both groups was sufficient to be clinically practical.
Values for plasma lactate concentration, a marker of anaerobic metabolism, were significantly higher in the manually restrained birds versus the chemically restrained birds. This was likely the result of increased muscle activity, a stress response associated with handling, or both. Of birds that received alfaxalone for the treatment comparison part of the study, the bird with the highest plasma lactate value also had the lowest sedation score. The protocol for collection of baseline measurements and the 5-minute acclimation period was the same across all treatment groups, making it less likely that this time frame contributed to the significantly higher plasma lactate values in the manually restrained birds.
Although no reference range has been established for resting plasma lactate concentration for budgerigars, the mean plasma lactate value for the manually restrained birds of the present study was notably higher than that reported for unrestrained domestic Landaise strain geese3 (Anser anser; mean ± SD, 0.94 ± 0.21 mmol/L) and baseline concentrations typically used for mammalian species26 (1 to 2 mmol/L). Because venipuncture was performed before physical examination, the potential time frame for a handling-associated increase in plasma lactate concentration in the manually restrained birds was relatively short, with blood samples collected from several of these birds in < 60 seconds. A study27 in chickens showed that plasma lactate concentrations were markedly increased (mean ± SD, 10.75 ± 0.62 mmol/L) after 30 seconds of shackling, compared with plasma lactate concentrations in control birds. This is important from a clinical perspective because the duration of conscious manual restraint for most procedures in avian species exceeds this short time frame, and increased restraint times may prolong stress and contribute to an increased risk of adverse effects or death. For the manually restrained birds of the present study, it is reasonable to assume that plasma lactate values at the conclusion of the physical examination were even higher than the reported values. Previous studies28,29 of mourning doves, boat-tailed grackles, house sparrows, and flamingos have shown plasma lactate concentrations following stress or conscious handling that are increased relative to those reported for unrestrained domestic Landaise strain geese.3 Although no adverse effects or deaths occurred in the manually restrained budgerigars of the present study, the same may not hold true for physiologically compromised birds or other avian species. With this in mind, we caution against prolonged manual restraint of conscious budgerigars and urge consideration of adjunct chemical restraint.
For birds of the present study, only minor effects were noted following administration of chemical restraint, and no deaths occurred. Excitement and hyperactivity were observed at the time of initial effects and during the recovery period in a subset of budgerigars that received alfaxalone. In the study24 of alfaxalone administration in flamingos, episodes of hyperactivity during recovery from isoflurane anesthesia occurred following induction with IV-administered alfaxalone (3/16 birds) and isoflurane (5/9 birds). Muscle tremors, ataxia, and opisthotonus-like posture were reported following IM administration of alfaxalone alone in cats30 and dogs,31 but not in rabbits.32 In none of these studies was hyperactivity observed during the anesthetic induction period. Although excitement was not noted following IM administration of alfaxalone-alfadolone to budgerigars in a previous study,8 a subset of birds had periods of generalized, self-limiting muscle spasms, including wing fluttering, tail elevation, limb extension, and neck torsion. Given the lack of true anesthetic (as opposed to sedative) effects observed in the present study, it is possible that alfaxalone administration at a higher dose or as part of a multiagent protocol would minimize or abolish excitement during the anesthetic induction and recovery periods. The underlying cause for the observed transient self-biting following alfaxalone administration is unknown. Because self-biting has not, to the authors’ knowledge, been reported for any avian species as a complication of anesthesia with other drug protocols, it is possible that this behavior may have been attributable to alfaxalone in the birds of the present study.
Bradycardia relative to baseline and a concurrent sinus arrhythmia were noted in a subset of budgerigars following alfaxalone administration in the present study; however, the serial auscultations performed during the alfaxalone dose comparison part of the study indicated that these changes were transient. Although a reference range for the HR of conscious budgerigars has not been published, the HR of budgerigars anesthetized with isoflurane is reported to be 600 to 750 beats/min.33 No significant HR aberrations from baseline were noted during alfaxalone-induced anesthesia of flamingos24; however, studies10,11,30,34 in dogs and cats have revealed tachycardia and, less commonly, bradycardia following alfaxalone administration. Because perfusion and oxygenation were not directly assessed in the present study, the aftereffects of transient presumed bradycardia in these budgerigars are unknown.
Bradypnea and apnea are commonly reported following alfaxalone administration in cats10,30,34 and dogs.11,31,34 Although RR after alfaxalone administration was significantly decreased relative to baseline in birds of the present study, the RRs were not lower than the RRs previously reported for conscious budgerigars35 and for budgerigars anesthetized with isoflurane33 (60 to 75 and 55 to 75 breaths/min, respectively). Following alfaxalone administration, pH and Pco2 remained within reported reference ranges for budgerigars (7.334 to 7.489 and 30.6 to 43.2 mm Hg, respectively)36 despite the wide range in RRs during physical examination of birds in this treatment group. Although an arterial blood sample would be required for true assessment of oxygenation, the clinically acceptable plasma lactate values and the lack of clinically important hypoventilation in birds that received alfaxalone suggested that hypoxemia did not occur, despite the lack of oxygen supplementation. Budgerigars receiving isoflurane (group I) had a significantly lower mean RR during physical examination than at baseline, and that group also had a significantly lower mean RR than the other treatment groups (alfaxalone and manual restraint) during physical examination. However, median RR, pH, and Pco2 for group I birds were within reported reference ranges.33,35,36 The observed Po2 values in group I were likely attributable to oxygen supplementation. It is possible that higher doses of isoflurane could produce clinically important hypoventilation as a result of dose-dependent respiratory depression.37 The significantly lower Pco2 in manually restrained birds versus chemically restrained birds was likely the result of stress-induced hyperventilation.
Intramuscular alfaxalone administration at 10 mg/kg produced effective and dose-dependent sedation in healthy budgerigars and provided a viable alternative to isoflurane anesthesia in the study reported here. Alfaxalone does not provide analgesia; thus, birds undergoing painful or potentially painful procedures should receive appropriate adjunctive analgesic treatment. In the authors’ opinion, the lack of clinically appreciable adverse effects, short time to recumbency, clinically useful duration of sedation, stable cardiorespiratory parameters, and clinically acceptable plasma lactate concentrations support the use of alfaxalone sedation as an alternative to conscious manual restraint in healthy budgerigars for brief, minimally invasive procedures. Although plasma lactate concentration was not measured in the budgerigars following alfaxalone administration at 5 mg/kg, we postulate that the mild sedative effects produced by this dose may ameliorate some of the distress that birds might experience during handling. All anesthetic drugs have the potential to result in adverse effects; however, the detrimental impact of manual restraint of conscious birds should not be underestimated.
Acknowledgments
Funded by the Grainger Foundation.
The authors declare that there were no conflicts of interest.
The authors thank Mary Ann Duda, Michelle Eastridge, Jenny Klasen, John Pauley, Kate Sladek, Michelle Soszynski, and Ashlee Webb for their animal care and technical assistance during this project.
ABBREVIATIONS
| HR | Heart rate |
| RR | Respiratory rate |
Footnotes
Alfaxalone (10 mg/mL), Jurox Inc, Kansas City, Mo.
Sterilite, Townsend, Mass.
Insulin syringe (28 gauge, 0.5 inches, 0.5 mL, 100 U), Covidien, Mansfield, Mass.
Henry Schein, Melville, NY.
Zoetis, Kalamazoo, Mich.
Small face mask, DRE, Louisville, Ky.
Abaxis Inc, Union City, Calif.
Lactate Plus, Nova Biomedical Corp, Waltham, Mass.
Prism 7.0, GraphPad Software Inc, La Jolla, Calif.
References
1. Cockrem JF, Silverin B. Variation within and between birds in corticosterone responses of great tits (Parus major). Gen Comp Endocrinol 2002;125:197–206.
2. Heatley JJ, Oliver JW, Hosgood G, et al. Serum corticosterone concentrations in response to restraint, anesthesia, and skin testing in Hispaniolan Amazon parrots (Amazona ventralis). J Avian Med Surg 2000;14:172–176.
3. Le Maho Y, Karmann H, Briot D, et al. Stress in birds due to routine handling and a technique to avoid it. Am J Physiol 1992;263:R775–R781.
4. Scope A, Filip T, Gabler C, et al. The influence of stress from transport and handling on hematologic and clinical chemistry blood parameters of racing pigeons (Columbia livia domestica). Avian Dis 2002;46:224–229.
5. Bailey TA, Toosi A, Samour JH. Anaesthesia of cranes with alphaxolone-alphadolone. Vet Rec 1999;145:84–85.
6. Machin KL, Caulkett NA. Investigation of injectable anesthetic agents in mallard ducks (Anas platyrhynchos): a descriptive study. J Avian Med Surg 1998;12:255–262.
7. Samour JH, Jones DM, Knight JA, et al. Comparative studies of the use of some injectable anaesthetic agents in birds. Vet Rec 1984;115:6–11.
8. Curtis R, Jemmett JE, Hendy PG. Saffan (CT 1341) as an anaesthetic agent for the budgerigar Melopsittacus undulatus. J Small Anim Pract 1977;18:465–472.
9. Berry SH. Injectable anesthetics. In: Grimm KA, Lamont LA, Tranquilli WJ, et al, eds. Veterinary anesthesia and analgesia. 5th ed. Ames, Iowa: John Wiley & Sons, 2015;277–296.
10. Muir W, Lerche P, Wiese A, et al. The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats. Vet Anaesth Analg 2009;36:42–54.
11. Muir W, Lerche P, Wiese A, et al. Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs. Vet Anaesth Analg 2008;35:451–462.
12. Grubb TL, Greene SA, Perez TE. Cardiovascular and respiratory effects, and quality of anesthesia produced by alfaxalone administered intramuscularly to cats sedated with dexmedetomidine and hydromorphone. J Feline Med Surg 2013;15:858–865.
13. Andaluz A, Felez-Ocana N, Santos L, et al. The effects on cardio-respiratory and acid-base variables of the anaesthetic alfaxalone in a 2-hydroxypropyl-β-cyclodextrin (HPCD) formulation in sheep. Vet J 2012;191:389–392.
14. del Álamo AM, Mandsager RE, Riebold TW, et al. Evaluation of intravenous administration of alfaxalone, propofol, and ketamine-diazepam for anesthesia in alpacas. Vet Anaesth Analg 2015;42:72–82.
15. Santos González M, Bertrán de Lis BT, Tendillo Cortijo FJ. Effects of intramuscular alfaxalone alone or in combination with diazepam in swine. Vet Anaesth Analg 2013;40:399–402.
16. Grint NJ, Smith HE, Senior JM. Clinical evaluation of alfaxalone in cyclodextrin for the induction of anaesthesia in rabbits. Vet Rec 2008;163:395–396.
17. Goodwin WA, Keates HL, Pasloske K. The pharmacokinetics and pharmacodynamics of the injectable anaesthetic alfaxalone in the horse. Vet Anaesth Analg 2011;38:431–438.
18. McMillan MW, Leece EA. Immersion and branchial/transcutaneous irrigation anaesthesia with alfaxalone in a Mexican axolotl. Vet Anaesth Analg 2011;38:619–623.
19. Minter LJ, Bailey KM, Harms CA, et al. The efficacy of alfaxalone for immersion anesthesia in koi carp (Cyprinus carpio). Vet Anaesth Analg 2014;41:398–405.
20. Posner LP, Bailey KM, Richardson EY, et al. Alfaxalone anesthesia in bullfrogs (Lithobates catesbeiana) by injection or immersion. J Zoo Wildl Med 2013;44:965–971.
21. Bouts T, Karunaratna D, Berry K, et al. Evaluation of medetomidine-alfaxalone and medetomidine-ketamine in semi-free ranging Bennett's wallabies (Macropus rufogriseus). J Zoo Wildl Med 2011;42:617–622.
22. Bertelsen MF, Sauer CD. Alfaxalone anaesthesia in the green iguana (Iguana iguana). Vet Anaesth Analg 2011;38:461–466.
23. Kischinovsky M, Duse A, Wang T, et al. Intramuscular administration of alfaxalone in red-eared sliders (Trachemys scripta elegans)—effects of dose and body temperature. Vet Anaesth Analg 2013;40:13–20.
24. Villaverde-Morcillo S, Benito J, Garcia-Sanchez R, et al. Comparison of isoflurane and alfaxalone (Alfaxan) for the induction of anesthesia in flamingos (Phoenicopterus roseus) undergoing orthopedic surgery. J Zoo Wildl Med 2014;45:361–366.
25. US FDA. Freedom of Information summary. Available at: www.fda.gov/downloads/AnimalVeterinary/Products/ApprovedAnimalDrugProducts/FOIADrugSummaries/UCM326904.pdf. Accessed May 1, 2017.
26. Haskins SC. Monitoring anesthetized patients. In: Grimm KA, Lamont LA, Tranquilli WJ, et al, eds. Veterinary anesthesia and analgesia. 5th ed. Ames, Iowa: John Wiley & Sons, 2015;86–113.
27. Bedanova I, Voslarova E, Chloupek P, et al. Stress in broilers resulting from shackling. Poult Sci 2007;86:1065–1069.
28. Harms CA, Harms RV. Venous blood gas and lactate values of mourning doves (Zenaida macroura), boat-tailed grackles (Quiscalus major), and house sparrows (Passer domesticus) after capture by mist net, banding, and venipuncture. J Zoo Wildl Med 2012;43:77–84.
29. Burgdorf-Moisuk A, Wack R, Ziccardi M, et al. Validation of lactate measurement in American flamingo (Phoenicopterus ruber) plasma and correlation with duration and difficulty of capture. J Zoo Wildl Med 2012;43:450–458.
30. Tamura J, Ishizuka T, Fukui S, et al. Sedative effects of intramuscular alfaxalone administered to cats. J Vet Med Sci 2015;77:897–904.
31. Tamura J, Ishizuka T, Fukui S, et al. The pharmacological effects of the anesthetic alfaxalone after intramuscular administration to dogs. J Vet Med Sci 2015;77:289–296.
32. Huynh M, Poumeyrol S, Pignon C, et al. Intramuscular administration of alfaxalone for sedation in rabbits. Vet Rec 2015;176:255.
33. Sinn LC. Anesthesiology. In: Ritchie BW, Harrison GH, Harrison LH, eds. Avian medicine: principles and application. Lake Worth, Fla: Wingers Publishing Inc, 1994;1066–1080.
34. Jurox Inc. Technical notes: Alfaxan anesthetic injection. Available at: alfaxan.com/documents/resources/downloads/US/Jurox_Technical_Notes_-_US_-_Alfaxan.pdf. Accessed May 1, 2017.
35. Hawkins MG, Guzman DS-M, Beaufrere H, et al. Birds. In: Carpenter JW, ed. Exotic animal formulary. 5th ed. St Louis: Elsevier, 2018;316.
36. Hochleithner M. Biochemistries. In: Ritchie BW, Harrison GH, Harrison LH, eds. Avian medicine: principles and application. Lake Worth, Fla: Wingers Publishing, 1994;223–227.
37. Ludders J. Comparative anesthesia and analgesia of birds. In: Grimm KA, Lamont LA, Tranquilli WJ, et al, eds. Veterinary anesthesia and analgesia. 5th ed. Ames, Iowa: John Wiley & Sons, 2015;800–813.
Appendix
Rubric used to score sedation in budgerigars (Melopsittacus undulatus).
| Score | Level of sedation | Characteristics |
|---|---|---|
| 0 | None | — |
| 1 | Minimal | Broad-based stance and head or wing droop, but resistant to manual restraint |
| 2 | Mild | Sternally recumbent and eyes closed, but resistant to manual restraint |
| 3 | Moderate | Permits positioning in dorsal recumbency, but maintains righting reflex |
| 4 | Heavy | Permits positioning in dorsal recumbency without resistance |
— = Not applicable.
