Raymund F. Wack

Development of an avian brachial plexus nerve block technique for perioperative analgesia in mallard ducks (Anas platyrhynchos).

Abstract Surgical procedures of the wing are commonly performed in companion, captive, and wild avian species. To develop a clinically applicable brachial plexus nerve block technique for perioperative analgesia in birds, 8 adult female mallard ducks (Anas platyrhynchos) were anesthetized and used in several local anesthetic trials with bupivacaine (2 or 8 mg/kg) or a combination of lidocaine (15 mg/kg) and epinephrine (3.8 µg/kg) perineurally; equal volumes of saline were administered as control treatments. Both axillary and dorsal approaches to the brachial plexus were evaluated. With the axillary approach, radial and ulnar compound nerve action potentials (CNAP), sensory nerve conduction velocities (SNCVs), and cord dorsum potentials (CDPs) were recorded after distal sensory nerve stimulation. Values were recorded before and at 5, 30, and 60 minutes after injection of local anesthetic or saline. Birds were monitored for the presence of a wing droop and a change in motor function on recovery from anesthesia. Results were highly variable for all techniques. No technique significantly decreased CDPs or resulted in consistent wing droop. Radial and ulnar CNAPs, SNCVs, and CDPs were consistently recorded in all birds. Variable results might indicate that the treatment, concentration, or volume of local anesthetic used was ineffective in producing local anesthesia. Electrodiagnostic methods used in these ducks to assess loss of sensory nerve conduction might not be sensitive enough to assess the effects of local anesthesia. Further research is needed to identify methods for assessing the efficacy of brachial plexus nerve blockade in birds.

Minimum anesthetic concentration of isoflurane in captive thick-billed parrots (Rhynchopsitta pachyrhyncha)

OBJECTIVE To determine the minimum anesthetic concentration (MAC) of isoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha). ANIMALS 15 healthy thick-billed parrots. PROCEDURES Anesthesia was induced and maintained with isoflurane in oxygen. In the first bird that was anesthetized, end-tidal isoflurane concentration was maintained at 1.0% for 15 minutes. After this period of anesthetic equilibration, an end-tidal gas sample was obtained for verification of isoflurane concentration. A toe was pinched to determine the birds response to pain, and the bird was then allowed to recover from aesthesia. To determine MAC, a so-called up-and-down approach was subsequently used in all 15 birds. Compared with the isoflurane concentration used for MAC determination in the first bird, maintenance isoflurane concentration for the second bird was increased by approximately 10% if the first bird reacted and decreased by approximately 10% if the first bird did not react to a toe pinch. These steps were then followed until all 15 birds had been anesthetized. Crossover events occurred when birds in sequence had discordant results (ie, 1 reactor and 1 nonreactor). The MAC was defined as the mean of the isoflurane concentrations measured during these crossover events. RESULTS Mean MAC of isoflurane in thick-billed parrots was estimated to be 1.07% (95% confidence interval, 0.97% to 1.16%). CONCLUSIONS AND CLINICAL RELEVANCE Isoflurane MAC appears to be lower in thick-billed parrots than the MAC determined for other bird species. Determination of the species-specific requirements of thick-billed parrots should allow isoflurane anesthesia to be performed more safely in this endangered species.

Cardiopulmonary Effects and Efficacy of Propofol as an Anesthetic Agent in Brown Tree Snakes, Boiga irregularis

ABSTRACT Nine wild-caught brown tree snakes, Boiga irregularis, were anesthetized with 5 mg/kg of propofol. Mean duration of anesthesia was 24 minutes. Eight of nine the snakes experienced 30 to 60 seconds of self-limiting apnea immediately following propofol injection. Two of the nine snakes failed to achieve a surgical level of anesthesia, as assessed by positive response to tail and vent pinch. Only mild changes in heart rate, cardiac blood gases, ETCO2, and SpO2 were observed. The magnitude of these changes were small, which correlated with smooth, uncomplicated anesthesias experienced by all study snakes. Propofol appears to be a safe and effective anesthetic for restraint or minor procedures in brown tree snakes. Standard techniques used to monitor heart and respiratory rates should be adequate to assess cardiopulmonary status of healthy brown tree snakes anesthetized with a single 5 mg/kg bolus of propofol.

INTRAOCULAR PRESSURE IN CAPTIVE AMERICAN FLAMINGOS (PHOENICOPTERUS RUBER) AS MEASURED BY REBOUND TONOMETRY

Abstract:  Intraocular pressure was measured using rebound tonometry in American flamingos (Phoenicopterus ruber), with the head in an upright standing position and when lowered in a feeding position, to establish a reference range. Mean ± standard deviation (SD) (range) intraocular pressure for flamingos with the head in an upright position was right eye (OD) = 10.9 ± 1.8 mm Hg (7–15 mm Hg) and left eye (OS) = 11.1 ± 2.3 mm Hg (8–21 mm Hg). Median intraocular pressure for flamingos with the head in an upright position was OD and OS = 11 mm Hg. Mean intraocular pressure for flamingos with the head in a feeding position was OD = 14.3 ± 2.5 mm Hg (10–22 mm Hg) and OS = 14.4 ± 2.7 mm Hg (11–24 mm Hg), which were significantly higher. Median intraocular pressure for flamingos with the head in a feeding position was OD and OS = 14 mm Hg.

Determination of the minimum anesthetic concentration of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha)

OBJECTIVE To determine the minimum anesthetic concentration (MAC) of sevoflurane in thick-billed parrots (Rhynchopsitta pachyrhyncha) and compare MAC obtained via mechanical and electrical stimulation. ANIMALS 15 healthy thick-billed parrots. PROCEDURES Anesthesia was induced in each parrot by administration of sevoflurane in oxygen. An end-tidal sevoflurane concentration of 2.5% was established in the first bird. Fifteen minutes was allowed for equilibration. Then, 2 types of noxious stimulation (mechanical and electrical) were applied; stimuli were separated by 15 minutes. Responses to stimuli were graded as positive or negative. For a positive or negative response to a stimulus, the target end-tidal sevoflurane concentration of the subsequent bird was increased or decreased by 10%, respectively. The MAC was calculated as the mean end-tidal sevoflurane concentration during crossover events, defined as instances in which independent pairs of birds evaluated in succession had opposite responses. A quantal method was used to determine sevoflurane MAC. Physiologic variables and arterial blood gas values were also measured. RESULTS Via quantal analysis, mean sevoflurane MAC in thick-billed parrots determined with mechanical stimulation was 2.35% (90% fiducial interval, 1.32% to 2.66%), which differed significantly from the mean sevoflurane MAC determined with electrical stimulation, which was 4.24% (90% fiducial interval, 3.61% to 8.71%). CONCLUSIONS AND CLINICAL RELEVANCE Sevoflurane MAC in thick-billed parrots determined by mechanical stimulation was similar to values determined in chickens and mammals. Sevoflurane MAC determined by electrical stimulation was significantly higher, which suggested that the 2 types of stimulation did not induce similar results in thick-billed parrots.

Validation of lactate measurement in American flamingo (Phoenicopterus ruber) plasma and correlation with duration and difficulty of capture.

Capture myopathy and associated death have been reported with capture and restraint of greater flamingos (Phoenicopterus ruber roseus) and lesser flamingos (Phoeniconaias minor). In chickens (Gallus gallus), blood lactate concentration levels have been used as indicators of muscle damage. Lactate has also been used to predict survival in humans and dogs. The goals of this study were to validate two common methods for measuring lactate (i-STAT and VetTest analyzers) in flamingo plasma by comparing measurements to a reference analyzer; and to correlate blood lactate concentration levels in captured flamingos with the duration and difficulty of capture as a possible indicator of capture myopathy. Twenty-seven banked flamingo plasma samples were run in triplicate on each of the three blood analyzers. Values from the i-STAT analyzer were consistently lower than those from the ABL analyzer, while values from the VetTest were consistently higher than those from the ABL analyzer. However, there was a good level of correlation between all three analyzers. Two of the three analyzers were determined to have acceptable total allowable error levels, calculated at 3.6% for the ABL and 10.7% for the VetTest. For clinical purposes, both the i-STAT and the VetTest analyzers provide adequate evaluation of lactate levels when serial samples are measured on the same analyzer. After validating the assay, 34 captive flamingos were captured for routine examinations. Blood lactate concentration levels were positively correlated with the length of time of the individual capture, but lactate did not increase significantly as capture difficulty increased. Only one animal was considered to have a difficult capture. No flamingos demonstrated clinical signs of capture myopathy during this study. Further research is required to determine if blood lactate concentration is a useful indicator of capture myopathy.

Parthenogenesis in a Brazilian Rainbow Boa (Epicrates cenchria cenchria)

A 22-year-old captive Brazilian rainbow boa (Epicrates cenchria cenchria) gave birth to four offspring after being housed with a vasectomized male. Sexual reproduction as a result of failed prior vasectomy, recanalization of the vas deferens, or prolonged sperm storage was ruled out using the clinical history, histopathology, and gross necropsy. Short tandem repeat (STR) DNA markers were genotyped in the male, female, and four offspring. None of the offspring possessed a diagnostic STR allele present in the potential sire. In addition, all offspring were homozygous at each STR locus evaluated, supporting parthenogenetic reproduction. This is the first report of parthenogenesis in a Brazilian rainbow boa and has implications for the conservation of reptiles maintained in captive breeding programs.

AVIAN PLASMA CHEMISTRY ANALYSIS USING DILUTED SAMPLES

Abstract Clinical chemistry tests are essential for the diagnosis and monitoring of disease in birds. The small volume of blood that can be obtained from many avian species limits the use of routine in-house chemistry analyzers. The aim of this study was to examine the accuracy and precision of avian plasma chemistry values obtained by use of a benchtop analyzer in samples diluted with sterile water, as compared with undiluted samples. Whole blood samples were collected from 13 clinically healthy thick-billed parrots (Rhynchopsitta pachyrhyncha). The samples were placed in lithium heparin tubes and centrifuged and the plasma decanted. One aliquot was analyzed immediately using a VetScan benchtop analyzer with an avian-reptile–specific rotor that included 12 analytes. The remainder of the plasma was divided into two aliquots and stored at −80°C until analysis. One of these aliquots was diluted 1∶1, 1∶1.5, 1∶2, and 1∶2.5 with sterile water to give final dilutions of 1∶2, 1∶2.5, 1∶3, and 1∶3.5, respectively. The other aliquot was pooled with the 12 other samples to create a plasma pool. The undiluted plasma pool and two final dilutions (1∶2 and 1∶3) of the pooled plasma were analyzed in replicate (n  =  20) to determine intra- and interassay imprecision. Each dilution was analyzed using the avian-reptile rotor and the results multiplied by the appropriate dilution factor to obtain the final result. Significant differences were observed in clinical chemistry results obtained from diluted plasma samples for all analytes except aspartate aminotransferase, creatine kinase, and glucose. Uric acid concentration was not significantly different at dilutions of up to 1∶3. Bile acids, globulins, and sodium concentrations were below the limit of detection in all diluted samples and were not statistically analyzed. Based on these results, dilution with sterile water is not recommended for biochemical analysis of avian plasma using the VetScan benchtop analyzer.

ACUTE PHASE PROTEIN AND ELECTROPHORESIS PROTEIN FRACTION VALUES FOR CAPTIVE AMERICAN FLAMINGOS (PHOENICOPTERUS RUBER)

Abstract:  Protein electrophoresis has recognized applications in determining the health status of various species. While reference intervals for electrophoresis have been determined for psittacine and raptor species, there are none reported for Phoenicopteriformes species. Reference intervals for haptoglobin and protein fractions obtained by electrophoresis were determined for the American flamingo (Phoenicopterus ruber) based on plasma samples from 39 captive birds. The reference intervals were as follows: haptoglobin, 0.17–0.8 mg/ml; total protein, 3.65–6.38 g/dl; prealbumin, 0.26–1.9 g/dl; albumin, 1.51–3.12 g/dl; α-1 globulin, 0.06–0.38 g/dl; α-2 globulin, 0.17–0.67 g/dl; β globulin, 0.38–1.33 g/dl; γ globulin, 0.26–0.68 g/dl; albumin : globulin ratio, 0.93–2.17. As captive flamingos often suffer from pododermatitis, feet of all flamingos were scored to determine if pododermatitis would be reflected in the acute phase proteins. Spearman rank correlation was performed on each of the protein fractions and pododermatitis scores, and only albumin had a significant correlation. This indicates that albumin, as a negative acute phase protein, may be a marker for this disease process.

PHARMACOKINETICS OF A SINGLE SUBCUTANEOUS DOSE OF SUSTAINED RELEASE BUPRENORPHINE IN NORTHERN ELEPHANT SEALS (MIROUNGA ANGUSTIROSTRIS)

Abstract:  Information regarding analgesics in pinnipeds is limited. This study aimed to establish the pharmacokinetic parameters of a single subcutaneous dose of sustained release buprenorphine (Buprenorphine SR®) in juvenile northern elephant seals (Mirounga angustirostris) with regard to its potential to provide long-lasting analgesia that requires infrequent dosing. Seals (n = 26) were administered a single dose of sustained release buprenorphine at 0.12 mg/kg s.c. Blood samples were collected from the extradural intervertebral vein at 0 hr and at three or four of the following time points: 0.5, 1, 2, 6, 12, 24, 36, 48, 60, 96, 120, and 144 hr. Seals were examined daily for systemic and local adverse reactions. Plasma was analyzed by liquid chromatography tandem–mass spectrometry for buprenorphine and norbuprenorphine concentrations. A noncompartmental analysis for pharmacokinetic parameters was calculated using standard methods and equations. An average maximum concentration of 1.21 ng/ml (0.3–2.9 ng/ml) was detected 12 hr postadministration. Concentrations were quantifiable up to 144 hr postadministration but were below those expected to provide analgesia in some other species. No systemic adverse effects were noted in healthy seals receiving sustained release buprenorphine. Cellulitis or abscesses at the injection site were observed in 6/26 (23%) seals between 24 and 168 hr postadministration. Adverse local effects suggest that this drug should be used with caution in northern elephant seals.