Brainstem auditory evoked potentials in Japanese Black and Holstein cattle

This study was performed to examine normal brainstem auditory evoked potential (BAEP) data for adult Japanese Black cattle and to evaluate whether differences exist in the peak latencies, interpeak latencies (IPL) and waveforms of BAEP between Japanese Black and Holstein cattle. The peaks were detected as major waves I, II, III and V in each group. The threshold of the BAEP waves in the Holstein cattle was 65-75 dB nHL, but the threshold in the Japanese Black cattle was 75-85 dB nHL. The I-III and I-V IPLs were significantly shorter in the Japanese Black compared with the Holstein cattle at an intensity of 105 dB nHL. The present findings suggest that the IPL and wave threshold of BAEP are influenced by bovine breed.     

Brainstem auditory evoked potentials and flash visual evoked potentials in Vietnamese miniature pot-bellied pigs

Brainstem auditory evoked potentials (BAEP) and flash visual evoked potentials (VEP) were recorded from juvenile (5-7 weeks of age) and adult Vietnamese miniature pot-bellied pigs to provide normative data for clinical applications. BAEP responses were collected in response to stimulus intensities of 85, 95, and 105 dB nHL. VEP responses were collected in response to flashes of white light in a darkened room. Left-right ear and left-right eye responses did not differ significantly, and were combined for analysis, with each animal providing two data points for each response. BAEP responses in juvenile subjects were mature, and in all subjects showed the typical pattern of decreasing peak latencies and increasing peak amplitudes with increasing stimulus intensity. VEP responses in juvenile subjects were near to mature values, but the latencies still exceeded those of adults. Differences in response maturation between precocial and altricial species are discussed.     

Gait analysis using 3D accelerometry in horses sedated with xylazine

The aim of the present study was to verify the efficacy and sensitivity of an accelerometric device in detecting and quantifying the degree of movement alteration produced in horses sedated with xylazine. Horses (n=6) were randomly administered either xylazine or a control by intravenous injection, with at least 1 week between each treatment. A triaxial accelerometric device was used for the accelerometric gait assessment 15 min before (baseline) and 5, 15, 30, 45, 60, 75, 90, 105 and 120 min after each treatment. Eight different accelerometric parameters were calculated, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsion power, mediolateral power and total power, with the force of acceleration and the dorsoventral, mediolateral and craniocaudal (propulsive) parts of the power then calculated. Administration of xylazine decreased many of the parameters investigated, with significant differences for speed, stride frequency, dorsoventral power, propulsion power and total power at 5, 15, 30 and 45 min after injection. There were no significant differences in stride length values at any time point. Decreases in regularity values were evident with significant differences at every time point from 5 to 120 min following xylazine injection. Force values were also significantly reduced from 5 to 30 min after treatment and a redistribution of the total power was observed 5 min after injection as the mediolateral power increased significantly, while the dorsoventral power decreased. Accelerometry offers a practical, accurate, easy to use, portable and low cost method of objectively monitoring gait abnormalities at the walk in horses after sedation with xylazine.     

Peaks of brainstem auditory evoked potentials in dogs

The effects of electrode configuration and click polarity on brainstem auditory evoked potentials (BAEP) in dogs were investigated to clarify the inconsistent nomenclature for each peak. Four positive peaks (waves 1, 2, 3 and 4) before a deep negative trough and a fifth positive peak (wave 5) following the trough were the basic components of BAEP in dogs, which were easily identified regardless of recording conditions such as electrode configuration and click polarity. Additional peaks tended to be present when a noncephalic reference electrode and/or single-polarity (rarefaction or condensation) click stimuli were used. The Roman nomenclature for the individual positive peaks of BAEP in dogs is confused owing to variations in the observed waveforms among researchers, but click polarity and/or reference electrode position can explain all the previously reported variations in BAEP waveforms in dogs. When the criteria concerning wave V in the guidelines of BAEP in human beings are applied to avoid further confusion of Roman nomenclature in dogs, it is recommended that the basic five positive peaks (waves 1, 2, 3, 4 and 5 as identified easily with Ai-Vertex configuration and alternating clicks) are designated as waves I, II, III, V and VI, respectively. Wave IV (wave 3b) occurs occasionally before wave V in dogs.Abbreviations BAEP brainstem auditory evoked potentials - dBHL dB hearing level - IPL interpeak latency - Ai the caudodorsal end of the zygomatic arch ipsilateral to the stimulated ear - Nape the neck over the spinous process of the fourth cervical vertebra     

Effects of dexamethasone on emesis in cats sedated with xylazine hydrochloride

OBJECTIVE: To determine antiemetic efficacy of prophylactic administration of dexamethasone and its influence on sedation in cats sedated with xylazine hydrochloride. ANIMALS: 6 healthy adult cats (3 males and 3 females). PROCEDURE: The prophylactic antiemetic effect of 4 doses of dexamethasone (1, 2, 4, and 8 mg/kg of body weight, IM) or saline (0.9% NaCl) solution (0.066 ml/kg, IM) administered 1 hour before administration of xylazine (0.66 mg/kg, IM) was evaluated. Cats initially were given saline treatment (day 0) and were given sequentially increasing doses of xylazine on days 7, 14, 21, and 28. After xylazine injection, all cats were observed for 30 minutes to allow assessment of frequency of emesis and time until onset of the first emetic episode.The influence of dexamethasone on xylazine-induced sedation in these cats also was evaluated. RESULTS: Prior treatment with 4 or 8 mg/kg of dexamethasone significantly reduced the frequency of emetic episodes and also significantly prolonged the time until onset of the first emetic episode after xylazine injection. Time until onset of the first emetic episode also was significantly prolonged for dexamethasone at a dose of 2 mg/kg. Time until onset of sedation after administration of xylazine was not altered by administration of dexamethasone. CONCLUSIONS AND CLINICAL RELEVANCE: Dexamethasone (4 or 8 mg/kg, IM) significantly decreased the frequency of emetic episodes induced by xylazine without compromising sedative effects in cats. Dexamethasone may be used prophylactically as an antiemetic in cats treated with xylazine.     

Hematological and splenic Doppler ultrasonographic changes in dogs sedated with acepromazine or xylazine

Objective

To evaluate the onset and duration of hematological changes and the use of Doppler ultrasound (spleen) in dogs sedated with acepromazine or xylazine.

Brainstem auditory evoked responses and ophthalmic findings in llamas and alpacas in Eastern Canada

Seventeen llamas and 23 alpacas of various coat and iris colors were evaluated for: (1) deafness by using brainstem auditory evoked response testing; and (2) for ocular abnormalities via complete ophthalmic examination. No animals were deaf. The most common ocular abnormalities noted were iris-to-iris persistent pupillary membranes and incipient cataracts.     

Brainstem auditory evoked potential wave V latency-intensity function in normal Dalmatian and Beagle puppies

This study investigated whether Dalmatian puppies with normal hearing bilaterally had the same click-evoked brainstem auditory potential characteristics as age-matched dogs of another breed. Short-latency brainstem auditory potentials evoked by condensation and rarefaction clicks were recorded in 23 1.5- to 2-month-old Dalmatian puppies with normal hearing bilaterally by a qualitative brainstem auditory evoked potential test and in 16 Beagle dogs of the same age. For each stimulus intensity, from 90 dB normal hearing level down to the wave V threshold, the sum of the potentials evoked by the 2 kinds of stimuli were added, giving an equivalent to the alternate click polarity stimulation. The slope of the L segment of the wave V latency-intensity curve was steeper in Dalmatian (-40 +/- 10 micros/dB) than in Beagles (-28 +/- 5 micros/dB, P < .001) puppies. The hearing threshold was lower in the Beagle puppies (P < .05). These results suggest that interbreed differences may exist at the level of cochlear function in this age class. The wave V latency and wave V-wave I latencies differences at high stimulus intensity were different between the groups of puppies (4.3 +/- 0.2 and 2.5 +/- 0.2 milliseconds, respectively, for Beagles; and 4.1 +/- 0.2 and 2.3 +/- 0.2 milliseconds for Dalmatians, P < .05). A different maturation speed of the neural pathways is one possible explanation of this observation.     

Results of cystometry and urethral pressure profilometry in dogs sedated with medetomidine or xylazine

OBJECTIVE: To compare effects of medetomidine and xylazine hydrochloride on results of cystometry and micturition reflexes in healthy dogs and results of urethral pressure profilometry (UPP) in sedated and conscious dogs. ANIMALS: 20 dogs. PROCEDURES: Urodynamic testing was performed 6 times in each dog (3 times after administration of xylazine [1 mg/kg of body weight, IV] and 3 times after administration of medetomidine (30 microg/kg, IM). Before each episode of sedation, UPP was performed. Heart and respiratory rates and indirect blood pressures were recorded prior to and 5, 10, 20, and 30 minutes after injection of sedative. Cystometry measurements included threshold volume, threshold pressure, and tonus limb. The UPP measurements included maximal urethral closure pressure (MUCP), functional profile length, and, in male dogs, plateau pressure. RESULTS: Mean MUCP was decreased markedly in xylazine- and medetomidine-sedated dogs. Xylazine and medetomidine also decreased plateau pressure in male dogs. The MUCP measurements were consistent among days for conscious and xylazine-sedated dogs but were inconsistent for medetomidine-sedated female dogs. The proportion of valid cystometry measurements was greater for xylazine (39 of 60) than for medetomidine (27 of 60). Cystometry was considered invalid when bladder pressure reached 30 cm H2O without initiation of a micturition reflex. CONCLUSIONS AND CLINICAL RELEVANCE: Medetomidine and xylazine have similar effects on measurement of UPP and cystometry. Medetomidine was less consistent among days for UPP in female dogs and produced fewer valid cystometry tests, compared with xylazine. For urodynamic evaluations, medetomidine administered IM cannot be substituted for xylazine administered IV.     

Effect of head and neck position on respiratory mechanics in horses sedated with xylazine.

We studied the temporal changes in respiratory mechanics associated with xylazine administration (1.1 mg/kg of body weight, IV) in standing horses (experiment 1), and determined the effects of head and neck position (experiment 2) and atropine administration (experiment 3) on the observed changes. Thoroughbred geldings, 3 to 5 years old (5 in experiment 1, 4 in experiments 2 and 3) were used. Flow rates were obtained from a pneumotachograph and a differential transducer attached to a tight-fitting mask. Electronic integration of the flow signal gave tidal volume. Total pulmonary pressure (PL) was defined as the difference between esophageal pressure, measured with a balloon sealed to the end of a polyethylene catheter, and mask pressure. In experiment 3, a blunt cannula positioned in the dorsal third of the eighth or tenth intercostal space was used to estimate transpulmonary pressure. Lateral tracheal pressure was measured, using a polypropylene catheter inserted percutaneously in the midextrathoracic tracheal lumen. Upper and lower airway pressures were defined as the difference between mask pressure or transpulmonary pressure and lateral tracheal pressure, respectively. Five observations were made: (1) There was a significant (P less than 0.05) increase in PL from 10 to 40 minutes after administration of xylazine. (2) Although an overall agreement between head and neck position and PL was detected, the maximal PL value was not always obtained with lowest head and neck position. (3) Lower and upper airway resistance increased with low head carriage, with a greater increase in upper airway resistance resulting in a decrease in lower to total airway resistance ratio.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of hot-iron disbudding on behaviour and plasma cortisol of calves sedated with xylazine

We investigated cortisol and behaviour for the first hour after hot-iron disbudding of calves aged 37 ± 4 days: disbudded after i/m xylazine (n = 10); disbudded after i/m xylazine and regional anaesthesia with lidocaine (n = 10); sham-disbudded after xylazine and lidocaine (n = 11); sham-disbudded after i/m saline and lidocaine (n = 10). Xylazine-treated groups had higher cortisol than saline-treated animals and showed no differences among them at any time. Sham-disbudded calves with xylazine had lower cortisol at 60 min compared with all other times. Xylazine-alone disbudded calves struggled more during the procedure than all other groups. Xylazine-alone disbudded calves showed more ear-flicks at 10, 25 and 40 min and head-shakes at 40 min than all other groups. We conclude that cortisol should not be used as an indicator of pain in disbudded calves while under the sedative effect of xylazine and that some behaviours during and after the procedure are useful in showing that xylazine alone does not control hot-iron disbudding pain.     

Short latency auditory evoked potentials recorded from non-anaesthetized thoroughbred horses.

The Brainstem Auditory Evoked Potential (BAEP) is a recording of the electrical activity of the brainstem following an acoustic stimulation. Up to seven peaks may be identified within 10 ms, and are labelled I to VII. The first five of these peaks are of most clinical importance, and in normal horses, peaks I, III and V are always present at stimulus intensities of 70-100 dB. Repeated sampling of clinically normal subjects at different stimulus intensities has enabled mean latency values to be determined for the ipsilateral and contralateral peaks I, III and V, and also for the interpeak latencies (IPLs) at each intensity. The maximum, normal, absolute latency for ipsilateral peak I was 1.86 ms, for peak III, 3.53 ms and for peak V, 5.52 ms. The equivalent contralateral values were 2.50 ms, 4.44 ms and 5.59 ms. The maximum, normal, contralateral IPL for I-III was 1.78 ms, that for III-V was 2.26 ms and for I-V was 3.76 ms. The maximum, normal, contralateral IPLs were 2.17 ms for I-III, 1.41 ms for III-V and 3.32 ms for I-V. If a peak or peaks are absent or delayed, or the IPL is greater than expected, the patient can be determined to have abnormal brainstem or auditory nerve conduction. The amplitudes of peaks I and V were measured, and the ratio of amplitudes was determined, to find the normal V:I values. At a stimulus intensity of 100 dB, the ipsilateral ratio was 0.49 +/- 0.19, and the contralateral value 1.49 +/- 0.48. Dispersal values were also calculated, by dividing the height of the III-V complex by its duration. For a stimulus intensity of 100 dB, the ipsilateral dispersal value was 0.416 +/- 0.104 microV/ms, and the contralateral value of 0.473 +/- 0.074 microV/ms. A range of normal values for both V:I ratio and dispersal were calculated. Height, weight and inter-aural distance were measured, and the relationship of the various peaks and IPLs to these variables was ascertained by statistical analysis. For the ipsilateral values, the correlation between the latency of wave V, and III-V and I-V IPLs and weight were significant (P less than 0.01). Significant correlations were found between weight and the latency of contralateral waves III (P less than 0.05) and V (P less than 0.05) and the I-III (P less than 0.01) and I-V (P less than 0.001) IPLs.(ABSTRACT TRUNCATED AT 400 WORDS)     

Caudal epidural analgesia in cattle using xylazine.

Each of 25 mature Holstein cows were given a single 5 mL epidural injection of one of four different concentrations of xylazine or saline. The onset, magnitude and duration of caudal epidural analgesia was quantitated with the use of a low voltage DC current applied to the perineal area. The dose that produced the longest duration of analgesia and produced the least ataxia or sedation was approximately 0.05 mg/kg (25 mg in 5 mL diluent). The analgesia produced by this xylazine dose was compared to a standard dose of epidural lidocaine (100 mg/5 mL) by the same method. To investigate the role of systemic absorption in the production of epidural analgesia, the previously utilized epidural xylazine dosage was given intramuscularly to four adult cows. Analgesia was quantitated as before and the results compared with epidural xylazine. Epidural xylazine produced a significantly greater duration of analgesia, as measured by this model, than did epidural lidocaine. Xylazine, given epidurally, produced greater perineal analgesia than did xylazine given intramuscularly.