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Objective

To identify factors associated with various arterial partial pressures of oxygen (PaO2) in anesthetized horses.

Design

Retrospective study.

Animals

1,450 horses anesthetized a total of 1,610 times with isoflurane or halothane.

Procedure

Anesthesia records, particularly results of blood gas analyses, were reviewed, and horses were grouped on the basis of lowest Pao2.

Results

For horses with lowest Pao2 < 120 mm Hg, those with low pulse pressure, that underwent anesthesia on an emergency basis, or that were males were more likely to have Pao2 < 80 mm Hg. For horses with lowest Pao22 < 250 mm Hg, those that were positioned in dorsal recumbency, that underwent anesthesia on an emergency basis, or that had a shorter duration of anesthesia were more likely to have lowest Pao2 < 120 mm Hg. For horses with lowest PaO2 < 400 mm Hg, those that were positioned in dorsal recumbency, that underwent anesthesia on an emergency basis, that had a shorter duration of anesthesia, that were older, that were heavier, or that were being ventilated mechanically were more likely to have lowest Pao2 < 250 mm Hg.

Conclusions and Clinical Relevance

Low pulse pressure, emergency case status, dorsal recumbency, and short duration of anesthesia were significantly related with lower Pao2 in anesthetized horses. (J Am Vet Med Assoc 1999;215:978–981)

Free access
in Journal of the American Veterinary Medical Association

Summary

Data from 10,769 dogs with rupture of the cranial cruciate ligament (ccl) were compared with data from a control population of 591,548 dogs to determine whether age, breed, gender, or body weight was associated with prevalence of ccl rupture. Prevalence of ccl rupture increased as dogs became older, with peak prevalence in dogs 7 to 10 years old. Among breeds represented by > 1,000 individuals, Rottweilers, Newfoundlands, and Staffordshire Terriers had the highest prevalence of ccl rupture, whereas Dachshunds, Basset Hounds, and Old English Sheepdogs had the lowest. Neutered dogs, whether male or female, had a higher prevalence of ccl rupture than did sexually intact dogs. The dog's age at the time of ovariohysterectomy was not associated with prevalence of ccl rupture. Dogs weighing > 22 kg had a higher prevalence of ccl rupture, compared with dogs weighing < 22 kg, and tended to rupture their ccl at a younger age.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To develop an objective, accurate method for quantifying forelimb ground reaction forces in horses by adapting a human in-shoe pressure measurement system and determine the reliability of the system for shod and unshod horses.

Animals—6 adult Thoroughbreds.

Procedure—Horses were instrumented with a human in-shoe pressure measurement system and evaluated at a trot (3 m/s) on a motorized treadmill. Maximum force, stance time, and peak contact area were evaluated for shod and unshod horses. Three trials were performed for shod and unshod horses, and differences in the measured values were examined with a mixed model ANOVA for repeated measures. Sensor accuracy was evaluated by correlating measured variables to clinically observed lameness and by a variance component analysis.

Results—4 of 6 horses were determined to be lame in a forelimb on the basis of clinical examination and measured values from the system. No significant differences were observed between shod and unshod horses for maximum force and stance time. A significant decrease in peak contact area was observed for shod and unshod horses at each successive trial. Maximum force measurements provided the highest correlation for detecting lameness ( r = 0.91, shod horses; r = 1.0, unshod horses). A variance component analysis revealed that 3 trials provided a variance of 35.35 kg for maximum force (± 5.78% accuracy), 0.007 seconds for stance time (± 2.5% accuracy), and 8.58 cm2 for peak contact area (± 11.95% accuracy).

Conclusions and Clinical Relevance—The in-shoe pressure measurement system provides an accurate, objective, and effective method to evaluate lameness in horses. ( Am J Vet Res 2001;62:23–28)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To describe the prevalence, characteristics, and severity of soft-tissue and osseous lesions in the caudal portion of the thoracic and lumbosacral vertebral column and pelvis in Thoroughbred racehorses.

Animals

36 Thoroughbred racehorses that died or were euthanatized at California racetracks between October 1993 and July 1994.

Procedure

Lumbosacral and pelvic specimens were collected and visually examined for soft-tissue and osseous lesions.

Results

Acute sacroiliac joint injury was observed in 2 specimens. Signs of chronic laxity or subluxation of the sacroiliac joint were not observed in any specimens. Impingement of the dorsal spinous processes and transverse processes was observed in 92 and 97% of specimens, respectively. Thoracolumbar articular processes had variable degrees of degenerative change in 97% of specimens. Degenerative changes were observed at lumbar intertransverse joints and sacroiliac articulations in all specimens. Some degenerative changes were widespread and severe.

Conclusions

Numerous degenerative changes affected vertebral processes, intervertebral articulations, and sacroiliac joints in these Thoroughbred racehorses.

Clinical Relevance

Various types of vertebral and pelvic lesions need to be considered during clinical evaluation of the back and pelvis in horses. Undiagnosed vertebral or pelvic lesions could be an important contributor to poor performance and lameness in athletic horses. (Am J Vet Res 1999:60:143-153).

Free access
in American Journal of Veterinary Research

Abstract

Objective

To describe the incidence and types of gross osseous developmental variations and ages of physeal closure in the caudal portion of the thoracic and lumbosacral spine and the pelvis in a sample of Thoroughbred racehorses.

Animals

Thoroughbred racehorses (n = 36) that died or were euthanatized at California racetracks between October 1993 and July 1994.

Procedure

Lumbosacropelvic specimens were collected, and all soft tissues were removed. The osseous specimens were visually examined.

Results

Only 22 (61 %) specimens had the expected number of 6 lumbar and 5 sacral vertebrae. Eight (22%) specimens had thoracolumbar transitional vertebrae, and 13 (36%) had sacrocaudal transitional vertebrae. Articular process asymmetries were present at 1 or more vertebral segments in 30 (83%) specimens. Intertransverse joints (2 to 4 pairs/specimen) were bilaterally distributed in the caudal portion of the lumbar spine and the lumbosacral joint in 31 (86%) specimens. Five (14%) specimens had asymmetric distribution of the intertransverse joints. Intertransverse joint ankylosis was found in 10 (28%) specimens. Lumbosacral vertebral body physeal closure occurred between 4.9 and 6.7 years of age; pelvic physeal closure occurred between 5.2 and 5.8 years of age. Iliac crest and ischial arch epiphyseal formation was evaluated, using a grading system, and fusion to the underlying bone occurred at 7.2 years and 5.4 years of age, respectively.

Conclusions

Numerous vertebral anatomic variations were commonly found in a sample of Thoroughbred racehorses.

Clinical Relevance

Normal anatomic variations and ages of skeletal maturity need to be considered in clinical evaluation of the equine spine and pelvis for differentiation from pathologic findings. (Am J Vet Res 1997;58:1083–1091)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To study the effects of inhalation anesthetic agents on the response of horses to 3 hours of hypoxemia.

Design

Controlled crossover study.

Animals

Five healthy adult horses.

Procedure

Horses were anesthetized twice: once with halothane, and once with isoflurane in O2. Anesthetized horses were positioned in left lateral recumbency. Constant conditions for the study began at 2 hours of anesthesia. A constant agent dose of 1.2 minimum alveolar concentration, PaO2 of 50 ± 5 mm of Hg, and PaCO2 of 45 ± 5 mm of Hg were maintained for 3 hours. Circulatory measurements were made at 0.5, 1, 2, and 3 hours of hypoxemia (anesthesia hours 2.5, 3, 4, and 5). Blood was collected from horses for biochemical analyses before anesthesia, within a few minutes after standing, and at 1, 2, 4, and 7 days after anesthesia.

Results

Cardiac index was greater (P = 0.018) during isoflurane than halothane anesthesia. Cardiac index remained constant during the 3 hours of hypoxemia during halothane anesthesia, whereas it decreased from the baseline during isoflurane anesthesia. Marginally nonsignificant P values for an agent difference were detected for arterial O2 content (P = 0.051), and oxygen delivery (P = 0.057). Serum activities of aspartate transaminase (P = 0.050) and sorbitol dehydrogenase (P = 0.017) were higher in halothane-anesthetized horses than in isoflurane-anesthetized horses. Circulatory function was better in hypoxemic horses anesthetized with isoflurane than with halothane. Isoflurane resulted in less muscular injury in hypoxemia horses than did halothane anesthesia. Halothane anesthesia and hypoxemia were associated with hepatic insult.

Conclusion

Isoflurane is better than halothane for hypoxemic horses.(Am J Vet Res 1996;57:351-360)

Free access
in American Journal of Veterinary Research

SUMMARY

Fifty Thoroughbred horses were examined. All horses had been in race training for a minimum of 4 months before examination and had worked at racing speed; 24 horses had raced. All horses were clinically sound at the time of examination. Ultrasonography was performed, using a 7.5-MHz transducer with built-in fluid offset. Videotaped images of the palmar soft tissue structures were obtained at 4, 8, 12, 16, 20, and 24 cm distal to the base of the accessory carpal bone (dacb). Images were digitized, and each image was calibrated. Values for cross-sectional area (csa) and mean echogenicity (me) were then determined from the cross-sectional images of the superficial digital flexor (sdf) and the deep digital flexor (ddf) tendons, using an image-analysis program.

The sdf tendons were compared between right and left forelimbs at each level, and from proximad to distad on each limb, as were the ddf tendons. The relation between the sdf and ddf tendons for the same forelimb was determined at each level. There were no significant differences in csa or me at equivalent levels of the left and right sdf tendons. Mean (± sd) csa was 1.01 (± 0.12) cm2 at 4 cm dacb, 0.95 (± 0.14) cm2 at 12 cm dacb, and 1.12 (± 0.15) cm2 at 24 cm dacb. Adjusted me was 2.34 (± 0.34) at 4 cm dacb, 2.03 (± 0.38) at 12 cm dacb, and 2.04 (± 0.35) at 24 cm dacb.

The left and right ddf tendons did not have significant differences in csa or me at any level. Cross-sectional area was 1.13 (± 0.18) cm2 at 4 cm dacb, 1.01 (± 0.12) cm2 at 12 cm dacb, and 1.75 (± 0.29) cm2 at 24 cm dacb. Adjusted me was 2.60 (± 0.46) at 4 cm dacb, 2.49 (± 0.49) at 12 cm dacb, and 2.50 (± 0.44) at 24 cm dacb.

At all levels, the left and right sdf tendons were smaller and less echoic than the ddf tendons of the same limb. The sdf and ddf tendons had an hourglass shape, with smallest csa at 12 cm dacb. Mean echogenicity generally decreased for the sdf and ddf tendons from proximad to distad on the limb.

These results indicate that for clinically normal trained Thoroughbred racehorses, there should be no significant difference in csa or echogenicity between the left and right sdf tendons at equivalent distances dacb. There should be no significant differences in the left and right ddf tendons at equivalent levels dacb. The sdf tendon is usually smaller and less echoic than the corresponding ddf tendon at each level.

Free access
in American Journal of Veterinary Research

Summary

To evaluate the efficacy of penicillin or penicillin and dexamethasone for treatment of infectious bovine keratoconjunctivitis, 6- to 8-month-old beef heifers with clinical signs of infectious bovine keratoconjunctivitis were randomly assigned to 1 of 3 treatment groups: penicillin only, penicillin and dexamethasone, or control. Cattle assigned to the penicillin group (n = 18) were treated with 3 daily subconjunctival injections of procaine penicillin G. Cattle assigned to the penicillin/ dexamethasone group (n = 13) were treated with 3 daily subconjunctival injections of procaine penicillin G and dexamethasone sodium phosphate. Control cattle (n = 14) were not treated. Healing times and frequency of recurrence for corneal ulcers; severity, diameter, and surface area measurements of corneal ulcers; and clinical scores did not differ among the 3 groups. Frequency of Moraxella bovis isolation from specimens of ocular secretions from ulcerated and nonulcerated eyes was similar in all groups. Minimum inhibitory concentration of penicillin G for 95 of the 102 tested M bovis isolates was 0.3 U/ml, and for 7 others was 0.03 U/ml. When first and last specimens from 42 of 45 calves with isolation of M bovis on serial microbial cultures were compared, the susceptibility of each last isolate was similar to that of the corresponding first isolate.

Free access
in Journal of the American Veterinary Medical Association

Summary

The metabolic responses of equine articular cartilage to incubation with bacterial lipopolysaccharide (lps) were studied, using explant cultures of articular cartilage obtained from the metatarsophalangeal joints of 15 horses, age of which ranged from 3 months to 20 years. For comparison, explants were also established from the metatarsophalangeal joints of 3 calves. Explants were cultured for 3 days in medium containing various concentrations of lps from 0 (control) to 100 μg/ml. Glycosaminoglycan (gag) released during the 3-day incubation was determined by a spectrophotometric assay, using the dye 1,9-di-methylmethylene blue. Newly synthesized gag content was assayed by measuring [35S]sulfate incorporation during a 3-hour pulse labeling period. In addition, prostaglandin E2 (pge 2) synthesis was quantified, using a [3H]pge 2 radioimmunoassay kit and magnetic separation. Finally, explants from 3 animals were used to evaluate the effect of supplementing culture medium with 5% serum on the response of explants to lps, and explants from 1 horse were used to compare responses to stimulation with lps derived from 2 bacterial sources.

Equine explants cultured with bacterial lps had a dose-dependent decrease in synthesis and increase in release of gag, and these responses were significantly (P < 0.0001) greater in explants from younger horses. In addition, equine explants had a significant (P = 0.0001) dose-dependent increase in concentration of pge 2 released into the culture medium in response to incubation with lps.

Comparison of data for gag synthesis from equine and bovine explants revealed a significant (P = 0.025) difference in responsiveness to lps between the 2 species. Equine explants tended to have a greater suppression of gag synthesis in response to incubation with increasing concentrations of lps than did age-corrected bovine samples. However, similar analysis of data on gag release did not indicate any difference in sensitivity between the 2 species for this response. There was no evidence that the presence or absence of serum supplementation or the use of lps derived from different bacterial sources made a significant difference in the response of explants to incubation with lps.

Free access
in American Journal of Veterinary Research

Summary

To study behavioral and cardiopulmonary characteristics of horses recovering from inhalation anesthesia, 6 nonmedicated horses were anesthetized under laboratory conditions on 3 different days, with either halothane or isoflurane in O2. Anesthesia was maintained at constant dose (1.5 times the minimum alveolar concentration [mac]) of halothane in O2 for 1 hour (H1), halothane in O2 for 3 hours (H3), or isoflurane in O2 for 3 hours (I3). The order of exposure was set up as a pair of Latin squares to account for horse and trial effects. Circulatory (arterial blood pressure and heart rate) and respiratory (frequency, PaCO2 , PaO2 , pHa) variables were monitored during anesthesia and for as long as possible during the recovery period. End-tidal percentage of the inhaled agent was measured every 15 seconds by automated mass spectrometry, then by hand-sampling after horses started moving. Times of recovery events, including movement of the eyelids, ears, head, and limbs, head lift, chewing, swallowing, first sternal posture and stand attempts, and the number of sternal posture and stand attempts, were recorded.

The washout curve or the et ratio (end-tidal percentage of the inhaled agent at time t to end-tidal percentage of the inhaled agent at the time the anesthesia circuit was disconnected from the tracheal tube) plotted against time was similar for H1 and H3. The slower, then faster (compared with halothane groups) washout curve of isoflurane was explainable by changes in respiratory frequency as horses awakened and by lower blood/gas solubility of isoflurane. The respiratory depressant effects of isoflurane were marked and were more progressive than those for halothane at the same 1.5 mac dose. During the first 15 minutes of recovery, respiratory frequency for group-I3 horses increased significantly (P < 0.05), compared with that for the halothane groups. For all groups, arterial blood pressure increased throughout the early recovery period and heart rate remained constant.

Preanesthesia temperament of horses and the inhalation agent used did not influence the time of the early recovery events (movement of eyelids, ears, head, and limbs), except for head lift. For events that occurred at anesthetic end-tidal percentage < 0.20, or when horses were awake, temperament was the only factor that significantly influenced the nature of the recovery (chewing P = 0.04, extubation P = 0.001, first stand attempt P = 0.008, and standing P = 0.005). The quality of the recoveries did not differ significantly among groups (H1, H3, I3) or horses; however 5 of 6 horses recovering from the H1 exposure had ideal recovery. During recovery, the anesthetic end-tidal percentage did not differ significantly among groups. However, when concentrations were compared on the basis of anesthetic potency (ie, mac multiple) a significantly (P < 0.05) lower MAC multiple of isoflurane was measured for the events ear movement, limb movement, head lift, and first attempt to sternal posture, compared with that for horses given halothane, indicating that isoflurane may be a more-potent sedative than halothane in these horses.

Free access
in American Journal of Veterinary Research