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Abstract

Objective

To determine whether clearance of capacity-limited drugs in horses differs from that in donkeys by comparing the serum disposition of caffeine and its metabolites, theophylline, theobromine, and paraxanthine after IV administration of caffeine to horses and donkeys.

Animals

4 healthy horses and 5 healthy donkeys.

Procedure

Blood samples were collected from each animal at time 0. (before) and 5,10, 15, 20, 30, and 45 minutes, and 1, 2, 3, 4, 6, 8, 12, 24, 30, 36, 48, 54, 60, 72, and 96 hours after IV administration of a bolus of caffeine. Serum was analyzed in triplicate by high-performance liquid chromatography to determine caffeine, theophylline, theobromine, and paraxanthine concentrations. The serum concentration-time curves for each animal were analyzed separately to estimate model-independent pharmacokinetic variables.

Results

Mean pharmacokinetic values for caffeine, theophylline, and paraxanthine did not differ significantly in horses, compared with donkeys. Mean peak serum concentration of theobromine was significantly higher in donkeys, compared with horses.

Conclusion

Clearance of the capacity-limited drug caffeine does not appear to differ in horses, compared with donkeys.

Clinical Relevance

For some drugs that undergo hepatic metabolism, the dose and dose interval used for horses may be appropriate for use in donkeys. (Am J Vet Res 1997;58:881–884)

Free access
in American Journal of Veterinary Research

SUMMARY

Cardiopulmonary effects of iv administered butorphanol tartrate (but) were assessed in 7 yearling steers medicated with atropine and anesthetized with guaifenesin, thiamylal sodium, and isoflurane in O2 for surgical placement of duodenal cannulae. Heart rate, respiratory rate, arterial blood pressures, pHa, Paco2 , Pao2 arterial [HCO3 -], esophageal temperature, and end-tidal isoflurane concentrations were measured before and after iv administration of but (10 mg).

Mean respiratory rate increased significantly (P < 0.05) only at 45 and 60 minutes after but administration. Mean respiratory rate was 26 ± 6.3 breaths/min before but administration and 46 ± 12.1 breaths/min 60 minutes after but administration. Arterial blood pressures were increased significantly (P < 0.05) at all times, except 5 minutes after but administration. The mean value for mean arterial pressure was 76 ± 9.6 mm of Hg before but injection and 117 ± 12.6 mm of Hg 60 minutes after but injection. Mean values for pHa and arterial [HCO3 -] were significantly (P < 0.05) higher at 60 minutes after but administration (baseline, pH = 7.25 ± 0.04 and [HCO3 -] = 29.9 ± 3.5 mEq/L; 60 minutes after but, pH = 7.28 ± 0.03 and [HCO3 -] = 33.0 ± 1.8 mEq/L). Although some statistically significant changes were recorded, iv administration of but to these steers did not have a marked effect on the cardiopulmonary variables measured.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare plasma disposition of phenylbutazone and its metabolite oxyphenbutazone after IV administration of phenylbutazone in horses and donkeys.

Animals

4 clinically normal horses and 6 clinically normal donkeys.

Procedure

Blood samples were collected from each animal at time 0 (before) and 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300, 360, and 480 minutes after IV administration of a bolus dose of phenylbutazone. Serum was analyzed in triplicate by use of high-performance liquid chromatography for determination of phenylbutazone and oxyphenbutazone concentrations. The serum concentration-time curve for each horse and donkey was analyzed separately to estimate model-independent pharmacokinetic variables.

Results

Significant differences were found in several pharmacokinetic variables of phenylbutazone and oxyphenbutazone in horses, compared with donkeys. Mean total body clearance of phenylbutazone in horses was fivefold less than that in donkeys (29.3 and 170.3 ml/kg/h, respectively). Mean values for area under the curve and mean residence time in horses (118.3 µg/h/ml and 3.6 hours, respectively) were significantly greater than values in donkeys (28.3 µg/h/ml and 1.7 hours, respectively). Mean values for apparent volume of distribution at steady state were not significantly different between horses and donkeys. For oxyphenbutazone, mean time to peak concentration in donkeys was significantly less than that in horses (1.6 and 6.4 hours, respectively).

Conclusion

Phenylbutazone clearance in donkeys was higher than that in horses, and appearance of the metabolite oxyphenbutazone in serum was more rapid in donkeys than in horses, indicating that hepatic metabolism of phenylbutazone is more rapid in donkeys than in horses.

Clinical Relevance

Because serum concentration of phenylbutazone after single IV bolus administration (4.4 mg/kg of body weight) decreases more rapidly in donkeys, compared with horses, phenylbutazone may require more frequent administration in donkeys to achieve therapeutic efficacy. (Am J Vet Res 1997;58:53–55)

Free access
in American Journal of Veterinary Research

Summary

Cortical bone screws were implanted into the proximal portion of the right and left radius and ulna of 6 newborn Quarter Horse foals as radiographic markers for measurement of growth. Distance between markers on a lateral radiographic view was measured. Radiographs were taken at 2-week intervals until the horses were 8 weeks old, at 4-week intervals until they were 48 weeks old, and at 12-week intervals until they were 72 weeks old.

The proximal radius and ulna grew at similar rates during the 72-week period of evaluation, and growth continued throughout 72 weeks. The proximal radius grew 3.5 cm, and the ulna grew 3.4 cm. Although the rates of growth were similar, growth from the ulnar physis contributed only to the length of the olecranon; growth was not transmitted to the ulnar diaphysis distal to the cubital joint. The proximal radius slid distally in relation to the ulna as growth occurred at the proximal radial physis.

These findings suggest that transfixing the ulna to the radius while growth is occurring at the proximal radial physis impedes the natural shifting process, and subluxation of the elbow can result. Severity of subluxation would be inversely related to the age of the horse at the time of transfixation.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of incremental radial shortening and subsequent ulnar ostectomies on joint surface contact patterns in a canine elbow joint model.

Sample Population—Paired forelimbs from 9 adult dogs.

Procedure—Joint casting was performed by placement of colored polymethylmethacrylate in the elbow joint cavity and loading in a materials testing system at physiologic angle and load. Joint casting was performed in unaltered specimens, after radial shortening, and after subsequent distal ulnar ostectomy, proximal ulnar ostectomy, and proximal ulnar ostectomy with intramedullary pinning. Computer-aided analysis of photographs of proximal radial and ulnar articular surfaces without joint casts was performed before and after each casting procedure.

Results—All increments of radial shortening changed the size and location of radial and ulnar contact areas. The radial contact area became smaller, the anconeal contact area disappeared, the medial coronoid contact area migrated craniolaterally, and the lateral projection of the coronoid process became a contact area. A proximal ulnar ostectomy stabilized with an intramedullary pin restored normal contact area size and location and restored continuity of the radial and coronoid contact areas across the radioulnar articulation in 6 of 10 specimens. A midshaft ulnar ostectomy, distal to the level of the radioulnar ligament, had no effect on contact patterns. A proximal ulnar ostectomy without stabilization resulted in varus deformity during loading.

Conclusion and Clinical Relevance—Proximal radial shortening, which creates articular step incongruity, changes the location and size of the radioulnar contact areas. Dynamically stabilized ulnar ostectomies proximal to the radioulnar ligament restore contact patterns in vitro . (Am J Vet Res 2001;62:1548–1556)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare in vitro mechanical properties of toggle pins and toggle rods used as suture anchors and of 3 suture materials (50-lb monofilament polybutester, No. 5 braided polyester, and 5-mm woven polyester) commonly used as prosthetic ligaments in the repair of hip joint luxation in dogs.

Sample Population—Femoropelvic specimens from the cadavers of 18 dogs.

Procedure—Suture anchors were compared by use of pullout tests. Suture materials were compared by use of monotonic and cyclic tensile tests; cyclic tensile tests were performed with the suture placed over the edge of an aluminum bar to simulate the edge of the femoral bone tunnel. In vitro mechanical properties of the ligament of the femoral head were determined by use of monotonic tensile tests, using boneligament-bone cadaveric specimens. The in vitro mechanical properties of the acetabulum-ligamentfemur complex and of this complex following rupture of the ligament and stabilization with a toggle rod and 5-mm woven polyester were determined by use of compression tests that simulated weight-bearing.

Results—Mechanical properties of the toggle rod were not significantly different from those of the toggle pin. Woven polyester had the longest fatigue life in cyclic testing. Hip joints stabilized with a toggle rod and woven polyester had less than half the strength in vitro of intact joints.

Conclusions and Clinical Relevance—Results suggested that a toggle rod or toggle pin can be used for stabilization of hip joint luxations in dogs. Of the materials tested, braided polyester had the best in vitro mechanical properties. (Am J Vet Res 2001;62: 721–728)

Full access
in American Journal of Veterinary Research

Summary

During a 5-year period, renosplenic entrapment of the large colon was diagnosed in 57 horses referred to the Texas Veterinary Medical Center. The signalment of and clinical signs of disease in these horses were compared with such variables in 200 horses referred for other types of colic. Findings did not support a male gender predilection for this disease, as was previously reported. The case survival rate was 93% for this group of horses. Fourteen of the horses were treated nonsurgically by rolling them clockwise while they were under general anesthesia. Data supported the safety and efficacy of nonsurgical treatment.

Free access
in Journal of the American Veterinary Medical Association

Summary

From 1980 to 1989, 8 cesarean sections were performed on an elective basis in 5 mares. Four mares had partially obstructed pelvic canals; 2 of these mares had previously lost foals because of dystocia. Cervical adhesions that might obstruct passage of the fetus through the pelvic canal was suspected in the fifth mare. Cesarean section was performed prior to mares entering the first stage of labor. Readiness for birth was estimated by development of the mare's mammary gland and the presence of colostrum in the udder. A ventral midline celiotomy provided excellent exposure and healed without complications in all instances. Eight viable foals were produced. One foal developed bacterial pneumonia and septicemia after surgery and died. Follow-up evaluation of the 7 foals discharged from the hospital failed to reveal complications associated with elective cesarean section.

All mares survived the procedure. Fetal membranes were retained for up to 72 hours following surgery; however, systemic complications secondary to retained placenta did not develop. Three mares were bred subsequent to elective cesarean sections, with each mare conceiving the year following surgery. Three foals were produced by 1 mare and 2 foals have been produced by another mare by elective cesarean sections.

Free access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To describe outcomes for dogs after treatment of craniodorsal hip luxation with closed reduction and Ehmer sling placement and investigate potential risk factors for sling-associated tissue injury or reluxation of the affected hip at or near the time of sling removal.

DESIGN Retrospective multicenter cohort study.

ANIMALS 92 dogs.

PROCEDURES Case information was solicited from 10 veterinary medical facilities through electronic communications. Data on patient demographic information, cause of injury, presence of concurrent injuries, details of Ehmer sling placement and management, and outcome at sling removal were collected. Data were analyzed for associations with outcomes.

RESULTS 40 of 92 (43.5%) dogs had reluxation of the affected hip joint at or near the time of sling removal. Odds of reluxation occurring for dogs that had the initial injury attributed to trauma were 5 times those for dogs without known trauma (OR, 5.0; 95% confidence interval, 1.3 to 18.7). Forty-six (50%) dogs had soft tissue injuries secondary to sling use; 17 of these dogs had injuries classified as severe, including 1 dog that required limb amputation. Odds of severe sling injury for dogs that had poor owner compliance with home care instructions noted in the record, those that had the sling placed by an intern rather than a board-certified surgeon or resident, and those that were noted to have a soiled or wet bandage on ≥ 1 occasion were 12.5, 4.0, and 5.7 times those for dogs without these findings, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE Placement of an Ehmer sling following closed reduction of a craniodorsal hip luxation had a low success rate and high complication rate.

Full access
in Journal of the American Veterinary Medical Association