Objective-To compare the urodynamic and hemodynamic effects of different dosages of phenylpropanolamine and ephedrine and determine effective dosages in increasing urethral resistance in female dogs. Animals-20 sexually intact female Beagles. Procedure-Dogs were allocated into 4 groups and received phenylpropanolamine once, twice, or 3 times daily, or ephedrine twice daily, for 14 days. On days 0, 7, and 14, urethral pressure profiles were performed while dogs were anesthetized with propofol. Variables recorded included maximum urethral pressure, maximum urethral closure pressure, integrated pressure, functional profile length, anatomic profile length, plateau distance, distance before maximum urethral pressure, and maximum meatus pressure. Arterial and central venous pressures were measured before anesthetic induction and 10 and 35 minutes after induction. Results-Administration of phenylpropanolamine once daily or ephedrine twice daily significantly increased maximum urethral pressure and maximum urethral closure pressure. Values for integrated pressure were significantly increased after 14 days of once-daily administration of phenylpropanolamine. Variables did not change significantly from day 7 to day 14. Diastolic and mean arterial blood pressures increased significantly during the treatment periods, and arterial pressure decreased during propofol infusion. Conclusions and Clinical Relevance-Oral administration of phenylpropanolamine once daily or ephedrine twice daily increased urethral resistance in clinically normal dogs and may be recommended for management of urethral sphincter mechanism incompetence. Treatment efficacy may be assessed after 1 week. Dogs with concurrent cardiovascular disease should be monitored for blood pressure while receiving alpha-adrenergic agents because of the effects on diastolic and mean arterial pressure.

Objective-To evaluate whether additive genetic correlations existed between certain aspects of the radiographic appearance of the distal sesamoid (navicular) bones (RNB) or between RNB and other types of radiographic changes in the limbs of Hanoverian Warmblood horses. Animals-5,157 horses. Procedures-Quasi-linear and binary traits were defined by the appearance of canales sesamoidales (CSs) and the structure and contour of the forelimb navicular bones (NBs). Prevalences of osseous fragments in the metacarphophalangeal and metatarsophalangeal (fetlock) and tarsocrural joints and deforming arthropathy in tarsal joints were analyzed as binary traits. Genetic parameters were estimated by use of multivariate linear models. Results-Heritability estimates for the RNB traits ranged from 0.10 to 0.34. Additive genetic correlations among those traits were usually close to unity. Extensive radiographic changes in the NBs, including changes in CSs and alterations in structure and contour, had correlations with less distinct radiographic changes. Negative additive genetic correlations were observed between small numbers of short and conical CSs in the central portion of the distal border of the NB and osseous fragments and arthropathy, and between most types of radiographic findings in the NBs and osseous fragments in tarsal joints. Conclusions and Clinical Relevance-The genetic bases for different types of RNB were not identical. The detection of correlations between normal RNB and findings of short and conical CSs versus deformed CSs and structural and contour changes warrants further study. Genetically justified distinction between physiologic and pathologic NB changes will increase the efficiency of selecting against NBs with radiographically apparent alterations.

Objective-To evaluate the effects of subarachnoidally administered hyperbaric morphine, buprenorphine, and methadone on avoidance threshold to noxious electrical stimulation of the perineal, sacral, lumbar, and thoracic regions in horses. Animals-6 healthy adult horses. Procedures-Horses were assigned to receive subarachnoid administration of hyperbaric morphine (0.01 mg/kg), buprenorphine (0.001 mg/kg), methadone (0.01mg/kg), or 10% dextrose solution in equal volumes (5 mL). Electrical stimulation was applied every 10 minutes for 60 minutes and every 30 minutes for 120 minutes after subarachnoid injection over the dermatomes of the perineal, sacral, lumbar, and thoracic regions, and the avoidance threshold voltage was recorded. Heart and respiratory rate, blood gas tensions, serum electrolyte concentrations, and sedative effects were also evaluated. Results-Administration of 10% dextrose solution did not change the avoidance threshold. Morphine and methadone significantly increased the avoidance threshold by 10 minutes after injection, which lasted until 120 minutes after subarachnoid administration in the perineal, sacral, lumbar, and thoracic regions. Profound analgesia (avoidance threshold > 40 V) was achieved in all regions. Buprenorphine also significantly increased the avoidance threshold by 10 minutes (36 V) after injection, which lasted 60 minutes and was considered moderate. Heart rate, blood pressure, respiratory rate, and blood gas tensions stayed within reference range. No ataxia, signs of sedation, or CNS excitement were observed. Conclusions and Clinical Relevance-Subarachnoid administration of hyperbaric morphine or methadone produces intense analgesia for 120 minutes over the dermatomes of the perineal, sacral, lumbar, and thoracic areas without cardiorespiratory depression, ataxia, or CNS excitement in horses.

Objective-To evaluate the effect of medetomidine on minimum alveolar concentration (MAC), respiratory rate, tidal volume, minute volume (V(M)), and maximum inspiratory occlusion pressure (IOCP(max)) in halothane- and isoflurane-anesthetized dogs. Animals-6 healthy adult dogs (3 males and 3 females). Procedure-The MAC of both inhalants was determined before and 5, 30, and 60 minutes after administration of medetomidine (5 microgram/kg, IV). Dogs were subsequently anesthetized by administration of halothane or isoflurane and administered saline (0.9% NaCl) solution IV or medetomidine (5 microgram/kg, IV). Respiratory variables and IOCP(max) were measured at specific MAC values 15 minutes before and 5, 30, and 60 minutes after IV administration of medetomidine while dogs breathed 0% and 10% fractional inspired carbon dioxide (FICO2). Slopes of the lines for V(M)/FICO2 and IOCP(max)/FICO2 were then calculated. Results-Administration of medetomidine decreased MAC of both inhalants. Slope of V(M)/FICO2 increased in dogs anesthetized with halothane after administration of medetomidine, compared with corresponding values in dogs anesthetized with isoflurane. Administration of medetomidine with a simultaneous decrease in inhalant concentration significantly increased the slope for V(M)/FICO2, compared with values after administration of saline solution in dogs anesthetized with halothane but not isoflurane. Values for IOCP(max) did not differ significantly between groups. Conclusions and Clinical Relevance-Equipotent doses of halothane and isoflurane have differing effects on respiration that are most likely attributable to differences in drug effects on central respiratory centers. Relatively low doses of medetomidine decrease the MAC of halothane and isoflurane in dogs.

Objective-To describe a novel interlocking nail (ILN) and locking system and compare the torsional properties of constructs implanted with the novel ILN or a standard 8-mm ILN (ILN8) by use of a gap-fracture model. Sample Population-8 synthetic specimens modeled from canine tibiae. Procedures-An hourglass-shaped ILN featuring a tapered locking mechanism was designed. A synthetic bone model was custom-made to represent canine tibiae with a 50-mm comminuted diaphyseal fracture. Specimens were repaired by use of a novel ILN or an ILN8 with screws. Specimens were loaded for torsional measurements. Construct compliance and angular deformation were compared. Results-Compliance of the ILN8 was significantly smaller than that of the novel ILN. Mean +/- SD maximum angular deformation of the ILN8 construct (23.12 +/- 0.65 degrees) was significantly greater, compared with that of the novel ILN construct (9.45 +/- 0.22 degrees). Mean construct slack for the ILN8 group was 15.15 +/- 0.63 degrees, whereas no slack was detected for the novel ILN construct. Mean angular deformation for the ILN8 construct once slack was overcome was significantly less, compared with that of the novel ILN construct. Conclusions and Clinical Relevance-Analysis of results of this study suggests that engineering of the locking mechanism enabled the novel hourglass-shaped ILN system to eliminate torsional instability associated with the use of current ILNs. Considering the potential deleterious effect of torsional deformation on bone healing, the novel ILN may represent a biomechanically more effective fixation method, compared with current ILNs, for the treatment of comminuted diaphyseal fractures.

Objective-To determine the prevalence and temporal onset of lung lesions in lambs and the impact of lung lesions on growth of affected lambs. Animals-259 crossbred wether lambs from a single flock in the upper Midwestern United States. Procedure-An observational study was conducted. Lambs born in the spring and fall were slaughtered at finished weight or at a predetermined time point. Lungs of each lamb were examined and classified as normal, moderate lesions (consolidation > 5% but less than or equal to 50% of any lobe), or severe lesions (consolidation > 50% of any lobe). Data were examined to detect effects of prevalence or severity of lung lesions on growth and carcass traits. Results-57 of 89 (64%) spring-born lambs had lung lesions characterized by consolidation of lung tissue. A small number of lambs had pulmonary adhesions or active abscesses. In contrast, only 31 of 108 (29%) fall-born lambs had lung lesions. Severe lung lesions were associated with a significant reduction in average daily gain. Severe lung lesions were not detected until the middle of the finishing period and were associated with culture of Mannheimia haemolytica or Pasteurella multocida. Conclusions and Clinical Relevance-Analysis of results indicates that the prevalence of severe lung lesions can be quite high in lambs. Severe lung lesions can lead to greatly decreased growth performance of lambs.

Objective-To assess the use of CSF testing with an indirect fluorescent antibody test (IFAT) for diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. Sample Population-Test results of 428 serum and 355 CSF samples from 182 naturally exposed, experimentally infected, or vaccinated horses. Procedure-EPM was diagnosed on the basis of histologic examination of the CNS. Probability distributions were fitted to serum IFAT results in the EPM+ and EPM- horses, and correlation between serum and CSF results was modeled. Pairs of serum-CSF titers were generated by simulation, and titer-specific likelihood ratios and post-test probabilities of EPM at various pretest probability values were estimated. Post-test probabilities were compared for use of a serum-CSF test combination, a serum test only, and a CSF test only. Results-Post-test probabilities of EPM increased as IFAT serum and CSF titers increased. Post-test probability differences for use of a serum-CSF combination and a serum test only were less than or equal to 19% in 95% of simulations. The largest increases occurred when serum titers were from 40 to 160 and pre-test probabilities were from 5% to 60%. In all simulations, the difference between pre- and post-test probabilities was greater for a CSF test only, compared with a serum test only. Conclusions and Clinical Relevance-CSF testing after a serum test has limited usefulness in the diagnosis of EPM. A CSF test alone might be used when CSF is required for other procedures. Ruling out other causes of neurologic disease reduces the necessity of additional EPM testing.

Objective-To determine the relationship between the output of an electrical treatment device and the effective field strength in the superficial digital flexor tendon of horses. Sample Population-Cadaver horse forelimbs without visible defects (n = 8) and 1 live pony. Procedure-Microcurrents were generated by a microcurrent electrical therapy device and applied in proximodistal, dorsopalmar, and mediolateral directions in the entire forelimbs, dissected tendons, and the pony with various output settings. Corresponding field strengths in the tendons were measured. Results-A linear relationship was detected between current and field strength in all conditions and in all 3 directions. In dissected tendons, significant differences were detected among all 3 directions, with highest field strength in the proximodistal direction and lowest in the dorsopalmar direction. In the entire forelimbs, field strength in the proximodistal direction was significantly lower than in the mediolateral direction. Results in the pony were similar to those in the entire forelimbs. Conclusions and Clinical Relevance-Electrode placement significantly affected field strength in the target tissue. Many surrounding structures caused considerable reduction of field strength in the target tissue. These factors should be taken into account when establishing protocols for electrical current-based therapeutic devices if these devices are proven clinically effective.

Objective-To evaluate various sampling strategies for potential use in measuring prevalence of antimicrobial susceptibility in cattle. Sample Population-500 isolates of non-type-specific Escherichia coli (NTSEC) isolated from the feces of 50 cows from 2 dairy farms (25 cows/farm and 10 isolates/cow). Procedures-Diameters of inhibition zones for 12 antimicrobials were analyzed to estimate variation among isolates, cows, and farms and then used to determine sampling distributions for a stochastic simulation model to evaluate 4 sampling strategies. These theoretic sampling strategies used a total of 100 isolates in 4 allocations (1 isolate from 100 cows, 2 isolates from 50 cows, 3 isolates from 33 cows, or 4 isolates from 25 cows). Results-Analysis of variance composition revealed that 74.2% of variation was attributable to isolates, 18.5% to cows, and 7.3% to farms. Analysis of results of simulations suggested that when most of the variance was attributable to differences among isolates within a cow, culturing 1 isolate from each of 100 cows underestimated overall prevalence, compared with results for culturing more isolates per cow from fewer cows. When variance was not primarily attributable to differences among isolates, all 4 sampling strategies yielded similar results. Conclusions and Clinical Relevance-It is not always possible to predict the hierarchical level at which clustering will have its greatest impact on observed susceptibility distributions. Results suggested that sampling strategies that use testing of 3 or 4 isolates/cow from a representative sample of all animals better characterize herd prevalence of antimicrobial resistance when impacted by clustering.

Objective-To characterize pharmacokinetics of voriconazole in horses after oral and IV administration and determine the in vitro physicochemical characteristics of the drug that may affect oral absorption and tissue distribution. Animals-6 adult horses. Procedures-Horses were administered voriconazole (1 mg/kg, IV, or 4 mg/kg, PO), and plasma concentrations were measured by use of high-performance liquid chromatography. In vitro plasma protein binding and the octanol:water partition coefficient were also assessed. Results-Voriconazole was adequately absorbed after oral administration in horses, with a systemic bioavailability of 135.75 +/- 18.41%. The elimination half-life after a single orally administered dose was 13.11 +/- 2.85 hours, and the maximum plasma concentration was 2.43 +/- 0.4 microgram/mL. Plasma protein binding was 31.68%, and the octanol:water partition coefficient was 64.69. No adverse reactions were detected during the study. Conclusions and Clinical Relevance-Voriconazole has excellent absorption after oral administration and a long half-life in horses. On the basis of the results of this study, it was concluded that administration of voriconazole at a dosage of 4 mg/kg, PO, every 24 hours will attain plasma concentrations adequate for treatment of horses with fungal infections for which the fungi have a minimum inhibitory concentration less than or equal to 1 microgram/mL. Because of the possible nonlinearity of this drug as well as the potential for accumulation, chronic dosing studies and clinical trials are needed to determine the appropriate dosing regimen for voriconazole in horses.