OBJECTIVE To determine the minimum alveolar concentration that blunts adrenergic responses (MAC(BAR)) for isoflurane and evaluate effects of fentanyl on isoflurane MAC(BAR) in sheep. ANIMALS 13 healthy adult Dorset-cross adult ewes. PROCEDURES In a crossover design, each ewe was anesthetized 2 times for determination of isoflurane MAC(BAR). Anesthesia was induced with propofol administered IV. Sheep initially received fentanyl (5 μg/kg, IV, followed by a constant rate infusion of 5 μg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (control treatment). After a washout period of at least 8 days, the other treatment was administered. For MAC(BAR) determination, a mechanical nociceptive stimulus (ie, sponge forceps) was applied at the coronary band for 1 minute. The MAC(BAR) values of the 2 treatments were compared by means of a paired t test. During MAC(BAR) determination, blood samples were collected for measurement of plasma fentanyl concentration. RESULTS Mean ± SD isoflurane MAC(BAR) of the fentanyl and control treatments was 1.70 ± 0.28% and 1.79 ± 0.35%, respectively; no significant difference was found between the 2 treatments. Plasma concentration of fentanyl reached a median steady-state concentration of 1.69 ng/mL (interquartile range [25th to 75th percentile], 1.47 to 1.79 ng/mL), which was maintained throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE Administration of fentanyl at 5 μg/kg, IV, followed by a constant rate infusion of the drug at 5 μg/kg/h did not decrease isoflurane MAC(BAR). Further studies to determine the effect of higher doses of fentanyl on inhalation anesthetic agents and their potential adverse effects are warranted.

OBJECTIVE To evaluate the potential usefulness of epiduroscopy for clinical diagnosis and treatment of vertebral canal and spinal cord lesions in dogs. SAMPLE Cadavers of 6 mixed-breed dogs. PROCEDURES Dogs were positioned in sternal recumbency, and an endoscope was introduced into the lumbosacral epidural space. A fiberscope (diameter, 0.9 mm; length, 30 cm) was used for 3 dogs, and a videoscope (diameter, 2.8 mm; length, 70 cm) was used for the other 3 dogs. Visibility and identities of anatomic structures were recorded, and maneuverability of the endoscopes was assessed. Extent of macroscopic tissue damage was evaluated by manual dissection of the vertebral canal at the end of the procedure. RESULTS Intermittent saline (0.9% NaCl) solution infusion, CO2 insufflation, and endoscope navigation improved visualization by separating the epidural fat from the anatomic structures of interest. Images obtained with the fiberscope were small and of poor quality, making identification of specific structures difficult. Maneuverability of the fiberscope was difficult, and target structures could not be reliably reached or identified. Maneuverability and image quality of the videoscope were superior, and spinal nerve roots, spinal dura mater, epidural fat, and blood vessels could be identified. Subsequent manual dissection of the vertebral canal revealed no gross damage in the spinal cord, nerve roots, or blood vessels. CONCLUSIONS AND CLINICAL RELEVANCE A 2.8-mm videoscope was successfully used to perform epiduroscopy through the lumbosacral space in canine cadavers. Additional refinement and evaluation of the technique in live dogs is necessary before its use can be recommended for clinical situations.

OBJECTIVE To determine the temporal effects on tear flow measurements obtained by use of a Schirmer tear test (STT) I after IM administration of various doses of medetomidine or xylazine to healthy dogs. ANIMALS 5 healthy purpose-bred male Beagles. PROCEDURES Each dog received IM injections of 2.0 mL of physiologic saline (0.9% NaCl) solution (control treatment); 0.1% medetomidine hydrochloride (5, 10, 20, and 40 μg/kg), and 2.0% xylazine hydrochloride (0.5, 1.0, 2.0, and 4.0 mg/kg). Treatments were injected into the semimembranosus muscles; there was at least a 1-week interval between successive injections. Order of treatments was determined via a randomized Latin square crossover design. The STT I was performed on both eyes before (baseline) and 0.25, 0.50, 0.75, 1, 2, 3, 4, 5, 6, 7, 8, and 24 hours after each injection.RESULTS STT I values decreased significantly within 45 minutes after injection of medetomidine or xylazine, which was followed by gradual recovery. The lowest mean STT I value was < 10 mm/min for all sedation treatments, except when dogs received 5 μg of medetomidine/kg. Linear regression of the area under the curve for the 8 hours after administration yielded significant effects for all sedation treatments. CONCLUSIONS AND CLINICAL RELEVANCE IM administration of medetomidine or xylazine to dogs reduced tear flow in a dose-related manner. Artificial tear solution or ophthalmic ointment should be used to protect the ocular surface when these drugs are administered to dogs.

OBJECTIVE To compare the anticollagenase efficacy of fresh feline, canine, and equine serum and plasma on in vitro corneal degradation. SAMPLE Grossly normal corneas from recently euthanized dogs, cats, and horses and fresh serum and plasma from healthy dogs, cats, and horses. PROCEDURES Serum and plasma were pooled by species and used for in vitro experiments. Corneas were collected and stored at −80°C. Sections of cornea were dried, weighed, and incubated in saline (0.9% NaCl) solution with clostridial collagenase and homologous fresh serum or plasma. Corneal degradation was assessed as the percentage of corneal weight loss and hydroxyproline concentration, compared with results for positive and negative control samples. RESULTS Homologous fresh serum and plasma significantly reduced the percentage of corneal weight loss, compared with results for positive control samples. No significant difference was found in percentage of corneal weight loss between incubation with serum or plasma for feline, canine, and equine corneas. Canine serum and plasma significantly reduced hydroxyproline concentrations, whereas inclusion of feline and equine serum or plasma did not, compared with results for positive control samples. Hydroxyproline concentrations were moderately correlated with percentage of corneal weight loss for feline samples and weakly correlated for equine samples, but they were not correlated for canine samples. CONCLUSIONS AND CLINICAL RELEVANCE In this study, the anticollagenase efficacy of fresh feline, canine, and equine serum was not different from that of plasma. Plasma should be an acceptable substitute for serum in the topical treatment of keratomalacia.

OBJECTIVE To evaluate pharmacokinetics of bupivacaine after IP administration to cats undergoing ovariohysterectomy. ANIMALS 8 healthy cats. PROCEDURES Anesthesia was induced with propofol and maintained with isoflurane. Buprenorphine (0.02 mg/kg, IV) and meloxicam (0.2 mg/kg, SC) were administered. A 20-gauge catheter was inserted into a jugular vein for blood sample collection. A ventral midline incision was made, and a solution of 0.5% bupivacaine (2 mg/kg) diluted with an equal volume of saline (0.9% NaCl) solution (final concentration, 0.25% bupivacaine) was injected into the peritoneal space over the right and left ovarian pedicles and caudal aspect of the uterus before ovariohysterectomy. Cats were monitored for signs of bupivacaine toxicosis. Venous blood samples (2 mL) were collected before (time 0) and 2, 5, 10, 15, 20, 30, 60, 120, and 240 minutes after bupivacaine administration. Plasma bupivacaine concentrations were determined with a liquid chromatography–tandem mass spectrometry method. Pharmacokinetic parameters were determined by data plotting followed by analysis with a noncompartmental model. RESULTS No signs of bupivacaine toxicosis were observed. Maximum bupivacaine plasma concentration was 1,030 ± 497.5 ng/mL at a mean ± SD value of 30 ± 24 minutes after administration. Mean elimination half-life was 4.79 ± 2.7 hours. Mean clearance indexed by bioavailability and volume of distribution indexed by bioavailability were 0.35 ± 0.18 L•h/kg and 2.10 ± 0.84 L/kg, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Intraperitoneal administration of bupivacaine resulted in concentrations that did not cause observable toxicosis. Studies to investigate analgesic effects for this technique in cats are warranted.

OBJECTIVE To evaluate 4 methods for generating decellularized equine synovial extracellular matrix. SAMPLE Villous synovium harvested from the femoropatellar and medial femorotibial joints of 4 healthy adult horses < 7 years of age. Synovial samples were frozen (−80°C) until used. PROCEDURES Synovial samples were thawed and left untreated (control) or decellularized with 1 of 4 methods (15 samples/horse/method): incubation in 0.1% peracetic acid (PAA), incubation in 0.1% PAA twice, incubation in 1% Triton X-100 followed by incubation in DNase, and incubation in 2M NaCl followed by incubation in DNase. Control and decellularized samples were examined for residual cells, villous integrity, and collagen structure and integrity by means of histologic examination and scanning electron microscopy; cell viability was evaluated by means of culture and exclusion staining. Decellularization efficiency was assessed by testing for DNA content and DNA fragment size. RESULTS Incubation in PAA once preserved the synovial villous architecture, but resulted in high DNA content and retention of large (> 25,000 base pair) DNA fragments. Incubation in Triton and incubation in NaCl resulted in low DNA content and short (< 200 base pair) DNA fragments, but destroyed the synovial villous architecture. Incubation in PAA twice resulted in low DNA content and short DNA fragments while retaining the synovial villous architecture. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that of the methods evaluated, incubation in 0.1% PAA twice was the best method for generating decellularized equine synovial extracellular matrix.

OBJECTIVE To determine effects of 2 tiludronate administration protocols on measures of lameness in horses with navicular syndrome (NS). ANIMALS 12 horses with bilateral forelimb NS. PROCEDURES Horses were randomly assigned to receive tiludronate (1 mg/kg), diluted in 5 L of isotonic electrolyte solution and delivered through a jugular vein catheter (systemic treatment group; n = 6), or tiludronate (0.1 mg/kg), diluted with saline (0.9% NaCl) solution to a total volume of 35 mL and delivered into the lateral digital vein of each forelimb with an IV regional limb perfusion (IVRLP) technique (IVRLP group; 6). Mean peak vertical ground reaction force (pVGRF) measured with a stationary force plate and subjective lameness scores (SLSs) were recorded before (day −1) and at predetermined time points after tiludronate administration on day 0. Mean pVGRFs (standardized as percentage body weight of force) and mean SLSs for the most lame forelimb and for both forelimbs of horses in each group were compared with day −1 values to determine treatment effect. RESULTS Mean pVGRF for both forelimbs and for the most lame forelimbs of systemically treated horses were significantly increased on days 120 and 200, compared with day −1 results. No significant difference in mean pVGRF was observed for IVRLP-treated horses. The SLSs were not improved at any time point following systemic treatment and were improved only on day 120 following IVRLP. CONCLUSIONS AND CLINICAL RELEVANCE Tiludronate (1 mg/kg, IV) as a single systemic treatment appeared to be beneficial for horses with NS, but no horses were judged as sound during the study period. Additional research on IVRLP with tiludronate is needed before this method can be recommended.

OBJECTIVE To compare antibacterial effects among 3 types of foam used with negative-pressure wound therapy (NPWT) in an ex vivo equine perfused wound model. SAMPLES Abdominal musculocutaneous flaps from 6 equine cadavers. PROCEDURES Each musculocutaneous flap was continuously perfused with saline (0.9% NaCl) solution. Four 5-cm circular wounds were created in each flap and contaminated with 106 CFUs of both Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA). After a 1-hour incubation period, 1 of 4 treatments (NPWT with silver-impregnated polyurethane foam [NPWT-AgPU], polyurethane foam [NPWT-PU], or polyvinyl alcohol foam [NPWT-PVA] or a nonadherent dressing containing polyhexamethylene biguanide without NPWT [control]) was randomly applied to each wound. An 8-mm punch biopsy specimen was obtained from each wound immediately before and at 6, 12, 18, and 24 hours after treatment application to determine the bacterial load for both P aeruginosa and MRSA. RESULTS The bacterial load of P aeruginosa for the NPWT-PVA treatment was significantly lower than that for the other 3 treatments at each sampling time after application, whereas the bacterial load for the NPWT-AgPU treatment was significantly lower than that for the NPWT-PU and control treatments at 12 hours after application. The bacterial load of MRSA for the NPWT-PVA treatment was significantly lower than that for the other 3 treatments at each sampling time after application. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that wounds treated with NPWT-PVA had the greatest decrease in bacterial load; however, the effect of that treatment on wound healing needs to be assessed in vivo.

OBJECTIVE To evaluate the efficacy of IV administration of a product containing hyaluronan, sodium chondroitin sulfate, and N-acetyl-d-glucosamine for prevention or treatment of osteoarthritis in horses. ANIMALS 32 healthy 2- to 5-year-old horses. PROCEDURES The study involved 2 portions. To evaluate prophylactic efficacy of the test product, horses received 5 mL of the product (n = 8) or saline (0.9% NaCl) solution (8; placebo) IV every fifth day, starting on day 0 (when osteoarthritis was induced in the middle carpal joint of 1 forelimb) and ending on day 70. To evaluate treatment efficacy, horses received either the product or placebo (n = 8/treatment) on days 16, 23, 30, 37, and 44 after osteoarthritis induction. Clinical, diagnostic imaging, synovial fluid, gross anatomic, and histologic evaluations and other tests were performed. Results of each study portion were compared between treatment groups. RESULTS Limb flexion and radiographic findings were significantly worse for horses that received the test product in the prophylactic efficacy portion than for placebo-treated horses or product-treated horses in the treatment efficacy portion. In the prophylactic efficacy portion, significantly less articular cartilage erosion was identified in product-treated versus placebo-treated horses. In the treatment efficacy portion, joints of product-treated horses had a greater degree of bone edema identified via MRI than did joints of placebo-treated horses but fewer microscopic articular cartilage abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that caution should be used when administering the evaluated product IV to horses, particularly when administering it prophylactically, as it may have no benefit or may even cause harm.

OBJECTIVE To compare clinical disease and lung lesions in calves experimentally inoculated with Histophilus somni 5 days after metaphylactic administration of tildipirosin or tulathromycin. ANIMALS Twenty-four 3-month-old Holstein and Holstein-crossbreed steers. PROCEDURES Calves were randomly allocated to 3 groups of 8 calves. On day 0, calves in group 1 received tildipirosin (4 mg/kg, SC), calves in group 2 received tulathromycin (2.5 mg/kg, SC), and calves in group 3 received isotonic saline (0.9% NaCl) solution (1 mL/45 kg, SC; control). On day 5, calves were inoculated with 10 mL of a solution containing H somni strain 7735 (1.6 × 109 CFUs/mL, intrabronchially; challenge). Calves were clinically evaluated on days 5 through 8 and euthanized on day 8. The lungs were grossly evaluated for evidence of pneumonia, and bronchial secretion samples underwent bacteriologic culture. RESULTS The mean clinical score for each group was significantly increased 12 hours after challenge, compared with that immediately before challenge, and was significantly lower for tildipirosin-treated calves on days 6, 7, and 8, compared with those for tulathromycin-treated and control calves. The mean percentage of lung consolidation for tildipirosin-treated calves was significantly lower than those for tulathromycin-treated and control calves. Histophilus somni was isolated from the bronchial secretions of some tulathromycin-treated and control calves but was not isolated from tildipirosin-treated calves. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that metaphylactic administration of tildipirosin to calves 5 days prior to H somni challenge prevented subsequent culture of the pathogen from bronchial secretions and was more effective in minimizing clinical disease and lung lesions than was metaphylactic administration of tulathromycin.