Effects of xylazine and dexmedetomidine on equine articular chondrocytes in vitro.

OBJECTIVE: To assess the effects of xylazine and dexmedetomidine on equine chondrocytes, in vitro. STUDY DESIGN: Prospective, experimental study. STUDY MATERIAL: Equine articular chondrocytes from five male horses. METHODS: Chondrocytes were isolated from healthy equine articular cartilage of the metacarpo/metatarsophalangeal joints. Cell viability was assessed using the WST-8 assay by exposing chondrocytes to xylazine (0.5, 1, 2, 4, 8, 16.6, 25, 50 mg mL-1) or dexmedetomidine (0.001, 0.005, 0.01, 0.05, 0.175, 0.25 mg mL-1) for 15, 30 and 60 minutes. Based on the results of these tests, cells were treated with xylazine (1, 4, 25 mg mL-1) or dexmedetomidine (0.05, 0.175, 0.25 mg mL-1) for 15 minutes to further evaluate: cell viability by neutral red uptake; cell membrane integrity by lactate dehydrogenase release and by fluorescence microscopy with Hoechst 33342 and propidium iodide (PI), and apoptosis by flow cytometry using double staining with annexin V-fluorescein isothiocyanate/PI and by cell morphology. RESULTS: Both drugs reduced cell viability in a dose-dependent manner. Specifically, all xylazine concentrations, except 0.5 mg mL-1 and 1 mg mL-1, significantly reduced cell viability, whereas the effects of dexmedetomidine were evident only at 0.175 mg mL-1 and 0.25 mg mL-1. The highest concentrations of xylazine (25 mg mL-1) and dexmedetomidine (0.25 mg mL-1) caused loss of membrane integrity. Cell morphology and flow cytometry analyses demonstrated signs of late apoptosis in xylazine-treated cells, and signs of late apoptosis and necrosis in dexmedetomidine-treated cells. CONCLUSIONS AND CLINICAL RELEVANCE: This study offers new insights into the potential chondrotoxicity induced by dexmedetomidine and xylazine. Therefore, the intra-articular administration of α2-agonists should be conducted with care, especially for doses of ≥ 4 mg mL-1 of xylazine and 0.175 mg mL-1 and 0.25 mg mL-1 of dexmedetomidine.

Retrograde Approach to Maxillary Nerve Block: An Alternative in Orofacial Surgeries in Horses.

The aim of this study was to retrospectively report outcomes resulting from the approach to the maxillary nerve block (MNB) through the infraorbital canal, in terms of needles selection, drawbacks or side effects during or after block execution, and analgesic efficacy leading to clinical and cardiovascular stability during surgery. Anesthetic records of 15 horses undergoing orofacial surgery in standing analgo-sedation (STA, n = 6) and in general anesthesia (GEN, n = 9) were retrieved and analyzed. Horses in group STA required surgery for dental extraction, nasal polyp resection and maxillary/frontal sinusitis. Horses in group GEN underwent surgery for fronto-maxillary, nasal and dental diseases. Size 19 and 20 G Tuohy needles were used in adult horses weighing 350-600 kg, while size 21 and 22 G were used in younger horses or ponies. None of the horses in both groups showed complications related to the block and physiological parameters were stable and within normal ranges during surgery; overall, an adequate anesthetic/sedation depth was achieved. Our results confirm the in vivo applicability of the MNB approached within the infraorbital canal, which had been described only on cadaveric specimens. The retrograde technique resulted in a valid and easy approach to the maxillary nerve that avoids damage to periorbital structures and side effects reported with traditional techniques.

Ureteral Endoscopy to Detect Upper Urinary Tract Diseases in Horses.

Ureteral endoscopy is a routine procedure in human medicine, whereas the reports of this procedure on horses are few and far between. The aim of this paper is to describe the endoscopic technique to evaluate the ureters in standing, sedated horses. An endoscopy of the ureters and lower urinary tract was performed using flexible endoscopes on 4 horses, 3 mares and one gelding. The animals were sedated with alpha-2-agonists and an epidural anaesthesia was given. An endoscopy of the ureter in the horse is easy to perform, causes the animal no adverse effects and could provide significant information on the diagnosis and prognosis of diseases of the urinary tract.

Detection and DNA quantification of Enterococcus casseliflavus in a foal with septic meningitis.

CASE DESCRIPTION A 3-month-old 180-kg (396-lb) Hanoverian colt was examined because of fever, lethargy, inappetence, drooping of the left ear, and stiff neck posture. Initial treatment included empirical antimicrobial treatment and NSAIDs. CLINICAL FINDINGS Initial findings were consistent with CNS anomalies. Endoscopy revealed hyperemia, ecchymosis, and some mucopurulent exudate in the right guttural pouch. Hematologic findings were consistent with neutrophilic inflammation. On the third day of hospitalization, severe neurologic signs were observed. Computed tomography of the skull revealed a comminuted fracture of the axial aspect of the right mandibular condyle. Examination of CSF revealed turbidity, xanthochromia, and intracellular and extracellular cocci, consistent with septic meningitis. After DNA extraction from blood and CSF, sequenced products from a PCR assay for the bacterial 16S rRNA gene were 99% identical to Enterococcus casseliflavus. Microbial culture of CSF and blood samples yielded bacteria with Enterococcus spp morphology; antimicrobials were selected on the basis of susceptibility testing that identified the isolate as vancomycin resistant. A quantitative PCR assay was used to estimate Enterococcus DNA concentrations in CSF and blood. TREATMENT AND OUTCOME Treatment for E casseliflavus meningitis, including trimethoprim-sulfadiazine and ampicillin sodium administration, resulted in resolution of clinical signs. Culture of CSF and blood samples after 12 days of the targeted treatment yielded no growth. CLINICAL RELEVANCE To the authors' knowledge, this was the first report of E casseliflavus meningitis in a horse. Treatment was successful; vancomycin-resistant enterococci can be a clinical problem and may potentially be zoonotic.