Implementation of a prototype dynamic laryngoplasty system in standing sedated horses provided arytenoid abduction control at seven days postoperatively.

OBJECTIVE: Evaluate a prototype dynamic laryngoplasty system (DLPS) in horses; a feasibility study. ANIMALS: 7 healthy Standardbred adult horses. METHODS: This was an in vivo experimental study. Horses had a standing surgical procedure to induce complete laryngeal hemiplegia, which was subsequently treated using the dynamic laryngoplasty system (DLPS). Activation of the DLPS was achieved using an injection port exiting through the skin (n = 2) or a subcutaneous injection port (n = 5). For each horse, endoscopic examinations of the upper respiratory tract were performed preoperatively, intraoperatively, and 7 days postoperatively. Left-to-right quotient ratios calculated during inactivated and activated states were obtained from still images of the rima glottidis acquired during day 7. In 3 horses, the device was intentionally overinflated to evaluate for device failure, and postmortem examinations were performed on day 7. For the remaining 4 horses, upper respiratory tract endoscopy was repeated at 1 month postoperatively, with no subsequent postmortem exam. RESULTS: No perioperative complications occurred, and the DLPS was effectively delivered in all horses under standing sedation. The left-to-right quotient ratio at day 7 postoperatively could be altered from a resting position of 0.76 (± 0.06) to a maximum of 0.97 (± 0.06; P < .05). The degree of arytenoid abduction could not be significantly altered after 1 month of device implantation, suspected to be due to peri-implant fibrosis. No coughing nor tracheal contamination was observed at all time points or during inflation. CLINICAL RELEVANCE: The ability to alter the degree of abduction at 7 days postoperatively with the DLPS may be beneficial in selective cases.

Dynamic nasopharyngeal collapse in horses: What we know so far.

Dynamic nasopharyngeal collapse (NPC) is an obstructive upper airway disease that affects mainly the inspiratory phase of respiration in horses undergoing strenuous exercise. It occurs when the neuromuscular activity of the nasopharynx is overwhelmed by the intense negative pressures generated during exercise. This leads to collapse of at least one of the four components of the nasopharynx which is comprised of the two lateral walls, the dorsal roof and the ventral soft palate. As a result, the airway diameter and thus airflow become compromised. Even small changes in the airway diameter produces profound increases in negative inspiratory pressure, perpetuating the cycle of collapse. Compared to other dynamic upper respiratory tract disorders, the amount of literature on NPC as a disease entity is limited. The exact pathophysiology of NPC is unknown; however, it impacts up to one quarter of high-performance equine athletes presenting for poor performance. There is currently no definitive treatment for this severely performance-limiting condition. Thus, the prognosis for future athletic prognosis is guarded, with most horses being retired from racing or athletic use in general. Further research is warranted in this field to reduce the impact of disease and in turn, reduce the turnover rate and economic loss by enhancing the career longevity of elite equine athletes diagnosed with NPC.

Adverse Reaction Following the Subarachnoid Injection of Xylazine in a Sheep.

Alpha2 receptor agonists are frequently used to provide sedation and analgesia in sheep. There are numerous reports of adverse pulmonary effects following intravenous (IV) injection; however, adverse effects following subarachnoid injection (SAI) are underreported. An adult Merino wether was one of eighteen animals anaesthetised during an experimental trial modelling intervertebral disc injury. The animal was premedicated with methadone 0.1 mg/kg and midazolam 0.3 mg/kg IV. Anaesthesia was induced using alfaxalone IV and it was maintained using isoflurane, delivered in 100% oxygen by controlled mechanical ventilation. An SAI of xylazine 0.05 mg/kg diluted to 1 mL with 0.9% saline was performed at the lumbosacral site prior to recovery. This resulted in rapid narcosis, oxygen dependency and ventilatory compromise. Treatment with frusemide 1 mg/kg IV and salbutamol 0.2 mg inhaled did not attenuate the adverse cardiopulmonary effects. A rapid improvement in all physiological variables was seen following high dose atipamezole 0.05 mg/kg IV. This case report adds to the current knowledge regarding the risk for potential side effects when using alpha2 receptor agonists, such as xylazine, for the sedation or regional analgesia in sheep.