Abstract
Left laryngeal hemiplegia (LH) is a frequently encountered cause of partial airway obstruction in the horse. Current corrective techniques consist of a surgical laryngeal ventriculectomy and an abductor muscle prosthesis (laryngoplasty). Four horses of racing type with LH were studied to determine the physiologic changes that occurred during exercise. Sequential arterial samples were acquired prior to surgical correction to establish blood-gas and acid–base status. Under general anesthesia, a laryngoplasty was then performed followed by a standing Nd:YAG ventricular ablation procedure. After rest and retraining, the horses were galloped and blood-gas and acid–base determinations were made. The identical exercise test and arterial sampling were performed on an additional five horses without respiratory abnormalities to determine normal values. Statistical analysis of the arterial values obtained indicated that LH horses and corrected LH horses demonstrated a decrease in pH and PaO2 values as the gallop progressed when compared to normal horses. The LH group had consistently significant elevation in PaCO2 throughout the test gallop. Surgical correction and Nd:YAG ventricular ablation improved the physiologic status of the horses toward normal but not equivalent to normal. Based on the information obtained from the test gallop, the Nd:YAG laser ablation procedure and laryngoplasty was conducted on 43 horses presented to the Veterinary Teaching hospital between January 1987 and September 1990. A postprocedure telephone survey was performed to assess the efficacy of the procedures. Success was defined as a reduction in noise or improvement in performance ability which was found to occur in approximately 70% of the animals.
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