Outcomes of horses treated with removal of a laryngoplasty prosthesis.

OBJECTIVE: To determine the proportion of horses treated by laryngoplasty prosthesis removal (LPR) for complications associated with prosthetic laryngoplasty (LP), the reason for LPR, and the outcome of horses undergoing LPR to manage iatrogenic coughing/dysphagia. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Client-owned horses treated with LP (n = 1202) and LPR (n = 58). METHODS: Clinical case records were reviewed to determine the number of horses treated with LP and LPR by the same surgeon. Historical, clinical, endoscopic, and surgical data were extracted for those horses undergoing LPR. Long-term outcome was assessed by questionnaire. RESULTS: The proportion of horses treated with LP and subsequently treated with LPR by the same surgeon was 3.5% (42/1202). Coughing/dysphagia was the reason for LPR in 90% (52/58) of horses. Sufficient follow-up to determine outcome in horses undergoing LPR for coughing/dysphagia was available in 32 horses. Arytenoid abduction grade at the time of LPR did not influence clinical response (P = .416). Presenting clinical signs resolved after LPR in 21 of 32 (66%) horses, and 24 of 32 (75%) horses returned to exercise. CONCLUSION: Coughing/dysphagia was the most common reason for LPR. Clinical signs improved in most horses after LPR. CLINICAL SIGNIFICANCE: Laryngoplasty prosthesis removal can be a useful treatment option for horses affected with unmanageable coughing/dysphagia caused by LP.

Effect of head position on radiographic assessment of laryngeal tie-forward procedure in horses.

OBJECTIVE: To assess the effect of head position on relative position of the larynx and hyoid apparatus in horses with palatal dysfunction, and to define a standard position for radiographic assessment of laryngeal tie-forward. STUDY DESIGN: Prospective clinical study. ANIMALS: Adult horses (n=9) with palatal dysfunction. METHODS: Left lateral radiographs of the larynx were obtained pre and postoperatively for 3 different head positions (flexed=90 degrees ; neutral=100 degrees ; extended=115 degrees ). Distance between thyrohyoid bone and thyroid cartilage was measured. Data were analyzed to investigate differences between head positions, and to compare differences between pre- and postoperative measurements. RESULTS: Head position had a significant effect on relative position of the larynx and hyoid apparatus preoperatively. There was no significant difference in postoperative measurements of the 3 head positions. A significant difference between pre- and postoperative measurements was found with the head in the neutral or extended position whereas there were no significant differences between pre- and postoperative measurements using the flexed position. CONCLUSIONS: Head position affects the relationship between the hyoid apparatus and larynx preoperatively, with greatest distance occurring when the head is extended. In a flexed position, it is not possible to ascertain whether laryngeal position has changed postoperatively. CLINICAL RELEVANCE: A standardized head position is necessary when assessing the laryngeal tie-forward procedure radiographically. An extended head position is most useful for this assessment.

Morphine administration in horses anaesthetized for upper respiratory tract surgery.

OBJECTIVE: To determine the effect of morphine administration on commonly monitored cardio-respiratory variables and recovery quality in horses undergoing anaesthesia and surgery. STUDY DESIGN: Prospective, randomized clinical study. ANIMALS: Thirty-eight thoroughbred horses, 32 geldings and six mares, 3-13 years old, weighing 411-600 kg. MATERIALS AND METHODS: A standard anaesthetic technique was used. Twenty minutes after induction of anaesthesia horses received 0.1 mg kg(-1) (0.1 m) or 0.2 mg kg(-1) (0.2 m) morphine by intravenous injection. A control group did not receive morphine. Heart rate, respiratory rate (fr), mean arterial pressure (MAP) and blood gases were measured before morphine administration and every 10 minutes thereafter. Horses were positioned for 35 minutes in right lateral recumbency for tension palatoplasty by cautery and were then moved into dorsal recumbency for additional intraluminal surgery comprising one or more of aryepiglottic fold resection, sub-epiglottal mucosal resection, ventriculectomy and cordectomy. A subjective recovery score from 0 (worst) to 5 (best) was assigned by a single observer who was unaware of treatment group. Two-way repeated measures anova, one-way anova, Kruskal-Wallis test, Mann-Whitney test, Pearson and Spearman correlation coefficients, and chi-squared tests were used to analyse the data where appropriate. RESULTS: Arterial partial pressure of oxygen (PaO(2)) decreased significantly over time and was significantly lower in horses that received morphine. One horse in the control group and two horses in each of the morphine groups had a PaO(2) <13 kPa. No other significant cardiopulmonary effects were detected. Recovery scores [median (range)] were higher in morphine recipients: 4 (2-5) in 0.1 m, 4 (3-5) in 0.2 m compared with 3 (2-4) in the control group. CONCLUSIONS AND CLINICAL RELEVANCE: The lower PaO(2) in morphine recipients did not appear to be of clinical significance in healthy horses because the number of horses with a low PaO(2) was similar between groups. The quality of recovery was significantly better in morphine recipients. These results indicate that morphine may be considered for use in clinical cases although further work is required to assess the analgesic properties of the drug in this species.