Technique description and outcome evaluation of Thoroughbred racehorses following soft palate thermocautery performed under standing sedation

Abstract

Background: Palatal dysfunction (PD), which encompasses palatal instability (PI) and intermittent dorsal displacement of the soft palate, is the most common performance-limiting upper respiratory tract obstruction in young Thoroughbred racehorses. Soft palate thermocautery (SPT) performed under general anaesthesia is a routinely performed procedure for PD in some countries, but the procedure for and outcome of SPT performed under standing sedation has not been published.

Objectives: (1) To describe a technique for SPT performed under standing sedation; and (2) to assess post-operative performance in horses compared to controls using the Racing Post rating (RPR), British Horseracing Authority official rating (OR), Performance Index and Earnings.

Study design: Retrospective case series.

Methods: Medical records were reviewed for all horses that had SPT performed under standing sedation following topical and local infusion of lidocaine hydrochloride into the rostral soft palate, and that were identified to have PI by overground endoscopy. Two matched controls were identified for each case. The median RPR, OR, Performance Index and Earnings for the three pre-operative and three post-operative races were compared.

Results: No significant differences were identified between the SPT (n = 23) and Control groups (n = 46) for baseline characteristics or outcomes.

Main limitations: Retrospective study design, small sample size.

Conclusions: No significant differences in racing performance were identified between horses that had SPT performed under standing sedation and controls.

Keywords: anaesthesia; endoscopy; equid; equine; respiratory tract; surgery.

FIGURE 1

Equipment used for thermocautery of the soft palate of horses performed under standing sedation: (a) dental mouth gag, (b) headstand, (c) headlight, (d) three curved L‐shaped iron instruments, (e) gas burner and (f) vacuum.

FIGURE 2

(a) Normal appearance of a soft palate when the horse's mouth is open with a gag in place. The green line is the submucosally injected point for the 20 mL of lidocaine performed in an inverse U shape on the rostral aspect of the soft palate. (b) Appearance of the soft palate after local anaesthesia is injected (60 mL of lidocaine hydrochloride). (c) Appearance of the soft palate several minutes after thermocautery has been performed.

FIGURE 3

Flow diagram illustrates the enrolment of horses in this retrospective study, reasons for exclusion and number of eligible horses in the Soft Palate Thermocautery and Control groups.