Videofluoroscopy shows clinically relevant changes in swallow metrics and esophageal transit in normal horses with xylazine, anticholinergic use, and varied feed consistency.

OBJECTIVE

To investigate the effects of varied feed consistency and administration of xylazine or N-butylscopolammonium bromide on 3 phases of swallowing and characterize esophageal motility following barium administration via nasoesophageal tube.

METHODS

8 healthy horses were enrolled for 2.5 consecutive weeks. Horses underwent experimental videofluoroscopic swallow studies before and after sedated and anticholinergic interventions. Esophageal motility was assessed with barium administered via nasoesophageal tube and with barium-admixed feedstuffs of 3 consistencies with increasing viscosity. Phases were assessed with swallow metrics adapted from canine studies.

RESULTS

The cranial esophageal transit rate was faster in horses with no treatment than after xylazine administration (n = 7; marginal effect, -0.018 m/s; 95% CI, -0.034 to -0.002 m/s). The cranial esophageal transit rate was faster for liquid compared to intermediate consistency (marginal effect, -0.015 m/s; 95% CI, -0.030 to -0.001 m/s) and liquid compared to solid consistency (marginal effect, -0.022; 95% CI, -0.038 to -0.007 m/s). There were no significant differences in esophageal transit rate for thoracic inlet to caudal esophagus between treatments or consistencies. Multiple horses experienced bolus retention following administration of N-butylscopolammonium bromide and xylazine. Thoracic inlet contrast pooling occurred during nasoesophageal intubation trials prior to initiation of peristalsis.

CONCLUSIONS

Xylazine administration resulted in prolonged esophageal transit time with increased feed consistency. N-butylscopolammonium bromide administration increased incidence of bolus retention. Nasoesophageal tube administration of barium results in initial contrast pooling within the thoracic inlet.

CLINICAL RELEVANCE: Equine videofluoroscopic swallow studies are feasible to evaluate dysphagia and esophageal disorders.