Global Dysphagia Scale Detects Swallowing Disorder Following a Clinical Dose of Buprenorphine

Abstract

Opioid use is associated with increased risk of chest infection due to opioid suppression of immune function, ventilation, cough, and secretion mobilization. Buprenorphine is a highly lipophilic, semi‐synthetic partial agonist of the mu opioid receptor. Intramuscular buprenorphine is commonly used for post‐operative analgesia at a dose range of 0.01‐0.04 mg/kg in the cat. While buprenorphine is considered to have a low side effect profile, its effects on the pharyngeal phase of swallow are unknown. We hypothesized that administration of opioid would result in clinically meaningful decline of pharyngeal swallow function. Experiments were performed on healthy adult cats (12 months old). Animals were administered intramuscular buprenorphine (0.015 mg/kg) q12 hours for 48 hours. One hour after the last dose was given, videofluoroscopic swallow studies were performed to evaluate the effects of the drug on swallow function. Animals were presented with 40% by volume barium sulfate in tuna water mixed to a thin consistency, and all animals ate voluntarily. Images were recorded in the lateral plane at 30 frames/second and compared to control feeding assessments using the Global Dysphagia Scale (GDS), a novel tool developed to rate swallow function in the cat. The GDS consists of an Airway Invasion Scale (AIS) and relevant components of the Modified Barium Swallow Impairment Profile (MBSImP), a standardized protocol for swallow assessment. The AIS is a 10‐point scale where scores of 0‐1 are normal, scores of 2‐4 indicate laryngeal penetration, and scores of 5‐9 indicate tracheobronchial aspiration. Four components of the MBSImP were included: Initiation of the pharyngeal swallow, pharyngeal stripping wave, pharyngoesophageal segment opening, and pharyngeal residue. The GDS rating was derived by adding the AIS and MBSImP sub‐totals. During control assessments mean GDS was 5.5 ± 1.3, and aspiration was not detected in any animal. On buprenorphine, mean GDS was 11.25 ± 4.2, and 50% of animals exhibited large volume tracheobronchial aspiration. In conclusion, after 48 hours on buprenorphine, airway protection during swallow failed without appreciable response in 50% of animals (no cough, throat clear, or cessation of eating). Our success in producing dysphagia (significant but varying by animal) with relatively small doses of opioid has potential implications for predicting aspiration pneumonia in post‐surgical clinical cases.