Remifentanil alters sensory neuromodulation of swallowing in healthy volunteers: quantification by a novel pressure-impedance analysis

Abstract

Exposure to remifentanil contributes to an increased risk of pulmonary aspiration, likely through reduced pharyngeal contractile vigor and diminished bolus propulsion during swallowing. We employed a novel high-resolution pressure-flow analysis to quantify the biomechanical changes across the upper esophageal sphincter (UES). Eleven healthy young (23.3 ± 3.1 yr old) participants (7 men and 4 women) received remifentanil via intravenous target-controlled infusion with an effect-site concentration of 3 ng/ml. Before and 30 min following commencement of remifentanil administration, participants performed ten 10-ml saline swallows while pharyngoesophageal manometry and electrical impedance data were recorded using a 4.2-mm-diameter catheter housing 36 circumferential pressure sensors. Remifentanil significantly shortened the duration of UES opening (P < 0.001) and increased residual UES pressure (P = 0.003). At the level of the hypopharynx, remifentanil significantly shortened the latency from maximum bolus distension to peak contraction (P = 0.004) and significantly increased intrabolus distension pressure (P = 0.024). Novel mechanical states analysis revealed that the latencies between the different phases of the stereotypical UES relaxation sequence were shortened by remifentanil. Reduced duration of bolus flow during shortened UES opening, in concert with increased hypopharyngeal distension pressures, is mechanically consistent with increased flow resistance due to a more rapid bolus flow rate. These biomechanical changes are congruent with modification of the physiological neuroregulatory mechanism governing accommodation to bolus volume.

Characterization of swallow modulation in response to bolus volume in healthy subjects accounting for catheter diameter

“…In oropharyngeal dysphagia, with insufficient extent and/or duration of UES opening, elevated hypopharyngeal distension pressures are expected. Therefore, when there is a mismatch between the volume swallowed and the UES opening time, the rate of trans‐sphincteric flow increases, and this leads to disproportionately elevated upstream pressures . A punctuated increase in hypopharyngeal distension pressure, at a particular volume, may mark the point of failure of bolus accommodation within the swallowing mechanism …”

“…Thus, our potential to measure volume‐related contractile pressure differences in this region may be compromised. Studies investigating the symmetry of deglutitive pharyngeal and UES pressures using state‐of‐the‐art three‐dimensional high‐resolution impedance manometry catheters have recently been published . Although it could be argued that circumferential sensors are optimal for pharyngeal manometry the provision of circumferentially averaged results for each sensor is not necessarily akin to obtaining multiple separate, radially orientated readings .…”

“…Swallow function metrics were calculated within each region (see below), and were averaged per volume for each catheter configuration. The reliability of this method and the specific details of the analysis algorithms have been previously described …”

Effects of remifentanil on esophageal and esophagogastric junction (EGJ) bolus transit in healthy volunteers using novel pressure‐flow analysis

“…In contrast to the effects on amplitude, the timing of the proximal contractile sequence was unaffected by remifentanil. This suggests that, like in the pharyngeal contraction sequence, the centrally determined neural timing sequence governing velocity of propagation of proximal esophageal contraction remains unchanged by opioids and that the observed effects are more likely due to peripheral MOR effects.…”

“…Many individuals, including healthy volunteers, complain of dysphagia during administration of remifentanil . Recent descriptions of the effects of remifentanil and other MOR agonists on swallowing function have revealed attenuated oropharyngeal and laryngeal sensory function, increased pulmonary aspiration, decreased distal esophageal latency, and decreased esophagogastric junction (EGJ) relaxation . Esophageal pressure topography (EPT) revealed a shortened distal latency and increased distal intrabolus pressure during remifentanil administration .…”