• Hiroshi Hanamoto, Eriko Togawa, Chizuko Yokoe, and Hitoshi Niwa.
• From the Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan (HH, CY, HN); Kobe Dental Center, Kobe, Japan (ET).
• Eur J Anaesthesiol. 2021 Nov 1; 38 (11): 1138-1147.

BackgroundThe cough reflex or aspiration under monitored anaesthesia care might be associated with sedative-induced changes in swallowing and intra-oral water-retaining abilities.ObjectivesTo investigate the effects of moderate propofol sedation on swallowing and intra-oral water-retaining ability.DesignProspective observational study.SettingSingle tertiary care centre during 2017.ParticipantsA total of 13 healthy adult volunteers.InterventionVolunteers in the supine position were asked to retain 10 ml of orally injected water for 5 min. After 5 minutes or when the water was spontaneously swallowed, the retention time and residual intra-oral water volume were measured. Subjects then voluntarily swallowed a further 10 ml of injected water and the residual water volume was measured. This whole process was repeated under sedation with propofol at effect-site concentrations of 0.5, 1.0 and 1.5 μg ml-1.Main Outcome MeasuresThe primary outcome was the estimated volume swallowed (swallowing volume); the secondary outcome was water retention time.ResultsMedian water retention time decreased from 300 to 11 s (P < 0.001), and greater spontaneous swallowing was induced with increased propofol effect-site concentrations measuring up to 1.5 μg ml-1 (P < 0.001). The median of the estimated swallowing volumes with voluntary swallowing while awake and with all three concentrations of propofol were 9.5, 9.6, 9.6 and 9.4 ml, respectively (P = 0.805); more water remained after spontaneous swallowing than after voluntary swallowing at all concentrations. Differences in mean estimated swallowing volumes between voluntary and spontaneous swallowing were 3.4 ml (95% CI, 0.9 to 6.0, P = 0.016) for 0.5 μg ml-1, 4.1 ml (95% CI, 1.8 to 6.3, P = 0.002) for 1.0 μg ml-1 and 5.1 ml (95% CI, 3.4 to 6.8, P < 0.001) for 1.5 μg ml-1.ConclusionsModerate propofol sedation decreases water-retaining ability but has no effect on voluntary swallowing. Ensuring that patients can respond under sedation may effectively prevent the unexpected cough reflex and aspiration by enabling occasional voluntary swallowing.Trial RegistrationUMIN Clinical Trials Registry identifier: UMIN000027517.Copyright © 2021 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.

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