title: The incidence and mechanisms of pharyngeal and upper esophageal dysfunction in partially paralyzed humans: pharyngeal videoradiography and simultaneous manometry after atracurium.
abstract: BACKGROUND
  Residual neuromuscular block caused by vecuronium alters pharyngeal function and impairs airway protection. The primary objectives of this investigation were to radiographically evaluate the swallowing act and to record the incidence of and the mechanism behind pharyngeal dysfunction during partial neuromuscular block. The secondary objective was to evaluate the effect of atracurium on pharyngeal function.
  
  
  METHODS
  Twenty healthy volunteers were studied while awake during liquid-contrast bolus swallowing. The incidence of pharyngeal dysfunction was studied by fluoroscopy. The initiation of the swallowing process, the pharyngeal coordination, and the bolus transit time were evaluated. Simultaneous manometry was used to document pressure changes at the tongue base, the pharyngeal constrictor muscles, and the upper esophageal sphincter. After control recordings, an intravenous infusion of atracurium was administered to obtain train-of-four ratios (T4/T1) of 0.60, 0.70, and 0.80, followed by recovery to a train-of-four ratio of more than 0.90.
  
  
  RESULTS
  The incidence of pharyngeal dysfunction was 6% during the control recordings and increased (P < 0.05) to 28%, 17%, and 20% at train-of-four ratios 0.60, 0.70, and 0.80, respectively. After recovery to a train-of-four ratio of more than 0.90, the incidence was 13%. Pharyngeal dysfunction occurred in 74 of 444 swallows, the majority (80%) resulting in laryngeal penetration. The initiation of the swallowing reflex was impaired during partial paralysis (P = 0.0081). The pharyngeal coordination was impaired at train-of-four ratios of 0.60 and 0.70 (P < 0.01). A marked reduction in the upper esophageal sphincter resting tone was found, as well as a reduced contraction force in the pharyngeal constrictor muscles. The bolus transit time did not change significantly.
  
  
  CONCLUSIONS
  Partial neuromuscular paralysis caused by atracurium is associated with a four- to fivefold increase in the incidence of misdirected swallowing. The mechanism behind the pharyngeal dysfunction is a delayed initiation of the swallowing reflex, impaired pharyngeal muscle function, and impaired coordination. The majority of misdirected swallows resulted in penetration of bolus to the larynx.
authors.affiliation: Department of Anesthesiology, Karolinska Hospital and Institute, Stockholm, Sweden. eva.sundman@kirurgi.ki.se
authors.forename: E
authors.initials: E
authors.lastname: Sundman
authors.forename: H
authors.initials: H
authors.lastname: Witt
authors.forename: R
authors.initials: R
authors.lastname: Olsson
authors.forename: O
authors.initials: O
authors.lastname: Ekberg
authors.forename: R
authors.initials: R
authors.lastname: Kuylenstierna
authors.forename: L I
authors.initials: LI
authors.lastname: Eriksson
mesh_terms: D000328:Adult; D001279:Atracurium; D003679:Deglutition / Q000187:drug effects; D004935:Esophageal Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology*; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D003473:Neuromuscular Nondepolarizing Agents; D010608:Pharyngeal Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology*; D010609:Pharyngeal Muscles / Q000502:physiology; D014741:Video Recording
chemical_list: D003473:Neuromuscular Nondepolarizing Agents; D001279:Atracurium