title: Effects of muscle relaxants on mask ventilation in anesthetized persons with normal upper airway anatomy.
abstract: BACKGROUND
  Recent studies suggest advantages of muscle relaxants for facemask ventilation. However, direct effects of muscle relaxants on mask ventilation remain unclear because these studies did not control mechanical factors influencing ventilation. We tested a hypothesis that muscle relaxants, either rocuronium or succinylcholine, improve mask ventilation.
  
  
  METHODS
  In anesthetized adult persons with normal upper airway anatomy, tidal volumes during facemask ventilation were measured while maintaining the neutral head and mandible positions and the airway pressures of a ventilator before and during muscle paralysis induced by either rocuronium (n=14) or succinylcholine (n=17). Tidal volumes of oral and nasal airway routes were separately measured with a custom-made oronasal portioning full facemask. Behavior of the oral airway was observed by an endoscope in six additional subjects receiving succinylcholine.
  
  
  RESULTS
  Total, oral, and nasal tidal volumes did not significantly change at complete muscle paralysis with rocuronium. In contrast, succinylcholine significantly increased total tidal volumes at 60 s after its administration (mean±SD; 4.2±2.1 vs. 5.4±2.6 ml/kg, P=0.02) because of increases of ventilation through both airway routes. Abrupt tidal volume increase occurred more through oral airway route than nasal route. Dilation of the space at the isthmus of the fauces was endoscopically observed during pharyngeal fasciculation in all six subjects.
  
  
  CONCLUSIONS
  Rocuronium did not deteriorate facemask ventilation, and it was improved after succinylcholine administration in association with airway dilation during pharyngeal fasciculation. This effect continued to a lesser degree after resolution of the fasciculation.
authors: Department of Anesthesiology, Chiba University Hospital, and Department of Anesthesiology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Aya
authors: A
authors: Ikeda
authors: Shiroh
authors: S
authors: Isono
authors: Yumi
authors: Y
authors: Sato
authors: Hisanori
authors: H
authors: Yogo
authors: Jiro
authors: J
authors: Sato
authors: Teruhiko
authors: T
authors: Ishikawa
authors: Takashi
authors: T
authors: Nishino
mesh_terms: D000328:Adult; D000368:Aged; D000732:Androstanols / Q000494:pharmacology*; D000758:Anesthesia; D005260:Female; D006801:Humans; D008297:Male; D008397:Masks; D008875:Middle Aged; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D012121:Respiration, Artificial / Q000379:methods*; D000077123:Rocuronium; D013390:Succinylcholine / Q000494:pharmacology*; D013990:Tidal Volume / Q000187:drug effects
chemical_list: D000732:Androstanols; D009466:Neuromuscular Blocking Agents; D013390:Succinylcholine; D000077123:Rocuronium