UPPER AIRWAY-CLOSURE - A PRIMARY SOURCE OF DIFFICULT VENTILATION WITHSUFENTANIL INDUCTION OF ANESTHESIA

Large-dose opioid induction of anesthesia can lead to difficult ventil ation via a mask. Poor ventilatory compliance (VC) may be secondary to ''rigid'' chest and abdominal wall musculature, glottic closure, or u pper airway obstruction. This double-blind study assessed the contribu tion of the upper airway to poor VC by inducing sufentanil anesthesia in patients undergoing cardiac surgery who are ventilated via a mask ( Group M) or endotracheal tube fiberoptically inserted (Group E). After induction of anesthesia with sufentanil 3 mu g/kg from time (T) = 0 m in to T = 2 in Group M (n = 17) or Group E (n = 23), VC and adductor p ollicis (AP) twitch tension was measured continuously. Immediately pri or to muscle relaxant (pipecuronium or doxacurium) administration at T = 3, Group E demonstrated significantly better VC (46 mL/cm H2O [39-5 5 interquartile range (IQR)]) than Group M (19 mL/cm H2O [7-24 IQR]). The effect of muscle relaxant administration on VC preceded its effect at the AP. After complete relaxation of the AP at T = 9, both groups had similar VC. Difficult ventilation during sufentanil induction of a nesthesia lies at the level of the glottis or above. Bypassing these s tructures with an endotracheal tube overcomes the usual decreased VC.