EFFECT OF ANESTHETIC GAS ON MIDDLE-EAR FLUID

Tympanometry was performed before (preoperative) and after (intraopera tive) the administration of inhalation anesthesia including nitrous ox ide and halothane on 109 children undergoing myringotomy with pressure equalization tube insertion. A total of 213 preoperative tympanograms were compared with their intraoperative counterparts and the presence or absence of middle ear effusion at myringotomy. When preoperative t ympanograms were consistent with pneumatized middle ears, intraoperati ve findings demonstrated a mean middle ear pressure increase of +147 d aPa. When preoperative tympanometry suggested middle ear effusion, les s than 1% demonstrated intraoperative tympanometric changes and/or fin dings at surgery that would support anesthesia clearing middle ear eff usion. Preoperative tympanometric data were poor predictors of the pre sence or absence of effusion at myringotomy. The relationship between inhalation anesthetics (i.e., nitrous oxide and halothane) and middle ear fluids, and the reliability of tympanometry to predict middle ear effusion are discussed.