Effect of anaesthetic agents on tympanometry and middle-ear effusions

Following informed parental consent 93 children underwent bilateral grommet insertion. Tympanometry was performed pre-operatively, and immediately pri or to myringotomy. A standardized anaesthetic was used. At myringotomy the presence or absence of fluid was recorded, as well as the time since induct ion of the general anaesthetic. A pre-operative type B tympanogram predicted a middle-ear effusion at myrin gotomy in 92 per cent of patients. A pre-operative type C-2 tympanogram pre dicted a middle-ear effusion at myringotomy in 39 per cent of patients. Six ty tympanograms (30 per cent) changed following a general anaesthetic. Four teen type B tympanograms changed to type A and eight of these had effusions . The duration of the general anaesthetic did not influence the probability of a middle-ear effusion bring present at myringotomy. A pre-operative typ e B tympanogram is a good predictor of middle-ear fluid. The duration of th e general anaesthetic is not significant in predicting the presence of a mi ddle-ear effusion.