Negative middle ear pressure and otitis media with effusion after surgery under general anesthesia

Negative middle ear pressure was observed in many patients and otitis media with effusion (OME) developed in 3.3% of ears after surgery under general anesthesia. Gas dynamics in the middle ear cavity induced by nitrous oxide inhalation anesthesia and transient blockage of the eustachian tube induced by surgery are considered to be involved in development of OME after surgery under general anesthesia.

The goal of this prospective study was to investigate middle ear pressure and the prevalence of middle ear effusion in patients after surgery under general anesthesia, to ascertain whether surgery under general anesthesia induces OME.

Otoscopic inspection and tympanometry were performed before surgery (Pre), 1-2 days after surgery (Post-1), and 5-9 days after surgery (Post-2) under general anesthesia in 180 ears of 97 adult patients.

Effusion accumulated in the tympanum in six ears (3.3%) of five patients at Post-1. All patients were anesthetized with nitrous oxide. At Post-2, effusion disappeared in all cases. The mean middle ear pressure in all ears was -17.8 daPa at Pre and -60.6 daPa at Post-1, showing a significant reduction from Pre to Post-1 (p < 0.001). At Post-2, the pressure was -18.4 daPa, with no significant difference from that at Pre (p = 0.74).