RESUMO
Some authors have studied the effect of nitrous oxideanesthesia on the middle ear function. They found that the middle ear pressure was subjected to consequtive rise and fall. This work was carried out to demonestrate the effects and after effects of prolonged general anesthesia with different techniques on the function of the middle ear. It was run over 50 patients undergoing time-consuming surgical operations away from ear, nose and throat regions. The patients were chosen to be clinically free from any pathological abnormality in the ears. The patients were divided into 4 groups. The first group; l5 patients, received nitrous oxide [oxygen] relaxant, the second group; 20 patients, received halothane nitrous oxide [oxygen] relaxants, the third group; 10 patients, received ether and oxygen anesthesia and the fourth group; 5 patients, received spinal analgesia and was considered as a control group. Tympanograms were done to all patients before operation, 24 hours and 6 days after operation. Histopathology was made on the middle ear of guinea pigs anesthetised with ether or halothane. The results of the work proved that prolonged general anesthesia has a definite effect on middle ear functions by lowering the intratympanic pressure. This was produced by direct effect of the anesthetic agent on the middle ear mucosa and the effect of anesthetic circumstances on the eustachian tube. Serial tympanograms were suggested in order to discover ears with high negative pressure which may end with the development of serous otitis media