A prospective study was performed to determine the factors influencing the extrusion rate of tympanostomy tubes. Nine hundred thirty-nine tubes were inserted in 589 patients and the extrusion of these tubes was reviewed up to a period of 27 months. The eight tubes used in the survey were the Shepard, Exmoor, Bobbin, Armstrong, Paparella, Shah, Arrow, and collar button. These tubes were inserted in strict rotation, the operator using the designated tube. The position, type of incision, presence of fluid, quality of tympanic membrane, and degree of difficulty of insertion were all recorded at operation. The sex, age, side of operation, and any simultaneous operative procedures were also recorded. The patients were reviewed the day after operation and then every 3 months thereafter until the tube was extruded. A definite pattern was identified for the extrusion of each type of tube. At one end of the spectrum, Exmoor and Shepard tubes were, for the most part, extruded between 6 and 9 months after insertion, while at the other end, most of the collar button tubes were still functioning at 18 months. The design of the tube was the only factor found to be a significant determinant of the extrusion of the tube, although the experience of the surgeon affected the extrusion rate of the Arrow tube. The different dimensions of the Exmoor and collar button tubes are examined and compared.
Current concepts of formation of tympanosclerosis in the middle ear are reviewed, as are various clinical considerations. Ultrastructural changes are discussed. A differential diagnosis includes disorders affecting middle ear sound conduction, with the most prevalent involving otosclerosis and cholesteatoma.
AbstarctA prospective study was undertaken of 10 chronic renal failure patients on Continuous Ambulatory Peritoneal Dialysis (CAPD) complicated by repeated bouts of peritonitis treated with gentamicin. Each 10-day treatment course consisted of a 120 mg loading dose, followed by 16 mg in 21 of peritoneal dialysate, given four times a day. Serum gentamicin analysed by enzyme immunoassay showed a mean level of 5.2 µg/ml, (range 3.7 to 6.6 µg/ml) four hours after the loading dose. Similar levels, well within the therapeutic range, were maintained on the 3rd, 5th, 7th and 9th days of intraperitoneal gentamicin therapy, suggesting no accumulation of gentamicin in the serum. Pure tone audiometry, electronystagmography and clinical assessment were performed during each course of treatment. Although no evidence of ototoxicity was found during the first two courses of gentamicin, but disequilibrium and bobbing oscillopsia were present during the third and fourth courses of gentamicin. These findings could be explained by cumulative injury to the vestibular apparatus caused by repeated therapeutic insults.
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