Prophylactic therapy for post-tympanostomy tube otorrhea.

Post-tympanostomy tube otorrhea (PTTO) can be classified as early, late, or chronic. The onset of early PTTO can begin as soon as postoperative day 1. Patients who have more than simple fluid in the ear--particularly an infection that has caused inflammation in the mastoid air cell system--can begin draining shortly after the tube has been placed. Late PTTO develops at least 2 weeks postoperatively, and it is caused by pathology that has developed in the middle ear subsequent to the tube placement. A discharge that persists for more than 8 weeks is considered chronic PTTO, which is likely caused by a well-established infection in the middle ear and in the mastoid air cell system. Chronic PTTO is a therapeutic challenge.

PTTO can also be classified as simple or complicated. Simple PTTO is nothing more than a painless discharge. In complicated PTTO, the discharge can cause other problems, such as upper respiratory tract infection, periauricular cellulitis, and occlusion of the external ear canal.

To gauge the incidence of PTTO, Rosenfeld performed a meta-analysis of 134 articles and found that delayed PTTO occurred in 26% of patients, transient PTTO in 16%, recurrent PTTO in 7.4%, and chronic PTTO in 3.8%.

Etiology

There is much we do not know about the cause of otorrhea. Does it originate in the middle ear? Or is it introduced from outside via the ear canal? We do know that otorrhea is not always caused by an infection. It is true that some cases are caused by a bacterial or viral infection, but others are the result of some form of inflammation or allergy, such as allergic fungal sinusitis. Not all fluid is infected.

Many other factors can cause ears to drain. Among them:

* upper respiratory tract infection

* acute otitis media 

* serous otitis media

* mucoid otitis media

* chronic suppurative otitis media

* eustachian tube obstruction

* tube granuloma 

* granular myringitis

* otitis externa

Prevention

There are several steps we and our patients can take in an attempt to prevent PTTO, both medically and surgically.

Medical prophylaxis. First, patients must avoid getting water into the ear. Second, we can administer prophylaxis with topical and/or systemic antibiotics. Oral antibiotic therapy is the least attractive of these alternatives; it is not cost-effective, and it causes systemic side effects. Topical antibiotics, on the other hand, are cost-effective, and they provide us with the ability to deliver high levels of drug directly to the site. Still, topical prophylaxis is not without its risks. The major risks we encounter are ototoxicity, plugging of the tube, tube granuloma, otomycotic otitis externa, and fungal superinfection.

My institution, the University of Toronto, was the first to describe tube granuloma, which occurs when granulation tissue develops around a tympanostomy tube (figure). We realized that the formation of granulation tissue is primarily a foreign-body reaction to keratin squames that become implanted during tube insertion in the middle ear cleft. In most cases, tube granuloma can be easily treated with topical antibiotics, and the granuloma will usually shrink away to nothing. If topical antibiotics should fail, the tube and the granulation can be physically removed.

I do not believe that otomycosis is much of a problem in patients who receive tubes. It seems to be more of a problem in patients treated for otitis externa who have a good deal of keratin debris and wax. After the bacteria are sterilized, we often see that a patient will return 2 weeks later with an acute otomycosis.

Before using topical drops to treat PTTO or acute otitis media, some issues must be considered. First, how effective will the drops be in an ear that is filled with fluid? The presence of fluid, of course, interferes with the distribution of the drug. If a patient has copious otorrhea and the fluid is pulsating outwardly, will the drops swim uphill? I doubt it. Another issue is whether the drops will reach the mastoid air cell system. They won't if there is fluid in there.

Surgical prophylaxis. There are two things that we can do in the operating room that might prevent the development of drainage, although perhaps not initially. One is to ensure that the eardrum is clean. If, for example, some keratin debris is present, we must be sure to remove it, because failure to do so might lead to a tube granuloma. The second factor has to do with the different types of tubes. Wide-bore tubes are associated with a higher risk of otorrhea than are narrow-bore tubes, probably because they allow more water to enter the middle ear.

The value of some other proposed prophylactic steps has not been proven. For example, there is some evidence that saline irrigation prior to tube placement lowers the risk of PTTO, (2) but I do not believe that this is necessary. Neither does sterilizing the surgical field provide any benefit; sterilization does not have any effect on the incidence of postoperative drainage.

Comments

Prof. Deitmer: Do you penetrate the tympanic membrane with the suction tube and remove everything that is in there? If so, I believe that this might have some influence on postoperative drainage. Also, I suspect that metal tubes have a better ratio of inner-to-outer diameter than do silicone tubes, and they are therefore more patent and they don't crust. Finally, you can place otic solutions well inside the middle ear if you pump the ear with your finger; you will know you are successful if the patient complains about the taste.

Prof. Hawke: First, I don't know what most physicians do, but I have always evacuated the middle ear. Second, it does appear that the wider the tube, the easier it is for water to get into the middle ear. Also, my experience has been that wider tubes create a very slight risk that a tube will extrude and cause a persistent perforation. I am not a big advocate of the wider tubes. Finally, any patient who can taste eardrops through the eustachian tube probably doesn't need any drops, because the eustachian tube is patent and the middle ear is clear.

Dr. Croxson: Do we know whether prophylactic medication confers any advantage on the patient with regard to the future development of discharge?

Prof. Hawke: I do not believe it does, but I don't believe that's an important consideration. The immediate reasons for preventing PTTO--to improve hearing and to avoid the unhygienic discharge--are in themselves sufficient to justify prophylaxis.

References

(1.) Rosenfeld RM. Surgical prevention of otitis media. Vaccine 2000;19(Suppl 1):S134-9.

(2.) Gross RD. Burgess LP, Holtel MR, et al. Saline irrigation in the prevention of otorrhea after tympanostomy tube placement. Laryngoscope 2000;110:246-9.

Michael Hawke, MD

Prof. Hawke is in the Department of Otolaryngology at the University of Toronto. His research interests include ear disease, sleep disorders, and sinus disease.