After the patients were enrolled in the study, we subjectively scored each ear and performed a quantitative culture. Clinical scoring was based on the amount of exudate present and the condition of the epithelial lining of the ear canal. Exudates were graded as none, scant, moderate, or copious and assigned a score of 0 to 3, respectively. The ear canal epithelium was graded as normal, erythematous, eroded, or ulcerated and also scored from 0 to 3. We added the two parameters to determine the final score.

For the quantitative culture, we instilled 1 ml of sterile saline solution into each affected ear canal, gently massaged the canal for 60 seconds, and then removed 10 µl of the resulting fluid from the vertical ear canal with a sterile, calibrated loop. We then diluted the samples in 1 ml of sterile saline solution. Next, we plated 10 µl of the diluted, agitated sample onto blood agar with another sterile, calibrated loop. Each diluted sample was plated this way in duplicate. We incubated the plates at 98.6 F (37 C) for 24 to 48 hours and then counted the resulting colonies. Plates with colonies too numerous to count were assigned as 4,500 colonies. We chose this number because it is near the limit of the number of colonies that can be accurately counted on a standard agar plate with the naked eye. We performed quantitative cultures one hour before treatment and again just before the initial treatment for comparison and to control for any possibility that the sampling process could distort the number of colonies grown.

Next, one of the investigators performed the initial cleaning with the Sanova cleanser. The sodium chlorite and citric acid solutions were mixed in equal parts just before administration. The cleanser was instilled into each affected ear. Enough cleanser was used to completely fill the patient's ear canal (ranging from 0.5 to 3 ml total volume). The ear was then massaged for 60 seconds and any resulting dislodged debris was wiped out of the ear with cotton balls. Another quantitative culture was performed one hour after the initial treatment.

After 14 days of treatment, we reexamined the patients and performed subjective clinical scoring, cytology on impression smears, and quantitative cultures (in duplicate). Cytology and quantitative cultures were repeated as described at least three hours after the last owner-administered treatment.

Statistical analyses

The mean of the two quantitative culture counts from each time interval was calculated. These means were unable to be converted to a normal distribution, so the data were analyzed by using a Wilcoxon signed rank test to determine the P values between the different collection times. Spearman's rank correlation coefficient was used to compare clinical scores and culture counts. All data were analyzed by using Stata 7 (StataCorp). This was an open clinical trial, and no patients were dropped from treatment once enrolled in the study.

The study results

Nineteen dogs with a total of 27 affected ears were enrolled in the study. The nine males and 10 females ranged in age from 1 to 13 years, with a median age of 7 years. All dogs were medium to large in size, and nine breeds were represented.