Introduction

Acute external otitis (AEO), defined as the inflammation or infection of the external auditory canal, is a common clinical problem in general practice. Its clinical implications range from a mild inflammation and discomfort to a life-threatening infection ₁,₂,₃,₄.

Major alterations in cellular and humoral functions of the body may occur during critical illness. The secretion of the cytokines, hormones and catecholamines may be disturbed. In addition, widely used agents such as dopamine, epinephrine or norepinephrine may alter the immune response of the body. If these alterations are prolonged and intense, the risk of infection will increase ₅. Furthermore, over prescribing of antibiotics either for a prophylaxis or a treatment of a known infection, disturbs the normal flora of the patients. All these factors may make the patient more prone to have AEO. Therefore, we undertook a prospective observational study to analyse the incidence and etiology of acute external otitis in critically ill patients.

Materials And Methods

After the institutional ethic committee approval and written informed consent of either patients or relatives have been taken, 30 critically ill patients aged between 40-75 years and followed up more than seven days in the intensive care unit (ICU) were included into the study. Patients with a previous history of external otitis were excluded from the study. At the admission to the ICU, both of the EAC of the patients were examined and the Senturia classification was done by the otolaryngologist. According to this classification, patients in the Senturia class IIa and higher were accepted to have AEO (Table 1) ₆,₇,₈,₉ . Swab of the EAC was taken for examination under light microscope and it was send for culturing. Peripheral blood sampling was obtained for culturing both in aerobic and anaerobic media. All cultures were analysed by the same microbiologist. Blood smear for leukocyte formula was done. These results obtained at the admission were accepted as a control. Also, axillary body temperature of the patients, antibiotics and steroids administered during the study were recorded. All of these procedures were repeated with seven days intervals.

Figure 1

Table 1: The Senturia classification

During the study, patients were discharged from the ICU at different days after the 8^th day, and the Senturia class of these patients might be either IIa or below. If we did not take into consideration of the Senturia class of these patients, our calculated incidence of AEO would be falsely high or low. To prevent this bias we calculated the incidence of acute external otitis as:

Figure 2

The results were compared statistically with Kruskal-Wallis, Chi-square and nonparametric correlation test and p< 0.05 was accepted as significant.

Results

The demographic characteristics of the patients, duration of the ICU stay and type of surgeries were shown in Table 2.

Figure 3

Table 2: Demographic characteristics, duration of ICU stay and types of surgeries

No correlation was found between gender and the incidence of AEO (p> 0.05).

No correlation was found between the type of the surgery and the incidence of acute external otitis (p > 0.05).

There was a positive correlation between the Senturia class and days spent in ICU (p< 0.01) (Table 3).

Figure 4

Table 3: The evaluation of Senturia class according to the days spent in ICU.

The Senturia class increased with high body temperature (p < 0.01) (Figure 1).

Figure 5

Figure 1: Correlation between Senturia class and body temperature.

Although there was no positive blood culture result for neither aerobic nor anaerobic media, the Senturia class was increased with left shift of the leukocyte formula (p< 0.01).

Direct examination of the swab of the EAC was revealed a significant increase in epithelial cells and leukocytes after 15^th day of ICU admission (p< 0.01).

Isolated microorganisms from the EAC were staphylococci species as staphylococci epidermidis and staphylococci albus, streptococci species, corynebacterium diphteroids and candida albicans. But no significant correlation was found between positive culture results and the incidence of acute external otitis (p> 0.05).

All the patients were under antibiotic therapy, such as cefuroxime, sulbactam-ampisillin, ciprofloxacine, ofloxacine, metranidazole. There was no significant correlation between antibiotics administered and the Senturia class (p> 0.05).

There was no correlation between the Senturia class and systemic corticosteroid administration (p> 0.05)

Discussion

The results of this study suggest that patients stayed more than 15 days at the intensive care unit, are under the risk of developing acute external otitis. The incidence of AEO was similar in both gender in our study. This finding correlates with that of Hawke et al ₁₀.

The cause of AEO is usually bacterial and occasionally fungal infections. Furthermore it may be associated with various noninfectious systemic or local dermatologic effects. EAC has its own bacterial flora and stays free of infection as long as its defense mechanisms are not disrupted ₁₁. Nevertheless, there are major alterations in cellular and humoral functions of the body in critically ill patients. Cytokine, hormone and catecholamine secretions may be disturbed in these patients. In addition to these disturbances, widely used agents such as dopamine, epinephrine or norepinephrine may alter the immune functions of the body. If this alteration of the immune system is prolonged and intense, the risk of infection will increase ₅.

In this study, we found that the Senturia class increased after the 8^th day of ICU admission and direct examination of the EAC swab showed increases in the number of epithelial cells and leukocytes after the 15^th day.; but the isolated micro organisms were normal flora of the skin as staphylococci species, streptococci species, corynebacterium diphteroids and candida albicans and the colonic count were low. In the literature, the most common pathogens isolated from the EAC are staphylococcus aureus, pseudomonas aeruginosa, acinetobacter calcoaceticus, proteus mirabilis, enterococcus faecalis, bacteroides fragilis and peptostreptococcus magnus ₁₂,₁₃,₁₄,₁₅. Furthermore no positive correlation was found between the Senturia class and positive cultures of EAC. The reason for this is probably that all of the patients in our study were under antibiotic therapy such as cefuroxime, sulbactam-ampisillin, ciprofloxacine, ofloxacine, metranidazole.

Systemic or local steroids are used in the treatment of AEO ₃,₁₁,₁₂,₁₆ . In our study, 19 neurosurgical patients (63.3 %) were under systemic steroid treatment. But there was no statistical difference in the incidence of external otitis between patients receiving systemic steroid treatment and those who were not receiving.

AEO is correlated with high environmental temperature, humidity, immersion-induced skin maceration, local trauma and excessive sweating ₆,₁₁,₁₇,₁₈,₁₉. In this study, we found a positive correlation between the Senturia class and high body temperature. The reason for this may be the increased secretion of the sebacious, apocrine and sweat glands of the EAC causing edema at high environmental and high body temperatures. This fact is also emphasized by Candor RM ₁₈. The temperature of the ICU was kept within constant ranges (17-22°C) so the environmental conditions may not be a reason for AEO in our study. We suggest that high body temperature caused the increase in the Senturia class.

Critically ill patients are usually immobile and they have to be washed in the bed. During washing procedures, entrance of water into the EAC is usually inevitable and this may be an important predisposing factor in the development of AEO. Furthermore EAC cleaning with cotton-tipped applicator may be another cause of AEO in ICU₁₁,₁₇.

We conclude that the incidence of AEO is higher than predicted and patients stayed more than 15 days in the ICU are under the risk of developing AEO. Therefore, to prevent AEO to be an overlooked problem in critically ill patients, measures to prevent, to diagnose and to treat it should be taken.