Necrotising otitis externa

Necrotising otitis externa (malignant otitis externa) is a rare complication of acute diffuse otitis externa; consider the diagnosis in patients whose symptoms have not improved after treatment of acute diffuse otitis externa. Necrotising otitis externa mostly occurs in patients with diabetes, advanced age or immune compromise (eg patients with advanced HIV infection, patients receiving cancer chemotherapy).

The condition is characterised by the spread of infection to cartilage and bone in the external ear canal and can progress to skull-based osteomyelitis. The key feature is pain despite resolution of skin swelling and redness (which should have resolved with the use of eardrops for acute diffuse otitis externa). Features include:

fever
severe persistent pain
visible granulation tissue
progressive cranial neuropathies.

Urgently refer patients with necrotising otitis externa to the emergency department for prompt administration of intravenous antibiotic therapy and diagnostic imaging (eg computed tomography [CT], magnetic resonance imaging [MRI]). These patients should be managed by an infectious diseases physician and otolaryngologist.

Note: Intravenous antibiotics must be started promptly for necrotising otitis externa – refer patients to the emergency department.

Necrotising otitis externa is almost always caused by Pseudomonas aeruginosa. Obtain superficial swabs, or samples of tissue or pus, for culture and susceptibility testing, preferably before starting antibiotic therapy.

For patients with necrotising otitis externa, until the results of culture and susceptibility testing are available, useAbdul-Aziz, 2024 Dulhunty, 2024:

piperacillin+tazobactam intravenously. For dosage adjustment in adults with kidney impairment, see piperacillin+tazobactam dosage adjustment piperacillin + tazobactam piperacillin+tazobactam piperacillin+tazobactam

patients without septic shock and not requiring intensive care support: 4+0.5 g (child: 100+12.5 mg/kg up to 4+0.5 g) 6-hourly

patients with septic shock or requiring intensive care support: 4+0.5 g (child: 100+12.5 mg/kg up to 4+0.5 g) administered as a loading dose over 30 minutes. After 3 hours, start a continuous infusion of 16+2 g (child: 400+50 mg/kg up to 16+2 g) administered over 24 hours¹.

For patients who have had a nonsevere (immediate or delayed) hypersensitivity reaction to a penicillin, use:

cefepime 2 g (child: 50 mg/kg up to 2 g) intravenously, 8-hourly². For dosage adjustment in adults with kidney impairment, see cefepime dosage adjustment. cefepime cefepime cefepime

For patients who have had a severe immediate³ hypersensitivity reaction to a penicillin, cefepime (at the dosage above) can be considered if a beta-lactam antibiotic is strongly preferred (for considerations, see Severe immediate hypersensitivity: Implications of cross-reactivity between penicillins and cephalosporins).

For patients who have had a severe immediate³ hypersensitivity reaction to a penicillin in whom cefepime is not used, or for patients who have had a severe delayed⁴ hypersensitivity reaction to a penicillin, until the results of culture and susceptibility testing are available, meropenem may be suitable⁵. Seek expert advice.

Modify therapy as soon as the results of culture and susceptibility testing are available. Prolonged treatment is required because the infection involves bone or cartilage. Seek expert advice on antibiotic choice and duration of therapy.

¹ For patients with septic shock or requiring intensive care support, administering the total daily dose of piperacillin+tazobactam over 24 hours is preferred to ensure adequate drug exposure. If this is not possible (eg the patient is receiving other drugs via the same line), administer the standard dose (4+0.5 g [child: 100+12.5 mg/kg up to 4+0.5 g] intravenously, 6-hourly) as an extended infusion over 3 hours. If a 3-hour infusion is not possible, administer over 30 minutes. For more information, see Practical information on using beta lactams: penicillins.Return

² In patients with septic shock or requiring intensive care support, there is a theoretical benefit from administering the intermittent dose of cefepime over 3 to 4 hours, or administering the daily dose over 24 hours. However, at the time of writing, there are inadequate data to recommend administration over 3 hours or longer for patients with septic shock or requiring intensive care support.Return

³ Severe immediate hypersensitivity reactions include anaphylaxis, compromised airway, airway angioedema, hypotension and collapse.Return

⁴ Severe delayed hypersensitivity reactions include cutaneous adverse drug reactions (eg drug rash with eosinophilia and systemic symptoms [DRESS], Stevens–Johnson syndrome/toxic epidermal necrolysis [SJS/TEN], severe blistering or desquamative rash), and significant internal organ involvement (eg acute interstitial nephritis).Return

⁵ In patients with penicillin hypersensitivity, the rate of immune-mediated cross-reactivity with carbapenems is approximately 1%; therefore, meropenem can be considered in supervised settings. However, in patients with a history of a severe cutaneous adverse reaction (eg drug rash with eosinophilia and systemic symptoms [DRESS], Stevens–Johnson syndrome/toxic epidermal necrolysis [SJS/TEN]), consider meropenem only in a critical situation when there are limited treatment options.Return