Hospital Medicine Guidelines for Management of Diabetic Foot Infections

Background

In the U.S. alone, there are an estimated 25.8 million people with diabetes, or about 8.3% of the population. Due to comorbidities of peripheral neuropathy and peripheral vascular disease associated with diabetes, these patients are at higher risk for developing foot infections. Among the myriad diabetes complications, diabetic foot infections (DFI) are the main reason for diabetes-related hospitalizations and lower-extremity amputations. U.S. hospitals admit roughly 5,700 patients per year for DFI; 71,000 lower-extremity amputations are attributed to diabetes.^1,2

Studies have demonstrated that DFI management according to guidelines improves survival, reduces complications, and is cost-effective with a major clinical outcome of reduced amputations.³ But prospective observational studies have shown that, in practice, guidelines often are not followed and can lead to poor outcomes.⁴ Studies suggest a need for more simple, straightforward guidelines.

Guidelines Update

In June 2012, the Infectious Diseases Society of America (IDSA) updated its 2004 guidelines on the management of diabetic foot infections.⁵ Although IDSA made no major changes to its recommendations, the 2012 guidelines were revised to be more simple and clear. These new guidelines have been reviewed and endorsed by SHM.

Specific recommendations include:

• All patients with suspected DFI should be assessed on three levels: the patient, the extremity involved, and the wound. Patients should be assessed for signs of systemic illness or metabolic derangements. The extremity should be examined for peripheral arterial disease (PAD) using the Ankle-Brachial Index (ABI), and those with an ABI <0.4 should be evaluated by a vascular surgeon.
• Uninfected wounds should be distinguished from infected wounds based on the presence of two or more classic signs of inflammation and purulence. All wounds should be classified based on validated systems, such as those established by IDSA or the International Working Group on the Diabetic Foot (IWGDF). The IDSA classification of wounds as uninfected, mild, moderate, and severe correlate well with the IWGDF’s PEDIS (Perfusion, Extent, Depth, Infection and Sensation) Grades 1, 2, 3, and 4. Wounds are distinguished by size (more or less than 2 cm in width), extent (depth of tissue involvement), and the presence of two or more signs of systemic inflammatory response syndrome.
• Whenever possible, management of DFI should involve multidisciplinary teams that include a microbiologist or ID expert, surgeon/podiatrist familiar with debridement of foot infections, and wound care experts familiar with dressings that provide pressure off-loading.
• All wounds should be debrided, and cultures should be sent from deep tissue via biopsy or curettage (scraping of the base of the ulcer). Wound surface swabs should not be sent for culture, as they often are inaccurate.
• All patients with severe infections and some patients with moderate infections with complicating features (i.e. severe PAD or inability to manage outpatient treatment due to psychosocial reasons) should be admitted. Those with mild infection or some moderate infections without complicating features can be managed as outpatients.
• All patients with suspected DFI should have plain radiographs of the affected limb to evaluate for bony abnormalities, soft-tissue gas, or foreign bodies, but they are only 54% sensitive and 68% specific for osteomyelitis. MRI is more sensitive (90%) and specific (up to 90%) for detecting osteomyelitis. When MRI is contraindicated, a bone scan coupled with a tagged white-blood count scan is the next best test for detecting osteomyelitis.
• Osteomyelitis, which is found in as many as 20% of mild to moderate DFI cases and as many as 50% of severe DFI cases, should be suspected in any patient with large (>2 cm square), deep, or chronic (>six weeks) wounds, as well as those who have wounds overlying a bony prominence or have a positive probe-to-bone (PTB) test. The most definitive diagnosis of osteomyelitis is via bone biopsy for culture and histology. Patients with osteomyelitis can be managed surgically with resection or medically with prolonged antibiotics (>four weeks). If surgical resection removes the infected bone with clean margins, the antibiotic course can be shortened to two to five days post-operatively.
• Effective treatment includes both wound care as well as antibiotic therapy. Antibiotics should be started after cultures are sent. Empiric antibiotics for mild to moderate infections in patients who have not been recently treated can be directed at gram-positive cocci (GPC), as Staphylococcus is the most common causal organism identified. Patients with severe infection can be started empirically on parenteral broad-spectrum antibiotics covering for GPC (particularly methicillin-resistant Staphylococcus aureus in at-risk patients), gram-negative bacteria, and obligate anaerobes. Antibiotics should be tailored once culture and sensitivity results are available. Generally, mild infections should be treated for one to two weeks and moderate to severe infections for two to three weeks, if there is no suspicion of osteomyelitis.