DIABETIC FOOT INFECTIONISABELLE TREPICCIONE, MD

OUTLINEScope of problem

Predisposition

PreventionDiagnosis

Treatment

SCOPE OF THE PROBLEMLifetime incidence of foot ulcer is 25%

50% are infected

50% of non-traumatic lower extremity amputations are due to DFI

131 million diabetics worldwide in 2000

366 million diabetics by 2030

COST OF THE PROBLEMMean annual cost of treatment in 2001:

$9,000 for an uninfected foot ulcer

$25,000 for an infected foot ulcer

$45,000 for a foot ulcer with osteomyelitis

PREDISPOSING FACTORS

NEUROPATHY VASCULAR DISEASE

IMMUNE DYSFUNCTION

NEUROPATHY VASCULAR DISEASE IMMUNE DYSFUNCTION

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NEUROPATHY Sensory neuropathy: Wounds go undetected and worsen with exposure to repetitive trauma

Autonomic neuropathy: Gland dysfunction makes skin dry and susceptible to tearing

Motor neuropathy: Atrophy of intrinsic foot muscles leads to anatomic deformities

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VASCULAR DISEASEHyperglycemia causes endothelial cell dysfunction and smooth muscle cell abnormalities

Hyperglycemia is associated with an increase in thromboxane A2 contributing to hypercoagulability

Co-existing hypertension and hyperlipidemia

IMMUNE DYSFUNCTIONFewer inflammatory cytokines

Impaired neutrophil chemotaxis

Impaired neutrophil phagocytosis

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IDENTIFYING THOSE AT RISKHemoglobin a1c >9% (OR 3.2)

>10 years with diabetes (OR 3.0)

Prior lower extremity amputation (RR 2.8)

Visual acuity less than 20/40 (RR 1.9)

Prior foot ulceration (RR 1.6)

PREVENTIONPatient education: Improvement in patient knowledge and behavior. No ulcer or amputation prevention.

Yearly screening foot exam: Decreased ulcer recurrence at 1 year if referred to podiatry. No reduction in amputation.

Diabetic footwear: Custom footwear prevents ulcer recurrence.

Optimize glycemic control: Improves neuropathy. Nonsignificant reduction in amputation.

Smoking cessation: Nonsmoking diabetics have lower rates of foot ulceration and amputation.

Not studied: Callus debridement, treatment of tinea pedis or onychomycosis, and lower extremity revascularization.

Infection indicated by presence of 2 or more of: Swelling or induration Erythema Tenderness Warmth Purulent discharge

Lavery LA, Armstrong DG, Murdoch DP, Peters EJ, Lipsky BA. (2007). Validation of the Infectious Diseases Society of America’s diabetic foot classification system. Clin Infect Dis

UNINFECTED MILD INFECTION-Local infection confined to skin

and subcutaneous tissue

-Circumference of erythema >0.5cm

and <2cm

MODERATE INFECTION

-Local infection with involvement

of deeper structures

-Circumference of erythema >2cm

SEVERE INFECTION-Local infection plus systemic inflammatory

response syndrome

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IDENTIFYING INFECTED ULCERSProbe to bone, RR 6.7

Ulceration present >30 days, RR 4.7

History of recurrent ulcers, RR 2.4

Traumatic foot wound, RR 2.4

Presence of vascular disease in same limb, RR 1.9

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WOUND CULTURE INDICATIONS

Culture and gram stain moderate to severely infected wounds

Consider culture of mild infection if there are MRSA or pseudomonas risk factors

Don’t culture uninfected wounds

TECHNIQUE

Clean and debride wound

Obtain culture specimen from base

Aspirate purulence if present

Do not send superficial swabs or swabs of wound drainagef wound or wound drainage for culture

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IMAGINGXrays of all new diabetic foot infections

MRI if there is concern for other deep space infection

MRI when a chronic ulceration becomes infected

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TREATMENT OF THE INFECTED ULCERAntibiotics

Wound care

Sometimes surgery

Does anything else make a difference?

ANTIBIOTICSMILD infection: target gram positive cocci, maybe MRSA (ORAL)

MODERATE infection: target gram positive cocci, maybe MRSA (ORAL)

SEVERE infection: target gram positive cocci, gram negative and obligate anaerobes, MRSA and pseudomonas (PARENTERAL)

WHEN DO I NEED TO COVER FOR MRSA?When the patient has a history of MRSA or MRSA colonization within the

past yearWhen the infection is severeWhen local MRSA prevalence is 50% (for mild) or 30% (for moderate)

WHEN DO I NEED TO COVER FOR MRSA?

25% MRSA

40% MRSA

DO NOT ROUTINELY NEED TO COVER (UNLESS SEVERE)

COVER IN MODERATE AND SEVERE INFECTION

WHEN DO I NEED TO COVER FOR PSEUDOMONAS?Not as common a pathogen in DFI as previously thoughtIncreasing evidence that it may be a wound colonizerThe IDSA recommends coverage in:Severe infectionsTropical climatesFrequent exposure of the foot to water

WOUND CARE

Debridement Off-loadingMoist wound environment

No topical antimicrobials

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WHEN SHOULD I CONSULT A SURGEON?Evidence of life or limb threatening infection

Evidence of critical ischemia

Evidence of deep-space infection or abscess

Failure to improve with otherwise appropriate treatment

OTHER TREATMENTSNegative-pressure wound therapy AKA wound vac

Hyperbaric oxygen

Granulocyte colony stimulating factors (G-CSF)

Stem cell

Not studied: intensive glycemic control limb revascularization

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LEARNING POINTSWhen it comes to prevention; focus on appropriate footwear, a1c control, and smoking cessation

Send a tissue culture in all but mild diabetic foot infections

Most mild and moderate infections do not require MRSA or pseudomonas coverage

Wound care is critical to complete healing

Call a podiatrist or orthopedic surgeon when the infection is deep or severe

QUESTIONS?

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