Diabetic foot infection

Background

• 1st key factor is to assess extent & depth of ulcer (typically more extensive than they appear)
  • Ulcer depth is important predictor of healing rate, osteomyelitis (OM) & risk of amputation.
• Failure of ulcer to heal by 50% or more after 1 month of Rx is a strong predictor that the ulcer is unlikely to heal after 3 mos.
• 75% of pts hv polymicrobial inf, usu 70% are g+. Severe limb/life threatening inf are more likely to involve g- aerobic & anaerobic bacteria w/ g+. MRSA is incr in freq.
• 50% or more of pts w/ SEVERE diabetic foot inf have no s/s of systemic tox (ie fever, tachy, incr wbc or Lt shift)

HPI

• Ask about recent trauma
• Duration of current lesions
• Associated systemic symptoms
• Prior treatments

Physical Exam

• Determine ulcer location, dimensions, depth, and appearance
• Note hair and nail growth, determine vascular status (palpate DP, PT, and popliteal pulse)
• Probe ulceration note involvement of bone, joint, tendon, or sinus tract formation
  • Use sterile probe, if hit bone chance of OM 90% higher
• DM foot ulcer infection presumed if:
  • 2 or more of following: erythema, warmth, tenderness, or swelling
  • OR if pus coming from ulcer site or nearby sinus tract
• Severe DM foot infection if:
  • abnormal vital signs
  • Rim of erythema surrounding ulcer or ulcer >2 cm in diameter
  • Lymphangitic streaking or signs of fasciitis (crepitus, skip lesions, severe TTP, bullae), or if probe reaches bone/joint/tendon
• Obtain ABI on all patients with: nonpalpable DP/PT, claudication sx, ischemic foot pain
  • Call vascular if:
    • ABI <0.4 (severe obstruction)
    • ABI 0.4-0.69 (mod obstruction)
• Reminder:
  • DM ulcers usually occur at areas of increased pressure (sole of foot) or friction
  • Venous ulcers usually present above malleoli with irregular borders
  • Arterial ulcers usually found on the toes or shins, with pale, "punched-out" borders (typically painful)

Diagnosis

Determine presence/extent of infection and likelihood of OM/fasciitis

Imaging

• X-rays to detect soft tissue gas, FB, OM, or structural foot deformities
  • OM x-ray changes occur late in dz, negative xrays do not exclude OM
• MRI to eval for OM (not usually done in ED)

Labs

• Chem 10, CBC, Coags, A1c, consider ESR/CRP (useful for monitoring response to Rx)
• ESR >40 incr chance of OM 12 fold, an ESR >70 makes dx nearly certain.

Likelihood of OM

• Factors that increase likelihood of OM:
  • Visible bone or probe to bone
  • Ulcer > 2cm in size
  • ESR >70
  • Ulcer duration > 2 weeks

Treatment

• For infected DM foot ulcers @ HUCLA:
  • Start pt on Diabetic Foot Infection with Wound (DFIW) pathway/order set (No ABX)
    • Do not start pts on this pathway if have rapidly spreading infection or with severe sepsis/septic shock

• Abx for mild= keflex or augmentin or diclox or clinda. Abx for severe= unasyn or clinda & quinolone or clinda & ceftaz, add vanco if life threat.

1. Focusing Rx on g+ aerobes w/ oral abx (1-2 wk) appears effective for most mild inf. Must eliminate pressure on wound until healed, nd to elminate or decr periph edema. Dress wound w/ warm/moist env after debridement, absorbant drsng if exudate present.
2. Recurrence of amp is 50-70% over 3-5 yrs. Overall, 50-80% will heal w/in 6 mos w/ optimal care.
3. Goal for best reults is A1c level <7%, BP <130/80, no Etoh or smoking & LDL <100.

Source

• Tintinalli
• UpToDate
• PANI