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

1. For noninfected chronic wounds
   1. NWB, nonadherent padded dressing, ppx abx not indcated
   2. Start pt on Diabetic Foot Infection with Wound (DFIW) pathway/order set (No ABX)
      1. Do not start pts on this pathway if have rapidly spreading infection or with severe sepsis/septic shock
   3. Primary management is surgical debridement, consult trauma surgery
2. Empiric therapy for DM foot infections:
   1. Mild infxn outpt Rx, non-limb-threatening (MSSA + strep):
      1. Keflex 500mg Q6H OR Augmentin 875/125mg Q12H OR Dicloxacillin 500mg Q6H OR Clinda 450mg Q8H
      2. Strict NWB, tight glycemic control, meticulous wound care
   2. Severe infxn, limb-threatening (admit):
   3. Unasyn 3g IV Q6H OR Ticarcillin-clavulanate 3.1g IV Q8H OR Clinda 900mg IV Q6H AND Ciprofloxacin 400mg IV Q12H OR Clinda 900mg IV Q6H and Ceftriaxone 1g IV Q12H (add vanco if life threat)
3. Recurrence of amp is 50-70% over 3-5 yrs. Overall, 50-80% will heal w/in 6 mos w/ optimal care.
4. Goal for best reults is A1c level <7%, BP <130/80, no Etoh or smoking & LDL <100.

Source

• Tintinalli
• UpToDate
• PANI