Approach to the diabetic foot

Approach to the diabetic foot

May 11, 2015 0
endocrinology,geriatrics,onthepods,vascular surgery

James talks to Dr Isuru Nammuni about an approach to the diabetic foot in this podcast. You’ll learn how to manage a patient with a foot ulcer during an after hours shift.

Summary Writer:  Brandon Lau

Editor:  James Edwards

Interviewee:  Isuru Nammuni

About Dr Isuru Nammuni

Dr Isuru Nammuni is a Vascular and Endovascular surgeon at Royal Prince Alfred Hospital. He has clinical expertise in the medical and surgical management of vascular disease with a special interest in minimally invasive endovascular surgery, having completed overseas training and fellowships in Cambridge and Germany. He has academic appointments at the University of Sydney and Macquarie University and is heavily involved in clinical research and teaching.

The Diabetic Foot

With Dr Isuru Nammuni, Vascular Surgeon at Royal Prince Alfred Hospital, New South Wales, Australia

Case

You are working the after hours shift and you are called to review a patient on the Endocrine ward. He is a 55-year-old man admitted with a foot ulcer and the nurses are concerned that they can no longer palpate his peripheral pulses.

  • The main question you want to answer: is this acute or chronic? Read: is this limb-threatening?
  • History:
    • Pain is a significant associated symptom: painful often suggests an arterial ulcer, but be careful of the neuropathic foot! Venous ulcers are typically painless.
    • Progressive course suggests arterial disease: claudication leading to noctural pain (relieved by swinging legs off the bed or walking) and eventually leading to rest pain (associated with tissue loss).
    • History of diabetes, diabetic control, diabetic foot surveillance.
  • Examination:
    • Lower limb pulses: start proximal to distal, compare left and right sides. Always be honest! It’s far better to not feel a pulse that is there than to feel a pulse that isn’t there.
    • Inspection of ulcers (see below).
    • Foot perfusion: warm or cool to touch, capillary refill.
    • Buerger’s test: elevate each limb until paleness – if pale, hang affected limb over side of the bed and watch for dependent rubor (erythema): the ‘sunset foot’ is indicative of arterial insufficiency (this is caused by reactive hyperaemia).
    • Signs of infection: associated cellulitis, systemic features of sepsis.
  • Arterial ulcers
    • Typically distal and over pressure areas (e.g. heel, malleoli, bony prominences of foot)
    • Deep with a punched-out appearance
    • Associated with other arterial vascular disease, especially coronary artery disease
    • Associated with progressive course (as above)
  • Venous ulcers
    • Typically located on anteromedial calf
    • Shallow with a cleaner base
    • Associated with chronic skin changes (haemosiderosis or fibrosis) → lipodermatosclerosis
  • Diabetic ulcers
    • Can have a mixed picture between arterial and venous
    • Sensory neuropathy can lead to unwitting injury – either acute or chronic
    • Motor neuropathy can lead to clawing of the foot and callus in atypical places, e.g. under metatarsal heads
    • Autonomic neuropathy can lead to a dry, cracked appearance
    • Charcot’s foot is a special circumstance where autonomic changes increase blood flow to the foot and lead to osteopenia and destructive changes to the bony architecture of the midfoot. There is typically a red hot foot with bounding pulses.
  • Doppler ultrasound: not a bad simple first test, but a positive signal does not necessarily mean that the circulation is normal…
  • Ankle-brachial index
    • Position the patient supine, then use a Doppler probe in each limb
    • Compress the calf or arm with a blood pressure cuff until the Doppler signal is lost, then release the pressure until the signal returns – this is the systolic pressure of the limb
    • Ankle-brachial index = (ankle systolic pressure) / (brachial systolic pressure)
    • Normal ABI > 0.9; ABI < 0.5 suggests tissue loss
    • Note that calcified lower limb vessels will produce a falsely elevated reading!
  • Blood tests
    • Inflammatory markers (white cell count, C-reactive protein)
    • Creatinine and estimated glomerular filtration rate → important for angiography
  • Foot X-ray: may indicate sepsis with gas trapping and bony involvement; if suspicious for infection, superficial swabs and debrided tissue can also be sent for culture.
  • Arterial duplex scan: gold standard test to confirm diagnosis and plan for intervention.
  • Ulcer management is driven by the type of wound:
    • A sloughy base needs a debriding dressing – a gel or alginate dressing is appropriate
    • Venous ulcers are often very wet and will require absorbent dressings
  • Venous insufficiency can be managed by compression, but recovery is often slow over months and months of management – note that arterial or mixed ulcers are worsened by compression!
  • Septic foot: signs of infection suggest a need for intravenous antibiotics. Diabetic patients are especially vulnerable and are typically managed with tazocin with possible inclusion of vancomycin for MRSA colonisers or frequent hospital visitors.
  • Arterial vascular disease is managed by surgical intervention – typically endovascular
  • Acute pulselessness in a foot is a limb-threatening emergency!
  • The vascular registrar will want to know of acute pulselessness or serious sepsis. Knowledge of diabetic control, cardiac risk factors, and renal function will aid in planning of treatment.
  • Are there pulses? If not, arterial duplex scan and call the vascular registrar!
  • Are there neuropathic features? If so, offload pressure to foot and involve podiatry.
  • Are there signs of infection? If so, give intravenous antibiotics.
  • Are there signs of tissue necrosis? If so, debride.

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Tags: #ABI,#arterial duplex scan,#arterial vascular disease,#diabetes,#diabetic foot,#Doppler ultrasound,#endocrine disease,#endocrine system,#endocrinology,#foot ulcer,#sepsis,#septic foot,#total and permanent disability,#ulcers

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