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Perspectives in Circulation Today
The Gangrenous Foot. A simple classification and its Treatment with the End-diastolic pneumatic boot
Wet Gangrene (Necrotizing Cellulitis):
For the history of this patient see www.circulatorboot.com/casehistory/case1.html. The picture shows her state on presentation to the Circulator Boot Center. Note the rubor on the dorsum of the foot up to her ankle. The necrotic material was revealed in the operating room where she had been taken for debridements. Note that while the dorsum of the foot has been destroyed by the infection, her toes appear relatively healthy. Her foot had undergone progressive deterioration in spite of a 12-day hospitalization with intravenous tobramycin and cefobid appropriate for the Beta-streptococcus and Eikenella species cultured from her foot. A bone scan showed ostemyelitis of her 3rd, 4th and 5th metatarsal heads. The x-ray at the Boot Center is seen below:
The 3rd-5th metatarsal heads were especially washed out and the 2nd less so. Because of sepsis and the progression of her disease in spite of appropriate therapy, she had been advised to undergo a life-saving beneath-the-knee amputation. She refused and asked for another institution.
Pathophysiology: What had happened? How could such a foot infection develop in spite of appropriate antibiotic therapy? This 33 year old lady had had diabetes for 24 years and had modest peripheral neuropathy.
Proximal arteriosclerosis obliterans may diminish arterial perfusion pressure. Medial calcinosis of the pedal vessels is common with neuropathy and occasional kinks in such vessels may further decrease perfusion pressure. Again, it has been known for many years that damage to the sympathetic nerves opens the A-V shunts normally operative in thermoregulation and diverts arterial blood from the nutrient capillary vessels to the veins and may thus lower the oxygen tension in the tissues (Davis MT and Greene NM: Polarographic studies of skin oxygen tension following sympathetic denervation. J Appl Physiol 14:961-965, 1959. Wollersheim H et al: Ephedrine improves the microcirculation in the diabetic neuropathic foot. Angiology 40: 1030-1033, 1989.). Damage to the cholinergic nerves may produce a dry foot subject to callus formation and skin-breaks that become portals for infection (Ryder REJ, Kennedy RL, Newrick PG, Wilson RM, Ward JD and Hardisty CA: Autonomic denervation may be a prerequisite of diabetic neuropathic foot ulceration. Diabetic Medicine 7:726-730, 1990). Further, the loss of acetylcholine release diminishes nitric oxide and prostacyclin production thus diminishing flow through the nutrient vessels. With the absence of protective pain reflexes, the patient may walk on the infected foot pressing the infection through the tissue plains. The bacteria may elaborate various digestive enzymes damaging the tissue and microcirculation further compromising blood flow. The bacteria protected in avascular areas are not responsive to antibiotics and may continue to elaborate destructive enzymes which can move progressively through the tissue. Thus, a small plantar skin crack in the lady above develops into a limb and life at risk. For more on diabetic neuropathy see www.circulatorboot.com/literature/neuropat.html.
A foot saved! Osteomyelitis healed! How did we do it? See www.circulatorboot.com/casehistory/case1.html.
Characteristics of necrotizing cellulitis:
- Commonly associated with diabetic peripheral neuropathy.
- A small portal of entry through a skin break in callus or fungus-laden toes.
- An enlarging area of rubor with or without pain.
- Photoelctricplethysmography tracings commonly showing pulsatile flow in the rubor while transcutaneous PO2 values are very low (a combination pathognomonic for an aerobic cellulitis and a combination requiring urgent intervention… e.g local antibiotic injections and MiniBoot therapy).
- Distal and adjacent tissue commonly close to normal.
- When rubor fails to blanch on local pressure, some tissue breakdown may be unavoidable… but much of the tissue can still be saved.
For more examples of necrotizing cellulitis see www.circulatorboot.com/casehistory/csemenu1.html