Director, Hermann Hospital Center for Hyperbaric Medicine, Associate Professor, Department of Anesthesiology, The University of Texas Medical School at Houston
Inadequate blood flow to the legs, peripheral vascular disease, is a major problem, particularly among diabetics, producing non-healing leg ulcers. The ulcers commonly progress and amputation is often necessary. However, an aggressive team approach, involving orthopedic foot specialists, interventional cardiologists and hyperbaric (high pressure oxygen) medicine specialists, working together, can make a big difference. Eighty percent of patients originally referred for amputation will have their limbs saved through such intensive treatment.
Peripheral vascular disease (PVD) deprives the extremities of vital nutrients, oxygen and even antibiotics, making infection in these extremities difficult to eradicate. We call this deprivation, ischemia. Unless adequate blood flow and oxygen/nutrient supply can be restored, healing cannot occur and amputation is usually necessary.
Warning Signs and Risk Factors
Oxygen-deprived wounds, in particular, are painful. It is this most important finding which helps the doctor make the diagnosis. If your feet are often cold, if the doctor can't easily find pulses in your legs, if they turn pale on elevation or red while hanging down, if they're skinnier or shinier, if no hair is growing on your feet and toes and your nails are thicker (often with fungal infections), you may have PVD.
Risk factors for peripheral vascular disease include: 1) diabetes, 2) smoking, 3) hypertension (high blood pressure), 4) hypertriglyceridemia (high blood levels of triglyceride), 5) advanced age, 6) a family history of PVD and 7) obesity. Combinations of risk factors further enhance the likelihood of peripheral ischemia. Cigarette smoking has been noted two and one half times more frequently in diabetic patients with ischemia and gangrene than in patients without diabetes. Even if adequate flow is restored, diabetic control and cessation of smoking are usually necessary for wound healing to occur.
Peripheral vascular disease (PVD) deprives the extremities of vital nutrients, oxygen and even antibiotics, making infection in these extremities difficult to eradicate. We call this deprivation, ischemia.
The Two Types of Wounds
There are two different categories of oxygen-deprived wounds. The first is that of distal ischemia, characterized by dry, dead skin and tissue on toes or feet. The second usually begins with trauma or pressure and occurs over bony prominences, such as the ankle bone (malleolus) or, perhaps, the heel. Ischemic limbs are particularly vulnerable to pressure related injury. If the patient also has swollen legs (edema), compression bandaging should not be used to reduce the swelling.
When wounds are located on ischemic toes, healing is unlikely. The ulcers are often atop bone because there isn't much soft skin tissue in the toes. Toe lesions should be kept dry and clean. Peroxide, while toxic to healing tissue, is useful in decreasing bacterial contamination. Antibiotic ointments may help a little but often cause softening and separation of the tissue. Dead tissue on toes should be covered with protective, non adherent bandages and checked daily by a visiting nurse or family member for evidence of infection. Some of these toes may fall off on their own, and the patient and family members should be prepared for this possibility. If bone is not exposed, surgery may be avoided. If infection occurs, or if pain becomes unmanageable, then amputation at a level likely to heal should be performed.
Open wounds should be managed carefully. Betadine®, peroxide and antibacterial soaps should be avoided. Saline wet to dry dressings are useful only when dead tissue must be removed surgically (debridement) and may increase pain in already painful lesions. Wet to dry dressings should be discontinued when scar tissue begins to develop. Many new dressing products are available for use in these delicate tissues, such as hydrogels. Pain management is imperative, as pain itself can decrease blood flow into the affected area.
Some wounds in ischemic tissues will heal eventually. The assessment of healing potential and the assessment of vascular disease are related. If possible, the physician can make an assessment using two non-invasive methods, Doppler toe pressures and transcutaneous oximetry.
Doppler toe pressures can be obtained with relatively inexpensive, hand-held devices or via hospital vascular laboratories. A disadvantage of this technique is that it requires a small blood pressure cuff to be inflated around the digit, which can be very painful in ischemic toes.
The transcutaneous oximeter (TcPO2) uses an electrode and can not be performed on the toes, since the most common commercial electrodes are too wide to adhere to these narrow, curved areas.
Some patients may be candidates for hyperbaric oxygen therapy. Hyperbaric oxygen therapy (HBOT) is breathing oxygen at pressures greater than sea level and requires the entire patient be enclosed in a pressure vessel ("chamber"). It is not achieved by topical application of oxygen to the limb.
The team approach makes sense for patients who have been walking prior to developing ischemic wounds but may be harder to justify in those who have already undergone amputation or are not ambulatory for other reasons. The best treatment of non-healing foot and lower leg wounds is restoration of blood flow to the foot. Recently, "balloon surgery," which uses a small balloon mounted on a flexible tube to stretch open the blocked arteries to the foot, has resulted in saving up to 80% of patients' feet which were previously referred for amputation11. If PTA (balloon surgery) or vascular surgery fail, the patient will probably need a below the knee, or even an above the knee, amputation. The potential financial cost and the human suffering of multiple, possibly unsuccessful, procedures make it imperative that functional outcome be discussed with the patient and family from the beginning.