Importance of Skin Perfusion Pressure in Treatment of Critical Limb Ischemia
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Foot ulcers or gangrene with associated peripheral arterial disease (PAD) are a challenge to treat. Amputation of the toes and metatarsal bones is better tolerated than more extensive amputation because patients who undergo the former can be rehabilitated easily and can return to a good quality of life. In addition, the bony structures of the foot may be remodeled in such a way to prevent further injury.1 The evaluation of blood flow in the lower extremities is crucial in managing foot ulcers or gangrene with PAD. The goal of achieving the lowest possible level of amputation and minimal invasive debridement is maximal preservation of functionality and mobility. However, if the amputation is selected at a more distal level where blood supply may be inadequate for healing, it may lead to further tissue necrosis and additional surgery. Repeated operations may subject patients to prolonged treatment and long-term hospitalization. Therefore, when blood flow is insufficient, surgical debridement of necrotic tissue in foot ulcers with PAD should be postponed until after the restoration of adequate blood flow to the skin.2 To achieve minimal invasive debridement, adequate blood flow must be supplied at the amputation level. It is essential to evaluate blood flow that promotes wound healing by only local management or by some peripheral arterial reconstruction. Several tests including ankle brachial index (ABI), toe pressure (TP), and transcutaneous oxygen tension (TcPO2),3–9 have been devised to provide objective data to determine the most distal level where wound healing is efficient. Although not one test has gained universal acceptance, the authors use the laser Doppler skin perfusion pressure (LD-SPP)10–12 method. Skin perfusion pressure has been shown to be a reliable predictor of wound healing.10–18 The authors measured SPP at the proximal margin of foot ulcers (not in the wound bed) in patients referred to the Wound Treatment Center at Shin-Suma General Hospital (Kobe, Japan) for the treatment of intractable foot ulcers, and compared it with the outcomes of treatment (healed or failed to heal). Skin perfusion pressure was compared before and after peripheral arterial reconstruction. The effect of SPP elevation on wound healing was also evaluated.
Materials and Methods
Patients. From January 2003 to September 2004, 69 foot ulcers or gangrene were studied in 47 patients (33 men and 14 women, 36- to 83-years-old; mean 69.5 years) referred to the Wound Treatment Center at Shin-Suma General Hospital (Kobe, Japan). Comorbidities were diabetes mellitus (27 patients, 55.3%) and ongoing renal dialysis (17, 36.2%). All study participants gave written informed consent.
Measurement of laser Doppler skin perfusion pressure. Testing was carried out at initial diagnosis with a Laserdopp PV-2000 (Kaneka, Osaka, Japan). The laser Doppler flow sensor was secured within the bladder of a blood pressure cuff equipped with a transparent polyvinyl chloride window for measuring microcirculatory perfusion during cuff inflation and deflation. Three cuffs of different sizes were used for the toe, ankle, and leg. Patients were placed in a supine position, kept still for 5 minutes, and then their brachial blood pressure was measured. The appropriate cuff was applied to the proximal margin of the ulcer, inflated to 20 mmHg above the brachial systolic pressure, and a stable laser Doppler output value near zero (< 0.1 volume%) was reached before deflating. The cuff was deflated first in 10 mmHg-stepwise decrements every 5 seconds to a pressure of 50 mmHg, and then in 5-mmHg decrements every 15 seconds until the laser Doppler output increased for 2 consecutive pressure values. The pressure at which this first occurred was considered as the SPP value (Figure 1).
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