Sldn perfusion pressure in the prediction of healing in diabetic patients with ulcers or gangrene of the foot

Transcription

1 Sldn perfusion pressure in the prediction of healing in diabetic patients with ulcers or gangrene of the foot I. Faris, M.D., F.R.A.C.S., and H. Duncan, B.M., B.S., Adelaide, Australia The measurement of skin perfusion blood pressure (SPP) estimated by an isotope clearance technique has been used to predict the healing of ulcers or gangrene of the foot in 61 diabetic subjects. Healing followed conservative treatment or local surgery in 1 of 21 cases ff the SPP was less than 40 mm Hg but in 35 of 40 with higher values for SPP. Healing was unlikely if the toe blood pressure was less than 40 mm Hg or the ankle systofic pressure was less than 80 nun Hg. It is recommended that the SPP be measured in patients in whom confident predictions of healing cannot be made on the basis of ankle pressure or other measurements. (J VASe SURG 1985; 2: ) The management of diabetic patients with ulcers or gangrene of the foot is a common problem in major hospitals. In some cases it may be difficult to predict if healing will occur. The foot will not heal unless the blood supply is adequate; however, the blood supply may be adequate to allow healing despite major arterial obstruction. The therapeutic strategy adopted may range from prolonged observation and local treatment through a trial of local amputation to arterial reconstruction. Laboratory methods to predict healing have produced mixed results. Measurement of Doppler pressure has been generally regarded as unsatisfactory? 3 However, there have been reports of successful use of toe blood pressure measurements 4-6 and isotope perfusion scanning. 7"8 This article reviews the outcome in a series of diabetic patients in whom the skin perfusion pressure (SPP), measured by a radioisotope clearance method, was used to predict healing. The predictive value of this test was compared with the results of measurement of toe and ankle systolic blood pressure. PATIENTS AND METHODS The study included 61 diabetic subjects aged 38 to 86 years (median 72 years). Thirty-seven subjects were men. Diabetes mellitus had been diagnosed for 6 months to 40 years (median 10 years). All were treated for ulceration (n = 35) or gangrene From the Department of Surgery, University of Adelaide. Reprint requests: I. Faris, M.D., Department of Surgery, Royal Adelaide Hospital, Adelaide S.A. 5000, Australia. (n = 26) of the foot during the period September 1982 through December The end points of treatment were: (1) healing of the foot with conservative treatment (n = 25) or local surgery (toe amputation or local drainage of abscess [n = i4]), transmetatarsal amputation (n = 2); (2) arterial surgery (femoropopliteal bypass In = 10], femorotibial bypass In = 7]), undertaken only if ischemic rest pain was present or if a lesion had failed to heal after prolonged observation; mad (3) below the knee amputation (six patients, three of whom had preceding reconstruction), undertaken if there was no suitable distal vessel that would allow the performance of a bypass graft. Measurement of skin perfusion pressure. The technique was modified from that described by Las~ sen and Holstein. 9 An intradermal injection of a 0. i ml solution containing histamine acid phosphate (50 ~g) and 99mTc-pertechnetate (250 p~ci) was made on the dorsum of the foot. The purpose of adding histamine was to ensure maximum dilation of the local vessels by eliminating any local factors affecting blood flow, The gamma emissions of the isotope were counted with a detector (model SR7, Nuclear Enterprises, Reading, U.K.) set around the 141 kev photopeak for 99haTe. The output of the scaler was connected to a minicomputer (model II, Apple Computer, Inc., Cupertino, Calif.), which was programmed to display a graph of the count rate each 10s. The slope of this line, calculated by the method of least squares, was used as the clearance constant (k min i). External counterpressure was applied over the 536

2 Volume 2 Number 4 July 1985 SPP in prediction of healing of ulcers in diabetic patients N E m OlO0 ip0 UN UN Fig. 2. Scattergram showing incidence of toe systolic blood pressure. Bars indicate mean ± 1 SD. Fig. 1. Scattergram showing SPP values. See text for definitions of healed and unhealed. Bars indicate mean ± 1 SD. isotope depot by means of an inflated polyethylene bag that was compressed by a standard arm sphygmomanometer cuff. The pressure in the polyethylene bag was measured by a mercury manometer. The external counterpressure was increased in steps of 10 to 20 mm Hg until the clearance of isotope ceased. The SPP was calculated from the x-intercept of the relationship between the value for k and the applied pressure, 10 Measurement of blood pressure. Ankle and toe systolic blood pressures were measured with the mercury-in-silastic strain-gaugc teclmiquc H with thc dctector around the foot and thc great toc, rcspectively. The cuffs used for the anklc measured 27 x 11 cm and for the toe 2.5 x 10 cm. RESULTS SPP values. The values for SPP obtained in the patients studied are shown in Fig. 1. The healed group includes those whose lesions healed spontaneously or after local amputation. The unhealed group includes those who had arterial reconstructive surgery or major amputation. The SPP for those patients whose feet had healed (59 +_ 16 mm Hg, mean + SD) was higher than for those whose lesions Table I. Accuracy of SPP ~> 40 mm Hg as a predictor of healing SPP (ram Hg) Healed Unhealed < t> remained unhealed ( mm Hg), (t = 6.44, 59 df, p < 0.001). The overall accuracy of the test is shown in Table I. The chances of local healing were only 5% if the SPP was less than 40 mm Hg but 85% in feet with higher SPP values. There were five patients with an SPP of more than 40 mm Hg in whom healing failed to occur. Two patients had very high values for minimal vascular resistance in skin, l which probably indicated Severe microangiopathy. A third patient had undiagnosed arteritis that resulted in bilateral below-knee amputation performed within 6 weeks of an episode of probable myocarditis. One patient flnderwent below-knee amputation for persistent sepsis in the foot despite a functioning femorotibial graft. Toe blood pressure. Toe blood pressure measurements were attempted in 51 patients. In eight there were technical difficulties so that a satisfactory end point could not be obtained. There was gangrene of the great toe, ulceration or infection of the toe so that measurement was not attempted, or previous

3 538 Faris and Duncan Journal of VASCULAR SURGERY N E O 50 :" o. o~ O TOE BLOOD PRESSURE mmhg Fig. 3. Scattergram showing relationship between toe blood pressure and SPP. amputation of the toe in 14 patients. The toe blood pressure (Fig. 2) in patients whose feet healed (78 _+ 37 mm Hg) was higher than those whose feet had not healed (21 _+ 19 mm Hg), (t = 4.83, 27 df, p < 0.001). Healing only occurred in one patient with a toe blood pressure of less than 40 mm Hg. The relationship between SPP and toe blood pressure is shown in Fig. 3. There was a significant correlation between the two sets of readings (r = 0.737, n = 35, p< 0.001). The equation to the line was SPP = (toe pressure). (Note that this figure includes data from six additional diabetic patients without ulcers or gangrene of the foot.) Ankle systolic pressure. Fig. 4 shows the outcome related to the ankle systolic pressure. Patients with local heating ( mm Hg) had a higher ankle pressure than those who required additional treatment ( mm Hg), (t = 3.56, 41 df, p < 0.001). Incompressible arteries were encountered in five subjects and surprisingly high readings were obtained in two others. Thus in about 10% of cases the ankle pressure measurements were known to be unreliable. With this qualification ankle blood pressure proved a useful criterion because local healing occurred in only one case if the systolic blood pressure was less than 80 mm Hg. DISCUSSION The major result of this study is that it is possible to predict, with a high degree of confidence, whether UN Fig. 4. Scattergram showing incidence of ankle systolic blood pressure. Bars indicate mean _+ 1 SD. an ulcer or area of gangrene on the foot of a diabetic patient will heal. A major benefit of this knowledge is that it allows a selective approach to the performance of arterial surgery. Despite the evidence from the measurement of low ankle pressure of arterial obstruction in the leg in more than 75% of patients, only 27% of patients were subjected to arterial surgery. This result has major benefits for the patient. If the SPP is low, an early decision can be made te,, perform angiography and, if possible, arterial reconstructive surgery. On the other hand, if the SPP is high, the lesion can be treated locally with confidence that healing will follow adequate treatment. The problem of the prediction of healing in diabetic patients has not previously been studied in this way, although there have been reports of methods to predict healing of amputations of toes or foot. The results of using the ankle systolic pressure have been generally unsatisfactory, 13 although Johnson and Patten ~2 and Wagner I3 have specified the lower limit below which healing is unlikely. We began this study with the assumption that ankle pressure measurement was inadequate. However, our results have supported the idea of a specified lower limit below which arterial surgery is indicated. The upper limit is less clear partly because of the unpredictable effects of

4 Volume 2 Number 4 July 1985 SPP in prediction of healing of ulcers in diabetic patients 539 arterial calcification and partly because of the presence of arterial disease in the foot. 14'is Two methods that have been used with reasonable success are measurement of the toe blood pressure and isotope perfusion scanning. The methods used to measure toe blood pressure have been in mercury-in-silastic strain gauge 6 photoplethysmography (PPG) 4"s and the Doppler ultrasound technique) 3 Using the PPG Barnes et al. 4 found that healing occurred in all cases with a toe pressure >40 mm Hg. Bone and Pomajzl s found that healing did not occur in any foot with a toe blood pressure <45 mm Hg but only failed in 2 of 22 cases above this level. The photoplethysmographic method may be applicable to both toe pressure and SPP 16 and may prove to be preferable to the isotopic method used :aa this study although, from our limited experience with it, the PPG method may have the same limitations as the strain-gauge method. The SPP is less than the toe blood pressure at higher levels of pressure. This is probably because the toe blood pressure reflects systolic pressure whereas the SPP is close to mean pressure (unpublished observations). Isotope perfusion has also given good prediction of healing either with 99mTc-labeled albumin administered intra-arterially 7 or 2 at1 intravenously. 8 The criterion has been the relative hyperemia around the ulcer or the absolute number of counts from the area of the ulcer) 2 These studies have produced good results although not specifically directed at diabetic patients and the hardware required is more expensive than for the SPP measurement. The results using toe blood pressure are good. However, it is not applicable in all patients. In this ~eries there were a substantial number of patients with gangrene, ulceration, or infection of the toe so that measurements could' not be made. Furthermore, there were three patients in whom the great toe had been amputated previously. In addition, toe pressure is difficult to measure at low levels and it was not possible to determine an end point in eight patients with low pressures. This is a major disadvantage of the method and we have more confidence in the measurement of the SPP. Technical problems have been few: if the patient is restless it may not be possible to obtain adequate readings. The injection of histamine causes pain that lasts several minutes. Fortunately, many patients had neuropathy and none required analgesia. The other technical problem is the presence of edema that makes estimates of SPP unreliable. 9 This was encountered in one additional patient who has not been included in the series. An additional advantage of the isotope clearance method is that it enables an estimation of vascular resistance in the area studied, l This has been shown to be important in patients with hypertensive, ischemic leg ulcers (ofmartorell) and it may also be important in indicating microangiopathy in diabetic subjects. Our present regimen for managing diabetic patients with ulcers or gangrene of the foot is: 1. SPP <40 mm Hg--angiography and consider reconstruction. If reconstruction is not feasible, major amputation will probably be required. 2. SPP 40 to 60 mm Hg--appropriate local procedure (e.g., amputation of toe, drainage of abscess). If healing is delayed perform angiography with a view to performing arterial surgery. 3. SPP >60 mm Hg--appropriate local treatment. REFERENCES 1. Baker WH, Barnes RW. Minor forefoot amputation in patients with low ankle pressure. Am J Surg 1977; 133: Gibbons GW, Wheelock FC, Hoar CS, Rowbotham JL, Siembieda C. Predicting success of forefoot amputations in diabetics by noninvasive testing. Arch Surg 1979; 114: Gibbons GW, Wheelock FC, Siembieda C, Hoar CS, Rowbotham JL, Persson AB. Noninvasive prediction of amputation level in diabetic patients. Arch Surg 1979; 114: Barnes KW, Thomhill B, Nix L, Rittgers SE, Turley G. Prediction of amputation wound healing. Arch Surg 1981; 116: Bone GE, Pomajzl MJ. Toe blood pressure by photoplethysmography: An index of healing in forefoot amputation. Surgery 1981; 89: Holstein P, Lassen NA. Healing of ulcers of the feet correlation with distal blood pressure measurements in occlusive arterial disease. Acta O~hop Scand 1980; 51: Siegel ME, Giargiana FA, Rhodes BA, Williams GM, Wagner HN. Perfusion ofischemic ulcers of the extremity. Arch Surg 1975; 110: Siegel ME, Stewart CA, Kwong P, Sakimura I. 2 it1 perfusion study of ischemic ulcers of the leg: Prognostic ability compared with Doppler ultrasound. Radiology 1982; 143: Lassen NA, Holstein P. Use of radioisotopes in assessment of distal blood flow and distal blood pressure in arterial insufficiency. Surg Clin North Am 1974; 54: Faris I, Lassen NA. Increased vascular resistance in vasodilated skin: An indicator of diabetic microangiopathy? Cardiovasc Res 1982; 16: Nielsen PG, Bell G, Lassen NA. Strain gauge studies of distal blood pressure in normal subjects and in patients with peripheral arterial disease. Scand I Clin Lab Invest 1973; 31(Suppl 128): Johnson WC, Patten DH. Predictability of healing of ischemic leg ulcers by radioisotopic and Doppler ultrasound examination. Am J Surg 1977; 133: Wagner FW. Transcutaneous Doppler ultrasound in the pre-

5 540 Faris and Duncan Journal of VASCULAR SURGERY diction of healing and the selection of surgical level for dysvascular lesions of toes and forefoot. Clin Otthop 1979; 142: Faris I. Small and large vessel disease in the pathogenesis of foot lesions in diabetics. Diabetologia 1975; 11: Ferrier T. Comparative study of arterial disease in amputated lower limbs from diabetics and nondiabetics (with special reference to foot arteries). Med J Aust 1967; 1: Holstein P, Nielsen PE, Barras JP- Blood flow cessation at external pressure in the skin of normal human limbs. Microvasc Res 1979; 17:71-9. BOUND VOLUMES AVAILABLE TO SUBSCRIBERS Bound volumes of the JOURNAL OF VASCULAR SURGERY for 1985 are available to subscribers only. Active members of the two sponsoring societies will automatically receive a complimentary bound volume. They may be purchased from the publisher at a cost of $26.00 ($38.40 international) for Vol. 2 (January to December). Price includes shipping charges. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Circulation Fulfillment, The C. V, Mosby Company, Westline Industrial Drive, St. Louis, MO 63146, USA. In the United States call toll free: (800) , ext In Missouri call collect: (314) , ext Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular JOURNAL subscription.