David A. Liedl

Expedited Wound Healing with Noncontact, Low-frequency Ultrasound Therapy in Chronic Wounds: A Retrospective Analysis

OBJECTIVE: To evaluate the clinical role of noncontact, low-frequency ultrasound therapy (MIST Therapy System; Celleration, Eden Prairie, Minnesota) in the treatment of chronic lower-extremity wounds. DESIGN: A retrospective observational study. SETTING: A multidisciplinary, vascular wound-healing clinic. PATIENTS: One hundred sixty-three patients who received MIST Therapy plus standard of care (treatment group) and 47 patients who received the standard of care alone (control group). INTERVENTIONS: All wounds in the control and treatment groups received the standard of wound care and were followed for 6 months. In the treatment group, MIST Therapy was administered to wounds 3 times per week for 90 days or until healed. MAIN OUTCOME MEASURES: Proportion of wounds healed and wound volume reduction. Rate of healing was also quantified using 1-way analysis of variance to determine the slope of the regression line from starting volume to ending volume, where a steeper slope indicates a faster healing rate. Outcomes were evaluated in all wounds and etiology-specific subgroups. MAIN RESULTS: A significantly greater percentage of wounds treated with MIST Therapy and standard of care healed as compared with those treated with the standard of care alone (53% vs 32%; P = 0.009). The slope of the regression line in the MIST arm (1.4) was steeper than the slope in the control arm (0.22; P = .002), indicating a faster rate of healing in the MIST-treated wounds. CONCLUSION: The rate of healing and complete closure of chronic wounds in patients improved significantly when MIST Therapy was combined with standard wound care.

Discordant Diagnosis of Lower Extremity Peripheral Artery Disease Using American Heart Association Postexercise Guidelines

Abstract To determine whether postexercise criteria for peripheral artery disease (PAD) diagnosis recommended by the American Heart Association (AHA) identifies the same group of PAD patients. Diagnosis of PAD is performed using ankle-brachial index at rest (resting-ABI). When resting-ABI is not contributive, an AHA scientific statement recommend to use 1 of 2 following criteria: a postexercise ABI decrease of greater than 20% or a postexercise ankle pressure decrease of greater than 30 mm Hg. Between 1996 and 2012, 31,663 consecutive patients underwent lower-extremity arterial study at Mayo Clinic. Among them, only unique patients who had exercise treadmill testing were analyzed. In this retrospective analysis, resting-ABI, postexercise ABI, and postexercise decrease of ankle pressure measured at 1-minute were measured in each patient. We conducted an analysis of agreement between postexercise criteria expressing the agreement separately for the positive and the negative ratings. Twelve thousand three hundred twelve consecutive patients were studied with a mean age of 67 ± 12 years, 61% male. According to resting-ABI, 4317 (35%) patients had PAD. In the whole population, if a clinician diagnoses “PAD” with 1 postexercise criterion, the probability that other clinicians would also diagnose “PAD” is 74.3%. If a clinician diagnoses “no PAD”, the probability that other clinicians would also diagnose “no PAD” is 82.4%. In the patients to be of potential benefit from treadmill test when the resting-ABI > 0.90, if a clinician diagnoses “PAD” with 1 postexercise criterion, the probability that other clinicians would also diagnose “PAD” is 58.4% whereas if a clinician diagnoses “no PAD,” the probability that other clinicians would also diagnose “no PAD” is 87.5%. Postexercise criteria do not identify the same group of PAD patients. In our opinion, postexercise criteria to define PAD deserve additional study.

Application of exercise transcutaneous oxygen pressure measurements for detection of proximal lower extremity arterial disease: A case report.

Proximal claudication is secondary to ischemia caused by peripheral artery disease (PAD), whereas proximal pseudo-claudication is secondary to other disease processes such as hip arthritis, spinal stenosis, neuropathy, and so forth. The differentiation between the two can be challenging. Exercise transcutaneous oxygen pressure measurement (exercise-TcPO2) allows noninvasive detection of flow-reducing lesions in the proximal arteries and tributaries of the lower extremity arterial tree. We present the first case report in the United States using an exercise-TcPO2 algorithm. A 71-year-old diabetic patient with proximal left-sided and right-calf claudication with indeterminate ankle-brachial indices underwent an exercise-TcPO2 study before and after endovascular intervention. Four TcPO2 probes were placed: one at chest level (reference probe), one on each buttock, and one on the symptomatic calf. The Delta from Resting Oxygen Pressure (DROP) index was calculated at each probe site using a previously validated protocol. Proximal left- and right-calf ischemia were confirmed by the initial exercise-TcPO2, and, after endovascular treatment of the left iliac artery lesion, improvements in proximal exercise-TcPO2 values were found. These data suggest that exercise-TcPO2 can be useful in PAD evaluation in patients with non-compressible arteries and/or proximal claudication.

Noninvasive arterial studies including transcutaneous oxygen pressure measurements with the limbs elevated or dependent to predict healing after partial foot amputation.

ObjectiveNoninvasive arterial studies have been used to determine level of amputation. The objective of this study was to examine each component of the noninvasive arterial studies to determine optimal cut points to predict healing and to evaluate whether physiologic maneuvers could improve the utility of transcutaneous oxygen pressure (TcPO2) values to predict healing of partial foot amputation. DesignThe authors conducted a retrospective, observational study of 307 patients who underwent partial foot amputation and had noninvasive arterial studies in the perioperative period. ResultsThe TcPO2 values were significantly predictive of healing. Specifically, a cut point TcPO2 value of 38 mm Hg had a sensitivity and a specificity of 71% for predicting healing or failure. The optimal cut point was mostly unaffected by patient characteristics. The addition of noninvasive arterial studies recorded in a position with the limb elevated improved prediction in the subgroup with supine TcPO2 values of 38 mm Hg or lower. ConclusionsThe findings of this study validate previous reports and confirm that TcPO2 measurements are valuable to more accurately determine the correct amputation level and, in turn, obtain better outcomes. TcPO2 measurements may provide better prognostic value than do ankle-brachial indices for healing after partial foot amputation. TcPO2 measurements are useful but should not be used in isolation to make treatment decisions regarding amputation level.

Use of intermittent pneumatic compression for treatment of upper extremity vascular ulcers

Ischemic vascular ulcerations of the upper extremities are an uncommon and frequently painful condition most often associated with scleroderma and small vessel inflammatory diseases. Digital amputation has been advocated as primary therapy because of the poor outcome with medical care. Intermittent pneumatic compression (IPC) pump therapy can improve ulcer healing in lower extremity ischemic ulcerations; however, the value of this treatment in upper extremity ischemic ulcerations is not known. This observational pilot study consisted of a consecutive series of 26 patients with 27 upper extremity ischemic vascular ulcers seen at the Mayo Gonda Vascular Center from 1996 to 2003. Inclusion criteria were documented index of ulcer size and follow-up ulcer size and use of the IPC pump as adjunctive wound treatment. Twenty-six of 27 ulcers (96%) healed with the use of the IPC pump. Mean baseline ulcer size was 1.0 cm2 (SD=0.3 cm2) and scleroderma was the underlying disease in 65% (17/26) of cases. Laser Doppler blood flow in the affected digit was 7 flux units (normal greater than 100). The mean ulcer duration before IPC treatment was 31 weeks. The average pump use was 5 hours per day. The mean time to wound healing was 25 weeks. Twenty-five of 26 patients reported an improvement in wound pain with pump use. Intensive IPC pump use is feasible and associated with a high rate of healing in upper extremity ischemic ulcers. A prospective, randomized, sham-controlled study of IPC is needed to determine whether IPC treatment improves wound healing compared to standard medical care.

The Use of Elevation and Dependency to Enhance the Predictive Value of Transcutaneous Oxygen Pressure Measurements in the Assessment of Foot Amputation Healing

To determine whether transcutaneous oxygen pressure (TcPO2) measurements taken while the patient is supine, with the limb elevated, and/or with the limb dependent (below the level of the heart) can be used to predict the healing of partial‐foot amputations.

Digital obstructive arterial disease can be detected by laser Doppler measurements with high sensitivity and specificity

OBJECTIVE This study was conducted to determine the sensitivity and specificity of laser Doppler flowmetry (LDF) measurements for digital obstructive arterial disease (DOAD) using angiography as the reference standard and to compare the accuracy of different classical tests used to assess DOAD. Diagnosis of vascular abnormalities at the digital level is challenging. Angiography is the gold standard for assessment of DOAD but is invasive and expensive to perform. METHODS We performed a retrospective analysis of consecutive patients referred at Mayo Clinic (Rochester, Minn) for upper extremity arterial assessment during a 27-month period. Finger-brachial index, skin blood flow (in arbitrary units [a.u.]), and skin temperature (in degrees Celsius) were recorded in each digit on the pulp at baseline and after a thermal challenge test (hand placed in a thermal box at 47.0°C for 15 minutes). Angiogram analysis was blinded and performed by a radiologist using a vascularization scale ranging from 0 (no vessel) to 4 (normal). The receiver operating characteristic curve was used to define a specific cutoff point to detect DOAD. Twenty-two patients had LDF measurements and complete angiograms. RESULTS A total of 185 digits were analyzed because some patients had only analysis of one hand. The best area under the curve (AUC) was 0.98 (range, 0.94-0.99) for postwarming skin blood flow, with a cutoff point of ≤206 a.u. This AUC was statistically different from AUCs of all the other tests (P < .01). Sensitivity and specificity were 93% (95% confidence interval, 85%-97%) and 96% (95% confidence interval, 90%-99%), respectively. CONCLUSIONS LDF combined with a thermal challenge is highly accurate, safe, and noninvasive means to detect DOAD.

The effect of obstructive sleep apnea on amputation site healing

Obstructive sleep apnea (OSA) is an independent risk for hypertension, cerebral artery stenosis, stroke and hypercoagulability.(1) Our research objective was to assess whether sleep disordered breathing affects the peripheral circulation, decreases perfusion as measured by TcPO2 and decreases the odds that a partial-foot amputation site will heal. We hypothesized that OSA would be an independent risk factor causing delayed healing of partial-foot amputations. We conducted a retrospective, observational study on a total of 307 patients who had TcPO2 measurements and underwent partial-foot amputation. Twenty-five of these patients had OSA. In our study, patients with OSA had a 3.7-fold increase in odds of healing within 3 months in comparison with patients without OSA. Of note, 16 patients (64%) with OSA were not treated with continuous positive airway pressure (CPAP) and healed within 3 months. Our results do not support our hypothesis that the presence of sleep apnea may impair healing of partial foot amputations. Further studies are needed to fully determine the effect of OSA and its treatment on TcPO2s and healing.

Using a silver-coated polymeric substrate for the management of chronic ulcerations: the initial Mayo Clinic experience.

BACKGROUND: This retrospective observational study was designed to review the use of a silver-coated polymeric substrate on various types of chronic wounds at the Mayo Clinic in Rochester, Minnesota. METHODS: The study was set in a community and referral multidisciplinary vascular wound clinic. The authors identified the first 112 patients treated with a silver dressing in the center. Of these, 15 were lost to follow-up or had incomplete data. Ninety-seven patients were included in the study. Thirty-seven of these 97 patients had multiple wounds; however, 1 wound per person was randomly chosen for analysis. The median age of these patients was 69 years. A wound was considered healed when the wound was completely epithelialized. Of the 97 wounds evaluated, the primary etiologies were as follows: 20 (20.6%) were neurotrophic, 24 (24.7%) were ischemic (arterial, arteriolar, or vasculitic), 20 (20.6%) were venous, 7 (7.2%) were traumatic, and 16 (16.5%) were multifactorial. The silver dressing was the primary wound care product on all wounds. Silverlon (Argentum LLC, Chicago, Illinois) was the silver dressing used for this study. The frequency of dressing changes and use of secondary dressings, to keep the wound moist, were based on the amount of drainage, debris, and slough on the wound. Data pertaining to patient demographics, risk factors, wound etiology, noninvasive arterial vascular studies, frequency of dressing changes, wound discomfort, wound size, and wound duration were collected by retrospective chart review. RESULTS: Thirty-five of the 97 wounds (36.1%) healed. The 62 nonhealed wounds (63.9%) decreased in size by a median of 55.2%. Among the 68 patients who had reported discomfort before the study, 77.9% reported no change in discomfort, 17.7% reported increased pain, and 4.4% reported decreased pain. CONCLUSION: A silver-coated polymeric substrate (Silverlon) can be used as an effective primary wound care dressing in patients with active wounds.

Peripheral arterial disease preoperatively may predict graft failure and mortality in kidney transplant recipients

Patients with end-stage renal disease undergoing kidney transplant often have diffuse atherosclerosis and high cardiovascular morbidity and mortality rates. We analyzed the correlation of peripheral arterial disease (PAD), here quantified by an abnormal ankle–brachial index (ABI) measured within the 5 years prior to kidney transplant, with graft failure and mortality rates (primary end points) after adjusting for known cardiovascular risk factors (age, sex, smoking history, hypertension, diabetes, stroke, known coronary artery disease or heart failure, years of dialysis). Of 1055 patients in our transplant population, 819 had arterial studies within the 5 years prior to transplant. Secondary end points included myocardial infarction; cerebrovascular accident; and limb ischemia, gangrene, or amputation. Low ABI was an independent and significant predictor of organ failure (OR, 2.77 (95% CI, 1.68–4.58), p<0.001), secondary end points (HR, 1.39 (95% CI, 0.97–1.99), p<0.076), and death (HR, 1.84 (95% CI, 1.26–2.68), p=0.002). PAD was common in this population: of 819 kidney transplant recipients, 46% had PAD. Low ABI was associated with a threefold greater risk of graft failure, a twofold greater risk of death after transplant, and a threefold greater risk of secondary end points. Screening for PAD is important in this patient population because of the potential impact on long-term outcomes.