Work

Evaluation and Management of Diabetes-related Foot Infections

Year: 2023

Type: article

Abstract: Diabetes-related foot ulcers (DFUs) have a global prevalence of 6.3%, reaching 13% in North America [1]. DFUs have a dismal prognosis, with 5- and 10-year survival rates of approximately 50% and 25%, respectively [2, 3]. Infection, complicating >40% of DFUs, is often the coup-de-grace; nearly half of patients hospitalized with a diabetes-related foot infection (DFI) undergo amputation within 1 year [4, 5]. These risks disproportionately affect Black, Hispanic, Native, rural, and low-income communities [6, 7]. Lower extremity amputations due to DFUs are the third most costly diabetes complication and are feared by many patients more than death [8]. In 2012, the authors of the Infectious Diseases Society of America (IDSA) DFI guidelines declared that “The main problem currently is less our lack of full understanding of the problem as our failure to apply what we know works.” [9] This statement remains accurate a decade later. Multidisciplinary DFI teams can reduce major amputations, and similar teams have dramatically reduced attributable mortality for infective endocarditis [10, 11]. Despite this, inconsistent and unstructured collaboration between specialists that lead to breakdowns in shared decision-making remains common. In this narrative review, we bring together experts in infectious diseases, endocrinology, podiatry, and vascular surgery to discuss shared decision-making in DFI care. We provide a focused overview of the comprehensive management of these patients, highlighting modern research spearheaded by our surgical colleagues and contemporary guidance from the International Working Group for the Diabetic Foot (IWGDF), arguably the lingua franca of DFI specialists [12]. Finally, we offer best practices for clinician–clinician and patient–clinician shared decision-making. Notably, while this review reflects our expert opinion based on data largely published after the now-archived IDSA DFI guidelines, it is not intended to supplant those guidelines. This review is also written from the perspective of US-based clinicians and intended primarily for infectious diseases (ID) specialists. International colleagues may find some of our considerations regarding barriers to care less relevant, and a comprehensive review of surgical decision-making in DFI is outside this article's scope. Lower limb amputations can be categorized as minor (at or below the ankle, sometimes also called foot amputation) or major (above the ankle). In retrospective DFI cohorts, minor amputation rates of 15%–30% and major amputation rates of 5%–20% are typical [7, 13, 14]. Concomitant peripheral artery disease (PAD) is the key, most consistently identified risk factor for major amputation and death [13, 15]. A number of DFU classification systems have been proposed, including the perfusion, extent/size, depth/tissue loss, infection and sensation (PEDIS), University of Texas, Wagner, sepsis, arteriopathy, denervation (SAD), Saint Elain, and IDSA criteria [16–19]; however, all have limitations in their differentiation of wounds, ischemia, and/or infection severity. The most modern and comprehensive criterion is the Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot infection) classification system, which iterates on the 2012 IDSA criterion with staging of the foot ulceration, the degree of accompanying gangrene, and the degree of accompanying limb ischemia [12, 20]. A straightforward approach to scoring and interpreting WIfI classifications is given in Tables 1 and 2. Summary of the Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot Infection) Classification System for Diabetes-related Foot Infection Total Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot Infection) class should be reported with the components of each score. For example, a patient with an ankle-brachial index (ABI) of 0.3 but no wound or signs of infection would be classified as WIfI 030. ABI may be falsely elevated. The International Working Group for the Diabetic Foot guidance prefers use of toe pressure (TP) or transcutaneous oximetry, which have been shown to predict ulcer healing. Table adapted from Mills et al [21]. Summary of the Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot Infection) Classification System for Diabetes-related Foot Infection Total Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot Infection) class should be reported with the components of each score. For example, a patient with an ankle-brachial index (ABI) of 0.3 but no wound or signs of infection would be classified as WIfI 030. ABI may be falsely elevated. The International Working Group for the Diabetic Foot guidance prefers use of toe pressure (TP) or transcutaneous oximetry, which have been shown to predict ulcer healing. Table adapted from Mills et al [21]. Simplified Approach to Interpreting the Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot Infection) Classification for Diabetes-related Foot Infection Prognostication Exceptions are classifications 003 and 021 (both moderate rather than low risk). Exceptions are classifications 003, 032, 103, 131, and 212 (all moderate rather than high risk). Table adapted from Mills et al [21]. Simplified Approach to Interpreting the Society for Vascular Surgery's WIfI (Wound, Ischemia, Foot Infection) Classification for Diabetes-related Foot Infection Prognostication Exceptions are classifications 003 and 021 (both moderate rather than low risk). Exceptions are classifications 003, 032, 103, 131, and 212 (all moderate rather than high risk). Table adapted from Mills et al [21]. The WIfI classification offers prognostication on both the risk of amputation and potential benefit of revascularization among patients with DFUs [21, 22]. Although not DFI-specific, WIfI encompasses the major determinants of DFU prognosis and predicts DFU healing and minor amputations [21, 23, 24]; the infection scoring component of WIfI also predicts hospitalization and amputation [25]. The WIfI classification system is well validated in DFI and an ideal basis for evidence-based decision-making among ID specialists, surgeons, and patients. At a minimum, the competent ID specialist should be familiar with WIfI classification and its interpretation, as this common tool incorporates several of the key criteria beyond infection severity that inform our surgical colleagues’ decision-making. Most diabetes-related foot infections are polymicrobial, with Staphylococcus aureus near universally the most prevalent organism [26, 27]. Other common pathogens include Enterobacterales, Enterococci, and Streptococci. Pseudomonas aeruginosa has a highly regional prevalence and is probably more common in tropical/subtropical regions and after antibiotic exposure. This variance has resulted in highly regional preferences for empiric antibiotic therapies [28]. Acknowledging this diversity and the limited data for specific regimens, we focus here on DFI treatment controversies that often frame decision-making discussions and for which new data are rapidly emerging. Published data demonstrate that successful treatment of diabetes-related foot osteomyelitis (DFO) can routinely be accomplished without bony debridement. Truong et al identified 18 studies that evaluated nonoperative outcomes of DFO with a mean treatment success rate of 68.2% over a median of 15 months of follow-up. In contrast, the same systematic review identified 13 studies of surgical DFO treatment that reported a mean success rate of 85.7% over 19.5 months [29]. Important limitations of this meta-analysis include its use of primarily retrospective studies, introducing confounding by indication in patients selected for surgical vs nonoperative medical management, and substantial heterogeneity between studies in antibiotic management as well as definitions of disease and cure. While higher-quality evidence that demonstrates whether medical management is noninferior to surgical treatment at a clinically acceptable effect size would be welcome, these data indicate that nonoperative management can frequently be successful. Amputations often threaten a patient's independent mobility, particularly when the patient's preoperative functional status is already mediocre, and perversely may predispose to foot ulceration and infection elsewhere by shifting weight-bearing mechanics, putting new areas under threat. These patients are most likely to benefit from limb preservation efforts. In such cases, the modest improvement in infectious cure with surgical management may not be justified, given the risk of decline in functional status with amputation [30]. On the other hand, in patients with DFO that involves the distal phalanx or proximal interphlangeal (PIP) of a hammer toe or claw deformity, early surgery can both eradicate the infection and treat the underlying biomechanical issue with little threat to mobility and should be preferred. Preserving independent mobility is key to patients’ prognoses, often central to their values and preferences, and must be weighed against antibiotic-associated adverse events. Antibiotics cannot restore devitalized tissue. Consequently, antibiotic therapy alone is not a reasonable strategy for infections that involve extensive tissue necrosis or copious undrained purulence, particularly when these have become sources of systemic infection. However, beyond these cases, a “therapeutic trial” of antibiotics is usually reasonable. The noninferiority of oral to intravenous antibiotics for chronic osteomyelitis has been shown in 8 randomized, controlled trials (RCTs) and their meta-analyses [31]. The most robust was the Oral vs Intravenous Antibiotics for Bone and Joint Infection (OVIVA) noninferiority RCT, which found no difference in long-term cure with all-intravenous (IV) antibiotics vs a rapid transition to oral therapy [32]. While OVIVA did not report DFI-specific outcomes, modern RCTs of DFIs have used an IV-to-oral antibiotic switch strategy with IV durations as short as a median of 2 days, achieving high rates of cure [33–37]. Our general recommendation for oral antibiotics in DFO comes with a few caveats. First, the OVIVA's subgroup analyses identified a trend toward worse outcomes with oral vs IV among patients with no defined pathogen. 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Source: Clinical Infectious Diseases

DOI: 10.1093/cid/ciad255