Diabetic foot centre of excellence Bedfordview

Excerpt from the dissertation by Dr NB van der Westhuizen
Title: Factors that predict sepsis control in surgical management of diabetic foot at Pretoria Academic Hospitals.

Diabetes mellites is a chronic condition that has a large financial impact on health systems worldwide. Currently an estimated 366 million adults are living with diabetes mellites, and this number is projected to double by the year 2030.¹

Diabetes mellites is an endocrine disorder which results in the dysregulation of blood glucose levels. DM has a deleterious effect on the immune system. Diagnosis of diabetic foot sepsis is made by clinical assessment, biochemical markers, and imaging. ¹

Gram positive Staphylococci are common in treatment naïve patients but those previously treated with foot infections may culture gram negative bacteria or in the case of wet gangrene, a mixture of pathogens including anaerobes. Culture directed antibiotic therapy should be started. ¹

Hyperglycemia leads to macro and microvascular changes and foot ischemia; with an altered immune system and unidentified foot trauma it leaves the foot susceptible to infections. ²

In the foot, peripheral neuropathy can cause dry skin and loss of pressure and pain sensation. The foot remains vulnerable to minor trauma. Peripheral neuropathy is more common in patients with HIV infection compared with concomitant HIV and DM.³

Macrovascular disease and possibly functional microangiopathy may exist concomitantly. Diabetic foot ulcers with or without concomitant PAD should be defined as two separate disease states and predictors of healing differ between these two patient groups.

Nearly 2 million Americans develop a diabetic foot ulcer each year; within 5 years of ulceration, 5% will undergo major amputation and. Involvement of a multidisciplinary team decreases the patient’s risk of amputation. This team usually includes surgeons, physicians, podiatrists, and allied health sciences. A team leader is identified, and a treatment algorithm applied. ⁴ The podiatrist is the gatekeeper of at-risk foot prevention and should be involved early. ⁵

Malnutrition, if not corrected, can lead to weight loss, poor nutrient utilization, skin breakdown and delayed healing. ⁶ Many studies have tried to prove the association with poor glycemic control and amputation rate, but an association has not been made on a large scale. ⁷

Several wound management strategies have been studied. Debridement by maggot directed therapy is significantly faster than conventional chemical debridement and occurs during the first week of treatment. ⁸

In chronic wounds the centre of the wound is hypoxic and cannot fully support enzymatic processes necessary for tissue repair. Studies have shown beneficial effect of hyperbaric oxygen therapy. ⁹ In addition, a meta-analysis revealed that treatment with HBO improved the rate of healing and reduced the risk of major amputations. ¹⁰ Topical oxygen therapy has shown improved healing rates when compared to Hyperbaric oxygen therapy. ¹¹

Several studies demonstrated in vivo that Mesenchymal stem cells may be beneficial to wound healing. ¹² Skin grafts and tissue replacements (bioengineered or artificial skin, autografts, allografts, or xenografts) can be used for people with diabetic foot ulcers. ¹³

The risk for major amputation is determined by the degree of tissue loss, ischemia, and severity of foot infection and many classification systems exist. In Wagner (grade) and the University of Texas (grade and stage) wound classification systems were studied and compared with predictive outcome. The University of Texas system's inclusion of stage makes it a better predictor of outcome. ¹⁴ The SVS WIFi classification is a comprehensive prognostic tool for patients with risk for lower limb amputation (grading of the wound, infection, and ischaemia) correlates with important clinical outcomes for limb salvage and wound healing. As the clinical stage progresses, the risk of major amputation increases. WIFi is the most predictive for major amputation. ¹⁵ The Wagner classification system does not account for severity of ischemia, nor does it delineate gangrene due to infection. The University of Texas classification determines the presence but not the severity grade of ischaemia and infection gradation for each category. The WIFi criteria supersedes the other two criteria but lacks large prospective studies. ¹⁶ Patients in stage 3(associated PAD) of the classification may benefit from revascularization. ¹⁷

Diabetic foot treatment has several challenges resource constrained setting like South Africa. ¹⁸ Awareness of diabetic foot disease is suboptimal and screening and prevention programmes are lacking. ¹⁹ Basic principles of managing a diabetic foot should be adhered to like glycaemic control, foot inspection and podiatry, prevention of minor trauma and early presentation to hospital. ²⁰ Early sepsis control and risk factor modification are core principles. ²¹

Diabetes mellitus causes a large majority of non-traumatic amputations worldwide. In amputated patients’ mortality at 1, 3 and 5 years were 13.62%, 30.25% and 50.55% respectively and mean of re-amputation at 1, 3 and 5 years were 20.14%, 29.63% and 45.72% respectively. Patients with a previous lower limb amputation for diabetic foot ulcer have a higher risk of re-ulceration than patients undergoing conservative treatment for diabetic foot ulcer (23%). Previous amputation is an important, independent risk factor for further amputations and have rates as high as 60% over 10 years. ²⁰ The presence and severity of peripheral arterial disease is a significant risk factor in the need for re-amputation. ²¹

Chu et al also reported ischemic heart disease as positive predictors for death. ²² Faglia et al reported higher rates of mortality of which ischemic cardiomyopathy was identified as the most frequent cause of death. ²³ Post amputation the 5-year mortality was recorded at 24.6%, increasing to 45.4% at the 10-year mark. Larson et al reported an increased risk for death after major amputation versus minor. ²⁴

The goals of diabetic foot treatment are to achieve tissue healing while maintaining adequate function and weight-bearing for ambulation. Antibiotic treatment of infection in conjunction with tissue debridement/amputation and off-loading foot pressure are key to aid the healing process. Limb sparing is a realistic goal with proper surveillance by a multidisciplinary diabetic clinic. ²⁵