A New Technique to Treat Foot Infections in Diabetes

Diabetes mellitus is a complex, chronic disorder in which the body is not able to effectively use a natural chemical called insulin. Insulin's main job is to quickly absorb glucose (a type of sugar) from the blood into cells for their energy needs and into the fat and liver cells for storage.

Because of this, high sugar levels can occur in people with diabetes which can damage the body. For example, people with diabetes are more prone to infections because high levels of sugar in the blood make it more difficult for the body to fight against infections.

One common area where infections are likely to occur in diabetes is the feet. This is because the accumulation of sugar can damage nerve fibers in the feet, causes decreased sensation, and poor blood circulation. This makes the feet more prone to ulcers (open sores), infection, and eventually gangrene (tissue death due to poor blood supply or infection of a wound). In the worst case scenario, this can lead to amputation of the foot or feet to prevent a more widespread and potentially deadly bodily infection.

When diabetic foot complications arise, they can be difficult to manage and treat because people with diabetes often have other medical diagnoses (e.g., kidney problems, heart problems) that make it more difficult to maintain adequate levels of antibiotic medication at the site of infection without causing harmful effects (e.g., organ damage) on the body as a whole. This can lead to ineffective treatment.

As a result of this problem, new methods are needed to deliver targeted antibiotics to the infected limb for extended periods while limiting harmful effects on the rest of the body. In the current issue of the American Journal of Translational Research, researchers reported success for the first time with a new non-surgical technique designed to accomplish exactly that and the hope is that this can be applied to humans, particularly those with diabetic foot infections.

In the study, the hind limb of 11 sheep was treated with an antibiotic named Gentamicin using one of two methods. The first method was standard intravenous administration to 6 sheep, as would typically occur in a hospital. The second method was a technique known as a percutaneous recirculation circuit. As the name implies, this technique involves establishing a circuit of blood supply by inserting a catheter (flexible plastic tube) in the femoral vein (large vein in the leg) and femoral artery (large artery in the leg). An artery carries blood away from the heart, whereas a vein carries blood to the heart.

The system caught the venous return of blood via the catheter, re-oxygenated it with a special device known as a membrane oxygenator, and returned it to the femoral artery with a special pump called a roller pump. In this way, when medication was administered via this system, it was kept more localized to the hind limb.

To test how much Gentamicin was in the hind limb, tissue samples of the back limb were taken, which included bone, skeletal muscle, and synovial (joint) fluid 30 to 60 minutes after the medication was administered. After the 60-minute point, the animals were euthanized and samples of the liver, kidney, and lung were taken to determine how much Gentamicin was present.

The results of the study showed that there was a significantly greater amount of Gentamicin in the bone, skeletal muscle, and joint fluid of those receiving Gentamicin via the circuit method versus compared to the standard intravenous method.  In fact, there was 10 times the amount of Gentamicin found in the joint fluid, which the authors stated could serve as a reservoir for longer effectiveness. With the circuit system, there was a non-significant amount of Gentamicin found in the liver, lung, and kidney. The difference in antibiotic levels in these organs was not significantly different between the two groups but there was a trend for less antibiotic levels in these organs with the circuit method.

The authors concluded that the circuit method is a safe and effective non-surgical method to deliver a greater amount of antibiotic to the affected limb without causing greater harm to the rest of the body. The authors stated that this method may be directly useful for patients with diabetes who are at high risk of tissue or limb loss due to infections that are otherwise non-responsive to treatment.

Suggested reading: The End of Diabetes: The Eat to Live Plan to Prevent and Reverse Diabetes

Reference: Byrne, M., Idrizi, R., Power, J., Kaye, D. (2013). Percutaneous re-circulating isolated limb perfusion of gentamicin in a large animal model: targeted delivery of gentamicin to limb. Am J Transl Res, 5(1):47-52