After surgery, wound margins are usually approximated by suturing, metal clips, glue or adhesive patches. These processes hold wound margins closed for a few days. This kind of healing is called “healing by first intention.” However, not all surgical incision are closed using these methods: if there is a risk of infection or there has been a significant loss of tissue so that the margins cannot be joined, the wounds are left open in order to allow them to heal bottom-up. This kind of healing is called “healing by second intention.” This process takes much longer than healing by first intention because the tissues that are missing or that are non-viable need to be replaced by viable cells. The open area is more extended and the consequent inflammatory reaction can become chronic. The healing may involve the formation of an eschar or scab composed of dry plasma and dead cells, and the cells of the surrounding vital tissues (fibroblasts and vascular tokens) migrate towards the center of the wound and form “granulation tissue” that is fragile and bleeds easily. Only in the last phase of healing does “re-epithelisation “occur, which is the growth of the outermost skin layer that sometimes partially retracts the wound.
For example, wounds resulting from the removal of pilonidal and fistulas, burns and other events that cause a loss of substance (such as after trauma), in which grafts and flaps are not indicated, are healed by second intention. Treating these open surgical wounds are challenging because they are large, deep, carry a high risk of infection and can produce a lot of fluid (called exudate), which is difficult to manage. The options available, in addition to absorbent dressings such as those with alginates, include the use of negative pressure therapy, which has become the most widely used form of advanced therapy for various types of wounds. The negative pressure therapy “aspires” the liquid that originates in the wound and collects it in a binder called a “canister.” This action keeps the wound dry and reduces the bacterial count. Some studies indicate that negative pressure therapy can reduce healing time by one-half to one-third compared to traditional dressings.
The diabetic foot is an open wound or injury that occurs mostly on the sole of the foot in about 15% of diabetic patients. These lesions usually appear in long-term diabetics and are the expression of a dual neurological and arteriopathic type of pathology. Diabetic neuropathy prevents the patient from feeling microtraumas to the foot, while diabetic arteriopathy reduces blood flow below what is sufficient to maintain the right tropism of the extremities and therefore the healing of small wounds.
The injuries of the diabetic foot are generally classified as follows (Wagner classification):
- Grade 0: No injury, the foot is not at risk
- Grade 1: Superficial ulcer
- Grade 2: Complicated ulcer
- Grade 3: Deeply complicated ulcer
- Grade 4: Local gangrene
- Grade 5: Gangrene of the entire foot
Diabetic foot ulcers, once formed, usually cause pain and tingling, especially if they concern the outside of the foot.
Negative pressure therapy plays a role in treating the diabetic foot, but the regimen of use differs from that of treatment of wounds by second intention.
In particular, a higher frequency of dressing changes is recommended.
What is necessary for the treatment of diabetic wounds:
- A surgical toilet with excision of all infected or devitalised tissue. Therapy in depression should not be applied to infected or necrotic tissue.
- It is best to perform the first negative pressure dressing in the operating room with a skilled surgeon.
- Subsequent treatments should be done by a doctor or nurse who is an expert in negative pressure therapy.
- Diabetic ulcers sometimes do bleed. In this case, an accurate haemostasis should be performed, verified by physiological solution washing, with the application of negative pressure therapy postponed for 24 hours, setting the depression at half the norm value (about 75 mmHg) for the first few days. Oscillating depression may be useful.
- If pus is present (diabetic ulcers become infected very frequently), it is necessary to apply the therapy in depression after an accurate cleansing and change the dressing strictly every 48 hours.
- At each change of dressing, detect if there is a bad smell; in this case, carefully redo the curettage of the ulcer.
- Patient albumin should exceed 32 mg / dL and haemoglobin 10 g / dL.
- It is recommended to use the dressing in depression only until healthy granulation tissue is evident. Subsequently, it is advisable to intervene with the positioning of a partial thickness graft.
- It is usually sufficient to reduce the wound by 40-60% by changing the dressing from 10 to 16 times over a period of 2 to 3 weeks.