Necrotizing fasciitis

Necrotizing fasciitis is a relatively rare, severe soft-tissue infection; unlike streptococcal necrosis, it is often a mixed infection of multiple bacteria. Rea and Wyrick confirmed that the pathogens include Gram-positive hemolytic streptococci, Staphylococcus aureus, Gram-negative bacteria and anaerobes. In the past, due to poor anaerobic culture techniques, anaerobes were often not detected, but in recent years it has been confirmed that anaerobes such as Bacteroides, Peptostreptococcus and cocci are often among the pathogens, though rarely as a pure anaerobic infection. Depending on the condition, necrotizing fasciitis is divided into two types: one in which pathogens spread through trauma or primary foci, causing sudden deterioration and rapid soft-tissue necrosis; and another in which the condition progresses more slowly, mainly as cellulitis with multiple skin ulcers, thin and extremely foul pus like dishwater, extensive undermining around the ulcers with crepitus, and local numbness or pain, features not seen in ordinary cellulitis. Patients often have marked toxemia with chills, high fever and hypotension; hypocalcemia may occur when there is extensive subcutaneous necrosis. Bacteriological examination is especially important for diagnosis, particularly smear examination of wound pus. The key to treating necrotizing fasciitis is early and thorough debridement, fully opening the undermined skin edges and resecting necrotic tissue, including necrotic subcutaneous fat or superficial fascia, though the skin can usually be preserved. The wound is left open, irrigated with 3% hydrogen peroxide or 1:5000 potassium permanganate solution, loosely packed with gauze, or several polyethylene catheters are inserted for postoperative lavage. Baxter recommended irrigation with normal saline containing neomycin 100mg/L and polymyxin B 100mg/L; some also recommend carbenicillin or 0.5% metronidazole solution. Frequent dressing changes after surgery accelerate the separation of necrotic tissue, and any necrotic tissue found requires repeat debridement. During dressing changes, repeat bacterial culture should be done to detect secondary bacteria early, such as Pseudomonas aeruginosa, Serratia marcescens or Candida.

Common Symptoms

Superficial fasciitis; disturbance of consciousness; severe pain; burning sensation on the sole; dehydration; chills; anorexia; hypotension

Causes

(1) Etiology. Necrotizing fasciitis is often a mixed infection of multiple bacteria, including Gram-positive hemolytic streptococci, Staphylococcus aureus, Gram-negative bacteria and anaerobes; with the development of anaerobic culture techniques, anaerobes have been confirmed as important pathogens, and necrotizing fasciitis is often the result of the combined action of aerobes and anaerobes. It is often accompanied by impaired systemic and local immune function; it can occur after minor skin injury such as abrasions, contusions and insect bites, after surgery of hollow viscera, after perianal abscess drainage, tooth extraction and laparoscopy, and even after injection (mostly after injecting drugs). People on long-term corticosteroids and immunosuppressants are prone to it; some patients have diabetes, atherosclerotic cardiovascular disease, obesity, malnutrition, kidney disease, shock, metastatic tumors or multiple myeloma. (2) Pathogenesis. Multiple bacteria invade the subcutaneous tissue and fascia; aerobes first consume oxygen in the infected tissue, lowering the tissue oxidation-reduction potential (Eh), while bacterial enzymes decompose tissue H2O2, creating a low-oxygen environment favorable to anaerobes. The infection spreads rapidly and extensively along the fascia, causing widespread inflammatory congestion and edema, then inflammatory embolism of small skin and subcutaneous vessels, nutritional disturbance, leading to ischemic trench-like skin necrosis and even circumferential necrosis. Microscopy shows marked inflammatory changes in vessel walls, neutrophil infiltration in the deep dermis and fascia, fibrous emboli in vessels of the affected fascia, and fibrinoid necrosis of arterial and venous walls; Gram staining reveals pathogens in the damaged fascia and dermis, while the muscle shows no injury.

Treatment

Surgery, medication, supportive treatment, rehabilitation therapy

Prevention

Improve immunity, actively treat primary systemic diseases and local skin injury; those on long-term corticosteroids and immunosuppressants should strengthen general nutrition and prevent trauma. When skin is injured, promptly remove contaminants and disinfect the wound; when systemic discomfort occurs, seek medical help actively.

Recommended Department

It is recommended to visit the orthopedic surgery department; before the visit you may first book an appointment and connect with experts through this platform.

Warm reminder: The above information is provided for health education reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek care at a regular hospital in time.