Definition and Overview
The majority of infections affecting the skin and soft tissues are superficial, requiring only antibiotic therapy. However, more serious infections, particularly cellulitis, occasionally require drainage as part of the management.
On rare occasions, pathogens enter the subcutaneous tissues and spread through deeper layers, such as the fascia and the muscles, causing tissue ischemia, necrosis, and death. Deep, necrotising infections have been referred to using various terminologies, depending on the layer of soft tissue involved and the specific pathogen responsible for them. These terms include gas gangrene, necrotising fasciitis, and Fournier gangrene, to name a few. In general, these conditions are known as necrotising soft tissue infections, or NSTI.
These kinds of infections are usually aggressive, necessitating a combination of urgent surgical intervention and strong antimicrobial therapy.
Who Should Undergo and Expected Results
Necrotising soft tissue infections encompass a spectrum of disease conditions characterised by rapidly progressive inflammation of the soft tissues, typically involving the muscles and the fascia.
Immunocompromised individuals are at highest risk for NSTIs. Elderly individuals and patients with co-morbid conditions, such as malnutrition, diabetes mellitus, cancer, and peripheral vascular disease, are commonly affected.
The clinical manifestations of NSTI vary widely, ranging from minimal erythema with extensive underlying tissue involvement to an early septic course with gross necrosis of the skin. The physician should be wary when clinical signs, such as crepitus, eruption of small vesicles on the skin, induration, and oedema outside the area of redness, occur as these suggest the involvement of deeper layers. The extremities, the perineum, and the torso are the commonly affected areas. Signs of advanced disease include fever, gangrene, and systemic shock.
Establishing a diagnosis early in the course of the disease is crucial to begin timely and appropriate treatment to avoid life-threatening complications. Although gram-positive bacteria are commonly encountered, the majority of NSTIs are caused by multiple organisms (polymicrobial); hence the need for powerful antibiotics. Broad-spectrum antibiotics are started empirically, and shifted to targeted anti-bacterial drugs once culture results are available. Surgical intervention, specifically debridement, is likewise performed without delay.
Despite significant developments in medicine and intensive care, necrotising infections remain associated with high mortality rates (16-25%). If not managed adequately, mortality rates can go as high as 80-100%. NSTI cases should be managed by a multi-disciplinary team of health care practitioners to ensure appropriate and specialised care for these patients.
How is the Procedure Performed?
Source control is a vital component in the management of necrotising infections. The principle of source control is facilitated by surgical intervention, specifically debridement. Debridement is a surgical procedure that involves the removal of all necrotic tissues, including the skin, subcutaneous tissues, muscles, and fascia. For necrotising soft tissue infections, debridement is best conducted under general anaesthesia.
Since NSTIs are progressive, debridement should be performed as soon as the condition is diagnosed. A liberal incision is done to remove as much dead tissue as possible. The debridement is continued until healthy, raw tissues with good blood supply are encountered. In certain instances, the procedure may necessitate extensive excision of tissues leading to disfigurement or amputation. However, complete debridement must be performed because an incomplete operation remains associated with higher mortality and morbidity rates.
If possible, primary closure is performed after debridement. However, radical excision may result in massive defects requiring reconstruction, which may be delayed or performed during the same operation, depending on the extent of the defect and the patient’s status. Flaps and skin grafts may have to be performed to ensure adequate coverage of healthy underlying tissues. On occasion, especially for dirty wounds and in cases where a repeat debridement is expected, the wound may be left open and covered with saline- or Daikin’s solution-soaked dressing. A “second look” procedure may be necessary to check if the debridement is adequate and if there is disease progression.
Specimens acquired during the procedure are sent for culture studies to facilitate directed antibiotic therapy postoperatively.
Possible Risks and Complications
After the operation, rigorous monitoring in the intensive care unit is paramount. A substantial systemic inflammatory response is expected postoperatively in patients with necrotising infections, which may lead to the development of organ failure such as respiratory distress, kidney injury, septic shock, and even death. Aggressive management and continued physiologic support, including fluid resuscitation, adequate nutrition, and even mechanical ventilation, are thus crucial. Comprehensive antibiotic coverage cannot be overemphasised. Early patient mobilisation is likewise recommended. New studies are focusing on the possible benefits of using hyperbaric oxygen and intravenous immunoglobulins for these cases.
Debridement for necrotising soft tissue infections typically results in large and complex wounds, which may lead to a number of complications. Exposure of important structures, such as cartilage and bone, to the external environment should be avoided to prevent these structures from drying out. Repeated irrigation and lavage of open wounds facilitate the removal of debris and bacteria. A negative pressure or vacuum-assisted device may be applied to the wound to improve vascularisation and healing. Adequate wound coverage minimises fluid and electrolyte loss, and protection from infection and desiccation. Various options, including xenografts and skin substitutes, may be employed. For large abdominal defects, synthetic materials, such as biologic implants or absorbable mesh, may serve as a bridge prior to definitive closure of the wound. The development of subsequent wound complications, such as a ventral hernia, can be managed at a later time.
Pain management after debridement, particularly during dressing changes, should be optimised. The use of appropriate pharmacologic therapies, such as narcotics, should be instituted to achieve pain relief. Neuropathic pain, such as that following amputation, may be managed with medications like gabapentin. Adequate pain control also promotes movement, which can help prevent complications, such as contractures.
Extensive debridement can result in significant loss of function for the patient. Rehabilitation should be done in order to ensure return of function, achieve independence, and optimise the patient’s quality of life.
Stevens DL, Bisno AL, Chambers HF, Everett ED, Dellinger P, Goldstein EJ. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis. 2005 Nov 15. 41(10):1373-406.
[Guideline] Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of america. Clin Infect Dis. 2014 Jul 15. 59(2):e10-52.