spread has not been fully elucidated but has been attributed to the expression of
hyaluronidase, which degrades the fascia. The key pathological process resulting from this
uncontrolled proliferation of bacteria is angiothrombotic microbial invasion and liquefactive
necrosis of the superficial fascia. As this process progresses, occlusion of perforating nutrient
vessels to the skin causes progressive skin ischemia. This event is responsible for the cutaneous
manifestations. As the condition evolves, ischemic necrosis of the skin ensues with gangrene of
subcutaneous fat, dermis, and epidermis, manifesting progressively as bullae formation,
ulceration, and skin necrosis (Fig. 4).
Clinical Features
In early stages (stage 1 NF), the disease is indistinguishable from severe soft tissue infection
such as cellulitis and erysipelas and presents with only pain, tenderness, and warm skin.
Margins of the skin are poorly defined with tenderness extending beyond the apparent area of
involvement. Blister or bulla formation is an important diagnostic clue. It signals the onset of
skin ischemia (stage 2 NF). The late stage (stage 3 NF) signals the onset of tissue necrosis and is
characterized by hemorrhagic bullae, skin anesthesia, and gangrene. Systemic manifestation
such as fever, hypotension, and multiorgan failure can occur (50–53). The effects are classically
caused by superantigen produced by group AStreptococcus. nonsteroidal anti-inflammatory
drugs (NSAIDs) are postulated to potentiate tissue damage by decreasing granulocyte
adhesion and phagocytosis and increasing cytokine production.
Diagnosis
NF is a clinical diagnosis with corroborative operative findings that include the presence of
grayish necrotic fascia, a lack of resistance of normally adherent superficial fascia, a lack of
bleeding of the fascia during dissection, and the presence of foul smelling “dishwater pus.”
Wong et al. identified six independent laboratory variables between patients with and without
NF. Total white cell count, hemoglobin, sodium, glucose, serum cretonne, and C-reactive
protein were selected. The total score had a range from 0 to 13 according to the likelihood of
NF (low5, intermediate 6–7, high8). In the developmental cohort of 89 patients, only 13
(14.6%) had a diagnosis or suspicion of NF on admission; 80 (89.9%) of these patient had a
Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score of6 (positive predictive
value was 92% and negative predictive value was 96%). LRINEC score can be a useful adjunct
tool in NF (54,55). In a study by Anaya et al., clostridial infection was an independent predictor
for limb loss and mortality and was highly associated with IV drug use and leukocytosis on
admission (15).
Figure 4 Necrotizing fasciitis of left leg in a diabetic patient with onset of bullae and tissue necrosis. Patient
underwent below the knee amputation.
Severe Skin and Soft Tissue Infections in Critical Care 303