Definition
A.Severe bacterial infection of the fascia (connective tissue that covers and separates the muscles and other internal organs) and overlying subcutaneous fat that causes extensive tissue death.
Incidence
A.Necrotizing fasciitis can occur at any age; however, the mean age is around 50 years.
B.Hospitalizations due to necrotizing fasciitis are gender neutral.
C.Necrotizing fasciitis occurs randomly and is not linked to similar infections in others.
Pathogenesis
A.The most common way of getting necrotizing fasciitis is when the bacteria enter the body through a break in the skin, such as a cut, scrape, burn, insect bite, or puncture wound.
B.The infection spreads along the muscle fascia as a result of its relatively poor blood supply, and muscle tissue may be spared. In addition, overlying tissue can appear unaffected.
C.Necrotizing fasciitis is typically classified based on the microbial source of infection.
1.Type I—polymicrobial with aerobic and anaerobic bacteria, such as Clostridioides, Peptostreptococcus, and Bacteroides species.
2.Type II—monomicrobial and generally caused by group A streptococcus (GAS; also known as hemolytic streptococcal gangrene).
Predisposing Factors
A.Type I: Certain comorbid conditions.
1.Diabetes.
2.Obesity.
3.Cardiovascular disease.
4.Peripheral vascular disease.
5.Liver disease.
6.Kidney disease.
7.Cancer.
8.Other chronic health conditions that weaken the body’s immune system.
B.Type II: Risk factors in healthy individuals (no past medical history).
1.Skin injury—laceration or burn.
2.Blunt trauma.
3.Surgery.
4.Childbirth.
5.Varicella.
6.Intravenous drug use.
Subjective Data
A.Common complaints/symptoms.
1.Pain—usually out of proportion to how the area looks; followed by anesthesia (due to thrombosis of small vessels).
2.Swelling.
3.Redness.
4.Fever.
5.Chills.
6.Fatigue.
B.Family and social history.
1.A detailed history is important, as it can suggest the likely cause of the infection.
2.A careful history, including several factors, should be taken.
a.Indicate if any trauma occurred at the site.
b.Onset and duration of symptoms.
c.Speed at which erythema is spreading.
d.Existence of any comorbid conditions (past medical history).
e.Any recent swimming in lakes, ponds, or areas of concern.
Physical Examination
A.Early on, healthy appearance, but possible rapid progression to ill/septic appearance.
B.Acute tenderness at site of infection.
C.Skin with area of rapidly increasing erythema, bullae, skin necrosis, and/or crepitus; sometimes with dusky or purplish discoloration.
1.Skin color can change in a few days from red/purple to patchy blue/gray, followed in 3 to 5 days with skin breakdown with bullae with thick pink/purple fluid and frank cutaneous gangrene.
D.Increased warmth and induration at site.
E.Possible crepitus at site.
F.Difficult to palpate muscle groups due to induration, with edema of subcutaneous tissue.
G.If the skin is open, gloved fingers can pass easily between the two layers and may reveal yellowish-green necrotic fascia.
H.If the skin is not open, a scalpel may be needed to open the site.
Diagnostic Tests
A.Lab work.
1.Complete blood count (CBC), basal metabolic profile (BMP), and blood and tissue cultures are necessary.
2.Lab findings are often nonspecific but may include leukocytosis with a marked left shift; coagulopathy; and elevated creatine kinase (CK), lactate, and creatinine.
B.Imaging: Noncontrast CT and MRI scans (especially in abdominal wall infections).
1.These can be helpful if gas is identified in the soft tissue and/or fascial planes.
2.MRI can be overly sensitive.
C.Surgical exploration.
1.Do not delay surgical exploration for results from blood, skin, or wound cultures.
2.Surgical exploration is the only way to confirm diagnosis. Histopathology of tissue will show extensive tissue damage, including:
a.Thrombosis of blood vessels.
b.Abundant bacteria along fascial planes.
c.Infiltration of acute inflammatory cells.
Differential Diagnosis
A.Acute epididymitis.
B.Cellulitis.
C.Orchitis.
D.Toxic shock syndrome.
E.Deep vein thrombosis (DVT).
F.Brown recluse spider bite.
Evaluation and Management Plan
A.Surgical emergency. Debridement needs to be done early to minimize tissue loss and possible amputation, and debridement will require review in the operating room every 24 hours.
B.Empiric antibiotics. These should be started immediately. Agents should be broad based to cover gram-negative and gram-positive organisms and anaerobes. More target-specific antibiotics may be started once tissue cultures and sensitivities are available.
1.Clindamycin is the antibiotic of choice to cover necrotizing fasciitis for its antitoxin effects.
2.In addition, the patient requires carbapenems (e.g., imipenem, meropenem, or ertapenem—please note that ertapenem does not cover pseudomonas) or beta lactamase inhibitor (e.g., piperacillin/tazobactam, ampicillin sodium/sulbactam sodium, or Ticarcillin/clavulanic acid), as well as an agent active against methicillin-resistant Staphylococcus aureus (MRSA; e.g., vancomycin, daptomycin, or linezolid).
C.Intravenous fluids. Massive fluids may be necessary due to diffuse capillary leak and hypotension. Also, nutritional support needs to be implemented to help support wound healing.
Follow-Up
A.Repeat imaging of area to make sure there is no lingering infection.
B.Follow-up with infectious disease after completion of antibiotics.
C.Follow-up with surgery as needed.
Consultation/Referral
A.Consult surgery emergently for surgical intervention.
B.Infectious disease for antibiotic duration.
C.Depending on extent of injury, may need plastics consult for flap.
D.Wound care.
Special/Geriatric Considerations
A.Necrotizing fasciitis is the most frequently overlooked infectious process of the skin in the elderly.
B.Skin and soft tissue represent a common site of infection, and it is a recognized focus of sepsis in the elderly.
Bibliography
Centers for Disease Control and Prevention. (n.d.). Necrotizing fasciitis: A rare disease, especially for the healthy. Retrieved from https://www.cdc.gov/features/necrotizingfasciitis
Edlich, R. (2018, October 17). Necrotizing fasciitis workup. In M. S. Bronze (Ed.), Medscape. Retrieved from http://emedicine.medscape.com/article/2051157-workup
Ghosh, A., & Johnstone, J. (2013). Necrotizing fasciitis in an immunocompromised elderly woman. Canadian Journal of Infectious Diseases and Medical Microbiology, 24(1), 38–39. doi:10.1155/2013/489587
Goh, T., Goh, L. G., Ang, C. H., & Wong, C. H. (2013). Early diagnosis of necrotizing fasciitis. British Journal of Surgery, 101(1), e119–e125. doi:10.1002/bjs.9371
Misiakos, E. P., Bagias, G., Patapis, P., Sotiropoulos, D., Kanavidis, P., & Machairas, A. (2014). Current concepts in the management of necrotizing fasciitis. Frontiers in Surgery, 1, 36. doi:10.3389/fsurg.2014.00036
Oud, L., & Watkins, P. (2015). Contemporary trends of the epidemiology, clinical characteristics, and resource utilization of necrotizing fasciitis in Texas: A population-based cohort study. Critical Care Research and Practice, 2015, 1–9. doi:10.1155/2015/618067
Southwick, F. S. (2008). Infectious diseases: A clinical short course (2nd ed, pp. 268–271). New York, NY: McGraw-Hill Professional Publishing.