Critical Care Medicine-Infections and Immunologic Disease>>>>>Soft-Tissue, Bone, Joint Infections
Question 3#

A 55-year-old male with non–insulin-dependent diabetes mellitus presents with lower leg swelling and severe pain. He fell while gardening yesterday and has a laceration on his heel. On examination has a fever of 39.4°C and is mildly confused. He has erythema, edema, and crepitus up to the midcalf. Notable laboratory values are a WBC count of 22,000 cells/mm2 and lactate 3.9.

What is the most appropriate next step in treatment?

A. Perform surgical debridement
B. Administer hyperbaric oxygen therapy
C. Administer intravenous immunoglobulin
D. Administer AB103, a mimetic of the CD28 T-lymphocyte receptor

Correct Answer is B

Comment:

Correct Answer: B

Necrotizing fasciitis (NF) is a bacterial infection characterized by friability of the superficial fascia, dishwater-gray exudate, and a notable absence of pus. It can occur after major traumatic injuries, as well as after minor breaches of the skin or mucosa or nonpenetrating soft-tissue injuries (eg, muscle strain or contusion). It is more common in immunocompromised patients. Necrotizing infections can result in widespread tissue destruction, which may extend from the epidermis to the deep musculature. 

Clinical manifestations of NF include soft-tissue edema, erythema, severe pain and tenderness, fever, and skin bullae or necrosis. Factors that can differentiate NF from cellulitis include pain out of proportion to clinical signs, hypotension, and shock. Patients who are immunosuppressed may present without these typical findings. 

NF can be subdivided into three types based on the pathogenic organisms involved:

  1. Type 1: Polymicrobial, with a heavy burden of anaerobes. Common in immunocompromised patients, with diabetes or peripheral vascular disease.
  2. Type 2: Monomicrobial, typically group A Streptococcus or S. aureus. Common in healthy individuals with skin injury as the portal to infection.
  3. Type 3: Gas gangrene caused by Clostridium perfringens.

For patients with aggressive soft-tissue infection, prompt surgical exploration is essential to determine the extent of infection, to assess the need for debridement, and to obtain specimens for gram staining and culture. No single clinical laboratory test or group of tests can adequately replace surgical inspection for diagnosis of these infections. In addition to prompt surgical intervention, appropriate antibiotic treatment and supportive care are essential to reduce morbidity and mortality. 

The benefits of hyperbaric oxygen therapy for treatment of NF remain controversial. Surgical debridement should not be delayed in order to pursue hyperbaric oxygen treatment. The rationale for using IVIG in patients with NF is based on its ability to neutralize extracellular toxins that mediate pathogenesis. Clinical studies supporting its efficacy have had serious limitations, and a consensus supporting its use has not been reached. 

Efforts to inhibit bacterial superantigens involved in the pathogenesis of necrotizing infections are ongoing but have not shown clinical success to date. 

References:

  1. Stevens DL, Bryant AE. Necrotizing soft-tissue infections. N Engl J Med. 2017;377(23):2253- 2265.
  2. Phan HH, Cocanour CS. Necrotizing soft tissue infections in the intensive care unit. Crit Care Med. 2010;38:S460.
  3. Vincent JL, Abraham E, Moore FA, et al, eds. Textbook of Critical Care. 7th ed. Philadelphia, PA: Elsevier; 2017.