What are the POCUS (Point-of-Care Ultrasound) findings and management for suspected necrotizing infection?

From the Guidelines

Point-of-care ultrasound (POCUS) findings for suspected necrotizing infections include subcutaneous gas appearing as hyperechoic foci with dirty shadowing, fascial thickening greater than 4mm, and fluid collections along fascial planes. Other supportive findings include tissue edema with cobblestoning appearance and loss of normal tissue architecture. When these findings are identified, immediate surgical consultation is essential as necrotizing infections require urgent surgical debridement. While awaiting surgery, start broad-spectrum antibiotics including piperacillin-tazobactam 4.5g IV q6h plus vancomycin 15-20mg/kg IV q8-12h (dosed by levels) plus either clindamycin 900mg IV q8h or linezolid 600mg IV q12h to inhibit toxin production, as recommended by the Infectious Diseases Society of America 1. Aggressive fluid resuscitation and hemodynamic support are necessary, with vasopressors if needed. Laboratory tests should include complete blood count, comprehensive metabolic panel, lactate, creatine kinase, and blood cultures. POCUS is particularly valuable in resource-limited settings or when other imaging modalities are unavailable, as early diagnosis significantly improves outcomes, as noted in the 2018 WSES/SIS-E consensus conference recommendations 1. The presence of subcutaneous gas on ultrasound is highly specific for necrotizing infections, though its absence does not rule out the diagnosis, as gas may not be present in all cases, particularly early in the disease course.

Some key points to consider in the management of necrotizing infections include:

• Prompt and aggressive antibiotic treatment, with consideration of local antimicrobial resistance patterns 1
• Surgical debridement as the primary therapeutic modality for necrotizing fasciitis 1
• The use of scoring systems, such as the Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) score and the Fournier’s Gangrene Severity Index (FGSI), to aid in diagnosis and risk stratification 1
• The importance of clinical judgment and a high index of suspicion in diagnosing necrotizing infections, as they can be difficult to diagnose and require prompt treatment to improve outcomes 1

From the Research

POCUS Findings for Necrotizing Infection

• The use of Point-of-Care Ultrasound (POCUS) has been evaluated for the identification of necrotizing fasciitis (NF) in patients presenting to the emergency department 2.
• POCUS images of the suspected site of infection can be interpreted based on sonographic findings of NF, which can aid in the diagnosis and management of the condition.
• A study found that POCUS can be used to identify NF with a high sensitivity and specificity, with all patients determined to be at high risk of having NF based on CT scan and/or surgical impression also having POCUS images interpreted as concerning for NF 2.

Management of Suspected Necrotizing Infection

• Prompt diagnosis, appropriate antimicrobial choice, and aggressive surgical interventions are essential in effecting a clinical cure and optimal outcomes for patients with necrotizing soft tissue infections 3.
• The management of necrotizing soft tissue infections includes broad spectrum antibiotics, fluid resuscitation for severe sepsis, and early aggressive surgical debridement 4.
• Patients with necrotizing infections often require multiple operative debridement to achieve source control, and a low threshold for repeat debridement should be maintained because these infections can progress rapidly 4.

Diagnostic Challenges

• Necrotizing soft tissue infections can be a diagnostic challenge due to the subtle physical examination findings, physiologic instability, and laboratory derangements 4.
• Aids to diagnosis such as scoring systems and cross-sectional imaging may be used, but the findings are not specific, so management should not be based on these alone 4.
• The involvement of anaerobic bacteria can be associated with an increase in the number of surgical revisions, and computed tomography may have limited significance as a diagnostic tool for initial diagnosis 5.

Clinical Presentation and Etiology

• Necrotizing fasciitis is a life-threatening soft-tissue infection with a high morbidity and mortality, characterized by widespread fascial necrosis with relative sparing of skin and underlying muscle 6.
• The disease can occur in any region of the body, but the abdominal wall, perineum, and extremities are the most common sites of infection 6.
• Polymicrobial necrotizing fasciitis is usually caused by enteric pathogens, whereas monomicrobial necrotizing fasciitis is usually due to skin flora 6.