Overview
Definition:
Necrotizing soft tissue infections (NSTIs) are rapidly progressive, life-threatening infections involving the superficial fascia and subcutaneous fat, characterized by extensive tissue necrosis and potential systemic toxicity
They require immediate aggressive surgical intervention.
Epidemiology:
NSTIs are rare but have high morbidity and mortality
Incidence varies, but they are more common in immunocompromised individuals, diabetics, IV drug users, and those with peripheral vascular disease
Common pathogens include Group A Streptococcus, Staphylococcus aureus, and polymicrobial flora.
Clinical Significance:
NSTIs are a surgical emergency due to their rapid progression and high mortality rate
Prompt and adequate debridement is the cornerstone of management
Delays in diagnosis and treatment significantly worsen patient outcomes, leading to sepsis, organ failure, and limb loss.
Clinical Presentation
Symptoms:
Severe, disproportionate pain out of proportion to visible findings
Erythema and edema spreading rapidly
Bullae formation, crepitus, skin anesthesia or paresthesia
Systemic symptoms include fever, tachycardia, hypotension, and altered mental status.
Signs:
Tense edema, dusky or violaceous skin discoloration
Bullae with serosanguineous or purulent fluid
Skin anesthesia upon probing
Palpable subcutaneous gas (crepitus)
Signs of systemic inflammatory response syndrome (SIRS) or sepsis.
Diagnostic Criteria:
Clinical suspicion is paramount
No single laboratory test confirms NSTI
Diagnostic criteria often include severe pain, rapid progression of erythema/edema, bullae, crepitus, skin anesthesia, and laboratory markers like elevated WBC count, lactate, and C-reactive protein.
Diagnostic Approach
History Taking:
Focus on onset and progression of pain, any preceding trauma or minor injury, presence of comorbidities (diabetes, immunocompromise, PVD), recent infections (e.g., skin lesions, pharyngitis), and intravenous drug use
Note any antibiotic use.
Physical Examination:
Thorough examination of the affected limb or area, assessing for erythema, edema, tenderness, induration, bullae, crepitus, and neurological deficits
Pay attention to the extent of superficial fascia involvement
Vital signs assessment is critical for SIRS/sepsis.
Investigations:
Laboratory: Complete blood count (leukocytosis), electrolytes, renal function tests, liver function tests, coagulation profile, blood cultures, arterial blood gas (for lactate), C-reactive protein
Imaging: Plain radiographs (for gas), Ultrasound (edema, gas), CT scan (extent of involvement, gas, abscess), MRI (best for soft tissue detail, extent).
Differential Diagnosis:
Cellulitis, erysipelas, deep vein thrombosis (DVT), pyomyositis, gas gangrene (clostridial myonecrosis), Fournier's gangrene, purulent abscess, diabetic foot infections, necrotizing fasciitis of other etiologies.
Management
Initial Management:
Immediate resuscitation with intravenous fluids and broad-spectrum antibiotics covering gram-positive, gram-negative, and anaerobic organisms
Prompt surgical consultation
Aggressive pain control
Hemodynamic monitoring and support for sepsis.
Medical Management:
Empirical broad-spectrum antibiotics: combination therapy typically includes vancomycin or linezolid (for MRSA), a broad-spectrum beta-lactam (e.g., piperacillin-tazobactam), and potentially clindamycin (for toxin suppression)
Adjust based on culture and sensitivity results
Hyperbaric oxygen therapy may be considered in selected cases, particularly for clostridial infections.
Surgical Management:
Radical debridement is the cornerstone
Initial exploration and debridement must be aggressive, removing all necrotic, non-viable tissue including skin, subcutaneous fat, fascia, and muscle if involved
Repeat debridements every 24-48 hours or as needed until all infected and necrotic tissue is eradicated
Fasciotomy may be necessary for compartment syndrome.
Supportive Care:
Intensive care unit (ICU) monitoring is essential
Nutritional support, glycemic control, wound care (moist dressings, negative pressure therapy), pain management, and psychological support are crucial
Management of co-existing conditions like diabetes and renal failure.
Complications
Early Complications:
Sepsis, septic shock, organ failure (renal, respiratory, cardiac), disseminated intravascular coagulation (DIC), wound dehiscence, compartment syndrome, local hemorrhage.
Late Complications:
Chronic wound, recurrent infection, significant scarring, contractures, limb dysfunction, amputation, psychological sequelae (PTSD, depression).
Prevention Strategies:
Early recognition and prompt treatment are key
Aggressive surgical debridement is the primary preventative measure against progression
Meticulous wound care
Optimizing host factors like glycemic control in diabetics
Prophylactic antibiotics in high-risk surgical procedures.
Prognosis
Factors Affecting Prognosis:
Timeliness of diagnosis and treatment, extent of infection, number of debridements required, patient comorbidities, hemodynamic stability, and causative organism.
Outcomes:
Mortality rates can be as high as 30-50% for severe NSTI
Survival depends heavily on early and aggressive management
Limb salvage is possible with extensive debridement, but amputation may be necessary in severe cases.
Follow Up:
Long-term follow-up is required to monitor wound healing, assess for recurrence, manage physical therapy needs, and address psychological impact
Rehabilitation and reconstructive surgery may be needed
Regular clinic visits for wound assessment and functional evaluation.
Key Points
Exam Focus:
NSTI is a surgical emergency
Radical debridement is the mainstay of treatment
Early recognition, broad-spectrum antibiotics, and frequent re-exploration are critical
Differentiate from cellulitis and gas gangrene.
Clinical Pearls:
The hallmark is pain disproportionate to physical findings
"When in doubt, cut it out" – it is better to over-debride than under-debride
Monitor wound beds for signs of viability (bleeding, vascularity).
Common Mistakes:
Delaying surgical intervention
Inadequate debridement, leaving behind even small areas of necrotic tissue
Underestimating the extent of infection
Inappropriate antibiotic choice or duration
Insufficient post-operative monitoring and re-exploration.