Suspected necrotising soft tissue infection (NSTI)
Adults. A surgical emergency: delay to surgery increases death. Children: paediatric doses and specialist input.
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Infectious DiseaseEmergency
Necrotizing Soft Tissue Infection Management (IDSA 2014)
Necrotizing Soft Tissue Infection Management (IDSA 2014): Suspected necrotising soft tissue infection (NSTI) → Suspect NSTI if any of these features → R...
Pathway Overview
18 steps
Algorithm Steps
18 total
01Start 02Action Suspect NSTI if any of these features
Clinical judgement decides. A low LRINEC score or normal imaging does not exclude NSTI.
- Pain out of proportion to the examination findings
- Rapid spread of erythema, swelling or induration, or spread despite antibiotics
- Skin necrosis, ecchymoses, haemorrhagic bullae, anaesthesia of the skin
- Crepitus or gas in the soft tissues
- Systemic toxicity: fever, tachycardia, hypotension, confusion
03Action Resuscitate now and call the surgeon at the same time
Do all steps in parallel. Antibiotics now, ideally within 1 hour. Nothing delays surgical review.
- IV access; IV fluid resuscitation; noradrenaline first line for septic shock
- Blood cultures x2 before antibiotics, if this causes no delay
- Bloods: FBC, UEC, glucose, CRP, lactate, CK, coagulation
- Group and crossmatch for theatre; tell ICU early
- Check tetanus immunisation; give tetanus vaccine and immunoglobulin as the Australian Immunisation Handbook advises
04Warning Water or seafood exposure, or liver disease? Add Vibrio/Aeromonas cover
Wound exposed to seawater, brackish or fresh water, raw seafood, or cirrhosis. Keep the empiric regimen and ADD cover now. Do not wait for cultures.
- Seawater, seafood or liver disease (Vibrio): ADD doxycycline 100 mg 12-hourly (IV, or oral or nasogastric) PLUS cefotaxime 2 g IV 8-hourly or ceftazidime 2 g IV 8-hourly; urgent ID advice if already on piperacillin-tazobactam or meropenem
- Fresh water (Aeromonas): ADD doxycycline 100 mg 12-hourly (IV, or oral or nasogastric) PLUS ciprofloxacin 400 mg IV 12-hourly; some strains resist carbapenems
- Children: doxycycline is still used when life-threatening (IDSA 2014)
05Action Start broad empiric antibiotics now (adult doses)
Give with resuscitation; do not wait for theatre. Full first doses even with renal impairment. Severe beta-lactam allergy or child: see the lines below.
- Piperacillin-tazobactam 4.5 g IV 6-hourly OR meropenem 1 g IV 8-hourly
- PLUS vancomycin 25-30 mg/kg IV loading dose (actual body weight, max 3 g), then dose by levels and renal function
- PLUS clindamycin 600-900 mg IV 8-hourly (stops toxin production); if clindamycin cannot be used: linezolid 600 mg IV 12-hourly
- Alternative: ceftriaxone 2 g IV daily plus metronidazole 500 mg IV 8-hourly, with vancomycin and clindamycin
- Severe immediate beta-lactam allergy: vancomycin plus clindamycin plus ciprofloxacin 400 mg IV 12-hourly plus metronidazole 500 mg IV 8-hourly; ID advice
- Immunocompromised or neutropenic: ask ID about antifungal cover
- Children: vancomycin (dose by RCH vancomycin guideline) plus meropenem 20 mg/kg (max 1 g) IV 8-hourly plus clindamycin 10 mg/kg (max 600 mg) IV 6-hourly (RCH); paediatric ID advice
06Action Emergency senior surgical review now
Surgery is the main treatment. Exploration both confirms the diagnosis and treats it.
- Call the surgeon at first suspicion; do not wait for imaging or blood results
- Transfer early if no surgeon can operate on site
07Decision Diagnosis clear, or patient unstable?
Yes: go to theatre now. No: stable patient with an unclear diagnosis.
- If Yes
- Clear or unstable: theatre now
08Action Emergency debridement in theatre now (within 6 hours at the latest)
Remove all necrotic tissue at the first operation.
- Excise all necrotic tissue back to healthy bleeding tissue; amputation may be needed
- Send deep tissue from the edge of healthy and necrotic tissue for Gram stain and culture
- Typical findings: swollen dull grey fascia, thin brown fluid, no true pus, planes separate with a finger
- Fournier gangrene: involve urology and colorectal surgery; faecal diversion only when needed
09Decision Gram stain and culture result?
Narrow the empiric regimen when the organism is known.
- Polymicrobial or no growth
10Action Polymicrobial or no organism grown (Type I): continue broad cover
Mixed aerobes and anaerobes. Common with diabetes, vascular disease, recent surgery and perineal (Fournier) infection.
- Continue the empiric regimen; narrow by culture and susceptibility with ID advice
- Stop vancomycin only when cultures exclude MRSA
- Vibrio or Aeromonas grown: directed therapy with ID advice
11Action All types: ICU care, planned re-look surgery, antibiotic stop rule
Return to theatre within 12-24 hours of the first debridement (WSES 2022; IDSA 2014: 24-36 hours), earlier if worse, then until no more debridement is needed.
- Continue aggressive IV fluids: open wounds lose large volumes of fluid
- Stop antibiotics only when no more debridement is needed, the patient has improved, and fever has settled for 48-72 hours
- Vancomycin levels; adjust doses for renal function
- Analgesia, enteral nutrition, wound care team; negative pressure dressings between debridements
12Action Adjuncts: never let them delay surgery or ICU care
Evidence for adjuncts is weak.
- IVIG: no benefit shown in NSTI overall (INSTINCT trial); consider only for streptococcal toxic shock, with ID advice
- Hyperbaric oxygen: unproven. IDSA 2014 recommends against it for gas gangrene. WSES 2022: only if on site, with no delay or transfer
- Reconstruction (plastic surgery) after the infection is controlled
13Decision Improving after debridement and antibiotics?
Reassess at least daily: sepsis, lactate, wound spread.
- If Yes
- Improving
14Outcome Improving: de-escalate and plan wound closure
Narrow antibiotics by cultures; plastic surgery for wound closure; rehabilitation. Earlier surgery gives better outcomes.
If No- Not improving
15Outcome Not improving: return to theatre and review antibiotic cover
Look for missed necrosis. Review cultures and cover (MRSA, Vibrio, Aeromonas, fungi). Senior surgical, ICU and ID review.
- Group A strep or S. aureus
16Action Group A strep or S. aureus (Type II): targeted therapy
Monomicrobial. Keep MRSA cover until cultures exclude MRSA.
- Group A strep: benzylpenicillin 2.4 g (4 million units) IV 4-hourly PLUS clindamycin 600-900 mg IV 8-hourly
- Severe penicillin allergy: vancomycin (or linezolid) PLUS clindamycin; ID advice
- S. aureus: by susceptibility (MSSA: flucloxacillin or cefazolin; MRSA: vancomycin); ID advice
- Streptococcal toxic shock: IVIG may be considered with ID advice; benefit not proven
- Invasive group A strep is notifiable in Australia: tell the public health unit, who advise on contact prophylaxis
- Path rejoins step 11Shared downstream outcome
- Clostridium
17Action Clostridium (Type III, gas gangrene): penicillin plus clindamycin
Urgent, repeated debridement is the main treatment.
- Benzylpenicillin 2.4 g (4 million units) IV 4-hourly PLUS clindamycin 600-900 mg IV 8-hourly
- Severe penicillin allergy: keep the allergy regimen from the empiric step (it includes clindamycin and metronidazole); ID advice
- Hyperbaric oxygen is not recommended (IDSA 2014); never delay surgery or transfer for it
- Spontaneous C. septicum infection: look for colorectal cancer or neutropenia
- Path rejoins step 11Shared downstream outcome
If No- Stable, unclear
18Action Stable and diagnosis unclear: urgent CT only if it does not delay theatre
Imaging must never delay surgery. If doubt remains, the surgeon explores. No necrosis on CT and exploration: treat the other diagnosis, reassess every few hours, and go to theatre if signs progress.
- CT: gas or fluid tracking along fascial planes, fascial thickening, fat stranding
- MRI is sensitive but slow; not first choice in an emergency
- Plain X-ray may show gas; a normal film does not exclude NSTI
- Bedside exploratory incision (finger test) under local anaesthetic can confirm or exclude
- Path rejoins step 08Shared downstream outcome
Guideline Source
Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by IDSA
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- A low LRINEC score or normal imaging does not exclude NSTI. If suspicion stays high, the surgeon explores.
- Adult doses. Children need weight-based doses (IDSA 2014 Table 4) and paediatric surgical and ID input.
- Empiric regimens follow IDSA 2014 and WSES 2022. Adapt them to local resistance patterns and ID advice.
- Mortality is about 20% even with optimal care; delay to surgery increases mortality.
Contraindicated Populations
Children: the doses shown are adult dosesSevere immediate beta-lactam allergy: use the allergy regimen and seek ID adviceNeutropenic or severely immunocompromised patients: need ID advice on antifungal and other cover
Applicable Regions
USEUAU
AU: Benzylpenicillin is dosed in grams in Australia (600 mg = 1 million units). In tropical and coastal Australia, ask about seawater, fresh water and seafood exposure (Vibrio, Aeromonas). Align empiric choices with eTG Antibiotic and local ID advice.
Version 2Next review: 2027-09-30
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Frequently Asked Questions
What is the Necrotizing Soft Tissue Infection Management (IDSA 2014)?
The Necrotizing Soft Tissue Infection Management (IDSA 2014) is a emergency clinical algorithm for Infectious Disease. It provides a structured decision tree to guide clinical decision-making, based on Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by IDSA.
What guideline is the Necrotizing Soft Tissue Infection Management (IDSA 2014) based on?
This algorithm is based on Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by IDSA (DOI: 10.1093/cid/ciu296).
What are the limitations of the Necrotizing Soft Tissue Infection Management (IDSA 2014)?
Known limitations include: A low LRINEC score or normal imaging does not exclude NSTI. If suspicion stays high, the surgeon explores.; Adult doses. Children need weight-based doses (IDSA 2014 Table 4) and paediatric surgical and ID input.; Empiric regimens follow IDSA 2014 and WSES 2022. Adapt them to local resistance patterns and ID advice.; Mortality is about 20% even with optimal care; delay to surgery increases mortality.. Individual patient factors may require deviation from these recommendations.
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