Necrotising soft tissue infection- etiologies and management

1. Necrotising Soft Tissue Infections
Student: Dr Tarun Peela
Guide: Col R Gopi

2. Introduction
• Infection –
– soft tissue compartment (dermis, subcutaneous
tissue, superficial fascia, deep fascia, or muscle)
– necrosis
• Inocuous wound, rapid spread, sepsis
• Surgery is the cure

3. History
• Hippocrates - 5th century BC.
• British surgeon Leonard Gillespie - late 18th
century --as phagedaenic ulcer
• Confederate Army surgeon Joseph Jones in
1871 from USA -- term hospital gangrene
• Wilson- Necrotizing fasciitis- 1951
• Later NSTI

4. Etiology
– Trauma
– IV drug and insulin
injection
– skin infections and ulcers
– animal and insect bites
– surgical complications
– percutaneous catheter
insertion
– Abscesses
– idiopathic etiologies
Inoculation of the pathogen into the subcutaneous
tissue via any break in an epithelial or mucosal surface
• More vulnerable
• Diabetics
• Obese
• Immunocompromised
• Peripheral vascular
disease

5. Clinical features
• Giuliano and colleagues 1977 - Classified
• Three types basing on pathogen
Type 1 Type 2 Type 3
Polymicrobial source
• Gram-positive
cocci
• Gram-negative
rods
• Anaerobes
(Bacteroides
species,
Clostridium
perfringens and
septicum)
Monomicrobial infection
• β-hemolytic
streptococci or
• staphylococci
(MRSA rising in
frequency to 40%)
V. vulnificus infection

6. Type 1 Type 2 Type 3
• 55-75%
• Elderly with
comorbidities
• 20-50% risk factor
not identified
• Clostridium
perfringens, C.
septicum, and C.
sordellii
• Symptomatic within
hours
• α-toxin
• 15-25%
• Healthy hosts
• Associated with toxic
shock
• Streptococcal M
proteins
• Superantigen activity
• 5%
• Sea divers
• oyster ingestion by
chronic liver dis
• Warm-water coastal
regions
• Apoptosis of
lympho/neutro
• Early evidence of
significant systemic
toxicity
• Multisystem organ
failure and
cardiovascular
collapse occur very
early

7. Clinical features
• Hallmark- Rapid progression of disease
• Strong suspicion
– An apparent superficial cellulitis progresses
rapidlyfails to respond to standard therapy
evolving systemic signs of sepsis

8. Clinical features
Early features Late features
• Pain out of proportion to
examination
• Erythema
• Hyperthermia
• Edema beyond the area
of erythema
• Skin anaesthesia
• Epidermolysis
• Bronzing of skin
• Tachycardia
• Fever
• Hemorrhagic bullae
• Foul odour
• Brownish-tan “dishwater”
drainage
• Dermal gangrene
• Crepitus
• Severe pain out of
proportion to exam
• Sepsis
• Shock
• Organ failure

9. Evaluation
• Chin-Ho Wong, Md et al The LRINEC score: A tool for distinguishing
necrotizing fasciitis from other soft tissue infections Crit Care Med 2004
Vol. 32, No. 7

10. LRINEC score
• Low risk- <5
• Mod risk- 6-7(positive predictive value 92.0%)
• High risk- >8(positive predictive value 93.4%)

11. • Serum lactate>6 mmol/L alone- 32% mortality
• Serum sodium level >-135 mEq/L with lactate
<6mmol/L - 0% mortality
• Arezou Yaghoubian, MD et al. Use of Admission Serum Lactate and Sodium
Levels to Predict Mortality in Necrotizing Soft-Tissue Infections Arch
Surg. 2007;142(9):840-846

12. • Procalcitonin ratio of POD1:POD2-
• >1.14 - successful eradication of the infectious
focus
• Jan Friederichs, M.D. et al. Procalcitonin ratio as a predictor
of successful surgicaltreatment of severe necrotizing soft
tissue infections Am j surg 2013

13. Imaging
• Delay caused by imaging outweighs its potential
benefit
• Plain film radiography- subcutaneous
emphysema- specific finding for clostridial NSTI

14. Imaging
• CT is more sensitive than plain radiography
– fascial thickening
– edema
– subcutaneous gas
– abscess formation
• Magnetic resonance imaging sensitive but
lacks specificity
• Ultrasonography lacks sensitivity or specificity

15. Diagnosis
• Strong history and physical examination
• “finger test”
– a 2-cm incision is made down to the deep fascia
– gentle probing with the index finger
– positive finger test
– lack of bleeding, presence of characteristic “dishwater
pus,” and lack of tissue resistance
• High clinical suspicion- Exploration not delayed
• Gold standard - operative

16. Management
• Proper patient triage to an ICU
• Resuscitation with IV fluids
• Nutrition
• Antibiotics
• Surgery

17. Antibiotics
G+ G- Anaerobes MRSA
Penicillins Third-generation
cephalosporin or
aminoglycosides
Flouroquinolones
Metronidazole/
clindamycin
Vancomycin/
Linezolid
• Clindamycin has relatively broad activity
– Decrease α- toxin production by clostridial species
– Reduce superantigen M protein by streptococcal
species
– Suppress LPS–induced TNF-α production by
monocytes

18. Operative
• Incisions –
– extend at least beyond the area of induration
– parallel to neurovascular bundles
– extending to and exposing the deep fascia
• Induration - dermal lymphatics are blocked
and postcapillary venules are thrombosed,
which lead to tissue necrosis

19. Operative
• Necrotic tissue - dull, gray, and
avascular- excised
• Characteristic “murky dishwater”–
like fluid
• Non contractile muscle
• Thrombosed vessels
• No resistance at fascial planes
• Borders for debridement
• Where tissue planes cease to readily separate
• Healthy bleeding tissue at all margins

20. Operative
• Aggressive debridement- en mass organs,
tissues, and structures
• Joint involvement- amputation
• Rapid quantitative tissue cultures (if available)
and frozen section analysis may help guide the
debridement

21. Repeat debridements
• Revision surgery (“second look”) within 24 to 48
hours
• Progressive necrosis –
– polymicrobial synergy
– infectious spread
– hypotension
• Adjuncts to surgery include topical antimicrobial
creams, subatmospheric pressure wound
dressings, and optimization of nutrition.

22. Wound care
• The goals of treatment
– to achieve a clean wound
– protect it from dessication
– Assess the need for further surgical debridement
– promote wound healing
• Prevent exposed tendons, bone, or cartilage
from dessication

23. Wound care
• Wound dressings - promote mobility of the
patient - prevent nosocomial complications
such as pneumonia, UTI,DVT
• Should not impede the range of motion of the
joint or extremity
• Should not pull the tissue into a position of
deformity.

24. Wound coverage and reconstruction
• Primary closure
• Split-thickness skin grafts
• Full-thickness skin grafts
• Delayed primary closure vs healing by
secondary intention
• Tissue expansion
• Pedicled or free flaps.

27. Skin sparing technique
• Perfused skin beyond the margins of the
frankly necrotic tissue should be preserved
• Limits excision of viable overlying skin and
subcutaneous tissue hence – a “skin-sparing”
debridement.
Laura K. Tom, MD et al. A Skin-Sparing Approach to the Treatment of Necrotizing Soft Tissue
Infections: Thinking Reconstruction at Initial Debridement. Journal of the American College of
Surgeons. Jan 2016

28. Skin sparing technique
• Incision design
– Over the most obviously infected, discolored or
necrotic area
– Place longitudinally on extremities
– Avoid incisions perpendicular to flexion creases
– Avoid incisions directly over boney prominences,
large vessels and nerves

29. Skin sparing technique
• Exposure and Troubleshooting
– Elevate full thickness skin and subcutaneous flaps
– Lengthen linear longitudinal incisions
– Use trap door or counter incisions
• Debridement
– Excise ALL necrotic tissue – leave viable tissue
– Debride overlying skin if it is necrotic
– Plan for repeat examinations under anesthesia

30. Skin sparing technique

31. HBOT
• Delivery of oxygen at 2-3 times typical atmospheric pressure
• Leads to arterial oxygen tension as high as 2000 mm Hg with
resulting tissue oxygen tension of 300 mm Hg(arterial oxygen
tension of 300 mm Hg and tissue oxygen tension of 75 mm Hg )
• Elevated levels of oxygen at the tissue level
– reduce edema
– stimulate fibroblast growth
– increase the killing ability of leukocytes by augmenting the
oxidative burst
– independent cytotoxic effects on some anaerobes
• No differences in mortality or length of stay
*George ME, Rueth NM, Skarda DE, et al: Hyperbaric oxygen does not improve outcome in
patients with necrotizing soft tissue infection. Surg Infect (Larchmt) 2009; 10:21–28

32. IVIG
• Pooled IVIg from human donors
• Binds exotoxins produced by staphylococcal
and streptococcal bacterial infections
• Limits systemic inflammatory response
• Limited to critically ill patients with only
staphylococcal or streptococcal NSTIs or both
• Hypersensitivity reactions

33. Rehabilitation
• The aims
– minimize the adverse effects caused by the injury
in terms of healing the wound
– minimizing the development and effect of scarring
– maximizing functional outcomes
– providing support to maximize psychological well-
being and reintegration into society
• Physical, psychological, and social aspects of
care for the patient

34. References
• Schwartz Principles of Surgery 10th e
• Timo W. Hakkarainen et al. Necrotizing soft tissue infections:
Review and current concepts in treatment, systems of care,
and outcomes. Curr Probl Surg. 2014 August 51(8): 344–362.
• Laura K. Tom, MD et al. A Skin-Sparing Approach to the
Treatment of Necrotizing Soft Tissue Infections: Thinking
Reconstruction at Initial Debridement. Journal of the
American College of Surgeons. Jan 2016
• Ho H. Phan et al Necrotizing soft tissue infections in the
intensive care unit Crit Care Med 2010 Vol. 38, No. 9 (Suppl.)