Soft Tissue and Surgical Site Infections

1. Soft Tissue and Surgical Site Infections Department of Surgery The Brody School of Medicine East Carolina University The Center of Excellence for Trauma and Surgical Critical Care Greenville, NC Brett Waibel, MD

2. Objectives • Soft Tissue Infections (STI) • Bacteria • Surgical Site Infections (SSI)

3. Soft Tissue Infections • Diverse group of diseases involving the skin and underlying structures

4. Soft Tissue Infections Meleney Ulcer

5. Soft Tissue Infections

6. Classification Superficial Deep

7. Classification • Nonnecrotizing infections involve superficial structures generally • Necrotizing infections involve deep structures generally

8. Symptoms • Range from subtle/nonspecific to obvious • Common findings • Pain • Edema • Erythema • Tenderness • Warmth

9. Host Factors COPD Cardiac Disease CHF PVD Diabetes Steroids Immune Compromise Malnourishment Host factors Environmental factors Specific clinical scenarios Diagnosis • Environmental factors • Cuts, lacerations • Injection sites • Bites • Skin diseases • Ulcers • Surgical Incisions • Specific Scenarios • Bites • Animal • Human • Chronic skin disease • Ulcers • Water exposure • Saltwater: V. vulnificus • Freshwater: A. hydrophila

11. Necrotizing Infections • Signs/Symptoms • Pain out of proportion to exam • Systemic toxicity • Ischemic tissues • Crepitus • Laboratory • Leukocytosis • Hyponatremia

12. Necrotizing Infections

13. Laboratory Studies • Blood cultures • Unusual organism • Refractory cellulitis • Facial involvement • Water exposure • CBC • Lytes • CK levels

14. Laboratory Studies • Necrotizing STI • WBC > 15.4 and sodium < 135 predictive of necrotizing STI • WBS < 15.4 and sodium > 135 had negative predictive value of 99%

15. Imaging Studies • X-ray • 15-30% demonstrate gas • CT • More sensitive than x-ray • MRI • Preferred imaging modality MRI

16. Diagnostic Algorithm

17. Treatment Superficial STI • Superficial • Mainly monomicrobial aerobes • Staphylococcus aureus • Streptococcus pyogenes • Antibiotics • Dicloxacillin • Cephalexin • Erythromycin • Clindamycin

18. Treatment Superficial STI • Immune Compromise • H influenza • S epidermidis • Animal Bites • P multocida • Seawater/Raw Seafood • V vulnificus • Freshwater • A hydrophila • Scenario specific • Immune compromised • Bites • Water exposure • Ulcers

19. Treatment Deep STI • Resuscitation • Isotonic IV fluids • Adjuncts • Foley • Central lines • PA catheters • Electrolyte correction • Hyponatremia • Hypocalcemia • Hyperglycemia • Broad Spectrum Antibiotics • Polymicrobial infection (70-75%) • Group A Strep common (90%) • Anaerobes • Gram negative rods • Resuscitation • Physiologic support • Broad spectrum antibiotics • Debridement • Supportive care • Supportive care • Nutritional support • Consider postpyloric feedings • Coverage of defect • Debridement • The critical step • Reexploration mandatory • Physiologic support • Renal failure • Metabolic acidosis • Septic shock

20. Surgical Debridement • Time from onset of symptoms to initial debridement critical • < 25 hours: 71% survival • > 40 hours: 29% survival • Clostridial myonecrosis: no survival if surgery delayed 48 hours

21. Antibiotic Choice • Penicillin/Ampicillin • Eagle effect • Clindamycin • Consider aminoglycoside • Consider Imipenem

22. Mortality • Overall approximately 30% • 63% of deaths due directly from the infection in first week • 37% due to multiple system organ failure latter • Reifler et al, 1988 • Limited debridement: 71% mortality • Radical debridement: 43% mortality

23. Synergy of Polymicrobial Infections • Seal and Kingston,1988 • GAS: 12% spread • GAS and S. aureus: 50% spread • GAS and a-lysin: 75% spread

24. Clostridium Exotoxins • a-toxin • Cell membrane destruction • q-toxin • WBC inhibition • Other toxins • Platelet aggregation

25. Streptococcal Toxins • M proteins • Prevent phagocytosis • Induce vascular leak • Cleave NAD • SPE • Induce inflammatory cytokines

26. Superantigens

27. Surgical Site Infections • 3rd most common nosocomial infection (14-16%) • Increase cost and length of stay • Most common nosocomial infection on surgical services

28. Surgical Wound Infection Task Force • 77% of deaths with nosocomial infections present due to infection • 93% of these infections involved organs or spaces accessed during surgery • 60-80% of infections involve the incision • 20-40% of infections involve the deep spaces accessed or organs operated upon

29. Pathogenesis • Host factors • Inoculum size • Length of operation

30. Host Factors • Nicotine • Remote infections • Colonization • Blood products

31. Anticipated Organisms Guidelines for Prevention of Surgical Site Infection, 1999

32. Surgical Wound Classification

33. S. pyogenes Clostridium sp.

34. Class I Wound (Clean) • Atraumatic wound without inflammation • Do not enter GI, GU, biliary, or respiratory tract • 1.5% infection rate

35. Class II Wound(Clean-Contaminated) • Respiratory, GI, GU, or biliary tract entered under controlled conditions • 7.5% infection rate expected

36. Class III Wounds(Contaminated) • Traumatic wounds • Breaks in sterile technique • Gross spillage from GI tract • Acute, nonpurulent inflammation • 15% anticipated infection rate

37. Class IV Wounds (Dirty) • Old traumatic wounds • Devitalized tissue • Clinical infection present • Perforated viscus • 40% expected infection rate

38. Abdominal operation Operation greater than 2 hours Class III or IV surgical wounds Three or more diagnosis at time of discharge Risk of Infection 0 1% 1 3.6% 2 9% 3 17% 4 27% SENIC Risk Index

39. NNIS Risk Index • ASA score above 2 • Level of contamination • Operative time greater than 75 percentile of normal

40. NNIS Risk Index

41. Surgical Prophylaxis

42. Summary • Superficial soft tissue infection • Generally monomicrobial aerobic gram positives • Don’t forget specific scenarios for unusual organisms (ex: ulcers, water exposure) • Deep soft tissue infections (necrotizing) • Polymicrobial is the norm • Rapidly fatal without surgical intervention

43. Summary • Polymicrobial infections display synergy from toxin production • Affect vascular supply, cause cell disruption, and inhibit immune response • Virulent strains of Group A Streptococcus and Clostridial sp. extremely effective at these functions

44. Summary • Surgical site infections are a definite problem in health care • Factors involved in surgical site infection development • Host factors • Inoculum size • Length of operation

45. Summary • Discussed several risk stratification schemes • Surgical Wound Classification • SENIC index • NNIS risk index • Prophylactic antibiotic choice