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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. Objectives. Soft Tissue Infections (STI) Bacteria
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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
Objectives • Soft Tissue Infections (STI) • Bacteria • Surgical Site Infections (SSI)
Soft Tissue Infections • Diverse group of diseases involving the skin and underlying structures
Soft Tissue Infections Meleney Ulcer
Classification Superficial Deep
Classification • Nonnecrotizing infections involve superficial structures generally • Necrotizing infections involve deep structures generally
Symptoms • Range from subtle/nonspecific to obvious • Common findings • Pain • Edema • Erythema • Tenderness • Warmth
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
Necrotizing Infections • Signs/Symptoms • Pain out of proportion to exam • Systemic toxicity • Ischemic tissues • Crepitus • Laboratory • Leukocytosis • Hyponatremia
Laboratory Studies • Blood cultures • Unusual organism • Refractory cellulitis • Facial involvement • Water exposure • CBC • Lytes • CK levels
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%
Imaging Studies • X-ray • 15-30% demonstrate gas • CT • More sensitive than x-ray • MRI • Preferred imaging modality MRI
Treatment Superficial STI • Superficial • Mainly monomicrobial aerobes • Staphylococcus aureus • Streptococcus pyogenes • Antibiotics • Dicloxacillin • Cephalexin • Erythromycin • Clindamycin
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
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
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
Antibiotic Choice • Penicillin/Ampicillin • Eagle effect • Clindamycin • Consider aminoglycoside • Consider Imipenem
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
Synergy of Polymicrobial Infections • Seal and Kingston,1988 • GAS: 12% spread • GAS and S. aureus: 50% spread • GAS and a-lysin: 75% spread
Clostridium Exotoxins • a-toxin • Cell membrane destruction • q-toxin • WBC inhibition • Other toxins • Platelet aggregation
Streptococcal Toxins • M proteins • Prevent phagocytosis • Induce vascular leak • Cleave NAD • SPE • Induce inflammatory cytokines
Surgical Site Infections • 3rd most common nosocomial infection (14-16%) • Increase cost and length of stay • Most common nosocomial infection on surgical services
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
Pathogenesis • Host factors • Inoculum size • Length of operation
Host Factors • Nicotine • Remote infections • Colonization • Blood products
Anticipated Organisms Guidelines for Prevention of Surgical Site Infection, 1999
S. pyogenes Clostridium sp.
Class I Wound (Clean) • Atraumatic wound without inflammation • Do not enter GI, GU, biliary, or respiratory tract • 1.5% infection rate
Class II Wound(Clean-Contaminated) • Respiratory, GI, GU, or biliary tract entered under controlled conditions • 7.5% infection rate expected
Class III Wounds(Contaminated) • Traumatic wounds • Breaks in sterile technique • Gross spillage from GI tract • Acute, nonpurulent inflammation • 15% anticipated infection rate
Class IV Wounds (Dirty) • Old traumatic wounds • Devitalized tissue • Clinical infection present • Perforated viscus • 40% expected infection rate
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
NNIS Risk Index • ASA score above 2 • Level of contamination • Operative time greater than 75 percentile of normal
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
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
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
Summary • Discussed several risk stratification schemes • Surgical Wound Classification • SENIC index • NNIS risk index • Prophylactic antibiotic choice