Wound Infection Surgical site infections (SSI) Definitions of SSI Superficial incisional SSI: Infection involves only skin and subcutaneous tissue of incision. Deep incisional SSI: Infection involves deep tissues, such as fascial and muscle layers also superficial and deep incision sites and organ/space SSI draining through incision. Organ/space SSI: Infection involves any part of the anatomy in organs and spaces other than the incision, which was opened or manipulated during operation.
Superficial incisional SSI Occurs within 30 days after the operation Involves only the skin or subcutaneous tissue At least 1 of the following: • Purulent drainage is present. • Organisms are isolated from fluid/tissue of the superficial incision. • At least 1 sign of inflammation (eg, pain or tenderness, induration, erythema, local warmth of the wound) is present. • The wound is deliberately opened by the surgeon. • The surgeon or attending physician declares the wound infected
Deep incisional SSI Occurs within 30 days of the operation or within 1 year if an implant is present Involves deep soft tissues of the incision At least 1 of the following: • Purulent drainage is present from the deep incision but without organ/space involvement. • Fascial dehiscence or fascia is deliberately separated by the surgeon because of signs of inflammation. • A deep abscess is identified by direct examination or during reoperation, by histopathology, or by radiologic examination. • The surgeon or attending physician declares that a deep incisional infection is present
Organ/space SSI Organ/space SSI Occurs within 30 days of the operation or within 1 year if an implant is present Involves anatomical structures not opened or manipulated during the operation At least 1 of the following: • Purulent drainage is present from a drain placed by a stab wound into the organ/space. • Organisms are isolated from the organ/space by aseptic culturing technique. • An abscess in the organ/space is identified by direct examination, during reoperation, or by histopathologic or radiologic examination. • A diagnosis of organ/space SSI is made by the surgeon or attending physician
CausesMicrobiology Most SSIs are contaminated by the patients own endogenous flora The usual pathogens on skin and mucosal surfaces are gram-positive cocci gastrointestinal surgery intrinsic bowel flora, gram-negative bacilli, and gram-positive microbes, including enterococci and anaerobic organisms Gram-positive organisms, particularly staphylococci and streptococci, account for most exogenous flora involved in SSIs
Host factors Systemic factors: age, malnutrition, hypovolemia, poor tissue perfusion, obesity, diabetes, steroids, and other immunosuppressants. Wound characteristics: nonviable tissue in wound; hematoma; foreign material, including drains and sutures; dead space; poor skin preparation, including shaving; and preexistent sepsis (local or distant). Operative characteristics: poor surgical technique; lengthy operation (>2 h); intraoperative contamination, including infected theater staff and instruments and inadequate theater ventilation; prolonged preoperative stay in the hospital; and hypothermia
Risk Factors for Development of Surgical Site InfectionsPatient factors Older age Immunosuppression Obesity Diabetes mellitus Chronic inflammatory process Malnutrition, Anemia Peripheral vascular disease Radiation Carrier state (e.g., chronic Staphylococcus carriage) Local factors Poor skin preparation Contamination of instruments Inadequate antibiotic prophylaxis Prolonged procedure Local tissue necrosis Hypoxia, hypothermiaMicrobial factors Prolonged hospitalization (leading to nosocomial organisms) Toxin secretion Resistance to clearance (e.g., capsule formation)
Wound ContaminationClassification Description Risk (%) Uninfected operative wound No acute inflammation Closed primarilyClean (Class I) Respiratory, gastrointestinal, biliary, and urinary tracts not <2 entered No break in aseptic technique Closed drainage used if necessary Elective entry into respiratory, biliary, gastrointestinal, urinary tractsClean-contaminated and with minimal spillage (Class II) No evidence of infection or major break in aseptic technique <10 Example: appendectomy Nonpurulent inflammation presentContaminated Gross spillage from gastrointestinal tract (Class III) Penetrating traumatic wounds <4 hours 20 Major break in aseptic technique Purulent inflammation presentDirty-infected (Class IV) Preoperative perforation of viscera 40 Penetrating traumatic wounds >4 hours
The National Nosocomial Infection Surveillance(NNIS) risk index risk index (1) American Society of Anesthesiologists (ASA) Physical Status score >2 (2) class III/IV wound (3) duration of operation greater than the 75th percentile for that particular procedure
American Society ofAnesthesiologists (ASA)Classification of Physical StatusASA Score Characteristics 1 Normal healthy patient 2 Patient with mild systemic disease Patient with a severe systemic disease that limits 3 activity but is not incapacitating Patient with an incapacitating systemic disease 4 that is a constant threat to life Moribund patient not expected to survive 24 hours 5 with or without operation
Predictive Percentage of SSIOccurrence by Risk IndexAt Risk Index Predictive Percentage of SSI 0 1.5 1 2.9 2 6.8 3 13.0
Time Relations Early (24-48h); streptococci and clostridia, Immunosuppression Usual; (5-10d); others Delayed (2-4w); infection of hematoma or seroma
Lab Staining methods: Gram stain simple, quick. Culture techniques: both aerobic and anaerobic. Fungal cultures. Then sensitivity testing Newer techniques Tests for antigens from the organism through enzyme-linked immunoassay (ELISA) or radioimmunoassay Detection of antibody response in the host sera Detection of RNA or DNA sequences or protein from the infective organism Polymerase chain reaction (PCR) to detect small amounts of microbe DNA.
RECOMMENDATIONS FROM THE HOSPITAL INFECTIONCONTROL PRACTICES ADVISORY COMMITTEE FOR THEPREVENTION OF SURGICAL SITE INFECTIONS Do not operate on patients with active infections Do not shave patient in advance Control glucose in diabetic patients Stop tobacco use in patient Have patient shower with antiseptic soap Prepare skin with appropriate agent Surgeons nails should be short Surgeons scrub hands Exclude infected surgeons Give prophylactic antibiotics when indicated Maintain prophylactic antibiotic levels during operation Keep O.R. doors closed
RECOMMENDATIONS FROM THE HOSPITAL INFECTIONCONTROL PRACTICES ADVISORY COMMITTEE FOR THEPREVENTION OF SURGICAL SITE INFECTIONS Use sterile instruments Avoid flash sterilization Wear a mask Cover all hair Wear sterile gloves Use gowns and drapes that resist fluid penetration Gentle tissue handling Closed suction drains (when used) Delayed primary closure for heavily contaminated wounds Sterile dressing for 24- 48 hr SSI surveillance with feedback to surgeons
Recommendations forProphylactic Antibiotics antibiotics had to be in the circulatory system at a high enough dose at the time of incision to be effective clean-contaminated and contaminated wounds clean procedures in which prosthetic devices is implanted
Recommendations forProphylactic Antibiotics The antibiotic should be administered preoperatively as close to the time of the incision as is practical before induction of anesthesia in most situations. The antibiotic should have activity against the pathogens likely to be encountered. Postoperative administration of preventive systemic antibiotics beyond 24 hours has not been demonstrated to reduce the risk of SSIs.
Recommendations forProphylactic Antibiotics good tissue penetration to reach wound involved. cost effectiveness. minimal disturbance to intrinsic body flora
Antibiotics as Indicated by Probable Infective MicroorganismOperation Expected Pathogens Recommended AntibioticOrthopedic surgery (including prosthesis insertion), cardiac S aureus, coagulase-negative surgery, neurosurgery, breast Cefazolin 1-2 g staphylococci surgery, noncardiac thoracic procedures Gram-negative bacilli andAppendectomy, biliary procedures Cefazolin 1-2 g anaerobes Gram-negative bacilli andColorectal surgery Cefoxitin 1-2 g anaerobes Gram-negative bacilli andGastroduodenal surgery Cefazolin 1-2 g streptococci S aureus, StaphylococcusVascular surgery epidermidis, gram-negative Cefazolin 1-2 g bacilli S aureus, streptococci, anaerobesHead and neck surgery and streptococci present in Cefazolin 1-2 g an oropharyngeal approach Gram-negative bacilli,Obstetric and gynecological enterococci, anaerobes, Cefazolin 1-2 g procedures group B streptococciUrology procedures Gram-negative bacilli Cefazolin 1-2 g
Special situations Elective colon surgery: Mechanical cleansing and antibiotics Dietary restrictions. Whole gut lavage ; 10% mannitol solution, Fleets phospho-soda, or polyethylene glycol, usually is performed on the day of surgical intervention. Enteral antibiotic regimes with oral neomycin and erythromycin being the most popular combination, metronidazole and tetracycline. Catheter- related infections: Morbidity and mortality (up to 20% in patients with catheter-related bloodstream infections).
Newer concepts in theprevention of SSIs close regulation of blood sugar in patients with diabetes,. body temperature; failure to maintain intraoperative core body temperature within 1-1.5°C of normal increases the SSI rate by a factor of 2. oxygenation. Maintaining or increasing oxygen delivery to the wound by increasing the inspired oxygen concentration administered to the patient perioperatively has also been shown to reduce the incidence of SSIs.
Treatment incision and drainage without the addition of antibiotics. Antibiotic therapy is reserved for patients in whom evidence of severe cellulitis is present, or who manifest concurrent sepsis syndrome. The open wound often is allowed to heal by secondary intention
Further CareInpatient Care: increased hospital stay due to SSI 7-10 days increasing costs by 20% Occasionally, wound debridement and subsequent packing and frequent dressing is necessary to allow healing by secondary intention.Outpatient Care:Most patients with wound infections are managed in the community. Management usually takes the form of dressing changes, which usually is by secondary intention.