Surgical Site Infections (SSI)

• Surgical site infections (SSI)
• Hospital-acquired infections
• Wound classification
• Care bundles
• Antibiotic prophylaxis

Hospital Acquired Infection

• Also known as nosocomial infections
• Infections occurring more than 48 hours after hospital admission
• Indicates poor quality health service and leads to avoidable costs

Hospital Acquired Infections related to surgery

• Surgical site infections
• Urinary Tract Infection (CAUTI)
• Indwelling Catheter/cannula Infection
• Ventilated Associated Pneumonia

Impact of SSIs in the US

• Approximately 300,000 SSIs occur per year, accounting for 17% of all Hospital Acquired Infections (HAI)
• SSIs are second/first to UTIs
• 2%-5% of patients undergoing inpatient surgery are affected
• 3% mortality rate
• Patients with SSIs have a 2-11 times higher risk of death, especially in major surgeries
• 75% of deaths among patients with SSI are a direct result of the infection
• SSIs result in long-term disabilities
• SSIs add ~7-10 additional postoperative hospital days
• SSIs cost between $3000-$29,000 per case, depending on procedure and pathogen, amounting up to $10 billion annually

Deep Incisional SSI

• Infection occurs within 30 days with no implant left in place
• Infection occurs within 1 year with an implant in place Occurs below the deep fascia
• Infection must be related to the operation
• Infection involves the deep soft tissue (fascia & muscle layers)

Superficial Incisional SSI

• Occurs within 30 days after the operation
• Involves only skin or subcutaneous tissue of the incision
• Occurs above the deep fascia

Organ/Space SSI

• Occurs within 30 days post-operation if no implant is left in place
• Occurs within 1 year if an implant is in place
• Infection must be related to the operation
• Involves any part of the anatomy, other than the incision, which was opened or manipulated during the operation

SSI – Wound Classification

• There are four classes, graded 1-4
• Classification depends on the type of surgery
• Class 1 = Clean
• Class 2 = Clean contaminated; prophylactic antibiotics are used
• Class 3 = Contaminated; antibiotic use is indicated
• Class 4 = Dirty infected; therapeutic antibiotics are used

Clean Wound Classification

• Operation where no inflammation is encountered
• Respiratory, alimentary, genital, urinary tracts are not entered
• Often following non-penetrating (blunt) trauma
• Primarily closed with no open drainage

Clean - Contaminated Wound Classification

• Operation entering respiratory, alimentary, genital, or urinary tracts
• No evidence of infection
• No major break in technique
• No unusual contamination encountered
• Operation involving biliary tract, appendix, vagina, and oropharynx

Contaminated Wound Classification

• Operation following open, fresh, accidental wounds
• Operation with major breaks in sterile technique (e.g., open cardiac massage)
• Gross spillage from GI tract
• Includes operation where acute, non-purulent inflammation encountered

Dirty Wound Classification

• Operation involving old traumatic wounds with retained devitalized tissue
• Existing clinical infection
• Perforated viscera
• The organisms causing post-op infection were present before the operation.
• Fecal peritonitis , perforated diverticular disease or peritonitis due to appendicitis

Types of Surgery and Infection Rates

• Clean surgeries like Hernia repair or breast biopsy have a 1.5% infection rate.
• Clean-Contaminated Cholecystectomy and Elective bowel resections have a 2-5% infection rate.
• Contaminated Emergency bowel resection, as well as dirty/infected Perforation, abscess surgeries have a 5-30% infection rate.

SSI – Risk Factors

• Surgical patient and Operation Factors increase infection risk
• Duration of surgical scrub
• Maintaining body temperature
• Skin antisepsis
• Preoperative shaving
• Prolonged Duration of operation
• Antimicrobial prophylaxis
• Operating room ventilation
• Inadequate sterilization of instruments
• Foreign material at surgical site
• Surgical drains
• Surgical technique (Poor hemostasis, Failure to obliterate dead space, Tissue trauma)

SSI – Risk Factors Patient Characteristics

• Age and Diabetes (High HbA1c or Glucose > 200 mg/dL postoperative period)
• Nicotine use delays primary wound healing
• Controversial steroid use
• Malnutrition has no epidemiological association
• Obesity: 20% over ideal body weight
• Prolonged preoperative stay indicates severity of illness and comorbid conditions
• Preoperative nares colonization with Staphylococcus aureus
• Perioperative transfusion
• Coexistent infections at a remote body site
• Altered immune response

SSI – Risk Stratification NNIS Project

• Risk stratification consists of 3 independent variables associated with SSI risk
• Contaminated or dirty/infected wound classification
• ASA > 2
• Length of operation > 75th percentile of the specific operation being performed

Operative Antibiotic Prophylaxis

• Decreases bacterial counts at surgical site
• Administer within 60 minutes prior to starting surgery (knife to skin)
• Repeat dose for longer surgery (T 1/2)
• Do not continue beyond 24 hours
• Factors: prevailing pathogens, antibiotic resistance, type of surgery
• Not a substitute for aseptic surgery or good technique

CDC Core and Supplemental Prevention Strategies

• Core strategies have high levels of scientific evidence and Demonstrated feasibility
• Core are standard practice
• Supplemental Strategies have some scientific evidence at variable levels of feasibility
• Supplemental strategy additions are considered when infections persist or rates are high

Prevention Strategies: Core Preoperative Measures

• Administer antimicrobial prophylaxis within 1 hour prior to incision; 2 hours for vancomycin and fluoroquinolones
• Administer antimicrobial based on Surgical procedure recommendations, and most common SSI pathogens
• Treat Remote infections before elective operation or Postpone operation until infection has resolved
• Do not remove hair unless it will interfere with the operation; do not use razors, clip or use depilatory agent
• Skin Prep includes appropriate antiseptic agent and technique
• Maintain immediate postoperative normothermia

Prevention Strategies Core - Intraoperative Measures

• Keep Operating Room (OR) doors closed during surgery except as needed for passage of equipment, personnel, and the patient

Prevention Strategies Core - Postoperative Measures

• Protect primary closure incisions with sterile dressing for 24-48 hrs post-op
• Control blood glucose level (cardiac) measuring levels at 6AM on POD#1 and #2 with procedure day = POD#0
• Maintain post-op blood glucose at <200mg/dL
• Discontinue antibiotics within 24hrs after surgery end time(48hrs for cardiac)

Prevention Strategies: Supplemental Preoperative

• Nasal screen and decolonize only Staphylococcus aureus carriers undergoing elective cardiac and other procedures with preoperative mupirocin therapy.

Prevention Strategies Supplemental - Perioperative

• Redose antibiotic at the 3-hour interval in procedures with duration >3 hour
• Adjust antimicrobial prophylaxis dose for obese patients (body mass index >30)
• Provide feedback on surgeon specific infection rates

Pathogen Sources

• Endogenous if contaminated or dirty surgery more likely
• Patient may have existing flora on skin, mucous membranes or in GI tract
• Seeding from a distant focus of existing infection
• Exogenous if clean surgery more likely
• Poor surgical Personnel (surgeon and team) including soiled attire, Breaks in aseptic technique, Inadequate hand hygiene
• OR physical environment and ventilation
• Tools, equipment, materials brought to the operative field

Microbiology of SSIs

• Common SSI pathogens
• Pseudomonas aeruginosa
• Staphylococcus aureus
• Enterococcus spp.
• Escherichia coli
• Coagulase-negative staphylococci
• S aureus is predominant in Skin and Skin Structure Infections (SSSIs)
• MSSA 30.9% and S aureus 45.9%
• MRSA~15%

Impact of MRSA on SSI

• MRSA is associated with increased morbidity, mortality, and cost outcomes
• 479 patients were studied
• MRSA greater 90-day mortality vs MSSA
• MRSA (adjusted odds ratio, 3.4; 95% CI: 1.5-7.2)
• MRSA longer LOS after infection (median additional days=5; P<0.001)
• MRSA associated with greater hospital charges (1.19-fold increase in hospital charges, P=0.03)

Importance of Timing of Surgical Antimicrobial Prophylaxis (AP)

• Prospective study of 2,847 elective clean and clean-contaminated procedures determined optimal timing
• Early AP (2-24 hrs before incision):3.8%
• Postop AP (3-24 hrs after incision):3.3%
• Periop AP (< 3 hrs after incision): 1.4%
• Preop AP (<2 hrs before incision): 0.6% (most effective)

Surgical Technique

• Removes devitalized tissue
• Maintains effective hemostasis
• Gently handle tissues
• Eradicating dead space
• Avoiding inadvertent entries into a viscus
• Utilizing drains and suture material appropriately

Parameters for Operating Room Ventilation*

• Temperature: 68°-73°F (20 – 22.7°C) depending on normal ambient temp
• Relative humidity: 30%-60%
• Air movement: from "clean to less clean" areas
• Air changes: >15 total per hour; >3 outdoor air per hour

Emerging Challenges

• Challenges in detecting SSIs
• Lack of standardized methods for post-discharge/outpatient surveillance
• Increased number of outpatient surgeries and Shorter postoperative inpatient stays
• Antimicrobial resistance makes antimicrobial Prophylaxis increasingly harder