Overview
Definition:
Wound classification systems categorize surgical wounds based on the degree of contamination at the time of surgery, directly influencing the risk of surgical site infection (SSI)
Antibiotic stewardship in surgery involves the judicious use of antimicrobial agents to optimize patient outcomes, prevent resistance, and reduce healthcare costs.
Epidemiology:
SSIs are a significant cause of morbidity and mortality following surgery, accounting for approximately 20% of all healthcare-associated infections
The incidence varies by wound class, procedure type, and patient factors
Antibiotic resistance is a growing global threat, making stewardship critical.
Clinical Significance:
Accurate wound classification guides perioperative antibiotic prophylaxis and treatment decisions
Effective antibiotic stewardship in surgery reduces SSI rates, shortens hospital stays, minimizes complications, and conserves the efficacy of essential antibiotics for future use.
Wound Classification System
Class I Clean:
Uninfected operative wounds in which there is no inflammation and no break in sterile technique
Primarily closed wounds
Respiratory, alimentary, genital, or uninfected urinary tracts are not entered
Clean wounds have a low SSI risk (typically <2%).
Class Ii Clean Contaminated:
Operative wounds in which there is no sign of infection but there is entry into the respiratory, alimentary, genital, or urinary tracts under controlled conditions and without unusual contamination
Examples include appendectomy or cholecystectomy where bile spillage is not significant
SSI risk is moderate (typically 2-5%).
Class Iii Contaminated:
Open, fresh, accidental wounds
Operations in which gross spillage from the gastrointestinal tract occurs, or where there are breaches in sterile technique or major breaks in technique
Examples include penetrating abdominal trauma or gross bile spillage
SSI risk is higher (typically 5-15%).
Class Iv Dirty Infected:
Open, old traumatic wounds with retained devitalized tissue and operations in which pus is encountered or there is evidence of perforations of viscus
Includes debridement of old traumatic wounds
These wounds are considered infected before the operation
SSI risk is highest (typically >15%).
Factors Influencing Risk:
Procedure duration
Patient comorbidities (diabetes, obesity, immunosuppression)
Surgeon's experience
Operative technique
Anesthesia type
Sterility maintenance.
Antibiotic Prophylaxis Guidelines
Principles Of Prophylaxis:
Administer the correct antibiotic
Administer at the appropriate time (usually within 60 minutes before incision)
Administer the correct dose
Administer for the correct duration (typically <24 hours)
Stop if no sign of infection.
Drug Selection By Wound Class:
Class I (Clean): Often no antibiotics needed, or narrow-spectrum if increased risk (e.g., prosthetic material)
Class II (Clean-Contaminated): First-generation cephalosporins (e.g., Cefazolin) are common
Alternatives include clindamycin or vancomycin for penicillin allergy
Class III (Contaminated): Broader spectrum agents may be needed, often covering gram-negatives and anaerobes (e.g., piperacillin-tazobactam or cefoxitin)
Class IV (Dirty-Infected): Antibiotics are therapeutic, not prophylactic, and should target identified pathogens based on cultures.
Timing Of Administration:
Intravenous administration within 60 minutes prior to skin incision is ideal
If using vancomycin or fluoroquinolones, due to longer infusion times, administration should commence 120 minutes before incision
Redosing is required for prolonged procedures (>2 half-lives of the drug) or significant blood loss.
Duration Of Prophylaxis:
For clean and clean-contaminated wounds, prophylaxis should generally not exceed 24 hours post-operatively
Continuing antibiotics beyond this period offers no proven benefit and increases the risk of resistance and adverse events
For contaminated or dirty wounds, antibiotic therapy is continued based on clinical assessment and culture results.
Redosing Criteria:
Significant blood loss (e.g., >1.5 liters)
Procedures lasting longer than the serum half-life of the chosen antibiotic
Changes in vital signs or hemodynamics suggesting redistribution of the drug.
Antibiotic Stewardship In Surgery
Role Of Stewardship Teams:
Developing institutional guidelines
Auditing antibiotic prescribing patterns
Providing feedback to prescribers
Educating healthcare professionals
Promoting the use of rapid diagnostic tests.
Surgical Site Infection Prevention:
Strict adherence to sterile techniques
Preoperative skin antisepsis
Perioperative normothermia
Glycemic control
Hair removal only when necessary (using clippers)
Optimal wound closure techniques.
Diagnosis And Treatment Of Ssi:
Prompt recognition of SSI signs (redness, swelling, pain, purulent discharge, fever)
Obtaining wound cultures for appropriate targeted therapy
Judicious use of broad-spectrum antibiotics while awaiting cultures, then de-escalating based on results
Surgical debridement of infected tissue.
Drug Resistance Considerations:
Understanding local resistance patterns
Avoiding empiric broad-spectrum use when narrower agents are effective
Promoting de-escalation strategies
Limiting the use of last-resort antibiotics.
Key Considerations For Examinations
Exam Focus:
Remember the wound class definitions and their associated SSI risk percentages
Know the recommended prophylactic antibiotics, timing, and duration for each class
Understand the principles of antibiotic stewardship and its application in preventing SSIs.
Clinical Pearls:
Always consider the patient's allergies and local resistance patterns when choosing prophylactic agents
Document the rationale for antibiotic use and discontinuation
Inquire about prior antibiotic exposure
Surgical site infections are often preventable with meticulous technique and appropriate prophylaxis.
Common Mistakes:
Overuse of prophylactic antibiotics beyond 24 hours
Failure to redose during prolonged procedures
Inappropriate antibiotic selection for the wound class
Not obtaining cultures from purulent wound drainage
Treating colonization as infection.
Key Points
Exam Focus:
Class I: Clean (Risk <2%)
Class II: Clean-Contaminated (Risk 2-5%)
Class III: Contaminated (Risk 5-15%)
Class IV: Dirty/Infected (Risk >15%)
Perioperative antibiotics (prophylaxis) are typically given within 60 minutes of incision and stopped within 24 hours for clean/clean-contaminated wounds.
Clinical Pearls:
For prosthetic material implantation, vancomycin is often added to standard prophylaxis
In cases of penicillin allergy, clindamycin or a cephalosporin (if no severe allergy) are alternatives
consider vancomycin for severe allergies or MRSA risk.
Common Mistakes:
Forgetting to redose antibiotics in long surgeries
Continuing antibiotics for prophylaxis beyond 24 hours
Not considering local antibiotic resistance patterns
Failure to de-escalate therapy once culture results are available.