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CDC surgical wound classification and infection risk assessment
The CDC wound classification system helps predict surgical site infection (SSI) risk and guide antibiotic prophylaxis decisions. Classification should be determined at the time of surgery.
Wound Classification
clean
Surgical Site Infection Risk
| Class | Classification | Criteria | SSI Risk |
|---|---|---|---|
| I | Clean | Non-traumatic, no viscus entered, primarily closed | 1-2% |
| II | Clean-Contaminated | Controlled entry into GI/respiratory/GU tract | 5-10% |
| III | Contaminated | Fresh trauma, gross spillage, major break, acute inflammation | 15-20% |
| IV | Dirty/Infected | Old trauma, devitalized tissue, existing infection, perforation | 30-40% |
Diabetes, obesity, smoking, immunosuppression, malnutrition, advanced age increase infection risk.
Prolonged surgery (>3 hours), inadequate antibiotic prophylaxis, hypothermia, poor glycemic control.
Contamination level, tissue perfusion, foreign bodies, hematoma, dead space, tension on closure.
Optimize comorbidities, smoking cessation, chlorhexidine bath, appropriate hair removal, antibiotic timing.
Maintain normothermia, glycemic control, appropriate skin prep, sterile technique, minimize tissue trauma.
Proper wound care, glycemic control, early mobilization, adequate nutrition, appropriate dressing changes.
Administration
Give within 60 minutes before incision (120 minutes for vancomycin/fluoroquinolones)
Redosing
Redose if surgery exceeds 2 half-lives of antibiotic or if major blood loss occurs
Duration
Discontinue within 24 hours after surgery end time for most procedures
Clean Procedures
Cefazolin 2g IV (3g if ≥120kg). Add vancomycin if MRSA risk.
Colorectal Surgery
Cefazolin + metronidazole OR cefoxitin OR ertapenem
Cardiac/Vascular
Cefazolin 2g IV. Vancomycin 15mg/kg if beta-lactam allergy or MRSA risk.
SSI is an infection that occurs at or near the surgical incision within 30 days of surgery (or within 90 days if implant placed). SSIs are classified as superficial incisional, deep incisional, or organ/space infections.
Contaminated (Class III) and dirty (Class IV) wounds may benefit from delayed primary closure or healing by secondary intention. This reduces deep infection risk. Consider closure 3-5 days later once wound appears clean and no signs of infection present.
For most surgeries, prophylactic antibiotics should be discontinued within 24 hours after surgery. Longer courses do not reduce SSI risk and increase antibiotic resistance and adverse effects. Cardiac surgery may warrant 48 hours.
Shaving with razors increases SSI risk due to microscopic skin cuts. If hair removal necessary, use clippers or depilatory cream. If razors must be used, remove hair immediately before surgery, not the night before.
Increasing pain, redness, warmth, swelling around incision. Purulent drainage, wound dehiscence, fever >38°C. Deep infections may present with systemic signs without obvious wound changes. Seek medical attention if concerned.
Yes, many SSIs present after discharge. Median time to SSI diagnosis is 5-7 days for superficial infections and 7-21 days for deep infections. This is why 30-day surveillance is standard (90 days for procedures with implants).
This calculator provides general guidance on wound classification and SSI risk. Individual patient factors, institutional protocols, and clinical judgment must guide antibiotic selection and duration. Consult institutional antibiotic stewardship programs and infectious disease specialists for complex cases.