Chart — Perioperative Nursing

Surgical Wound Classes

CDC/National Research Council surgical wound classification — four classes defined by degree of contamination and predicted infection risk. Classification is determined intraoperatively by the surgeon and drives antibiotic selection, wound closure method, and postoperative monitoring intensity.

Educational use only. SSI risk rates are population-level estimates. Individual patient risk varies based on comorbidities, procedure duration, surgeon technique, and institutional infection control practices. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.

Class	SSI Risk	Definition	Examples	Closure	Nursing Focus
Class IClean	1–2%	No hollow viscus entered. No inflammation. No break in sterile technique. Respiratory, alimentary, genital, and urinary tracts not entered.	·Hernia repair ·Thyroidectomy ·Total joint replacement ·Cardiac surgery (sternotomy) ·Breast biopsy ·Craniotomy (elective)	Primary (immediate closure)	✦Standard wound care; monitor for any erythema or drainage ✦Lowest SSI risk — complications unexpected ✦Patient education: keep dry 24–48 hrs; call provider for redness, warmth, drainage
Class IIClean-Contaminated	2–10%	Hollow viscus entered under CONTROLLED conditions. No unusual contamination. Includes biliary, GI, GU, and respiratory tracts entered without significant spillage.	·Appendectomy (non-perforated) ·Cholecystectomy ·Hysterectomy ·Bowel resection (prepped) ·Tonsillectomy ·Nephrectomy	Primary (immediate closure)	✦Antibiotic timing: document administration time ✦Monitor closely for SSI days 3–5 ✦Fever >101°F after day 2 → assess wound first
Class IIIContaminated	10–15%	Open/fresh traumatic wounds, acute non-purulent inflammation, or major break in sterile technique. Gross GI spillage or entry without bowel prep included.	·Perforated appendix (no abscess) ·Traumatic wound <4–6 hrs old ·Bowel resection with spillage ·Open fracture (recent) ·Major sterile technique failure	Delayed primary or open packing	✦Wound may be left open — moist packing and frequent dressing changes ✦Monitor for SSI vigilantly — higher baseline risk ✦Nutritional support important for wound healing
Class IVDirty / Infected	>15% (up to 40%)	Existing clinical infection or perforated viscera at time of surgery. Organisms causing postoperative infection were present before operation. Old traumatic wounds with devitalized tissue.	·Ruptured appendix with abscess ·Perforated bowel with fecal contamination ·Abscess incision and drainage ·Traumatic wound with retained foreign body ·Infected fasciotomy	Open — negative pressure wound therapy or delayed closure	✦Wound VAC (negative pressure wound therapy) often used ✦Frequent wound irrigation and dressing changes ✦Monitor for sepsis: fever, elevated WBC, hemodynamic instability ✦Isolation precautions if organism identified

Class I

Clean

1–2%

SSI risk

Class II

Clean-Contaminated

2–10%

SSI risk

Class III

Contaminated

10–15%

SSI risk

Class IV

Dirty/Infected

>15%

SSI risk

NCLEX Quick Reference — Wound Classification

No hollow viscus entered, no inflammation

Class I — Clean (1–2%)

Bowel entered in controlled manner, no spillage

Class II — Clean-Contaminated (2–10%)

Major break in sterile technique OR gross GI spillage

Class III — Contaminated (10–15%)

Existing infection or perforated viscera at time of surgery

Class IV — Dirty/Infected (>15%)

Antibiotic prophylaxis: administer within _____ of incision

60 minutes (120 min for vanco/fluoroquinolone)

Hair removal method before surgery

Clippers ONLY — never razor (micro-abrasions increase SSI risk)

Wound left open for packing — which class?

Class III or IV (contaminated/dirty wounds)

Antibiotics are THERAPEUTIC (not just prophylactic) — which class?

Class IV — Dirty/Infected

Related Resources

Surgical Wound Classification ReferenceFull reference with CDC definitions, nursing implications, and SSI prevention bundle

Open →

Surgical Complications GuideSSI types, signs, and postoperative complication management

Open →

Wound Drainage ChartSerous, sanguineous, serosanguineous, purulent drainage characteristics

Open →

Standards & sources

Fact-checked Jun 21, 2026

This page is written to align with CDC/National Research Council Wound Classification; AORN Surgical Standards; SCIP Core Measures. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →