Definition of wound infection
- 1992 US Centre for Disease Control
- Defined the following:
- Surgical site infections
- Superficial incisional infection
- Deep incisional infections
- Organ space infections
- Surgical site infections must fulfill the following criteria
Predisposing factors
- General factors
- Age, obesity, malnutrition
- Endocrine and metabolic disorders
- Hypoxia, anaemia
- Malignant disease
- Immunosupression
- Local factors
- Necrotic tissue
- Foreign bodies
- Tissue ischaemia
- Haematoma formation
- Poor surgical technique
- Microbiological contamination
- Type and virulence of organism
- Size of bacteriological dose
- Antibiotic resistance
Aerobic pathogens in wound infections
- Staphylococcus aureus (17%)
- Enterococci (13%)
- Coagulase-negative staphylococci (12%)
- Escherichia coli (10%)
- Pseudomonas aeruginosa (8%)
- Enterobacter species (8%)
- Proteus mirabilis (4%)
- Klebsiella pneumoniae (3%)
- Candida species (2%)
Prevention of wound infection
- Exogenous
- Sterilisation of instruments, sutures etc
- Positive pressure ventilation of operating theatres
- Laminar air flow in high risk areas
- Exclusion of staff with infections
- Endogenous
- Skin preparation
- Mechanical bowel preparation
- Antibiotic prophylaxis
- Good surgical technique
Wound infection rates
- Risk of wound infection varies with type of surgery
- Infection rate can be reduced with antibiotic prophylaxis
Clean
- An incision though uninflamed tissue
- Elective surgery and the wound is primarily closed
- Only closed drainage systems are used
- No breach in aseptic technique
- No viscus opened
- Examples include mastectomy and hernia repair
- Infection rates typically 1-2%
Clean-contaminated
- Wound (that is otherwise clean) created at emergency surgery
- Reoperation via a clean incision with 7 days
- Viscus opened but no spillage of gut contents
- Minor break in aseptic technique
- Examples include right hemicolectomy and cholecystectomy
- Infection rate usually <10%
Contaminated
- Wounds left open
- Penetrating trauma less than 4 hours old
- Viscus opened with inflammation or spillage of contents
- Major break in sterile technique
- Examples include appendicectomy and stab wound
- Infection rate 15-20%
Dirty
- Presence of pus
- Intraperitoneal abscess formation or visceral perforation
- Penetrating trauma more than 4 hours old
- Examples include all perforated abdominal viscera
- Infection rate 40%
Antibiotic prophylaxis
- Prophylaxis is the use of antibiotics to prevent infection
- Treatment is their use to eradicate established sepsis.
- Prophylaxis important in:
- Surgery with a high incidence of post-operative infection (e.g.
colonic surgery)
- Surgery where infection would be hazardous (e.g. prosthetic
valves)
- Need to consider:
- The use of an appropriate antibiotic based on likely bacteria and
tissue penetration
- Cefuroxime & metronidazole for colonic surgery
- Benzylpenicillin for peripheral vascular surgery
- Timing and duration of administration
- Intravenous administration at induction
- Number of doses - usually no more than three doses
Bibliography
Horan T C, Gaynes R P, Martone W J,
Jarvis W R, Emon T G. CDC definitions of nosocomial surgical
site infections, 1992: a modification of CDC definitions of surgical
wound infections. Am J Infect Control 1992; 20:
271-274.
McDonald M,
Grabsch E, Marshall C,
Forbes A.
Single-versus multiple-dose antimicrobial prophylaxis for major surgery:
a systematic review.
Aust N Z J Surg 1998;
68: 388-396. |