TOPIC 3. ASEPSIS IN SURGERY – CONCEPT AND MAIN PRINCIPLES
1. Definition
Asepsis means the absence of pathogenic microorganisms in a field or environment. Surgical asepsis (sterile technique) aims to prevent microorganisms from entering a wound, sterile tissue or sterile body cavity. It differs from antisepsis, which uses antimicrobial agents on living tissue.
2. Sources and routes of contamination
Endogenous: the patient's own skin, mucosa or hollow-organ flora.
Exogenous: healthcare workers' hands, droplets, contaminated instruments, surfaces, equipment, air or solutions.
Direct contact: transfer from hands, gloves, instruments or dressings.
Droplet/airborne and environmental spread: depending on organism, procedure and environment.
Breaks in barriers: damaged gloves, wet or torn drapes, non-sterile instruments or touching a sterile item with a non-sterile object.
3. Core principles of surgical asepsis
- Only sterile items may contact a sterile field or sterile tissue.
- If sterility is uncertain, the item is considered contaminated and must be replaced.
- The sterile field must be prepared immediately before use and continuously observed.
- Sterile personnel touch only sterile items; non-sterile personnel and objects remain outside the sterile field.
- Keep the sterile field in view and above waist level; do not reach over it or turn away from it.
- Moisture can carry microorganisms through barriers (strike-through); wet sterile barriers are treated as contaminated.
- Edges of sterile packages/fields are considered non-sterile according to institutional policy.
- Minimise theatre traffic, unnecessary talking and door opening; maintain appropriate ventilation and cleaning standards.
- Perform hand hygiene at the required moments and surgical hand antisepsis before donning sterile gown and gloves.
- Use sterile gowns, gloves, drapes and instruments for procedures requiring a sterile field.
4. Cleaning, disinfection and sterilisation
5. Sterilisation methods
Steam sterilisation (autoclave): moist heat under pressure; reliable for heat- and moisture-resistant instruments. Correct cycle, loading, packaging and monitoring are essential.
Dry heat: used for selected heat-stable materials; requires validated time and temperature.
Ethylene oxide: low-temperature gas method for compatible heat-sensitive equipment; requires aeration because the gas is toxic.
Hydrogen peroxide/plasma or vapour systems: low-temperature methods for compatible devices; material and lumen limitations apply.
Filtration: removes microorganisms from heat-sensitive fluids or air; it is not sterilisation of the fluid by heat.
6. Monitoring and sterile storage
- Mechanical records confirm cycle parameters; chemical indicators show exposure to process conditions; biological indicators assess microbial killing using resistant spores.
- Packages should be dry, intact, correctly labelled and stored in clean, dry areas.
- Damaged, wet, open or expired packages are not used; event-related sterility policies apply.