Goals
The operating theatre should:
- reduce microbial contamination
- support safe anaesthesia and surgery
- permit efficient workflow
- maintain appropriate temperature, lighting and ventilation
- separate clean and contaminated pathways
Sources of contamination
Potential sources include:
- patient skin and endogenous flora
- theatre personnel
- instruments and equipment
- airborne particles
- movement and door opening
- contaminated surfaces or workflows
Zoning
Theatre suites are commonly organised into progressively controlled areas, with unrestricted access outside and increasingly restricted access near the operating room and sterile field.
The exact terminology varies between institutions. The principle is separation of:
- public or external circulation
- clean preparation areas
- operating rooms
- dirty utility and waste pathways
Ventilation
Modern theatres use controlled ventilation to:
- provide filtered air
- maintain airflow from cleaner to less-clean areas
- dilute airborne contamination
- control temperature and humidity
HEPA filtration removes very small airborne particles with high efficiency.
Positive pressure
Many operating rooms are maintained at positive pressure relative to adjacent spaces so that air tends to flow outward rather than allowing unfiltered corridor air to enter.
Unidirectional airflow
Unidirectional or laminar-flow systems deliver highly filtered air in a controlled direction over the operative zone.
They can reduce airborne particle counts, but infection prevention is multifactorial. Theatre design cannot replace:
- appropriate antibiotic prophylaxis
- skin preparation
- careful tissue handling
- sterility
- control of theatre traffic
- sound implant and wound technique
Theatre traffic
Opening doors and unnecessary movement disturb airflow and increase particle movement. Practical measures include:
- limiting traffic
- preparing equipment before incision
- minimising unnecessary door opening
- maintaining discipline around the sterile field
Hand antisepsis and gloves
Surgical hand preparation reduces microbial burden. Alcohol-based surgical hand rubs and approved antiseptic scrubs are both used according to local protocols.
Double gloving is commonly used in orthopaedic procedures because glove perforation is relatively frequent.
Temperature
Maintaining patient normothermia is important for perioperative safety. Staff comfort must be balanced with patient needs, particularly in children, frail patients and major exposure procedures.
Monitoring
Theatre environmental monitoring may assess:
- pressure relationships
- air changes and ventilation function
- filter performance
- particle or microbiological burden where required
Thresholds and engineering standards should follow current local regulations rather than older memorised numerical values.
Viva framework
Structure the answer around:
- sources of contamination
- zoning
- filtered positive-pressure ventilation
- staff behaviour and traffic
- sterility and patient factors
Air quality and theatre design
Airborne contamination depends on filtration, air exchanges, pressure relationships and human activity. Modern operating rooms use filtered air and are commonly kept at positive pressure relative to adjacent areas to reduce inward movement of contaminated corridor air.
Unidirectional airflow systems aim to move highly filtered air across the operative field in a controlled pattern. Their effect on particle counts is clearer than their effect on every category of surgical-site infection, because infection is determined by many factors beyond air quality.
Human contribution to contamination
People are a major source of airborne particles. Contamination increases with:
- staff numbers
- movement
- door opening
- poor gown or mask practice
- unnecessary traffic
Practical infection prevention therefore includes behavioural discipline, not just engineering controls.
Zoning and workflow
Theatre design should separate clean and contaminated activity. Instrument preparation, waste handling and staff/patient movement should avoid crossing dirty and clean pathways wherever possible.
The sterile field must be protected from:
- strike-through
- contamination from non-sterile surfaces
- unnecessary handling
- poorly planned movement of equipment
Surgical hand preparation and gloves
Hand preparation reduces transient and resident microbial burden. Double gloving is particularly relevant in orthopaedic surgery because bone edges and instruments increase glove perforation risk.
Changing outer gloves before implant handling or at selected procedure stages may be incorporated into local protocols.
Skin preparation and draping
Skin antisepsis reduces bacterial load but cannot sterilise skin completely. Hair should be removed only when necessary and preferably using clippers rather than razors to avoid microabrasion.
Drapes isolate the operative field but should not create a false sense of security if fluid tracks beneath or adhesive edges lift.
Antibiotic prophylaxis
Prophylactic antibiotics should achieve effective tissue concentration before contamination at incision. Repeat dosing may be needed in prolonged surgery or major blood loss depending on the agent.
Antibiotics complement good surgery; they do not compensate for devitalised tissue, excessive operative time or contamination.
Implant surgery
Implant procedures have a lower tolerance for contamination because bacteria can adhere to foreign material and establish biofilm. Measures that reduce inoculum are therefore particularly important.
Temperature and patient physiology
Maintaining normothermia supports coagulation, wound healing and general perioperative stability. Theatre temperature must balance surgical needs, staff comfort and patient warming strategies.
FRCS synthesis
When asked about theatre infection prevention, structure the answer around:
- patient preparation
- staff and traffic
- air and theatre engineering
- sterile technique
- antibiotic prophylaxis
- tissue handling and operative duration
- postoperative wound care
This shows that infection prevention is a system rather than a single intervention.