Theatre

Theatre Layout and Design

Zones

  • Outer Zone: Reception
  • Clean Zone: Reception up to the theatre itself
  • Aseptic Zone: Theatres
  • Disposal Zone: Dirty corridor for disposal

Note: Zones should be linked via corridors that prevent cross-contamination.

Within Theatre

Control of Key Factors

  1. Temperature and Humidity:
    • Controlled via ventilation and thermostats.
    • Patients under anaesthesia are at risk of hypothermia.
    • Optimal theatre temperature: 25°C to prevent hypothermia; 19°C for surgical temperature.
    • Solutions: Bair Hugger, warmed fluids, blankets, airflow mattress.
    • Higher temperature needed for paediatric patients due to larger body surface area.
    • Optimal Humidity: Around 50%.
  2. Light:
    • Illumination at the wound site should be 40,000 lux.
    • Satellite lights: Positioned directly, although they generate heat and convection currents.

Bacterial Contamination in Theatre

Sources of Infection

  1. Patient
  2. Instruments
  3. Surgeon
  4. Airborne (95% of infections)

Airborne Contamination

  • Primarily due to people in the theatre (talking, shedding microorganisms, skin, and clothing).
  • 90% of airborne bacteria come from below neck level, especially from axillae and groins.

Measuring Bacterial Contamination of the Air

  • Measured in Colony Forming Units (CFU) or Bacteria Carrying Particles (BCP) per cubic meter.
  • Microbiological Volumetric Slit Sampler: Draws air over a culture plate, incubated for 48 hours, then counts colonies formed.

Frequency of Measurement

  • Plenum theatres: Every time they are refurbished.
  • Extra clean theatres: Every 3 months.

Acceptable CFU/m3 values

  • Plenum: <35 CFU & <1 CFU of Clostridium Perfringens and Staphylococcus Aureus.
  • Ultra-Clean: <20 CFU in the periphery and <10 CFU in the centre.

Ventilation

Key Points

  • The ideal air system should:
    • Provide a bacteria-free source of air.
    • Use positive pressure to displace contaminated air from the operative field.

How Air Enters the Theatre

  • Air enters via roof-level HEPA filters (removing particles of 0.5 microns with 99.9% efficiency).
  • Filters must be monitored regularly.

Ventilation Systems

Type of Flow Description Pros Cons
Plenum Positive pressure maintained by air entering via ceiling/wall diffusers and exiting via floor vents. Air changed 20x per hour. Reduces ingress of contaminated air Turbulence due to personnel movement, door openings. Each door opening introduces 2m3 of contaminated air.
Laminar Flow Uniform velocity, unidirectional air flow, usually vertical. Shown to reduce infection in some surgeries Equipment and personnel can deflect contaminated air towards the wound.

Types of Laminar Flow

  • Horizontal Laminar Flow:
    • HEPA filters on walls; airflow across the entire theatre.
    • Reduces infection in total hip replacement but increases infection in total knee replacement.
  • Vertical Laminar Flow:
    • Introduced by Charnley.
    • Room within a room concept, air enters through HEPA filters and moves downwards.
    • Most commonly used type.
    • Problems occur if personnel or equipment deflect airflow.
  • Exponential Flow (Ex Flow) System:
    • Overcomes vertical flow problems.
    • Air flows down and out in a trumpet shape.
    • Requires fewer air changes per hour.

Clinical Effects of Laminar Flow

  • MRC 1982 RCT: Found vertical laminar flow to be more effective in reducing wound contamination.
  • Charnley: Demonstrated a reduction in deep infections with laminar flow.

MRC Trial Findings on Reducing Deep Joint Sepsis

Method Effectiveness
Antibiotic Cement 11-fold reduction
Systemic Antibiotics 5-fold reduction
Ultra-clean air 2.5-fold reduction
Body Suits 2-fold reduction

Clothing

Ideal Clothing Characteristics

  • Prevent shedding of airborne bacteria.
  • Effective when wet.
  • Allows air and water vapor circulation.
Material Pore Size Features Disadvantages
Standard Cotton 80 microns Comfortable Poor bacterial migration prevention, strike-through problem.
Ventile 50 microns Reduced pore size Uncomfortable, not breathable.
Gore Tex 0.2 microns Breathable Heavy, expensive.
Disposable Non-Woven Variable Traps bacteria, prevents migration Single-use, expensive.

Body Exhaust Suits

  • Maintain negative pressure within the gown, preventing bacteria escape.

Surgical Drapes

  • Disposable Non-Woven Drapes: Commonly used to prevent bacterial migration.
  • Incision Drapes: No independent benefit shown, primarily used to keep body drapes attached to the skin.

Masks

  • Recommended for all personnel in orthopaedic procedures.
  • Prevent upper respiratory tract bacterial contamination (5% of airborne bacteria).
  • Evidence shows only those near the wound need masks.

Gloves

  • Protect both the wound and surgeon.
  • Glove Changing:
    • Before making an incision (due to contamination during prepping and draping).
    • Before handling implants (due to glove colonization during a procedure).
  • Double Gloving: 40% incidence of glove perforation in orthopaedic procedures, so double gloving is advised.
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