Surgical Asepsis

​Chapter 7 Surgical Asepsis & Sterility

The Real Sterile Deal. . . No BioBurden

 Methods of Sterilization

Sterilization is the complete elimination of all microorganisms, including spores. The most common method in hospitals is steam sterilization (autoclave), which uses high heat and pressurized steam.

For heat- or moisture-sensitive items, gas sterilization (ethylene oxide) is used, though it requires aeration to remove toxic residue.

Dry heat may be used for powders and oils, while low-temperature plasma or hydrogen peroxide systems provide safer, faster alternatives for delicate instruments.

Liquid chemical sterilants, such as glutaraldehyde or peracetic acid, are immersion options for scopes and items that cannot withstand high temperatures.

Biological and Air Removal Tests

Sterilizers must be tested regularly to ensure effectiveness. Biological indicators (BIs) contain highly resistant bacterial spores and confirm whether sterilization conditions were truly achieved; they are the gold standard.

Chemical indicators (CIs) change color to show exposure to sterilizing conditions, but do not guarantee sterility.

The Bowie-Dick test is a daily air removal test for pre-vacuum steam sterilizers, confirming that all air is removed so steam can penetrate the load evenly.

 Package Integrity

A sterile package must remain intact and dry. Sterile integrity is compromised if a package is torn, punctured, wet, opened, compressed, or past its expiration (if applicable).

External and internal chemical indicators must show proper exposure. Items should be stored in clean, dry, controlled environments. Any package in doubt should be discarded—“If in doubt, throw it out.”

​Sources of Contamination and Bioburden

Contamination may be exogenous (from personnel, environment, or instruments) or endogenous (from patient’s own flora).

Common sources include surgical team members’ skin, hair, or nares; environmental factors like air currents and dust; and contaminated or damaged instruments, especially those with rust or pitting.
Moisture is a significant risk—wet packages allow bacteria to wick through.

Reducing bioburden begins with proper cleaning, handling, and adherence to sterile technique.

​ Instrument Preparation

After surgery, instruments must be kept moist (sterile water or enzymatic solution) to prevent dried blood and tissue from adhering.

They are transported in a closed container to the decontamination area, where they are disassembled and either hand-cleaned or run through a washer-disinfector.

The goal is to remove gross soil and bioburden before sterilization. Instruments must be dried and inspected carefully before being wrapped or placed into trays for sterilization.

​Use of Liquid Disinfectants

Liquid disinfectants vary in strength and application.

High-level disinfectants (glutaraldehyde, peracetic acid) are used for scopes and heat-sensitive equipment, requiring specific contact times.

Intermediate and low-level disinfectants (such as quaternary ammonium or alcohols) are used for surfaces, furniture, and non-critical equipment.

Correct dilution, contact time, and adherence to manufacturer instructions for use (IFU) are critical for effectiveness.

​Room Turnover Between Surgeries

Room turnover focuses on preparing the OR for the next case quickly and safely.

Between procedures, all linen and trash are removed, surfaces around the sterile field are wiped down with approved disinfectants, and the floor in the immediate area is mopped.

Equipment and furniture are checked and restocked. The goal is efficiency without sacrificing asepsis, minimizing downtime while maintaining patient safety.

​End-of-Day Cleaning and Supply Return

At the end of the day, a terminal clean is performed.

This includes wiping down all horizontal and vertical surfaces, cleaning OR lights and tables, and moving furniture to disinfect underneath and around bases.

Floors are fully mopped, and all high-touch areas are disinfected. Supplies not used must be checked for package integrity and returned properly.

End-of-day cleaning resets the room to a fully sterile and safe condition for the next day.

​Sterilization Process Flow

Sterilization begins at the point of use. Instruments are kept moist and gross debris is wiped off. They are then sorted and disassembled to expose all surfaces.

Next, they move into cleaning, which may involve manual scrubbing, an ultrasonic cleaner (for fine debris), and/or a washer–decontaminator/washer–sterilizer.

Once cleaned, instruments are thoroughly dried and inspected for function and integrity. They are then assembled and wrapped or placed in rigid containers, ensuring proper arrangement for steam penetration.

After this, they undergo the sterilization cycle.

Finally, sterile packs are cooled, stored under controlled conditions, and released back to use when needed.

​Critical Steam Sterilization Parameters

For steam sterilization to be effective, four conditions must be met:

    •    Time: Sufficient exposure duration to kill all microbes, including spores.

    •    Temperature: Adequate heat to achieve sterilization.

    •    Moisture: Steam must contact all surfaces; dry heat alone is insufficient.

    •    Pressure: Needed to achieve temperatures above 212°F (100°C) for sterilization.

All four factors work together; if any is compromised, sterility is not assured.

​Steam Sterilization Minimum Settings

 •    Gravity Displacement Sterilizer:

    •    Temperature: 250°F (121°C)

    •    Pressure: 15–17 psi

    •    Time: Minimum of 30 minutes (dependent on load type)

    •    Dynamic Air Removal (Pre-vacuum) Sterilizer:

    •    Temperature: 270–275°F (132–135°C)

    •    Pressure: 27–30 psi

    •    Time: Minimum of 3–4 minutes exposure