5.2 Aseptic Principles and Infection Control

Standard Precautions

Standard Precautions (formerly Universal Precautions) is the foundational infection control practice in the operating room: every patient is treated as potentially infectious, and the same barrier protections are used for every case regardless of the patient's diagnosis. Standard Precautions are mandated by OSHA's Bloodborne Pathogens Standard (29 CFR 1910.1030) and are the default behavior underlying every aseptic technique discussed in this chapter.

The Core Elements of Standard Precautions

1. Hand hygiene before and after every patient contact, before donning and after removing gloves, using alcohol-based hand rub or soap and water when hands are visibly soiled.
2. Personal protective equipment (PPE) appropriate to the task: surgical mask, eye protection or face shield, sterile gown and gloves, and shoe covers when required.
3. Respiratory hygiene and cough etiquette for any patient with respiratory symptoms.
4. Safe injection practices and sharps handling; needles are not recapped and go directly into a rigid sharps container.
5. Sterile technique for all surgical procedures and the maintenance of the sterile field throughout the case.
6. Patient placement with appropriate air-borne, contact, or droplet precautions as needed.

Standard Precautions in the Operating Room

The CSFA applies Standard Precautions to every case without exception. The preoperative briefing includes the patient's infection status (e.g., MRSA, C. difficile, VRE), but the protective behaviors do not change based on that status. The CSFA must:

• Don PPE in the correct sequence before entering the sterile field.
• Maintain the sterile field and immediately report any break in technique.
• Dispose of all contaminated sharps, gowns, gloves, and drapes according to Standard Precautions at the end of the case.
• Perform hand hygiene after glove removal, since surgical gloves have been shown to develop microperforations during use.

The Chain of Infection and Standard Precautions. The chain of infection has six links: the infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host. Standard Precautions break the chain at the mode of transmission (through barrier protection and hand hygiene) and at the portal of entry (through sterile technique and PPE).

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5.2 Aseptic Principles and Infection Control

The Foundation of Asepsis

Aseptic technique represents the core methodology by which the surgical team prevents the transmission of pathogenic microorganisms to the patient, thereby minimizing the risk of surgical site infections (SSIs). The Certified Surgical First Assistant (CSFA) is a guardian of the sterile field, expected to exhibit uncompromising surgical conscience—the ethical commitment to report and correct any break in sterile technique immediately, regardless of who caused it or whether it was observed by others.

Key Definitions:

• Sterility: The absolute and complete absence of all living microorganisms, including highly resistant bacterial spores. Sterility is an absolute state; an item is either completely sterile or it is unsterile.
• Asepsis: The absence of disease-causing microorganisms. Aseptic technique includes all practices utilized to create and maintain a sterile field.
• Disinfection: The process of destroying most pathogenic microorganisms on inanimate surfaces, but not necessarily bacterial spores.
• Antisepsis: The reduction of microbial populations on living tissue (e.g., patient skin prep, surgical scrub).

Sources of Pathogens in the OR

Understanding the origin of surgical pathogens is critical for implementing effective prevention strategies.

1. Endogenous Sources Endogenous pathogens originate from the patient's own body. The patient’s own skin flora, gastrointestinal tract, and respiratory tract are the most common sources of SSIs. Procedures involving incisions through heavily colonized areas (such as the perineum or oral cavity) carry higher intrinsic risks.

• Prevention: Preoperative showers with antimicrobial soap (chlorhexidine gluconate), effective intraoperative surgical skin preparation, prophylactic antibiotics, and maintaining normothermia.

2. Exogenous Sources Exogenous pathogens are introduced from the surgical environment or personnel.

• Personnel: The surgical team is a primary exogenous source. Pathogens are shed via squamous skin cells, respiratory droplets, and hair.
• Environment: Airborne dust, contaminated OR surfaces, and improperly processed instruments.
• Prevention: Adherence to strict OR attire policies, rigorous environmental cleaning, high quality air filtration, and meticulous instrument sterilization.

The Spaulding Classification System

Developed by Dr. Earle Spaulding, this system categorizes medical devices and instruments based on their intended use and the consequent level of processing required.

Critical Items

• Definition: Instruments or devices that enter sterile tissue, the vascular system, or body cavities.
• Processing Requirement: Must be completely sterile.
• Examples: Surgical instruments, orthopedic implants, cardiovascular catheters, hypodermic needles.

Semi-Critical Items

• Definition: Devices that come into contact with intact mucous membranes or non-intact skin but do not ordinarily penetrate sterile tissue.
• Processing Requirement: Minimum of high-level disinfection (HLD), though sterility is preferred if the item can withstand it. HLD kills all vegetative bacteria, fungi, and mycobacteria, but may not destroy high numbers of bacterial spores.
• Examples: Flexible endoscopes (e.g., colonoscopes, bronchoscopes), cystoscopes, respiratory therapy equipment, anesthesia circuits.

Non-Critical Items

• Definition: Items that contact only intact skin, which serves as an effective barrier to most microorganisms.
• Processing Requirement: Low-level or intermediate-level disinfection.
• Examples: Blood pressure cuffs, OR furniture, pulse oximeters, patient stretchers.

Verification of Sterility: Indicators

Sterilization is a multi-step process that relies heavily on accurate monitoring to ensure all parameters for microbial destruction have been met. Indicators do not replace the actual sterilization process; they verify that the conditions necessary for sterilization were achieved.

1. Physical (Mechanical) Indicators These are the gauges, dials, printouts, and digital displays on the sterilization equipment itself. They monitor and record time, temperature, and pressure during the cycle. While they verify that the machine reached the proper settings, they do not guarantee that the steam or sterilant actually penetrated the center of the surgical packs.

2. Chemical Indicators (CIs) Chemical indicators utilize heat-sensitive, chemically impregnated dyes that change color when exposed to specific sterilization conditions.

• Class 1 (Process Indicators): Used externally on packages (e.g., autoclave tape). A color change merely indicates that the package has been exposed to the sterilization process, distinguishing processed from unprocessed items. It does not guarantee sterility.
• Class 2 (Specialty Indicators): The most common is the Bowie-Dick test. This test is conducted daily in dynamic-air-removal (prevacuum) steam sterilizers to verify the complete evacuation of air from the chamber. Air entrapment prevents steam penetration.
• Class 5 (Integrating Indicators) & Class 6 (Emulating Indicators): Placed internally within packs. They react only when all critical parameters (time, temperature, and steam quality) have been achieved, providing a high degree of assurance that the sterilant penetrated the pack.

3. Biological Indicators (BIs) Biological indicators provide the ultimate, definitive proof that sterilization was achieved. BIs contain highly resistant, non-pathogenic bacterial spores. If the sterilization process kills these incredibly robust spores, it is safely assumed that all other less-resistant pathogens were also destroyed.

• Steam Sterilization: The BI uses spores of Geobacillus stearothermophilus. BIs must be incubated for a specific period (usually 24 hours, or less for rapid-readout types) at 55–60°C. If the liquid in the vial remains the original color (no acid production), the spores are dead, and the cycle is successful. If it turns yellow, the spores survived, indicating a failure.
• Ethylene Oxide (EtO) and Dry Heat: The BI uses spores of Bacillus atrophaeus.
• Frequency of Use: BIs should be used at least weekly for routine monitoring, but must be included in every load containing an implantable device. An implant should never be released for use until the BI results are confirmed negative.

Environmental Controls and SSI Prevention

The physical environment of the operating room is meticulously engineered to minimize airborne contamination.

Air Handling and Ventilation

• Air Exchanges: The OR requires a minimum of 20 total air exchanges per hour, with at least 4 of those being fresh outdoor air. High-efficiency particulate air (HEPA) filters are used to remove particles as small as 0.3 microns.
• Positive Pressure: The OR must maintain a positive atmospheric pressure relative to adjacent corridors. When OR doors are opened, the clean air flows outward, preventing contaminated air from the hallway from entering the sterile environment. Keep OR doors closed as much as possible.
• Laminar Airflow: Often used in orthopedic implant procedures, laminar airflow provides unidirectional, ultra-clean air directly over the sterile field, dramatically reducing the concentration of airborne particles.

Temperature and Humidity

• Temperature: Must be maintained between 68°F and 73°F (20°C to 23°C). This range provides a comfortable working environment for gowned personnel (reducing sweat contamination) while discouraging the rapid proliferation of bacteria.
• Humidity: Must be maintained between 20% and 60%. Humidity below 20% increases the risk of electrostatic discharge, which could ignite flammable substances or damage delicate electronic equipment. Humidity above 60% promotes bacterial and fungal growth and can compromise the integrity of sterile paper packaging through "strike-through" contamination.

Patient Optimization

• Normothermia: Maintaining the patient's core body temperature is critical. Hypothermia causes peripheral vasoconstriction, reducing tissue oxygenation and leukocyte mobility, significantly raising SSI risk.
• Hair Removal: If hair must be removed, it should be done using clippers immediately prior to surgery outside the OR, never with a razor, as razors create micro-abrasions that harbor bacteria.
• Antibiotic Prophylaxis: Prophylactic antibiotics should be administered within 60 minutes prior to the surgical incision to ensure peak tissue concentration during the procedure, and discontinued within 24 hours postoperatively to prevent antibiotic resistance.