Principles of Asepsis: Definitions, Standards, and Regulatory Framework

What Is Asepsis and Why It Matters

Asepsis is the absence of pathogenic microorganisms in a defined space or on an object. In the operating room (OR), achieving and maintaining asepsis is the single most important strategy for preventing surgical site infections (SSIs). SSIs are among the most common and costly healthcare-associated infections; they prolong hospitalization, increase patient morbidity, and can be life-threatening. Every member of the surgical team shares responsibility for protecting the patient from contamination at all times.

Two levels of asepsis exist. Medical asepsis (clean technique) reduces the number and spread of microorganisms and is used outside the sterile field—for example, hand hygiene between patient contacts. Surgical asepsis (sterile technique) eliminates all microorganisms, including spores, from items that will contact the surgical wound or enter sterile body cavities. This lesson focuses on surgical asepsis.

The Association of Surgical Technologists (AST) Seven Principles of Aseptic Technique

The AST publishes Standards of Practice that define the professional expectations for surgical technologists. The seven principles of aseptic technique are the conceptual foundation of every sterile-field decision you will make in the OR. Learn them precisely—the CST exam and, more importantly, your patients depend on it.

Principle 1: Only sterile items are used within the sterile field.

Any item introduced into the sterile field must have been sterilized by an accepted method (steam, ethylene oxide, hydrogen peroxide gas plasma, or another validated process). Packages must be inspected for integrity, expiration or event-related sterility dating, and chemical indicator changes before opening. If sterility is in doubt, the item is considered contaminated—no exceptions.

Principle 2: Sterile persons are gowned and gloved.

Once a surgical team member has performed the surgical hand rub or scrub and been gowned and gloved, only the front of the gown from chest to table level and the gloved hands are considered sterile. The back of the gown, the axillary regions, and any area below the level of the sterile field are not sterile. Sterile persons must keep their hands in the sterile zone and avoid turning their backs to the sterile field.

Principle 3: Tables are sterile only at table level.

A draped table is sterile only at the horizontal surface. Items that fall or hang below table level are contaminated and must not be brought back up to the sterile field. This applies to sutures, instrument cords, and drape edges.

Principle 4: Sterile persons touch only sterile items or areas; unsterile persons touch only unsterile items or areas.

This principle defines the boundary between the sterile and non-sterile teams. The circulator (non-sterile) opens packages to the sterile field without reaching over it. The scrub (sterile) does not reach out of the sterile zone to retrieve items. Violations of this boundary are a primary source of contamination.

Principle 5: Unsterile persons avoid reaching over the sterile field; sterile persons avoid leaning over an unsterile area.

Physical barriers between sterile and non-sterile zones must be respected in three dimensions. Reaching over a sterile field introduces the risk of shedding particles, microorganisms, or perspiration into the field.

Principle 6: The edges of a sterile package or container are considered unsterile.

The border of a peel-pack, the lip and outside of a bottle, and the outermost inch of a sterile drape are unsterile. Contents must be delivered to the sterile field without touching these edges, or items must be flipped or poured in a way that avoids contamination of the inner sterile surface.

Principle 7: The sterile field is continuously monitored and maintained.

The sterile field must never be left unattended, covered and then uncovered, or allowed to become wet (strike-through contamination—moisture creates a pathway for microorganisms through drapes or wrappers). Any break in technique must be recognized and corrected immediately, even if it means replacing sterile items or re-gowning and re-gloving.

Regulatory and Accreditation Context

Surgical technologists practice within a layered framework of standards and oversight.

AST Standards of Practice are professional guidelines developed by surgical technologists for surgical technologists. They establish competency expectations and are widely cited in litigation, facility policy, and accreditation reviews. While they are not federal law, they represent the accepted standard of care for the profession.

AORN (Association of periOperative Registered Nurses) Guidelines for Perioperative Practice address sterile-field management, surgical attire, environmental controls, and instrument processing. AORN guidelines are evidence-based and updated regularly. In many ORs, institutional policy is built directly from AORN guidelines. The CST must be familiar with both AST and AORN documents and understand that they are complementary, not contradictory.

The Joint Commission (TJC) accredits hospitals and surgical facilities and surveys infection prevention practices, including sterile technique. Facilities that fail to meet TJC standards risk loss of Medicare and Medicaid reimbursement.

OSHA and CDC provide guidelines on bloodborne pathogen exposure and infection control that apply to all OR personnel.

State practice acts govern the specific scope of practice for surgical technologists and may require continuing education or certification as a condition of employment. Always know your state's requirements.

Safety Points

• When in doubt, throw it out. Assumed sterility is a patient safety failure. Challenging a break in technique is not insubordination—it is your professional and ethical obligation.
• Strike-through contamination is immediate. Wet drapes or wrappers must be removed from the sterile field right away.
• Never abandon the sterile field. If you must leave, the field must be broken down or another qualified sterile team member must take your place.
• Document breaks in technique per facility policy so the surgical team can assess patient risk.