7.1 Sterile Technique and Aseptic Principles

Sterile Technique and Aseptic Principles

The success of any surgical procedure depends heavily on minimizing the introduction of microorganisms into the patient’s body. For the Approved Veterinary Assistant (AVA), understanding the principles of asepsis and maintaining the sterile field is a primary responsibility that directly impacts patient recovery and prevents surgical site infections (SSIs).

Clean vs. Sterile: The Fundamental Distinction

In a veterinary hospital, environments and items are categorized as either clean or sterile:

• Clean: This refers to the reduction of the number of microorganisms to a safe level. Cleaning involves the removal of organic debris (blood, tissue, dirt) and washing with detergents or disinfectants. Clean items are sanitized but may still harbor viruses, fungi, or bacterial spores. Examples of clean procedures include dental scaling, routine ear cleaning, and abscess flushing.
• Sterile: This represents the complete destruction and absence of all living microorganisms, including highly resistant bacterial endospores (such as Bacillus and Clostridium species). Sterility is achieved through physical or chemical processes (like autoclaving or ethylene oxide gas). Items that enter sterile tissue or the vascular system (e.g., surgical scalpels, suture needles, orthopedic implants) must be sterile.

Clean vs. Sterile Comparison Table

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Aseptic Technique

Asepsis is the state of being free of pathogenic microorganisms. Aseptic technique describes the collective practices used to prevent contamination of a surgical site or sterile field. It is divided into:

1. Antisepsis: The use of chemical agents (antiseptics) on living tissue (like a patient's skin or a surgeon's hands) to inhibit or destroy microorganisms.
2. Disinfection: The use of chemical agents (disinfectants) on inanimate objects (like surgical tables, anesthesia machines, and floors) to destroy vegetative pathogens, though they usually do not kill spores.

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Principles of Maintaining the Sterile Field

The sterile field is the specific area surrounding a patient that has been prepared for a surgical procedure. It includes the draped patient, the sterile instrument table (Mayo stand), and the gowned and gloved surgical team. The AVA must strictly adhere to the following rules to maintain the integrity of this field:

• Defining the Sterile Gown Zone: Once scrubbed, gowned, and gloved, a team member is only sterile on the front of the gown from the chest to the level of the sterile field (table height). Sleeves are considered sterile from 2 inches above the elbow down to the cuffs. The back of the gown is never sterile, even if it is a wrap-around gown, because the scrubbed person cannot see it or guarantee it hasn't touched a non-sterile surface. The collar, shoulders, underarms, and cuffs (which accumulate sweat and touch skin) are also considered non-sterile.
• Hand Placement: Scrubbed personnel must keep their hands above waist level and below shoulder level. The safest position is to clasp hands together in front of the chest when not actively manipulating instruments. Dropping hands below the waist or raising them above the shoulders immediately contaminates them.
• Draping: Surgical drapes are placed over the patient and tables to create a barrier. Non-sterile personnel must never reach over a sterile draped area. When placing drapes, gowned personnel should stand back from the non-sterile table to prevent their gown from touching the edges.
• Movement in the Operating Room:
  • Sterile personnel must pass each other either face-to-face (maintaining eye contact to ensure front-of-gown contact only) or back-to-back (ensuring non-sterile back areas touch only non-sterile back areas).
  • Non-sterile personnel (like the circulating assistant) must maintain a minimum distance of 12 inches (1 foot) from the sterile field at all times. They must always face the sterile field when passing it to ensure they do not accidentally brush against it with their backs. They must never walk between two sterile fields.

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Identifying Contamination

Contamination occurs when a sterile item touches a non-sterile item or environment. The AVA must be hyper-vigilant in recognizing contamination events:

1. Direct Contact: Any contact between a sterile object and a non-sterile object instantly invalidates sterility. For example, if a sterile suture strand touches the non-sterile edge of the surgical table, it is contaminated.
2. Moisture Strike-Through: When a sterile drape or pack wrap becomes wet, liquid can wick bacteria from the non-sterile surface underneath (like the patient’s skin or the stainless-steel table) up into the sterile field. Any wet pack or drape is contaminated and must be replaced.
3. Physical Damage: Any wrap that is torn, punctured, has broken seals, or displays water stains must be deemed non-sterile.
4. Time and Environmental Exposure: If a sterile pack is left open and unattended, it is considered contaminated due to airborne microorganisms settling on the field.

• Golden Rule of Surgical Asepsis: “When in doubt, throw it out.” If there is any suspicion that a sterile item has been compromised, it must be treated as non-sterile.

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Operating Room Roles: Circulating vs. Sterile Assistant

The veterinary assistant plays a vital role in one of two capacities during surgery:

• Circulating Assistant (Non-Sterile): This assistant is not scrubbed-in. Their duties include:

  • Preparing the surgical suite (adjusting room temperature, wiping down surfaces with disinfectant).
  • Positioning and securing the anesthetized patient on the table.
  • Performing the initial skin prep (scrubbing) on the patient. This involves clipping the hair with a #40 clipper blade (being careful to avoid clipper burn which harbors bacteria) and performing a target surgical scrub. The scrub pattern starts at the proposed incision line and spirals outward in concentric circles, never returning to the center with the same sponge. This is repeated at least three times, alternating an antiseptic (like chlorhexidine or povidone-iodine) with a rinse agent (like isopropyl alcohol or sterile water).
  • Connecting non-sterile equipment (suction hoses, cautery cords, monitoring cables).
  • Opening sterile packs: When opening a sterile pack for the sterile field, the circulating assistant holds the pack away from their body, peels back the outermost flap away from themselves first, then peels back the side flaps, and finally peels the bottom flap toward their body. This ensures their non-sterile arm never crosses over the exposed sterile inner wrap. They then present the inner wrap or drop the item aseptically onto the sterile table.

• Sterile Assistant (Scrubbed-In): This assistant performs a surgical hand scrub (typically a 5-minute scrub starting at the fingers and moving down to the elbows, rinsing in one direction from fingertips to elbows), gowns, and gloves. Their duties include:

  • Arranging instruments on the Mayo stand.
  • Passing sterile instruments to the surgeon in the correct orientation (e.g., rings first, curve facing the palm of the surgeon's hand).
  • Providing tissue retraction and hemostasis (using sterile gauze sponges).
  • Cleaning blood off instruments during surgery using sterile saline-dampened gauze (never sterile water, which can cause red blood cells to lyse and damage instruments).
  • Performing sponge and instrument counts with the circulating assistant before the incision is closed to ensure no items are left inside the patient.

Operating Room Assistant Roles