Principles of Sterility

Definition of terms

Sterile means free of microorganisms including the pores while asepsis means absence of microorganisms that cause disease.  Sterile techniques are methods employed inside the operating room to prevent contamination of organisms throughout the surgical procedure. It is very important for nurses to know and understand the principles governing sterility to promote safety of the patient during operation.

When are sterile techniques used or applied?
  1. Preparation for an invasive procedure
  2. In preparation of the sterile team to handle sterile supplies and contact to the surgical site (gowning, gloving and scrubbing)
  3. Skin preparation and draping of the patient
  4. Sterility maintenance throughout the operation
Principles of Sterility

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

Drapes, basins, sponges are obtained from a stock room with sterile packages. The instruments used are sterilized and are placed in a sterile table. Any person who holds the sterile equipments should be very cautious to maintain sterility. One important consideration in implementing sterility is this: IF YOU ARE IN DOUBT ABOUT THE STERILITY OF A CERTAIN OBJECT, CONSIDER IT UNSTERILE. Any suspected or known unsterile items should not be placed the sterile field.

  • Any sterile package found in an unsterile or contaminated area is considered unsterile.
  • If the actual timing or sterilization procedure is undetermined and the nurse is unsure about the sterilization process, the equipments sterilized with the suspected procedure are considered contaminated.
  • A sterile table which has been touch or rubbed accidentally by an unsterile person or vice versa is no longer considered sterile.
  • If the packaging material is broken or has missing pieces it is no longer sterile.
  • Microorganisms can enter a packed sterile package when it is damp or wet. Thus, damp packages are unsterile.
  • A sterile package dropped on a floor is considered contaminated.

Principle Number 2: Sterile persons are gown and gloved.

When wearing a gown, the considered sterile area is the part where you can see in front down to the level of the sterile field. Thus, gowns are only considered sterile in front of the chest, sleeves above the elbow to the cuffs down to the level of the sterile field. Certain methods should be employed in the OR:

  • Gowning is not done on the sterile table to avoid dripping water onto the sterile equipments. Gloving and self-gowning should be done in a distinct sterile surface.
  • Stockinette cuffs of the gowns are absorbent and may retain moisture, thus making it a suitable area for bacteria or microorganisms to thrive in. because of the said principle, stockinette cuffs should be inserted beneath the sterile gloves.

Principle Number 3: Tables are only sterile at Table Level

  • Edges and sides of the table drape are considered contaminated. Below the table level is also considered unsterile.
  • Any sterile person who touches a part of the drape hanging below the table level is considered unsterile. Any object or equipment that drops below the table surface is considered contaminated.
  • In unfolding and placing a sterile drape any portion of that falls below the table surface is unsterile and should not be moved or touched or brought back up to the level of the table.
  • To prevent cords and tubing from sliding to the edge of the table, it should be fastened with a non-sharp device or object.

Principle Number 4: Sterile Persons Touch ONLY Sterile Items while Unsterile OR Personnel Touch Only Unsterile Items

  • Sterile OR personnel comes in direct contact with persons who wears gowns and gloves only. The items that they will touch are the sterile equipments. Any supply brought by an unsterile staff should transfer the item in a sterile manner.
  • Unsterile OR personnel (circulator), should not directly come in contact with a gowned and gloved person.

Principle Number 5: Unsterile persons avoid reaching over sterile field and sterile persons avoid touching or leaning over an unsterile area.

  • In cases where a solution has to be poured into a sterile basin, the unsterile OR personnel should only hold the lip of the bottle over the basin to prevent any contact with the sterile area.
  • To prevent the circulator from reaching over a sterile area when pouring solutions, the scrub person places the basin and glasses or any container for solutions near the edge of the table. This prevents the circulator from reaching over the sterile area by just standing near the edge of the table to fill the container with the liquid solution.
  • When surgeons perspire on their brows, he or she should to turn away from the sterile field and have the sweat removed by the circulator.
  • In draping or covering an unsterile table the scrub person drops the sterile drape at the center of the table while holding the fan-folded drape high and standing back from the table to protect the sterile gown.
  • Sterile gloves are protected by cuffing a drape. The sterile OR personnel should place the gloved hands inside the sterile part of the drape.
  • The scrub person unfolds the drape towards him or herself first to allow him or her to move closer to the table when working on the opposite side of the table since the first part of the unfolded drape now protects the sterile gown.

Principle Number 6: Edges of anything that encloses sterile contents are considered unsterile

  • Sterile supplies are packed. In opening sterile packages, the area within 1 inch from the edges is considered unsterile. Supplies are handled by the circulator. The upper portion of the package is flapped away from the self and turns the side under. In doing so, the end of the flaps is secured by the band of the circulator to prevent it from dangling loosely. The other flap is pulled towards the circulator; hence, the contents are exposed yet away from the unsterile hands.
  • To open a sterile package, the flaps on peel-open packages should be pulled not torn. The sterile contents should be flipped and lifted upward. The circulator should prevent the sterile contents to slide over the unsterile edges.
  • When lifting contents from packages, sterile personnel should lift the object straight up while holding their elbows high.
  • In cases where a sterile wrapper is used as a table cover instead of a drape, it should cover the entire table surface. Only the interior surface of the wrapper is considered sterile.
  • Sterile bottles when opened cannot be recap without contaminating the pouring edges. Thus, all contents must be used or in cases where there is still a solution left, it should be discarded.

Principle Number 7: Sterile field is set-up just before a surgical procedure

  • The longer a sterile item is exposed to air and environment, the higher the possibility of contamination.
  • The practice of covering a sterile set-up does is not in the best interest of the patient. Sterility cannot be guaranteed by just covering a sterile set-up, unless it is under a constant   surveillance.
  • Covering and uncovering a table may contaminate the sterile items.

Principle Number 8: Sterile areas are continuously kept in view.

  • Sterility cannot be guaranteed by just covering a sterile set-up, unless it is under a constant   surveillance.
  • Sterile persons should face the sterile area.
  • While waiting for the patient to come inside the OR, someone must stay in the sterile area to maintain vigilance on the sterile set-up.
  • Direct observation ensures sterility.

Principle Number 9: Sterile persons keep well within sterile area.

  • In draping the patient, sterile persons stay at a safe distance from the operating table to maintain sterility.
  • Movements in a sterile area are done by passing with each other back to back at a 360 degree turn.
  • When a sterile person passes by an unsterile person or area, he or she should turn back to maintain sterility.
  • When sterile persons pass by a sterile field or area, they face towards it.
  • To prevent contamination during movements in an area, the sterile person asks the unsterile personnel to step aside.
  • Movement inside the sterile area is kept at a minimum to avoid contamination.
  • Sterile persons stay inside the sterile field or area.

Principle Number 10: Sterile persons keep in contact with sterile areas to minimum.

Inside the operating room or within a sterile field the following are strictly observed:

  • Sterile persons avoid leaning over sterile tables or drapes.
  • Sterile personnel who lean over or sit on an unsterile area is considered contaminated.

Principle Number 11: Unsterile persons avoid sterile areas

  • Unsterile personnel should have the knowledge on the proximity to the sterile field. They must be aware of their distance to the sterile area or field to prevent contamination. A distance of at least 1 foot or 30 cm from a sterile field should be maintained and observed by the unsterile staff.
  • Unlike the sterile persons who turn their back towards the unsterile surface, unsterile personnel (circulator) face the sterile area (within 1 foot) when passing by to observe and maintain the distance and to avoid touching any sterile objects.
  • All activity of a circulator should be kept to a minimum.

Principle Number 12: Destruction of integrity of microbial barriers result in contamination

A sterile package’s integrity is destroyed by the following instances:

  • Perforation
  • Puncture
  • Strike-through – soaking of moisture through unsterile or sterile layers or vice versa.

Before opening a sterile package to be used in a certain procedure or operation the package should be checked thoroughly before opening. The following principles should also be employed in handling packages:

  • To prevent strike-through all sterile packages should be placed on a dry surface.
  • If any part of the package becomes damp or wet it is considered unsterile and should be discarded or re-sterilized.
  • Tables used for operation should be dried before draped.
  • If the sterile drape is soaked with a solution the wet area should be covered with an impermeable sterile towels or drape.
  • Sterile items should be placed not only in clean but also in dry areas.
  • In handling sterile packages, the hands should be dried first.
  • Air can also cause contamination. Thus, undue pressure on sterile packs should be avoided. This prevents the ejection of sterile air and the entry of unsterile air into the pack.

Principle Number 13: Microorganisms must be kept to irreducible minimum

Sterilization is the process of removing ALL microorganisms including the bacterial spores. However, not all things or area can be sterilized. The following principles are employed to employ sterile technique in:

  • Skin

Skin cannot be sterilized thus, it can be very good source of contamination in any operation. To prevent entrance of microorganism to the patient’s wound the following are done:

  1. Surgical hand washing
  2. Chemical antisepsis of the skin around the surgical site
  3. Gowning and gloving
  4. Application of sterile draping.
  • Air

Air contains dust, droplets and shedding that may cause contamination. Environmental control measures include:

  1. Movement around the sterile field is kept to a minimum.
  2. Drapes are not flipped and fanned to avoid the spread of dusts.
  3. Talking inside the operating room is kept to a minimum because moisture droplets are expelled with force into the mask when a person is talking.
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