Sterilization Techniques (Encyclopedia of Nursing & Allied Health)
Sterilization techniques include all the means used to completely eliminate or destroy living microorganisms on any object, including tools used to test or treat patients.
The term microorganism, or microbe, refers to any single-celled living organism, including bacteria, viruses, and fungi. (Though viruses are not true single-celled organisms, medical science still usually classifies them as microorganisms.) Microbes can be transferred by direct contact or indirectly through a vehicle (like a surgical tool) or via the air the patient breathes. If favorable conditions for growth exist in the new host, microbes reproduce and establish colonies. Many of these microscopic organisms are normal inhabitants of the human body (called microflora). For example, varieties of the bacterium Staphylococcus are normal inhabitants of the skin and nasal passages, and many different species of bacteria live in the small and large intestine, aiding in the process of digestion.
However, many types of microorganisms are pathogenic (considered foreign to the host body) and, upon entering the body, cause infection when they either damage cells directly or release toxins that will eventually cause damage. The prevention of disease-causing microbes in a patient-care environment is generally accomplished through aseptic or sterile techniques. The goal is to create as germ-free an environment as possible, primarily through sterilization and the maintenance of sterile/nonsterile barriers.
Like foods sold in the grocery store, sterile medical and surgical solutions and some other equipment have expiration dates indicating when the product is no longer considered sterile. Although many hospitals consider sterile, prepackaged disposable materials to be sterile indefinitely if the packaging is undamaged, sterile goods must be examined carefully to ensure that there are no breaks in the integrity of the packaging or that the package has not gotten wet. Microbes are able to enter sterile goods through either breaks in the wrapping (the sterile barrier) or moisture. If the wrapper is no longer intact, or has been wet, sterile goods must be repackaged and resterilized.
Patients having invasive medical or surgical procedures are at risk for infection primarily from four sources:
- Infection is transferred from other people, including patients and health care providers. Such infection is called direct transmission, which usually occurs as a result of direct contact with skin or bodily fluids, including saliva, coughing, and spitting.
- Infection results from equipment or other objects that come in contact with the patient. This is called vehicle-borne infection because the microbe is transported from another place on some object or vehicle and introduced through a break in the skin or mucosal membranes. Primary examples are food poisoning caused by contaminated food items or infection caused by the use of non-sterile equipment in an invasive pro cedure like bronchoscopy or phlebotomy.
- Infection arises from the patient's own body, such as the possible contamination of a surgical site during intestinal resection if the patient's own fecal material contaminates the abdominal cavity contents.
- The air transports microbes. An example of air-borne infection is tuberculosis, in which bacteria are transmitted on air currents to others through coughing or spitting.
Managing as germ-free an environment as possible is necessary for surgical procedures and even minor medical treatments normally done in a doctor's office, such as suturing a laceration. Patients with conditions or under treatments that cause the immune system to be compromised are sometimes treated in an artificially created environment called reverse isolation. Leukemia patients, especially those on aggressive chemotherapy who receive bone marrow transplants and people with immunodeficiency disorders (which can lead to little or no natural defense against infection), are all potential candidates for reverse isolation procedures. Patients with AIDS (acquired immune deficiency syndrome) may be treated in an environment of isolation, both direct and reverse isolation for their protection, as well as the protection of caregivers. An extreme example of reverse isolation is the use of a sterilized plastic tent with filtered air circulation called an isolator. (Premature infants may be placed in special sterile plastic bassinets called an isolette.)
It has been known since the days of Florence Nightingale that clean surroundings are definitely less conducive to the growth of microorganisms than unclean ones. The creation of sterile environments always includes scrupulous cleanliness. The use of disinfectants in washing furniture, walls and floors, as well as in soaking medical equipment or other patient-care items is another important measure. Disinfectants are harsh chemical compounds described as bactericidal (capable of killing bacteria), or bacteriostatic (capable of stopping the growth or reproduction of bacteria). Some of these disinfectants may also be antiviral agents or antifungal. Disinfectants are usually too toxic to tissue to be used directly on the body. Antiseptics are chemical compounds that are also either bactericidal or bacteriostatic. But these are usually more diluted solutions and can safely be used in direct contact with human tissues. Common antiseptics include iodine, hydrogen peroxide, and thimerosal.
The importance of hand washing before and after the care of any patient cannot be over-stressed. It remains the simplest and most effective means of preventing infection. The Center for Disease Control (CDC) estimates that American hospitals produce two million hospital-borne infections (known as nonsocomial infections) each year, and approximately one-quarter of these are postoperative surgical incision infections. Postoperative infections result from breaks in sterile technique during surgery or breaks in aseptic technique during wound care. Further, CDC studies have shown that the average compliance with hand washing by health care providers from 1981 to 1999 has never risen above 50%. Proper procedure is for health care personnel to scrub their hands prior to and immediately after performing any procedure on a patient, regardless of whether latex gloves were worn or not. Gloves, as a barrier, can be breached via holes the size of pinpoints.
For both surgery and reverse isolation, staff are usually required to wear presterilized gloves, hair nets, masks, and gowns, with clean shoe coverings. Insertion of a urinary catheter, changing a surgical drain, cleaning a tracheotomy tube or doing a sterile dressing are all instances when health care providers wear gloves. They also create what is termed a sterile field or area that has been prepared with antiseptics or covered with impenetrable sterile drapes to reduce the likelihood of organism transfer.
Before surgical procedures, the operative site skin area is cleansed with an antiseptic solution, and sterile drapes are applied to the periphery. In the case of bowel surgery, laxatives and enemas are given prior to the surgery to remove as much fecal material as possible, thus limiting the amount of contamination from feces. When the bowel is clamped shut, all instruments, drapes, and sponges that may have come in contact with the patient are removed and replaced with sterile equipment before proceeding any further. In both surgical suites and in reverse isolation patients' rooms, air is passed through a special ventilation system that filters out microorganisms.
Five means are commonly used to sterilize objects in the patient's environment. These include:
- Moist heat is used via steaming or autoclaving (steaming under high pressure). Much like a pressure cooker used to can food at home and destroy bacteria, an autoclave circulates steam at temperatures of 260°F (120°C) at sustained pressure of 20 pounds per square inch for designated periods of time. All equipment used in carrying out medical or surgical procedures such as instruments, tubings (including catheters), bandages, and linens used for drapes are sterilized, usually in an autoclave.
- Ionizing and non-ionizing radiation is sometimes used. Ultraviolet light is a type of non-ionizing radiation used for items sensitive to heat.
- The passage of liquids through a filter sufficiently fine so as to trap microbes.
- Gas sterilization, usually using ethylene oxide, interferes with the metabolism and therefore the development of microorganisms and inhibits the growth of spores. It is effective in the sterilization of heat-sensitive items and penetrates deeply, but it has to be used with care since it is poisonous.
- Strong disinfectants are used primarily for instruments, such as thermometers and scopes that could not survive autoclaving. Medical equipment soaked in disinfectants to destroy microbes should be rinsed off prior to use due to the toxicity of many of the compounds used for disinfecting. Certain gasses such as ethylene oxide used for sterilization are extremely toxic to human beings and should be used with care.
In general, preparations include standard sterilization techniques for the patient, health care staff, and environment. Surgery patients requiring reverse isolation procedures should be told about the actions of microorganisms, including the ways they gain entry into the human body, the diseases that can be caused, and how sterilization techniques work to prevent infection. Hair is no longer routinely removed from the site of the surgical incision prior to surgery as the skin is a natural barrier to infection and shaving it often produces small skin breaks.
Aftercare following use of sterilized or surgically clean equipment would include monitoring patients for the signs and symptoms of infection, which usually occur within 48 to 71 hours. Signs and symptoms of infection include:
- inflammation, or redness and swelling at the site of infection, often accompanied by edema and erythema
- purulent or pus-like drainage from wounds
- abnormally elevated white blood count
- pain at the site of infection
There should be no complications from using proper sterilization and aseptic techniques. An allergy to any of the various antiseptics used to sterilize skin prior to surgery may produce dermatitis or irritation. If disinfectant used to clean instruments are not properly rinsed before use, an inflammatory response similar to a first-degree burn may result on surfaces contacted by the solution.
Proper sterilization techniques result in the prevention of infection. Sterilization techniques must be monitored and continually improved upon.
Health care team roles
All health care personnel are responsible for the primary means of preventing infection, which is hand washing. In the early days of nursing, sterilization of equipment and cleanliness of the patient's environment was the nurse's principal responsibility The nurse still bears responsibility or accountability in these areas even though they may be implemented by others.
- Sterilization technicians work in either the operating room area of a hospital or in the hospital's central supply. They receive special orientation and training in sterile techniques at the health care facility where they are employed. They are responsible for carrying out sterilization procedures and for monitoring sterile equipment conditions and expiration dates. Sometimes nurses or operating room technicians are responsible for providing sterile equipment.
- Some registered nurses (RNs) are certified in infection control and are required to keep statistical data on the incidence and types of infections in a health care facility. These RNs typically serve on infection control committees, along with physicians and clinical pharmacists.
- Clinical laboratory scientists have specialized training and must pass a state examination. They draw blood samples and culture wound drainage specimens, which are ordered by the physician to monitor patients for infection and for routine assessment of nonsocomial infection sources throughout a facility.
Bacteria group of single-celled organisms that can only be seen under a microscope and sometimes cause disease in other living things.
Fungiarasitic single-celled life forms that range from yeasts and mildews to mushrooms. Several minute or microscopic forms cause disease in other living things.
Ionizing radiationadiation that causes atoms or groups of atoms to carry a positive or negative electrical charge. Vital processes of life depend upon ions moving across cell membranes.
Non-ionizingadiation that does not cause atoms or groups of atoms to carry a positive or negative electrical charge. Vital processes of life depend upon ions moving across cell membranes.
Virus submicroscopic infective agent regarded as an extremely simple microorganism or extremely complex molecule capable of growth and multiplication only in living cells.
Berkow, Robert, et al., eds. Merck Manual of Diagnosis and Therapy, Home Edition. New York: Pocket Books, 1999.
Kozier, Barbara, et al. Fundamentals of Nursing: Concepts, Process and Practice. New Jersey: Prentice Hall, Inc., 2000.
Timby, Barbara K. Fundamental Skills and Concepts in Patient Care, 7th ed. Philadelphia, PA: J.P. Lippincott Co., 2001.
Nichols, Ronald Lee. "Preventing Surgical Site Infections: A Surgeon's Perspective." CDC 7, no 2 (March-April 2001).
Pittet, Didier. "Improving Adherence to Hand Hygiene Practice: A Multidisciplinary Approach." CDC 7, no 2 (March-April 2001).
Cleaning and Disinfection. Johns Hopkins Hospital, HEIC, <<a href="http://www.johnshopkins.org">http://www.johnshopkins.org>. (2000)
"Guidelines for Isolation Precautions in Hospitals." CDC <<a href="http://www.cdc.gov/ncidod/hip/isolat/isolat.htm">http://www.cdc.gov/ncidod/hip/isolat/isolat.htm>. (June 30, 2001).
Shelf Life of Sterile Packages. Johns Hopkins Hospital, HEIC, <<a href="http://www.johnshopkins.org">http://www.johnshopkins.org> (2000).
Joan M. Schonbeck