Infection, Asepsis, and Sterile Techniques



In ancient times, demons and evil spirits were though to be the causes of pestilence and infections.  Hippocrates (460-377 BC), the great healer of his time irrigated wounds with wine or boiled water foreshadowing asepsis.  Galen (130-200 A.D.), a Greek that practiced medicine in Rome and was the most distinguished physician after Hippocrates boiled his surgical instruments used in the caring of wounded gladiators.  The writing of Hippocrates and Galen were the established authority for many centuries.  In the early to mid 1800's, people like Ignaz Semmelweis, Louis Pasteur, and Robert Koch introduced us to the world of microorganisms. Since this time, we have witnessed the invention of the first steam sterilizer (1886), the practice of passive and active immunization, and the use of antibiotics.  Today, we practice asepsis and sterile technique based on scientific principles.  Infection control, asepsis, body substance, and sterile technique should always be a part of patient care at any level.


               Infection- invasion of the body by pathogenic microorganisms and the reaction of tissues to their presence and to toxins generated by the organisms


Process of Infection

(1)        Involves three stages

(a)        Invasion

(b)        Localization/Containment

(c)        Resolution

(2)        Infection may revert back or become worse at any stage of the process

(3)        Identification of the infecting agent is essential so that specific antibiotic therapy may be initiated if appropriate

(4)        Invasion - introduction of pathogenic microorganisms into the tissue

(a)        May be result of violating aseptic or sterile technique during wound preparation or medical procedure.

(b)        Poor skin/ wound preparation of a contaminated wound

(c)        Other routes

(5)        Localization/Containment

(a)        The inflammatory response is the body's initial defense directed toward localization and containment of the infecting organism

(i)         RBCS, WBCS, and Macrophages infiltrate the tissue with possible abscess formation

(ii)        The body attempts to ward off the abscess by building a membrane encapsulating the tissue or cells

(6)        Resolution

(a)        Depends on immunological responses capable of overcoming the infectious process

(b)        Associated with drainage and removal of foreign material, including debris of bacteria and cells, lysis (disintegration) of microorganisms, reabsorption of exudate, and sloughing of necrotic tissue


Classification of infection

(1)        Infections are classified by source and etiology

(a)        Source

(i)         Community acquired - natural disease process that develop or were incubating prior to admission to the hospital

(ii)        Nosocomial - infection in hospitalized patients that were not present or incubating when the patient was admitted

(b)        Etiology

(i)         Bacterial - caused by bacteria

(ii)        Nonbacterial - All other causes such as viruses, fungi, athropod, etc.


Factors that influence wound healing

(1)        General health

(a)        Diabetes, alcoholism, malignancy and other chronic conditions upset normal physiology, delaying wound healing and making the patient more susceptible to infection

(b)        Remote focus infections

(c)        Smoking contributes to respiratory complications and causes change in mucosa and decreases blood flow

(2)        Age -- premature infants and geriatric patients are especially prone to infection due to deficient immune systems

(3)        Nutritional status

(a)        Wound healing is impaired by deficiencies in proteins, carbohydrates, zinc, and vitamins A, B, and K

(b)        Body weight--loss greater than 10% and protein energy malnutrition, compromise wound healing and increase the risk of infection

(c)        Patients with extensive burns, and multiple injuries will have increased caloric requirements

(4)        Obesity

(a)        Fat is the most vulnerable of all tissues to trauma and infection because of its poor vascularity

(b)        Patients with more than 100 lbs over ideal body weight will have some degree of cardiac decompensation and respiratory insufficiency

(5)        Fluid and electrolyte balance

(a)        Fever associated with infection will affect the bodies ability to maintain a normal balance

(b)        Fever can raise fluid requirements as much as 15% for each 1.5 degrees Fahrenheit of body temperature


Factors that contribute to infection -- Infection results from the interaction between three elements: organisms, tissues, and host defenses

(1)        Organism - size and virulence have to do with the microbes ability to cause disease

(2)        Tissue - the condition of the tissues is significant; necrotic, devitalized, avascular tissue or the presence of blood or foreign bodies provide an excellent media for pathogenic growth

(3)        Host defense - the general health of the patient influences resistance to microbial invasion



Aseptic Technique

Aseptic technique

Methods by which microbial contamination is prevented in the environment


Contact contamination plays a major role in bacterial spread.

Barriers are established to control the spread of microorganisms by:

(1)        Protecting sterile areas

(2)        Isolating surgical wounds

(3)        Keeping free microbes to a minimum



Types of barriers

(1)        Skin

(a)        Washing with soap (antimicrobial) before and after patient contact

(b)        Donning surgical attire


NOTE:            It is important to note that under emergency surgical conditions, all steps necessary to maintain asepsis are taken.


(c)        Covering abrasions and cuts on hands with gloves

(2)        Hair -- caps should be worn

(3)        Mouth and nose

(a)        A mask should be worn

(b)        People with respiratory tract infections should not work with open wounds

(c)        Talking should be kept to a minimum

(4)        Fomites - nonliving material such as bed linen that may transmit microorganisms

(a)        Should be packaged and stored properly

(b)        Clean and soiled supplies should be physically separated

(c)        Prompt decontamination of used equipment and reusable supplies




NOTE: Depending on the tactical or clinical environment, cleaning and disinfection should be according to local infection control policies.


(1)        Surfaces should not remain wet

(2)        Organic debris should be promptly removed and surfaces disinfected

(3)        Housekeeping equipment should be kept clean and dry

(4)        Appropriate waste receptacles should be used



Isolation precautions

(1)        Purpose

(a)        To prevent transmission of pathogenic microorganisms from the patient, and personnel to the patient

(b)        Isolation techniques separate infected patients and noninfected susceptible patients

(c)        When employing isolation techniques, hand washing remains the most important control measure

(2)        Methods of isolation

(a)        Category-specific isolation -- for patients with suspected or confirmed infectious disease transmitted by droplets via airborne route or enteric excretions, drainage, and secretions.

(b)        Disease-specific isolation -- precautions for contact with patients known to be infected with blood borne pathogen, such as HBV.

(c)        Body-substance isolation (BSI)-- incorporating universal precautions for contact with all moist body substances, including blood, urine, feces, saliva, sputum, tears, wound drainage, etc., body substance isolation is interaction driven, rather than diagnosis driven.


NOTE: Hand washing cannot be overemphasized; this means vigorous scrubbing with lathered soap followed by rinsing under a stream of water.




Sterile Technique

NOTE: Aseptic techniques control microorganisms in the environment, sterile techniques prevent transfer of microorganisms into the body tissues.


Need for sterile technique

(1)        Freshly incised or traumatized tissue is easily infected

(2)        Intact skin is the bodys first line of defense against infection

(3)        Any break in the integrity of the skin is a potential route of entry for infection

(4)        Items coming into contact with the skin or mucous membrane are a potential hazard

(a)        Critical -- items entering the body tissues underlying skin and mucous membrane must be sterile; they are handled to maintain sterility.

(b)        Semicritical -- sterility is less critical for items used on intact skin and mucous membrane, these items may have been cleaned, disinfected, or even sterilized prior to use, but sterility is not maintained.

(c)        Noncritical -- sterility is not maintained on these items, they will be used on intact skin and mucous membrane only.  These items will be terminally cleaned and shelved until the next use.


Principles of sterile technique

(1)        The patient is the center of the sterile field.  This includes the surface the patient is lying on, furniture, and properly attired personnel.

(2)        Sterile staff have scrubbed, gowned, and gloved

(3)        Only sterile items may be used within the sterile field

(a)        Items may be obtained commercially sterilized, or be locally sterilized by CMS

(b)        Each person that dispenses a sterile item must be sure of its sterility and protect its sterility until it is used


NOTE: If you have a question about the sterility of an item, consider it unsterile!  When in doubt, throw it out!


(4)        Gowns are considered sterile only from the waist to the shoulder-level in the front, and the sleeves

(5)        Sterile people keep their hands in sight and above waist level

(6)        Hands are kept away from the face, elbows are kept at the sides

(7)        Items dropped below waist level will be considered unsterile

(8)        Tables are considered sterile at table level only

(a)        Only the top of a sterile draped table is considered sterile (edges and sides are not)

(b)        Anything falling or extending over the edge of the table is considered unsterile

(c)        Outer 1 inch edge of table top is considered unsterile

(9)        Only persons that are sterile touch sterile items

(10)      Unsterile persons do not reach over a sterile field; sterile persons avoid leaning over a sterile field.

(11)      The sterile field is created as close as possible to the time of use.  The degree of contamination is proportional to the time the sterile items are exposed to the environment.

(12)      Sterile areas are continuously kept in view.  Avoid turning your back to a sterile field, or walking between two sterile fields.

(13)      Integrity of the sterile package is destroyed if it is perforated, punctured, or contaminated with moisture

(14)      Microorganisms must be kept to an irreducible minimum

(a)        Skin cannot be sterilized and is a potential source of contamination.  Scrubbing, gowning, and gloving reduce the possibility of contamination to a minimum.

(b)        Where some areas cannot be scrubbed (i.e., mouth, nose, throat), masking reduces the risk of contamination

(c)        Air is contaminated by dust and droplets.  Environmental control measures must be employed to control this source of contamination.




Sterility should never be taken for granted and there should be no compromise. It is the responsibility of each health care provider to ensure to the best of their ability that aseptic and sterile techniques are being maintained. Infection control is a consideration in any patient care environment and every individual is accountable.