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Preventing Transmission of Infectious Diseases
Overview
This chapter focuses on preventing the spread of infectious disease during anesthesia care, especially when equipment is used. Box 15.1 provides a glossary of common terminology.
BOX 15.1
Glossary
Airborne transmission: Spread of disease by means of liquid particles small and light enough to become suspended in air currents. These particles are termed droplet nuclei. Air currents can carry droplet nuclei a considerable distance from their source. Sneezing and coughing can aerosolize respiratory secretions, generating droplet nuclei. Procedures such as tracheal intubation and extubation, tracheal suctioning, and brochoscopy can also produce liquid particles small enough to be carried by air currents.
Asepsis: The absence of or the exclusion of potentially pathogenic microorganisms.
Aseptic technique: Aseptic technique comprises specific practices to minimize contamination by pathogens and to prevent their spread. It may include specific practices (hand hygiene, use of disinfectants) and methods of handling, administration, and storage.
Barriers: Equipment such as gloves, gowns, aprons, masks, or protective eyewear, which when worn can reduce the risk of exposure of the health care worker’s skin or mucous membranes to potentially infective materials.
Between-case transmission: The spread of an infectious agent from one individual to another.
Blood-borne transmission: This occurs when pathogens that normally are present in blood spread through contact with blood or infected body fluids.
Chemical disinfectants: Chemical substance that kills or deactivates microorganisms, especially when used on a reusable medical device. The Food and Drug Administration (FDA) regulates liquid chemical disinfectants. These may also be termed “liquid chemical sterilants” because they may sterilize an item when contact is prolonged, at a higher concentration, or under conditions that promote greater effectiveness.
Cleaning: Using enzymes, detergents, and/or mechanical action, the removal of visible soil or debris from the internal and external surfaces of equipment in preparation for safe handling and/or further disinfection or sterilization.
Clostridium difficile : C. difficile is a spore-forming, gram-positive anaerobic bacillus that produces endotoxin. It accounts for 15% to 25% of all episodes of antibiotic-associated diarrhea and can cause more serious diseases, such as pseudomembranous enterocolitis and toxic megacolon, both of which can be complicated by perforation, sepsis, and death. C. difficile spores are spread from patient to patient by contact transmission. Because alcohol does not kill C. difficile spores, use of soap and water is more efficacious than alcohol-based hand rubs. For environmental surface disinfection, consider using an EPA-registered germicide with a sporicidal claim after cleaning in accordance with label instructions; a hypochlorite solution, using household chlorine bleach, may also be appropriately diluted and used.
Contamination: The presence of microorganisms on an item or surface.
Contact transmission: Spread of a pathogen by means of immediate contact between the source and the host.
Critical device: An item that enters sterile tissue, cavities, or the vascular system. Such items must undergo sterilization prior to reuse.
Decontamination: The use of physical or chemical means to remove, inactivate, or destroy pathogens on a surface or item, such that transmission of infectious particles is no longer possible, and the surface or item is rendered safe for handling, use, or disposal.
Disinfection: The use of a chemical or physical process that eliminates virtually all recognized pathogenic microorganisms, but not necessarily all microbial forms (e.g., bacterial endospores), on inanimate objects.
Droplet: A liquid particle that is larger than 5 μm in diameter; generally, droplets will settle on surrounding surfaces within 3 feet of the source of their emanation.
Droplet nuclei: Liquid particles that are smaller than 5 μm in diameter. Droplet nuclei can become suspended in air currents and may travel on air currents for considerable distances.
Engineering controls: Controls designed to isolate or remove pathogens from the workplace (e.g., sharps disposal containers, airborne-infection isolation rooms).
Extended-spectrum beta lactamases: A rapidly evolving group of β-lactamases that are capable of hydrolyzing third-generation cephalosporins and aztreonam, but are inhibited by clavulanic acid.
Infectious agent: See Pathogen.
Hand hygiene: The single most important practice to reduce the transmission of infectious disease in health care settings. Refers to rubbing hands with an alcohol-based product or, if hands are visibly soiled, handwashing with water and plain or antiseptic soap.
Health care–associated infections (HAI’s): Infections associated with health care delivery in any setting, including hospitals, long-term care facilities, ambulatory settings, medical and dental offices, and home care.
High-level disinfection: A process that destroys all organisms except high levels of bacterial spores; the process may use a chemical disinfectant cleared for marketing by the FDA.
Highly transmissible disease: A pathogen capable of wide and uncontrollable spread in human populations.
Host: A person harboring another organism or organisms on or in itself; the person may become colonized or infected while harboring the organism.
Infectious disease: A clinically manifest disease of humans or animals resulting from a transmissible disease caused by the presence and growth of pathogenic biologic agents. Infectious pathogens include viruses, bacteria, fungi, protozoa, parasites, and prions (aberrant proteins).
Injection safety, safe injection practices: A set of measures taken to perform injections in an optimally safe manner for patients and health care personnel. Injection safety includes practices intended to prevent transmission of blood-borne pathogens during the use of syringes, cannulas such as needles, and medication and fluid containers.
Intermediate-level disinfection: Disinfection that kills mycobacteria, most viruses, and bacteria with a chemical germicide registered as a “tuberculocide” by the Environmental Protection Agency (EPA).
Low-level disinfection: Disinfection that kills some viruses, fungi and bacteria with a chemical germicide registered as a hospital disinfectant by the EPA.
Multidose medication vial: Medication container that holds more than one dose (e.g., insulin preparations, vaccines). Multidose vials used by anesthesia professionals may contain medications such as succinylcholine or neostigmine.
Noncritical device: An item that contacts intact skin; these items require reprocessing either by mid- or low-level disinfection techniques before re-use on another patient.
Pathogen or infectious agent: A biologic, physical, or chemical entity capable of causing disease. Biologic agents may be bacteria, viruses, fungi, protozoa, parasites, or prions.
Personal protective equipment (PPE): Specialized clothing or equipment worn by personnel for protection against a hazard, such as infectious agents.
Portal of entry: How an infectious agent enters the susceptible host.
Source: The location in or on which an infectious agent can survive but may or may not multiply. Colonized or infected patients often are sources for pathogens.
Semicritical device: Equipment that comes in contact with mucous membranes or nonintact skin during normal use. These items require reprocessing by high-level disinfection prior to reuse.
Single-dose vial: A single-use vial that contains medication or fluid for single-patient use; the contents do not include preservatives or bacteriostatic agents.
Source: The person on which a pathogen lives and propagates.
Spaulding scale: A classification system that divides patient care equipment and devices into three classes based on their intended use. Each of the three classes requires a different degree of decontamination: intermediate- or low-level disinfection, high-level disinfection, or sterilization.
Standard precautions: Infection prevention and control practices based on the principle that all blood, body fluids, secretions, excretions (except sweat), nonintact skin, and mucous membranes may contain transmissible infectious agents. Standard precautions apply to all patients, regardless of suspected or confirmed infection status, in any setting in which health care is delivered. Standard precautions include hand hygiene, safe injection practices, and use of barrier protection such as gloves, gowns, masks, eye protection, or face shields, depending on the anticipated exposure. Standard precautions also include the proper handling and cleaning, disinfection, and/or sterilization of reprocessed patient care devices.
Sterile: The absence of all microbial life, including both vegetative organisms and endospores.
Sterilization: The use of a physical or chemical procedure to destroy all microbial life, including highly resistant bacterial endospores.
Surgical site infection: An infection that occurs after surgery in the part of the body where the surgery took place. Surgical site infections can be superficial (skin only) or can involve tissues under the skin, the organs, or implanted material.
Susceptible host: A person who is vulnerable to develop infectious disease when exposed to a pathogen. Host vulnerability may arise from intrinsic factors (e.g., immunocompromise, an immature immune system, poor nutritional status) or from the fact that the usual barriers to infection (intact skin or mucous membranes) have been bypassed.
Transmission: Any mechanism by which a pathogen is spread from a source or reservoir to a host; the host may subsequently develop an infectious disease or become colonized.
Vector: An animate or inanimate object that carries (on or within itself) a pathogen and transmits the pathogen from a source to a host. A vector may be an organism (e.g., a mosquito or fly) or an object (e.g., a particle or a medical device).
Within-case transmission: The spread of a pathogen from a source to a susceptible host when the source and the susceptible host are the same person.
Work practice controls: Recommended procedures that reduce the likelihood of exposure to blood-borne pathogens by altering the manner in which a
task is performed (e.g., prohibiting recapping of needles by a two-handed technique).
Three factors are necessary to cause infection, as illustrated by the epidemiologic triangle ( Fig. 15.1 ). The first factor is a pathogen , the source of which may be an infected or colonized patient. The second factor is a susceptible host . Host susceptibility may arise from intrinsic factors (e.g., immunocompromise due to chemotherapy or radiation therapy, an immature immune system, poor nutritional status) or from the fact that the usual barriers to infection (intact skin or mucous membranes) are bypassed during medical care. For example, during laryngoscopy and intubation, the anesthesia professional contacts mucous membranes and may temporarily disrupt this barrier. During intravenous injections, medications and fluids are introduced directly into the normally sterile intravascular space.
The third factor is an intermediary mechanism enabling the transfer of the pathogen from the source to the vulnerable host. In the health care setting, pathogens are most commonly transferred by contact , airborne , or blood-borne means.
Spread by contact may occur due to improper reprocessing of reusable equipment. More commonly, contact transmission occurs when the hands of health care workers pick up pathogens after touching a colonized or infected patient. Hands subsequently transfer a pathogen to a vulnerable site on the same or a different patient. When the same patient serves as both the source of a pathogen and the host, then this is termed “within-case” transmission. Colonized or infected patients may serve as the source of their own infection when the hands of a health care worker transfer pathogens to a high-risk site, such as a portal connected to the patient’s intravenous access. These pathogens may then gain access to the intravascular space. When a colonized or infected patient serves as the source of a pathogen spread to another patient, then this is known as “between-case” transmission.
Airborne spread occurs by means of particles. Droplets are liquid particles larger than 5–10 μm in diameter. Due to their size, droplets fall rapidly to the floor or other surfaces, and their spread is limited to a three to six-foot radius from their source. Droplet nuclei are liquid particles less than 5 μm in diameter; particles of this size can remain suspended in air for longer time periods, allowing them to be transmitted over greater distances. Diseases spread by airborne droplet nuclei (e.g., measles, chickenpox, tuberculosis, smallpox, COVID-19, severe acute respiratory syndrome[SARS]), and Coronavirus Disease 2019 (COVID-19) are considered highly transmissible because they can travel for relatively long distances from their source. When liquid particles are produced, their size distribution depends on factors such as the exhaled air velocity and the diameter of the flow path. Sneezing and coughing can aerosolize liquid particles (i.e. generate particles small and light enough to become suspended in air currents). Procedures such as tracheal intubation and extubation, tracheal suctioning, and brochoscopy can also aerosolize respiratory secretions. The transmission of liquid particles depends upon various environmental factors, such as gravity, the direction and strength of local airflows, temperature and relative humidity. Gravity is the primary factor influencing the spread of droplets; however, smaller droplets may evaporate to become droplet nuclei, the spread of which is more affected by airflow.
Blood-borne infectious disease transmission in health care settings has been associated with the improper use of injection equipment. Frequently, these outbreaks were the result of either reusing a syringe or needle between patients or reusing a syringe or needle to access a medication or fluid container that was subsequently re-accessed and administered to another patient. Tissue transplantation and blood product transfusion were not a means of transmission in these cases. Delivery of anesthesia care was involved in many of these outbreaks.
When infections are acquired during medical care in a hospital or other health care facility, these are termed health care–associated infections (HAI’s). Formerly described as “nosocomial” or “hospital” infections, HAI’s are clinically important because they are the most common complication associated with hospital care and contribute significantly to patient morbidity and mortality. HAI’s do not include infections present or incubating at the time the patient is admitted; however, they may include infections diagnosed after discharge from a health care facility if not present on admission and evidence indicates that the infection was acquired during care. Infections incurred by health care workers during patient care (i.e., occupationally acquired infections) are also classified as HAI’s.
Staphylococci , Enterococci , and members of the family Enterobacteriaceae are classes of bacterial pathogens most commonly associated with HAI’s. Strains within these bacterial classes have developed resistance to one or more classes of antimicrobial agents. These include methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococcus (VRE) , and some gram-negative bacilli (e.g., Escherichia coli , Klebsiella pneumoniae , and Acinetobacter baumannii ) that produce extended spectrum beta-lactamases (ESBLs). Although the names imply resistance to only one agent, these pathogens often carry resistance to multiple classes of available antimicrobial agents. These highly resistant organisms deserve special attention in health care facilities.
Hand Hygiene
Timely and effective hand hygiene (HH) has frequently been cited as the single most important practice to reduce the transmission of infectious disease in health care settings. Hand hygiene refers to either handwashing with water and plain or antiseptic soap ( Fig.15.2 ) or rubbing hands with an alcohol-based product in the form of a gel, rinse, or foam ( Fig. 15.3 ) and then air-drying. Handwashing with soap and water is recommended when hands are visibly soiled or after care for a patient with known or suspected Clostridium difficile infection. In the absence of visible soiling and C. difficile exposure, approved alcohol-based hand rubs are recommended.
Proper HH consistently reduces bacterial transmission and the subsequent development of infections. The distinct five moments for HH, as developed by the World Health Organization (WHO), include: (1) before patient contact; (2) before aseptic tasks; (3) after exposure to body fluids; (4) after patient contact; and (5) after contact with patient surroundings.
Anesthesia professionals can easily become vectors for the transfer of pathogens from their hands to patients and the surrounding environment. During bedside anesthesia care, traditional handwashing with soap and water is not possible. When alcohol-based hand products are used, the actual time for HH is about 30 seconds.
During anesthesia care, multiple critical tasks are performed in a short amount of time, especially during induction and emergence. Changes in the patient’s condition may demand immediate and unanticipated access to items stored on anesthesia work surfaces or within drawers. Resuscitation may require multiple contacts between the patient, the anesthesia machine controls, and horizontal work surfaces. In many instances, performing HH at each “moment” would impair timely action and jeopardize patient safety. ,
On the contrary, the frequency of HH has a direct correlation to decreasing the overall environmental contamination. Simply increasing HH events to seven to eight events per hour has been shown to decrease overall contamination by four-fold. Alternative strategies are needed, such as simply performing HH at regular intervals during anesthesia care and using alcohol-based product dispensers that are attached to the anesthesia professional’s attire and conveniently accessed as needed.
Birnbach et al. investigated contamination in the anesthesia workspace by utilizing an invisible fluorescent marker used to identify high-touch surfaces. The dye was applied to a mannikin’s mouth before a simulated anesthetic induction. After the simulation, the residual dye was detected on multiple devices and environmental surfaces, including laryngoscopes, anesthesia machine dials, breathing circuits, anesthesia carts, and operating room beds. These investigators also used this fluorescent marker in a study designed to assess contamination following the use of a “double-glove” technique. Two pairs of gloves were donned during induction and the outer gloves were removed after induction and airway management. The proper use of this double-gloving technique was shown to dramatically reduce the contamination of frequently touched objects by a factor of ten. These investigators proposed double gloving as an alternative to reduce contamination when HH is not immediate or practical.
Because of glove leakage and self-contamination upon removal, wearing sterile or nonsterile single-layer gloves is not a substitute for proper HH. Gloves that have been used during patient care should be removed prior to touching equipment or the surrounding environment. In these cases, HH should be performed as soon as patient safety allows.
Equipment
Inadequate cleaning and disinfection of reusable anesthesia equipment (e.g., laryngoscopes, bronchoscopes) has led to outbreaks of infection. Improper cleaning and disinfection of laryngoscope blades between uses was determined as the cause of spread of gram-negative pathogens within a neonatal intensive care unit. , Even equipment that normally contacts only intact skin (e.g., blood pressure cuffs, stethoscopes) have been found to harbor pathogenic organisms and may serve as a vector to transmit infectious disease. ,
The Spaulding Classification: Overview
If the manufacturer’s instructions indicate that reprocessing is acceptable, the requirements for cleaning, disinfection, and sterilization are based on a classification system developed in the mid to late 1970s known as the Spaulding scale. Spaulding and colleagues categorized medical devices based on the risk of infection associated with their clinical use. The medical device category determines the method of reprocessing.
Equipment used on normally sterile body locations (e.g., tissue planes, the intravascular space, the peritoneal or pleural cavity, or the urinary bladder) is termed critical. Critical equipment such as syringes, needles, and percutaneous intravascular catheters, and urethral catheters are often labeled for single-patient use and are disposable. Critical equipment, if reusable (e.g., certain surgical instruments), must be cleaned and sterilized. Sterilization is a process by which all vegetative organisms and endospores are destroyed.
Equipment that contacts mucous membranes (e.g., respiratory or alimentary tract) or nonintact skin is defined as semicritical . If reusable, these devices (e.g., laryngoscope blades, laryngeal mask airways, transesophageal echocardiogram probes, bronchoscopes) require cleaning followed by high-level disinfection. High-level disinfection is a process by which all vegetative organisms are destroyed, but small numbers of residual bacterial endospores are acceptable. As in the case of critical devices, many semicritical devices (e.g., tracheal tubes, nasogastric tubes, and nasopharyngeal and oropharyngeal airways) are disposable.
Equipment that contacts unbroken skin on body surfaces is labeled noncritical. These devices require intermediate- or low-level disinfection and they include stethoscopes, blood pressure cuffs, and surfaces within the immediate patient care area.
Cleaning
Thorough cleaning is an important and essential first step in reprocessing equipment. Cleaning removes organic matter, salts, visible soiling, and lubricants on the external and internal surfaces of equipment; this residual debris may act as a barrier to prevent disinfectants and sterilants from contacting pathogens. Cleaning involves washing with a detergent or enzymatic agent and effective cleaning may require mechanical friction. Because desiccation makes cleaning organic debris more difficult, equipment should be presoaked or rinsed as soon as possible after use. Following cleaning, rinsing also is important because residual detergents may inactivate the chemicals used to disinfect or sterilize the items.
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