Patients have a reasonable expectation that anesthesia care will not expose them to infectious disease. Anesthesia professionals, as part of the health care team, have a responsibility to limit the potential for patients to acquire an infection while receiving care. This chapter discusses infection-prevention recommendations and practices as they apply to the anesthesia professional ( Box 20-1 ).
Asepsis: The absence or creation of the absence of potentially pathogenic microorganisms; preventing access by pathogens to any locus of potential infection.
Aseptic technique: Aseptic technique comprises specific, careful practices to minimize contamination by pathogens. It is utilized in the clinical setting to maximize and maintain asepsis, the absence of pathogens, to protect the patient from infection, and to prevent the spread of pathogens. For injection safety, this refers to handling, preparation, administration, and storage of medications, solutions, and injection equipment. This applies to all supplies used for injections and infusions, including medication vials, ampoules, syringes, needles, cannulas, fluid containers, intravenous administration tubing, and associated access ports and stopcocks.
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.
Cleaning: The removal, usually with detergents and mechanical action, of all adherent visible soil or debris from the surfaces, crevices, serrations, joints, and lumens of instruments, devices, and equipment by a manual or mechanical process that prepares the items for safe handling and/or further decontamination.
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.
Common vehicle: Contaminated material, product, or substance that serves as an intermediate means by which an infectious agent is introduced into a susceptible host through a suitable portal of entry.
Contamination: The presence of microorganisms on an item or surface.
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 blood-borne 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.
Engineering controls: Controls designed to isolate or remove pathogens from the workplace (e.g., sharps disposal containers, airborne-infection isolation rooms).
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, hand washing with water and plain or antiseptic soap.
Health care–associated infections (HAIs): 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 germicide cleared for marketing by the FDA.
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, health care personnel, and others. A safe injection does not harm the recipient, does not expose the provider to any avoidable risks, and does not result in waste that is dangerous for the community. Injection safety includes practices intended to prevent transmission of blood-borne pathogens between one patient and another, or between a health care worker and a patient, and to prevent harmful incidents such as needle-stick injuries.
Intermediate-level disinfection: Disinfection that kills mycobacteria, most viruses, and bacteria with a chemical germicide registered as a “tuberculocide” by the EPA.
Low-level disinfection: Disinfection that kills some viruses 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. When used in an immediate patient care setting, multidose vials should be used as if they are single-dose vials (i.e., for single-patient use only).
Noncritical device: An item that contacts intact skin and requires low-level disinfection.
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: The means by which an infectious agent enters the susceptible host.
Reservoir: Place in or on which an infectious agent can survive but may or may not multiply. Health care workers may serve as reservoirs for organisms known to cause health care–associated infections.
Semicritical device: An item that comes in contact with mucous membranes or nonintact skin and requires, at a minimum, high-level disinfection.
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.
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.
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 or animal who does not possess sufficient resistance to a particular infectious agent to prevent contracting an infection when exposed to the agent.
Transmission: Any mechanism by which a pathogen is spread by a source or reservoir to a person, and the person subsequently develops an infectious disease or evidence of infection.
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).
EPA, Environmental Protection Agency; FDA, Food and Drug Administration.
Health care–associated infections (HAIs), formerly termed nosocomial infections, are clinically important because they are the most common complication associated with hospital care. In 2002, investigators estimated an incidence of 1.7 million HAIs annually in the United States—1 of every 20 hospitalized patients—leading to 99,000 deaths.
It is important to note that these HAI estimates are extrapolations based on generalizations. Nonetheless, if these 2002 estimates had been accurate, the annual incidence of HAIs would have exceeded that of many reportable diseases, such as hepatitis C and meningococcal meningitis.
Some infections may be inevitable. Harbarth and colleagues estimate that only 20% of all HAIs are likely preventable by using the latest technologies and recommended medical practices. The Study on the Efficacy of Nosocomial Infection Control (SENIC), an investigation conducted from 1971 through 1976, suggested that 6% of nosocomial infections could be prevented by minimal infection control efforts, and that “well-organized and highly effective programs” could forestall 32%.
Nonetheless, some investigators have reported dramatic declines in the incidence of certain HAIs after implementing clinical processes derived from published recommendations. For example, after implementing a “bundle” of five initiatives designed to reduce the chance of infection, Pronovost and colleagues reported a 66% decrease in the rate of bloodstream infections associated with central venous catheters (CVCs). Prior to catheter insertion, the steps these researchers implemented included 1) avoiding the femoral site if possible; 2) performing proper hand hygiene; 3) preparing the skin with chlorhexidine; and 4) using full-barrier precautions prior to catheter insertion. After catheter insertion, the investigators provided ongoing surveillance of the need for the catheter and prompt removal when the central line was no longer essential for clinical care. Other studies have demonstrated that to achieve sustained results, these bundled practices as a whole must be continuously monitored for high compliance. Similar results were achieved using bundled practices to manage hospitalized patients with known or suspected infection with methicillin-resistant Staphylococcus aureus (MRSA).
Listed in order of estimated direct socioeconomic costs, the following are the five most prevalent HAIs, comprising more than 80% of those reported: 1) surgical site infection (SSI); 2) Clostridium difficile– associated infections (CDIs); 3) central line–associated bloodstream infections (CLABSIs); 4) ventilator-associated pneumonia (VAP); and 5) catheter-associated urinary tract infections (CAUTIs). Direct cost estimates do not take into account indirect costs, such as loss of productivity. HAIs are categorized as 1) those associated with a medical device (e.g., CLABSI [CVCs]; CAUTI [urinary bladder catheters]); 2) those associated with a medical procedure (e.g., VAP [endotracheal intubation and mechanical ventilation]; SSI [surgical procedure]); and, 3) those associated with antibiotic use, such as CDIs and infections from multidrug-resistant organisms such as MRSA and vancomycin-resistant Enterococcus (VRE).
By following recommended infection-prevention practices, the incidence of infection transmission between patients, between health care personnel and their patients, and from equipment and other inanimate objects to patients can be decreased or eliminated. Timely and effective hand hygiene has frequently been cited as the single most important practice to reduce the transmission of infectious disease in health care settings. After making observations and deductions from clinical practices associated with infectious outcomes, Ignaz Semmelweis, in the mid-1800s, introduced a simple handwashing regimen. The incidence of puerperal sepsis was dramatically reduced when clinicians washed their hands. Since this time, hand hygiene has been a key element of every infection-prevention strategy. Handwashing with soap and water is recommended when hands are visibly soiled or contaminated ( Fig. 20-1 ); hands may be decontaminated with an alcohol-based hand rub when they are not visibly soiled. Gloves do not substitute for or eliminate the need for hand hygiene. Compliance with the hand-hygiene guidelines published by the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) was one of The Joint Commission’s National Patient Safety Goals for hospitals in both 2011 and 2012.
Injection practices are associated with the use of needles, syringes, medication and fluid containers (ampules, vials, bags, bottles), and infusion supplies (administration sets, ports, connectors, and flush solutions). Recent outbreaks of blood-borne infectious disease have underscored the need for anesthesia professionals to reexamine injection practices. Between 1998 and 2008, there were 33 reported outbreaks associated with the iatrogenic transmission of hepatitis B virus (HBV) and hepatitis C virus (HCV) to patients. These outbreaks were not associated with blood-product transfusions or tissue transplantations; each was 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 reaccessed and administered to another patient. Delivery of anesthesia care was involved in 7 of the 33 outbreaks. In these 7 outbreaks associated with anesthesia professionals, more than 55,000 patients were identified “at risk,” and 144 patients acquired HBV or HCV infections.
Many of the devices, supplies, and equipment used in anesthesia care are labeled “single-use only.” After use for one patient, these items should be discarded and not reprocessed for reuse. For equipment and devices labeled as “reusable” by the manufacturer, anesthesia professionals should be familiar with reprocessing techniques appropriate for anesthesia equipment, including those applicable to the various components of the anesthesia machine.
Anesthesia professionals also should be knowledgeable of how infection prevention recommendations apply to the anesthesia work area, including anesthesia machines, work surfaces, and supply carts. Such knowledge can be extrapolated to other anesthesia care settings: offsite anesthetizing locations, critical care units, obstetric suites, pain management centers, and office-based surgery facilities. In all these settings, anesthesia professionals should be familiar with infection prevention recommendations and practices applicable to all patients (standard precautions) and those that apply to patients known or suspected to have infectious diseases of epidemiologic importance (expanded precautions). Diseases may be epidemiologically important because the infecting pathogen is either highly transmissible ( Mycobacterium tuberculosis, varicella) or multidrug-resistant, and therefore difficult to treat (MRSA, VRE).
In addition to standard precautions, anesthesia professionals should be familiar with infectious occupational hazards associated with anesthesia care and recommendations intended to limit the potential for acquiring these infections from patients. This discussion will focus on anesthesia work practices, device and facility designs, postexposure prophylaxis, and vaccination.
Hand hygiene refers to either handwashing with water and plain or antiseptic soap or rubbing hands with an alcohol-based product in the form of a gel, rinse, or foam ( Fig. 20-2 ) followed by air drying. In the absence of visible soiling, approved alcohol-based hand rubs are recommended. Hand hygiene should be performed before and after direct patient contact, before and after wearing gloves, after touching patient care equipment or surfaces in the patient environment, and before and after performing invasive procedures.
Standard Precautions and Safe Injection Practices
Because patient examination and medical history cannot reliably identify the presence of infectious disease, the CDC developed standard precautions to apply to all patients. Standard precautions require health care personnel to assume that all bodily fluids except sweat are potentially infectious regardless of the diagnosis or perceived risk of the patient. Barrier protection should be used whenever there may be contact with a patient’s nonintact skin, mucous membranes, and blood or other bodily fluids; this includes secretions and excretions, regardless of whether they contain visible blood.
Safe injection practices are the application of standard precautions to injection equipment and procedures. Whenever a needle, syringe, medication or fluid container (ampules, vials, bags, bottles), or infusion supply (administration sets and flush solutions) is used, the anesthesia professional must adhere to the principle that each item is intended for use on a single patient. A syringe or needle that contacts a patient’s blood or body fluids or any part of the administration set connected to a patient’s vascular (intravenous or arterial) access should not be reused, either for another patient or to reaccess a fluid or medication container. This is the principle behind the CDC’s public health campaign entitled the “One and Only Campaign” to promote the “one needle, one syringe, one time” concept ( Fig. 20-3 ). Safe injection practices also apply to the handling and disposal of injection devices and are designed to protect the anesthesia professional from accidental infection with blood-borne pathogens.
Two unsafe practices by anesthesia professionals have been associated with transmission of blood-borne pathogens: reusing a needle, cannula, or a syringe to administer intravenous (IV) medication to more than one patient and reaccessing a medication vial or flush preparation with a used needle or syringe, then subsequently administering medication or fluid from this contaminated container to another patient. Syringe and/or needle reuse may appear to be a glaring breach of basic infection prevention practices. Unfortunately, it is not universally understood that replacing only the needle on a contaminated syringe is not safe; it does not reliably eliminate the potential for transmission of pathogens from the residual syringe contents. Conversely, flushing a contaminated needle with saline and placing it on a new syringe is also not safe. A recent survey of clinicians in U.S. health care settings revealed that a small percentage of health care professionals continue to engage in syringe and needle reuse between patients.
Vials designated for multiple-dose use may be reaccessed to administer residual medication or fluid. If a syringe or needle used for patient care is used again to reaccess a medication or fluid container, contamination occurs, and gross visual inspection is not a reliable means of determining its presence. Medication vials labeled for multidose use contain bacteriostatic and/or bactericidal agents; however, these agents cannot prevent transmission of infection after contamination from external sources and have no antiviral action. Because blood-borne infections have been transmitted through medication or fluid containers contaminated when accessed by used needles and syringes, the CDC recommends that health care professionals refrain from reusing syringes, needles, and cannulas for any purpose, even to access a medication or solution container for use for the same patient.
The CDC gives anesthesia work areas and similarly intense bedside areas the term “immediate patient care areas” ( Fig. 20-4 ). In these areas, medications and fluids are sometimes prepared urgently for patients whose medical condition may be rapidly changing, and distracting events may increase the potential for these medications and fluids to become inadvertently contaminated. Within the immediate patient care area, the CDC recommends additional precautions. First, medication and fluid containers should be accessed only by a clean, sterile syringe, needle, or cannula. Second, medications and fluids used in these areas should be supplied as single-patient use only (single-dose) containers if possible. Medications in single-use-only containers, regardless of the location in which they are administered, should be discarded after access or when empty; residual medication should not be retained for later use. Third, if the manufacturer does not supply a medication in a single-dose container (e.g., neostigmine, succinylcholine), the multidose container should be discarded when empty or at the end of each patient’s anesthetic care. The latter procedure provides a second layer of safety to prevent the potential for transmission of blood-borne pathogens.
In accordance with these practices, two techniques are acceptable to the CDC to administer aliquots of medication or fluid to the same patient from a container labeled for multidose use. The entire contents of the container may be drawn into a sterile syringe, which may be used for sequential doses for the same patient. Alternatively, sequential doses may be obtained from the medication or fluid container for the same patient using a new, sterile syringe and needle or cannula for each access. The vial should be discarded when empty, or no later than the end of the procedure.
Prefilled syringes provide a well-labeled, ready-to-use medication that is sterile and stable for extended periods, often up to 6 to 8 weeks. The dosage supplied may be tailored to the end user. For example, a clinician may elect to have succinylcholine supplied either as 5 mL of a 20 mg/mL solution, for a total dose of 100 mg, or as 10 mL of a 20 mg/mL solution, for a total dose of 200 mg. Tamper-proof packaging makes it obvious when sterility has been compromised, and no supplies or handling is necessary to prepare the medication. Prefilled syringes are supplied by compounding pharmacies. The anesthesia professional should seek assurance that these sources follow current Good Manufacturing Practices and have a quality control program to test each lot for sterility.
Syringes, needles, medication and fluid containers, the internal surfaces of IV tubing, and any devices in contact with the vascular system or other normally sterile body areas (e.g., epidural, intrathecal, plexus, or peripheral nerve infusion catheters) are required to be sterile —that is, free from all bacteria, viruses, fungi, and bacterial spores—before use and maintained as such during use. These include stopcocks and other injection ports for medication injection, fluid infusion, and collection of blood samples and medication vial stoppers. All these represent potential entry sites for pathogens and should be kept free from contamination with a sterile cap and by wiping with 70% isopropyl alcohol during access. Hand hygiene is important before handling injection devices. All the aforementioned items are intended for a single patient and should be discarded after use.
Because of its higher specific gravity compared with IV fluid, blood can travel in a retrograde direction through tubing. A one-way valve does not prevent retrograde blood flow through IV administration tubing. In accordance with standard precautions, all syringes, needles, cannulas, injection equipment, medication and fluid containers, flush systems, and administration sets that contact a patient’s IV access should be discarded at the conclusion of the case except those that remain directly connected to the patient.
Multiday infusions should be purchased as premanufactured sterile products or compounded in the hospital pharmacy in accordance with United States Pharmacopoeia (USP) 797 guidelines. Anesthesia work areas do not meet these requirements, and medications mixed in this setting should be used or discarded within a period of hours. Infectious risk may be minimized by limiting the number of entries, including top-ups or bag changes, into the sterile infusion sets of continuous systems providing postoperative analgesia, such as epidural or peripheral nerve block infusion systems.
Upon further investigation of the largest outbreaks of blood-borne diseases associated with breaches of injection safety principles, the CDC published “Safe Injection Practices” recommendations ( Box 20-2 ). These recommendations were subsequently adopted by the Healthcare Infection Control Practices Advisory Committee (HICPAC) of the CDC and were incorporated into the 2007 standard precautions. These practices have also been adopted by the American Society of Anesthesiologists (ASA), The Joint Commission, the Association of Professionals in Infection Control and Epidemiology (APIC), the Safe Injection Global Network of the WHO, the Centers for Medicare and Medicaid Services (CMMS), and several state and municipal health departments.
The following apply to the use of sterile injection equipment, including syringes, needles, cannulas that may be used in place of needles, medication and fluid containers, and IV delivery systems.
Use aseptic technique to avoid contamination of sterile injection equipment.
Do not administer medications or other solutions from a syringe to multiple patients, even if the needle or cannula on the syringe is changed.
Needles, cannulas, and syringes are sterile, single-use items
Do not reuse syringes, needles, or cannulas:
For another patient
To access a medication or solution
Use single-dose vials whenever possible.
Use single-dose vials, instead of multidose vials, for parenteral medications or other solutions whenever possible.
Do not administer medications or other solutions from single-dose containers to multiple patients or combine the remaining contents in the containers for later use.
Multidose vials contain more than one dose of medication.
If multidose vials must be used:
Each time the multidose container is accessed, use a new sterile syringe and needle or cannula.
Store in accordance with the manufacturer’s recommendations and discard if sterility is compromised or questionable.
In the immediate patient care area ∗
∗ The Centers for Disease Control and Prevention (CDC) define “immediate patient care areas” as intense “bedside” settings, where medications and fluids are sometimes prepared urgently for patients whose medical condition may be changing rapidly. In these locations, the potential is higher for medications and fluids to contact body fluids, and health care professionals should exercise more stringent safety practices to prevent transmission of blood-borne pathogens. When possible, medications and fluids used in these settings should be supplied in single-patient-use only (single-dose) containers. Even if labeled for multiple-dose use, medication and fluid containers should be discarded when empty or after use for one patient.:
Discard multidose containers when empty or at the end of the case.
IV fluid infusion sets and administration and flush systems—including IV bags, tubing, and connectors—are single-use items.
Use for one patient only and dispose of appropriately after use.
Consider a syringe, needle, or cannula contaminated once it has contacted any part of the system; this includes all tubing, bags, ports, and stopcocks.
Do not use bags or bottles of IV solution as a common source of supply for multiple patients.
Infection control practices for neuraxial puncture procedures are critical.
Wear a surgical mask when inserting a needle, with or without a catheter, into the spinal canal or subdural space (e.g., spinal or epidural anesthesia, diagnostic lumbar puncture, intrathecal injections for imaging studies, or chemotherapy administration).
Safe injection practice recommendations also state that the proceduralist who inserts a needle, with or without a subsequent catheter, into the intrathecal or epidural space—such as for spinal or epidural anesthesia and/or analgesia, diagnostic lumbar puncture, myelography, or injection of intrathecal chemotherapeutic agents—should wear a face mask ( Fig. 20-5 ). This recommendation stems from investigations into eight cases of meningitis following lumbar puncture. Blood and/or cerebrospinal fluid cultures obtained from the affected patients yielded streptococcal species consistent with the oropharyngeal flora of the proceduralist. Aseptic technique had otherwise been followed, and contamination of the equipment and medications had been excluded.
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.
These devices—syringes, needles, stopcocks, IV tubing, percutaneous cardiac interventional catheters, surgical instruments, and urethral catheters—either penetrate the skin or are in contact with normally sterile areas such as the bloodstream, tissue planes, neural sheaths, peritoneal or pleural cavity, and urinary bladder. These devices are either disposable or are reprocessed by cleaning followed by sterilization techniques that destroy all endospores, viruses, and vegetative bacteria.
Semicritical items contact mucous membranes (e.g., respiratory or alimentary tract) or nonintact skin. These devices—gastrointestinal endoscopes, esophageal echocardiography and temperature probes, laryngoscope blades, endotracheal tubes, laryngeal mask airways, and nasopharyngeal and oropharyngeal airways—require at least cleaning followed by high-level disinfection. Sterilization is not necessary; small numbers of bacterial spores are acceptable.
Devices that are in contact with unbroken skin on body surfaces require intermediate- or low-level disinfection; these include stethoscopes, blood pressure cuffs, stretcher side rails, and surfaces within the immediate patient care area.
The Spaulding system has limitations, and oversimplification is both its strength and its weakness. First, delicate equipment that requires sterilization under the Spaulding system may be heat sensitive, precluding steam autoclave use. Ethylene oxide gas sterilization may require prolonged turnover and may not be suitable for reprocessing equipment needed for sequential cases. Without evidence of demonstrable differences in outcome, the choice between sterilization and high-level disinfection for reprocessing some of this equipment remains challenging.
Second, at the time the Spalding criteria were established, standard sterilization destroyed all known microorganisms and bacterial spores; however, in the late 1970s, prions were discovered. Prions are “misfolded” proteins that induce normal proteins to also fold abnormally. The word prion is derived from the words protein and infection . These pathogens affect the structure of the brain or other neural tissue; they are associated with currently untreatable and universally fatal transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease.
“Sterilizing” prions requires denaturation of the infectious protein structure such that the molecule is no longer able to exert its effect on adjacent proteins. Prions contain no nucleic acids and are resistant to standard sterilization techniques, including heat, radiation, and formalin. Effective prion decontamination relies on protein hydrolysis or destruction of the protein tertiary structure. First, the item is immersed in a sodium hydroxide (e.g., one normal NaOH) or a sodium hypochlorite (bleach) solution. Second, the item is steam autoclaved at 121° C to 134° C for 1 hour. Guidelines are available for reprocessing of heat-stable surgical instruments that have been used for patients with known or suspected spongiform prion disease. Single-use equipment should be used when possible; it may be necessary to sacrifice some equipment because of the extreme sterilization measures required to prevent prion transmission and the lack of treatment for the progressive and fatal diseases they cause.
Microorganisms can be categorized on a continuum according to their innate resistance to disinfectants. Figure 20-6 illustrates the variation in resistance to disinfectants among general classes of organisms. Resistance to disinfectants is primarily associated with permeability barriers, such as the cell wall or the outer coat of a spore. For example, Mycobacteria have impermeable cell walls that act as a barrier to chemical disinfectants; Mycobacteria therefore are the most resistant of the vegetative microorganisms. In general, nonenveloped viruses such as poliovirus are more resistant to disinfectants than enveloped viruses (human immunodeficiency virus [HIV], herpesvirus) and vegetative microorganisms except Mycobacteria . Resistance to disinfectants does not equate with resistance to antibiotics. Antibiotic-resistant bacteria, such as MRSA and VRE, are just as susceptible to sterilization and disinfection as nonresistant bacteria of the same species.
As previously discussed, the Spaulding criteria are designed to determine the appropriate reprocessing technique based on the intended clinical use of the device. Devices that contact normally sterile tissues, potential spaces, or fluid chambers—the bloodstream, tissue planes, neural structures, and urinary bladder—require sterilization. The majority of critical items used in the delivery of anesthesia are single-use items; they are disposed of after use and do not undergo reprocessing.
If a hospital chooses to reprocess a single-use device for reuse, the Food and Drug Administration (FDA) holds the hospital to the same standards as it would the original manufacturer of the device. In the anesthesia care setting, reprocessing of disposable devices is not recommended because of the potential for adverse outcomes from device malfunction associated with reprocessing.
Thorough cleaning is an important and essential first step in reprocessing equipment. Cleaning removes soil, debris, 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 to remove blood, mucus, and foreign material. Rinsing also is important because residual detergents may inactivate the chemicals used to disinfect or sterilize the items.
Sterilization is the destruction of all forms of microbial life, exclusive of prions, including bacterial spores. Sterilization can be accomplished by either high-temperature steam autoclaving or low-temperature gas (ethylene oxide or ozone) or hydrogen peroxide gas plasma exposure; low-temperature sterilization is also possible by liquid immersion in chemical sterilants. Manufacturers’ instructions regarding cleaning of equipment always should be followed to enable sterilization methods to be effective and to avoid damage to the integrity and/or function of the device.
If a device will tolerate high temperatures (typically 134° C; the manufacturer’s labeling or documentation will indicate this), it may be processed by steam autoclaving. Steam autoclaving often is the first choice because it is the fastest and most effective method available. At a given temperature, moist heat is more effective than dry heat in penetrating and destroying organisms. When water vaporizes to steam, the change in physical state requires heat energy (the enthalpy of evaporation). Furthermore, the increased pressure effectively increases the steam saturation temperature, or the boiling point of water, within the autoclave. At temperatures of 125° C or higher, saturated steam under pressure readily penetrates and destroys microorganisms, and the amount of time to achieve sterilization is significantly reduced compared with dry heat or boiling at atmospheric pressures. After steam autoclaving, items must be cooled before handling and use.
Ethylene oxide (EtO), an alkylating agent, is a penetrating and reactive gas capable of destroying all known viruses, bacteria, and fungi, including bacterial spores; it is compatible with most materials, even when repeatedly applied. However, it is highly flammable, toxic, and carcinogenic. Gas autoclaving with EtO is useful for items that cannot tolerate exposure to high temperatures and/or water vapor, such as plastic and rubber devices and fiberoptic endoscopes. EtO sterilization requires at least 24 hours for exposure and subsequent aeration; aeration is essential to eliminate residual gas that would otherwise leach out into the tissues and potentially cause chemical burns. EtO sterilizers and aerators need to be installed in separate, well-ventilated areas that have dedicated air-extraction systems to evacuate gas residues to the outside.
Heat-sensitive objects may also be treated with oxidative processes; these include systems that use hydrogen peroxide gas plasma or ozone gas. Hydrogen peroxide plasma sterilization units require no venting (the by-products are water vapor and oxygen); shorter cycle times also are possible, and they avoid the explosive and carcinogenic risks of EtO units. However, they are not compatible with certain cellulose, packaging, dressing, and paper products. Furthermore, the penetrating ability of hydrogen peroxide is not as good as EtO and ozone, so there are limitations on the length and diameter of lumens that can be effectively sterilized and on the volume and complexity of the load.
Ozone is a toxic and unstable gas that has strong oxidizing properties capable of destroying a wide range of pathogens. Ozone is generated within the sterilizer from medical-grade oxygen, so there is no need for handling hazardous chemicals. Waste ozone is destroyed by exposure to a simple catalyst that reverts it back to oxygen. Penetration is excellent, and the cycle time is relatively short (about 270 minutes). However, ozone is immediately hazardous to life and health, so continuous monitoring must be in place to provide a rapid warning in the event of a leak.
Sterilization may also be achieved by exposure to liquid chemical sterilants, such as glutaraldehyde, ortho-phthalaldehyde, or peracetic acid. The FDA maintains a list of liquid chemical sterilants and high-level disinfectants that can be used to reprocess heat-sensitive medical devices; this listing is posted on the Internet. Liquid chemical sterilants reliably produce sterility only if cleaning precedes treatment and strict guidelines are followed regarding the contact time, concentration, temperature, and pH of the sterilant.
Semicritical devices contact mucous membranes or nonintact skin and therefore require high-level disinfection. Such disinfection destroys all viruses, bacteria, and fungi but does not destroy high numbers of bacterial spores (small numbers are acceptable), and it does not destroy prions. Intact mucous membranes, such as those of the lungs and gastrointestinal tract, generally are resistant to infection by common bacterial spores, but they may be susceptible to infection by other pathogens. As with sterilization, meticulous cleaning and rinsing must precede the high-level disinfection process.
Devices that require high-level disinfection include, but are not limited to, laryngoscopes, face masks, laryngeal airways, oral/nasal airways, lightwands, bronchoscopes, endotracheal tubes, transesophageal echocardiography probes, esophageal/rectal temperature probes, and the external anesthesia breathing circuit (distal to the one-way valves). Examples of high-level disinfection techniques include pasteurization and liquid immersion in high-level disinfectants. Depending on the contact time, concentration, temperature, and pH, liquid chemical disinfectants may effectively sterilize a device. For this reason, liquid chemical disinfectants may also be referred to as liquid chemical sterilants. Chemical disinfectants and sterilants used to reprocess critical or semicritical medical devices are regulated by FDA. The Environmental Protection Agency (EPA) regulates disinfectants and sterilants used on environmental surfaces.
High-level disinfection of some medical devices may be difficult because of long, narrow lumens and crevices or hinges. More outbreaks involving the spread of infectious disease from patient to patient have been associated with improperly reprocessed endoscopes than with any other medical device. Consequently, guidelines have been established for reprocessing these devices. The challenge is to achieve high-level disinfection without compromising the functionality of the device. Before high-level disinfection, the endoscope must be leak tested. If the device fails leak testing, it cannot undergo cleaning without risking further damage, and the manufacturer should be contacted regarding repair.
High-level disinfection with a liquid chemical generally requires five important steps: 1) cleaning of all surfaces, which includes brushing and flushing internal channels with water and a detergent or enzymatic cleaner; 2) disinfection by immersion and perfusion of all accessible channels (exposure time will vary with the product); 3) rinsing with sterile, filtered, or high-quality potable tap water that meets federal standards; 4) drying by rinsing with alcohol, which may necessitate directing forced air through channels in the device; and 5) storage in a manner that prevents recontamination and promotes drying.
As an important first step, items that require high-level disinfection reprocessing should undergo mechanical cleaning of all surfaces, including internal channels, with a low-sudsing enzymatic detergent as soon as possible after use. This action prevents drying of organic material that may later interfere with the effectiveness of disinfection/sterilization. Organic material retained in the internal channel is a major cause of transmission of infectious disease related to endoscope reprocessing.
After thorough cleaning, endoscopes should undergo a minimum immersion processing of high-level disinfection with a chemical disinfectant. Disinfecting solution should also perfuse the channels within the scope throughout the processing. Glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde, and peracetic acid with hydrogen peroxide are reliable high-level disinfectants, provided the conditions for their optimal activity are met.
After all surfaces and internal channels of the device have been exposed to chemical disinfectant at the temperature and for the duration recommended, the item should be rinsed thoroughly to remove any residual disinfectant and to reduce the chance of mucous membrane irritation from residual chemicals. After rinsing, the item must be dried both internally and externally. Flushing 70% ethyl alcohol and compressed air through the channel will facilitate drying. The item should be stored (e.g., packaged) in a manner that prevents recontamination and promotes drying (e.g., hung vertically).
Pasteurization is a method of high-level disinfection named after Louis Pasteur, the French chemist who discovered bacteria. After cleaning, a device is submerged in water at 77° C for 30 minutes. The item must then be transferred to a drying cabinet; once dry, it is packaged in plastic bags.
Medications that come in contact with mucous membranes (eye lubricants, topical anesthetics) or those used in conjunction with devices that contact mucosal surfaces (lubricants and topical anesthetics applied to endotracheal tubes) also must be free of pathogens. Contamination cannot always be determined visually; the use of unit-dose packages of these items therefore is recommended.
Noncritical devices contact only intact skin and require intermediate- or low-level disinfection. Noncritical items include blood pressure cuffs, pulse oximeters, stethoscopes, cables, and surfaces of the anesthesia machine and cart. Intermediate-level disinfectants kill vegetative bacteria and fungi, mycobacteria, and most viruses but are not efficient against small, nonenveloped viruses such as human papilloma virus (HPV), and they are ineffective against bacterial spores. The EPA generally classifies intermediate-level disinfectants as tuberculocidals. Low-level disinfectants kill vegetative bacteria and some fungi and viruses but not mycobacteria or spores. The EPA registers these agents as hospital disinfectants. The manufacturers’ instructions should be followed regarding concentration and contact time for these products, such as chlorine-based products, phenols, 70% to 90% alcohols, and quaternary ammonium products. Many of these products are supplied as wipes for convenient use ( Fig. 20-7 ).