Infectious Disease Considerations for the Operating Room

THE RABBIT HOLE THAT IS THE PERIOPERATIVE ENVIRONMENT is not well understood by the majority of our general pediatric colleagues. Similarly, the rabbit hole of the primary care clinic or the pediatric inpatient ward is not well understood by the majority of our anesthesiology colleagues. A pediatric patient may repeatedly enter the rabbit hole over the course of a hospital admission, a journey fraught with dangers of airway mishaps, respiratory and/or cardiac arrests, hemorrhage, profound anxiety and stress experienced by the young patient and his or her family, as well as infection risks.

Anesthesiologists have long been patient safety advocates. It is not surprising that anesthesia providers in the 21st century have taken on increasing responsibility for preventing health care–associated infections (HAIs), including surgical site infections (SSIs). Anesthesia providers practice in a nonsterile environment within the operating room (OR) and frequently contact areas of the patient known to have a high rate of contamination such as the axilla, nares, and pharynx. There are two recognized but poorly implemented interventions: preoperative patient skin and other bacterial reservoir decontamination and hand hygiene by anesthesia providers.

Anesthesia providers have an impact on bacterial transmission and infection rates. Specifically, anesthesiologists are known to contaminate their work environment within the OR. Contamination of the work environment includes contamination of intravenous (IV) access ports. Without encouragement, anesthesiologists perform hand hygiene less frequently than once per hour during a case, but with reminders, the rate of hand hygiene is more frequent. Improved hand hygiene reduces contamination of the work area and IV access ports from 32% to 8%, which in turn significantly reduces HAIs.

The transmission of infection depends on the presence of three interconnected elements: a causative agent, a source, and a mode of transmission ( Fig. 50.1 ). Understanding the characteristics of each element provides the practicing anesthesiologist with methods to protect susceptible patients and themselves to avoid spreading infection.

There has always been concern about the transmission of infectious agents to the patient from the anesthesiologist and vice versa. In addition, there are many sites within the hospital environment where moist or desiccated organic material with the ability to host potentially pathogenic microbes may survive for extended periods of time ( Table 50.1 ) ; some may even resist the usual cleaning and disinfection techniques. Their transmission from the source to the host may occur via indirect nonapparent mechanisms (e.g., most commonly through hand contact).

TABLE 50.1

Nosocomial Pathogens and Environmental Contamination

Modified from Hota B. Contamination, disinfection, and cross-colonization: are hospital surfaces reservoirs for nosocomial infection? Clin Infect Dis. 2004;39(8):1182–1189.

Pathogen	Types of Environmental Contamination	Organism Survival Time
Influenza virus	Aerosolization after cleaning; fomites	24–48 hours on nonporous surfaces
Parainfluenza virus	Clothes and nonporous surfaces	10 hours on nonporous surfaces; 6 hours on clothes
Norovirus	Extensive environmental contamination, possible aerosolization	≤14 days on fecal specimens, ≤12 days on carpets
Hepatitis B virus	Environmental contamination with blood	7 days
Coronavirus-SARS	Possible results from emergency department specimens; super-spreading events	24–72 hours on fomites and fecal specimens
Candida	Fomite contamination	3 days for Candida albicans and 14 days for Candida parapsilosis
Clostridium difficile	Extensive environmental contamination	5 months on hospital floors
Pseudomonas aeruginosa	Drain sink contamination	7 hours on glass slides
Acinetobacter baumannii	Extensive environmental contamination	33 hours on laminated plastic surfaces
MRSA	Extensively contaminated burn units	≤9 weeks after drying; 2 days on laminated plastic surfaces
VRE	Extensive environmental contamination	≤58 days on working surfaces

MRSA, Methicillin-resistant Staphylococcus aureus; SARS, severe acute respiratory syndrome; VRE, vancomycin-resistant enterococci.

Causative Agent

The infectious vector may be any microorganism capable of causing infection. The pathogenicity is the ability to induce disease, which is characterized by its virulence (infection severity, determined by the germ morbidity and mortality rates) and the level of invasiveness (capacity to invade tissues). No microorganism is completely avirulent. An organism may have a very low level of virulence, but if the host (i.e., patient or health care provider) is highly susceptible, infection by the organism may cause disease. The risk of infection increases with the infecting dose (the number of organisms available to induce disease), the reservoir (the site where the organisms reside and multiply), and the infection source (the site from where it is transmitted to a susceptible host either directly or indirectly through an intermediary object). The infection source may be a human (e.g., health care providers, children, visitors, housekeeping personnel) with a symptomatic or an asymptomatic infection during the incubation period. The source may also be temporarily or permanently colonized (the most frequently colonized tissues are the skin, digestive, and respiratory tracts).

Host

The presence of a susceptible host is an important element in the chain of infection that paradoxically results from advances in current medical therapies and technology (e.g., children undergoing organ transplantation or chemotherapy, or extremely premature neonates) and the presence of children with diseases that compromise their immune systems (e.g., AIDS, tuberculosis, malnutrition, or burns). The organism may enter the host through the skin, mucous membranes, lungs, gastrointestinal tract, genitourinary tract, or the bloodstream via IV solutions, after laryngoscopy, or from surgical wounds. Organisms may also infect the individual because of work accidents with cutting or piercing devices. The development of infection is influenced by the host defense mechanisms that may be classified as either nonspecific or specific:

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Nonspecific defense mechanisms include the skin, mucous membranes, secretions, excretions, enzymes, inflammatory responses, genetic factors, hormonal responses, nutritional status, behavior patterns, and the presence of other diseases.
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Specific defense mechanisms or immunity may occur because of exposure to an infectious agent (antibody formation) or through placental transfer of antibodies; artificial defenses may be acquired through vaccines, toxoids, or exogenously administered immunoglobulins.

Methods of Transmission

Microorganisms are transmitted in the hospital environment through a number of different routes; the same microorganism may also be transmitted via more than one route. In the OR, the three main routes of transmission are through the air and by direct and indirect contact.

Air Transmission

Airborne infections that may infect susceptible hosts are transmitted via two mechanisms: droplets and droplet nuclei.

Droplets

Droplet contamination is considered a direct transmission of organisms because there is a direct transfer of microorganisms from the colonized or infected person to the host. This generally occurs with particles whose diameters are greater than 5 µm that are expelled from an individual's mouth or nose, mainly during sneezing, coughing, talking, or during procedures such as suction, laryngoscopy, and bronchoscopy ( Fig. 50.2 ). Transmission occurs when the microorganism-containing droplets, expelled or shed by the infected person (source), are propelled a short distance (usually not exceeding 60 cm or about 2 feet through the air) and deposited on the host's conjunctivae or oral or nasal mucous membranes. Droplets remain suspended for only a short duration and distance from the source, but this may be affected by temperature, humidity, force of expulsion, and air currents. Larger particle sizes contact the mucosa of the upper airway, whereas aerosols are capable of penetrating into the lower respiratory tract. Infectious agents vary in their affinity for receptors in different regions of the respiratory tract. When a person coughs, the exhaled air may reach a speed of up to 965 km/hour (600 mph). However, because the droplets are relatively large, they tend to descend quickly and remain suspended in the air for a very brief period, thus obviating the need for special handling procedures for the OR air. Examples of droplet-borne diseases include influenza, respiratory syncytial virus (RSV), severe acute respiratory syndrome (SARS), diphtheria, Haemophilus influenzae, Neisseria meningitidis, mumps, pertussis, rhinovirus, rubella, and Ebola. Droplet precautions include communication of infectious risk between caregivers, single room isolation, gown, glove, mask, and eye protection. Patients undergoing surgery must be brought directly to the OR and recover in isolation. Some medical interventions (intubation, extubation, biphasic airway pressure [BiPAP], continuous positive airway pressure [CPAP], bronchoscopy, sputum induction, open airway suction) are categorized as aerosol-generating procedures. When performing an aerosol-generating procedure on a patient with an infectious disease that can be transmitted through droplets, the recommendation is to maximize protection by using airborne precautions.

Droplet Nuclei

Droplet nuclei result from the evaporation of droplets while suspended in the air. Unlike droplets, the nuclei have an outer layer of desiccated organic material and a very small diameter (1–5 µm) and remain suspended in air indefinitely. The microorganisms contained within these nuclei may be spread by air drafts over great distances, depending on the environmental conditions (dry and cold atmosphere, with limited or no exposure to sunlight favoring the spread). In contrast to droplets, which are deposited on mucous membranes, droplet nuclei may enter the susceptible host by inhalation; examples of droplet nuclei–borne diseases include tuberculosis, varicella, and measles, zoster, smallpox, SARS, and Middle Eastern respiratory syndrome.

Contact Transmission

Direct and indirect contacts are the most significant and frequent methods of hospital infection transmission.

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