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Environmental decontamination and isolation strategies in the ICU 

Environmental decontamination and isolation strategies in the ICU
Chapter:
Environmental decontamination and isolation strategies in the ICU
Author(s):

Leigh Ann Slater

and Pamela A. Lipsett

DOI:
10.1093/med/9780199600830.003.0285
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date: 30 November 2020

Key points

  • The care environment is an important factor in the transmission of health care-associated infections, but its role is incompletely understood.

  • Potential avenues for infection transmission include hospital construction, unit and room layout, design materials, disinfection materials and methods, isolation equipment, and staff ratios and training.

  • Limited evidence supports many currently employed cleaning and isolation techniques. Many are simply intuitive or based on non-controlled observations.

  • Compliance is currently poor with both cleaning and isolation policies.

  • Reduced colonization does not always translate to reduced infection rates.

Introduction

There are over 1.7 million health care associated infections annually in the US and 99,000 deaths [1]‌. With the clinical and financial burden of antibiotic resistance increasing exponentially, agencies such as the Joint Commission have clearly articulated regulations. The environment of care is a potentially important contributor to preventable health care associated infections. Potential avenues for infection transmission range from the initial hospital construction itself to unit and room layout, design materials, disinfection materials and methods, isolation equipment, and staff ratios and training. Better understanding of these avenues for transmission will suggest potential means to decrease the burden of environmental contamination. Several studies have demonstrated a two to three-fold increased risk of acquiring VRE (vancomycin resistant Enterococcus), MRSA (meticillin resistant Staphylococcus aureus), Clostridium difficile or ACB (Acinetobacter baumanii) when occupying a room previously used by a patient with one of these organisms [2]. Meanwhile, enhanced surveillance strategies demonstrate suboptimal routine disinfection with the potential to decrease transmission of VRE, MRSA, and ACB by 40% simply by improving compliance with existing cleaning protocols [3]. However, whether improvements in cleaning can lead to a clear decrease in acquired infections remains controversial. This chapter will provide a brief overview of the current understanding of the environment of care and its impact on infection control practices.

Construction

Construction-related risks include the release of airborne fungal diseases, most notably Aspergillus spp. The number of health care associated Aspergillus infections directly attributable to construction is unknown, but Aspergillus has a large cost burden, estimated at over $600 million in 1996 alone [4]‌. Treatment of Aspergillus infection adds 17 days to length of stay, or over $62,000 in costs per patient. Case fatality rate is over 50% overall and over 80% for bone marrow transplant recipients despite treatment, thus the urgency to prevent transmission. Thus during construction periods, high risk individuals such as transplant patients should avoid exposure to these areas.

Waterborne diseases are also a significant risk to the immunocompromised via the potable water supply. These include Aspergillus spp. and Fusarium spp., which can be transmitted via disruption of the biofilm after a water service interruption. Pseudomonas spp. and Stenotrophomonas spp. are opportunistic free-floating bacteria and can contaminate surfaces that come in contact with the water. Risk of transmission is heightened if contaminated water is used to wash equipment in direct contact with patients, or if water is allowed to stagnate and microbial count increases above 10,000 cfu/mL. Legionella spp. are found widely in soil and water and is easily introduced to the potable water supply, where it can spread through hospital water heaters and distribution systems to individual room faucets. Legionella spp. are commonly transmitted via inhalation of the aerosol at waterheads and there is no commonly utilized monitoring or eradication method. It is addressed by surveillance of patients for symptoms, prompt identification and treatment.

Unit design

Historically intensive care unit design emphasized arrangement of patient beds around a centralized nursing station to maximize visibility and communication and to more readily enable rapid response in the event of patient clinical decompensation. With more concern over the potential for cross contamination as well as more attention to the need for privacy and increased family presence, the emphasis has shifted to single occupancy rooms. Single rooms have demonstrated reduction in transmission of MRSA, Pseudomonas spp., and Candida spp. when compared with multi-bed wards [4]‌.

Important aspects of unit design include optimizing availability of hand hygiene equipment near point of care. Water and alcohol based modalities are equally efficacious for most hand hygiene. However, soap and water should be used for Clostridium difficile, since alcohol based cleansers have no effect against the spores. Alcohol based hand rub stations should therefore not be used in place of appropriate water based hand hygiene for this pathogen. Attention should be paid to sink size and depth to prevent splashing, avoidance of contamination of the faucet aerators, hands-free activation of the stream, direction of stream away from the drain, water pressure and temperature, proper drainage, and separate sinks for the toilet area versus for the remainder of the patient room. No storage should be allowed underneath the sinks. Travel distance for waste disposal should be minimized.

Water access for acute dialysis is another important consideration and care should be taken to avoid plugged lines and hoses with resultant mould growth. Waterproofing can be accomplished by gypsum board installed 10 mm (3/8ʺ) above the floor board to prevent fluid wicking from floods [4]‌.

Room design

The current trend is toward single occupancy rooms. Attention should be paid to ergonomic locations and heights of hand hygiene stations as well as to minimizing travel distance for waste disposal and separating it from the remainder of the room. The ideal arrangement may be a toilet room between every two patient rooms, to avoid transporting waste to a distant central area. In addition, patient rooms should have flexibility to increase acuity so that patient room transfers can be minimized, as increased transfers are linked to increased infection transmission. Specific isolation room design concepts will be discussed in a later section.

Surfaces and materials

Contaminated surfaces play an important role in the spread of MRSA, VRE, norovirus, Clostridium difficile, hepatitis B virus, and Candida spp., as well as Acinetobacter spp., Pseudomonas spp. and other multi-drug resistant Gram-negative bacilli. All of these organisms are able to colonize patients’ and health care workers’ (HCW) hands and can survive and remain virulent for prolonged periods on environmental surfaces. Surfaces in general need to be easy to clean with topical disinfectants at the appropriate concentration, duration, and frequency. There is little evidence identifying clearly superior surface materials that contribute to the reduction of health care associated infection. Desirable surfaces will be nonporous, non-cloth, smooth, water resistant, sealed, flat or with rounded corners, free of crevices, and durable against corrosion with the required frequent cleaning. Furniture should have 150–300 mm (6–12ʺ) clearance above the floor to permit thorough cleaning. Soft or upholstered furniture or carpet must be discarded if soiled, as must be any furniture with soiled exposed particleboard. Intact hardwood laminate can be cleaned with dilute bleach. Some manufacturers use fungicides, antimicrobials, or insecticides in their floor treatments or upholstery. Copper has intrinsic antimicrobial properties and is gaining acceptance over the more common stainless steel, but has not been shown to decrease cross-contamination [4]‌. Drapes, curtains, and other porous materials must be discarded after each patient if they cannot be sterilized for reuse. Particular care must be taken with the sterilization of ventilator equipment between patients.

Disinfection materials and methods

Commonly used surface disinfectants include sodium hypochlorite, sodium hydroxide, alcohols at 70 or 90% (ethanol, 1-propanol, 2-propanol), phenols, and quaternary ammonium compounds. Care must be taken to use these per the package instructions to ensure they are applied at adequate concentration, duration, and frequency. In addition, knowledge of specific pathogens is necessary as they may be selectively resistant to certain agents.

Norovirus, Clostridium difficile, and Acinetobacter spp. can all survive on environmental surfaces for weeks and are resistant to commonly used disinfectants. Norovirus can be transmitted by faecal-oral route either directly person-to-person, via surfaces or contaminated food or even by inhalation of aerosolized vomitus. It has high infectivity with a low inoculating dose and a long shedding time. As it cannot be cultured, surrogate data from caliciviruses suggests that alcohol, phenols, and quaternary ammonium compounds are less likely to be effective cleaning agents, with the effect highly dependent on the precise formulation. Sodium hypochlorite solution is effective when used at 1000–3000 ppm. Hand hygiene with soap and water for at least one minute completely removes norovirus as demonstrated by reverse transcription polymerase chain reaction (RT-PCR) [1]‌.

Clostridium difficile can be transmitted by faecal-oral route directly, via fomites or the hands of HCW. The vegetative form survives 15 minutes on a dry surface, but up to 6 hours on a moist surface, and spores can persist up to 5 months. 70% isopropanol, phenols, and quaternary ammonium compounds are not sporicidal [1]‌. Use of 1:10 diluted (5000 ppm) sodium hypochlorite is effective at reducing Clostridium difficile infections in the setting of an epidemic or high endemic caseload; this is advocated as effective against spores, but still leaves 10% Clostridium difficile positive toilets in rooms with Clostridium difficile positive patients [5]. Spores are thus a frustrating problem and the key to reducing transmission with this pathogen. Accelerated 0.5% H2O2 was found to be effective at spore removal in non-epidemic conditions [5]. Proper hand hygiene with soap and water is most effective at removing spores.

Acinetobacter spp. can survive for weeks on many different dry surfaces as well as in water; humidity prolongs its survival. It is often present in reservoirs such as respiratory equipment. It is susceptible to phenols, quaternary ammonium compounds, accelerated 0.5% H2O2, and UV light. 70% ethanol and 10% povidone-iodine are most effective at cleaning heavily contaminated hands [1]‌.

For terminal cleaning of rooms or eradication of units such as during an epidemic, various no touch disinfection methods may be utilized after the initial room cleaning. An automated ultraviolet-C device for hospital room disinfection has been demonstrated to reduce frequency of positive MRSA and VRE cultures by 93% and Clostridium difficile cultures by 80%, with 45 minutes of treatment required to reduce spores > 2–3 log10 cfu/cm2; MRSA and VRE killing were equivalent with 20 minutes versus 45 minutes of treatment [6]‌. However, such devices only function optimally after proper surface decontamination and only when used with the proper duration and treatment radius and intensity. Inferior cleaning rates (< 30%) have been demonstrated with commonly contaminated fixtures including doorknobs and light switches.

Alternative no touch disinfection methods include the use of gaseous agents such as H2O2, chlorine dioxide, and ozone, which are all powerful oxidizing agents [7]‌. All require the room to be precleaned and pose some small hazard to staff. The vapourized H2O2 system manufactured by Bioquell reduced Clostridium difficile infection 53% during an epidemic, but no controls were utilized in the study [8]. The system requires removal of the patient from the room so it can be sealed completely with tape, including heating, ventilation, and air conditioning ducts. Treatment with vaporized H2O2 requires up to 5 hours compared with 1 hour for bleach cleaning, an important factor in patient throughut and bed availability. The newer system manufactured by Bioquell has considerably reduced the required disinfection time, minimizing this concern. Chlorine dioxide is sporicidal, but can penetrate plastics commonly found in the clinical setting, as well as being explosive at concentrations above 10% and yielding toxic chlorine gas. Ozone’s corrosiveness and toxicity likewise limits its application in the clinical setting, as 15 minutes at 0.2 ppm is enough to induce respiratory symptoms while providing insufficient antimicrobial effect [7].

Isolation

Basic isolation concepts begin with the use of standard precautions for all patients, including hand hygiene before and after each contact and use of gloves for contact with any body fluid other than sweat. Transmission of blood-borne pathogens such as HIV, and hepatitis B and C can be minimized by adherence to standard precautions. For patients with certain specific infections, more stringent isolation protocols are required. The presence of such pathogens should be identified early and communicated broadly with appropriate signage and order sets to alert all HCW to the need to observe heightened precautions and cleaning protocols. The universal use of mandatory isolation remains controversial [9]‌.

Certain infections require designated isolation rooms within an ICU. With the airborne infection isolation room (AIIR), air flow is directed into the room, i.e. these are negative pressure rooms suitable for airborne precautions. A minimum of 12 air changes per hour are required, as are gloves, gown, and N95 type particle respirator masks [4]‌. AIIR protect against airborne droplets, which are 5 µm or smaller and can remain suspended in the air for a long time and disperse widely. Such infections include tuberculosis, measles, varicella, herpes zoster, and the viral haemorrhagic fevers such as Lassa, Ebola, and Marburg viruses [10].

Standard droplets do not require a negative pressure room, but simply a single room along with gloves, gown, and mask. These droplets are larger than 5 µm and do not remain suspended in air as long or disperse as widely as the airborne droplets. Dispersal is typically limited to one meter. These infections include influenza, rubella, mumps, and meningitis (Haemophilus influenzae and Neisseria meningitidis) [10].

Contact precautions include single room and use of gown and gloves for each contact. In some settings and countries they are required for MRSA/glycopeptide intermediate Staph. aureus, VRE, Clostridium difficile, varicella, herpes zoster, and the viral haemorrhagic fevers (Lassa, Ebola, Marburg) [10]. Local epidemiology authorities may identify other pathogens, such as Acinetobacter spp., Pseudomonas spp., or other multi-drug resistant or Gram-negative bacilli that should have strict isolation precautions. These measures are reinforced by appropriate universal surveillance for pathogens, such as MRSA nasal swab, and VRE rectal swab, as well as by prompt recognition of diarrhoea or ileus prompting Clostridium difficile stool antigen and culture [11]. The routine use of isolation procedures (gown, gloves +/- masks) for all ICU patients has been favoured by some authors as a means to improve hand hygiene and more generally to decrease transmission of infections. While in some cases these more global isolation measures have been effective, the widespread use of mandatory isolation for all patients cannot be endorsed.

For immunosuppressed patients, a protective environment room is required, with the airflow directed out of the room and use of gloves, gown, and mask. Key opportunistic pathogens targeted include Aspergillus spp. and other airborne fungi, Pneumocystis spp., Toxoplasma spp., CMV, John Cunningham virus, tuberculosis, and Mycobacterium avium complex.

Staffing issues

Caregiver:patient ratio is a major contributor to staff stress level and understaffing clearly can lead to staff being overwhelmed and overburdened with increased chance of cross-contamination while moving between patient rooms. There may be more frequent trips required and less time to perform adequate hand hygiene. Hand hygiene campaigns and other educational interventions are useful reminders, but of limited impact in the face of inadequate staffing for the level of acuity and nursing activities. Other staffing approaches can include cohorting infected or colonized patients or cohorting staff caring for such patients to limit cross-contamination opportunities.

Patient specific interventions

Patient specific interventions for the prevention of transmission of pathogens include global measures such as providing daily chlorhexidine baths and frequent changes and skin care, use of linens made of cotton or other material designed to wick away moisture, maintenance of normothermia and glycaemic control, and proper antibiotic husbandry to cover likely pathogens while avoiding selection of resistant microbes.

Surveillance/quality control

Feedback about the efficacy of environmental cleaning and isolation strategies is paramount to achieving significant reduction in health care associated infection. Of particular importance, many currently employed cleaning and isolation strategies have a very limited evidence base. Many are simply intuitive or based on non-controlled observations. The cost of performing rigorous studies may be prohibitive. In addition, reduced colonization does not always translate to reduced infection rates. As one example, a crossover study of enhanced cleaning accomplished a significant reduction in MRSA hand carriage rate of HCW, but no change in the infection rate of patients. The authors calculated that data from at least 40,000 patients would be required to demonstrate a difference in MRSA infection rate with 80% power [12,13].

Quality control can be understood in terms of both process measures and outcome measures. Process measures could include education, checklists, or covert practice observation to assure that disinfectants are being diluted and applied properly, according to manufacturer recommendations for concentration, duration, and frequency [2,14]. Outcome measures include various forms of surveillance for post-clean contamination, such as swab or agar slide cultures, fluorescent gel, and adenosine triphosphate (ATP) bioluminescence technologies [2,15,16]. They may also involve some assessment of the cost-effectiveness of different disinfection products and strategies. A key concept is that of measuring cleaning process (observation and fluorescent gel) versus cleanliness (swab and slide cultures, ATP bioluminescence) [2,16]. It is estimated that only 34% of surfaces currently are cleaned in accordance with institutional policy, providing a significant opportunity for improvement [2]‌. Data gleaned from such investigations should be utilized in recurrent educational programs to improve compliance with the best evidence based guidelines, promulgated by national authorities. Feedback rendered in a blame-free context with clear specific recommendations for improvement will yield the best result.

Conclusion

The care environment is an important factor in the transmission of health care-associated infections, but its role is incompletely understood. In particular, there is a limited evidence base for many currently employed cleaning and isolation techniques. There is, however, ample evidence of poor compliance with established cleaning and isolation protocols. Given the severe health and cost burden of health care-associated infections, increasing attention is being devoted to the impact of the environment of care. Work is ongoing to establish optimal regimens from an efficacy and cost perspective.

References

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