Which method is most effective for the decontamination of individuals?

Technique

There are a number of key components in the management of HAZMAT incidents and the care of contaminated patients seen in the ED.109 These components should include early recognition of a HAZMAT event, rapid activation of a plan to manage contaminated patients, initiation of primary triage, appropriate patient registration, patient decontamination, secondary triage, and final treatment.

First, the ED must be able to recognize that an event has occurred before contaminated patients gain entrance into the health care facility (Fig. 42.17,step 1). Communication with the local fire, police, and paramedic systems provides early detection of such events and allows preparation before patients arrive. Security should be arranged to prevent contaminated patients from entering the hospital, and “lockdown” of the facility should be considered.

Second, the ED should have the authority to activate a plan expeditiously to prepare the decontamination facility and allow appropriate preselected personnel to don PPE (seeFig. 42.17,step 2). If necessary, the hospital disaster plan should be activated quickly at the discretion of the ED clinician who is in contact with scene operations and incoming patients. Specific data to determine the appropriate level of PPE to maintain protection of hospital workers remain limited. The minimum PPE for hospital-based decontamination (level C) consists of a splash-proof, chemical-resistant suit with tape, double-layer protective gloves, and a powered air-purifying respirator per the National Institute of Occupational Safety and Health. Higher levels of protection, such as a level A self-contained breathing apparatus (SCBA), fully encapsulated chemical-resistant suit, or level B SCBA chemical-resistant suit, are recommended with unknown chemical and biologic exposures and for entering “hot” zones, but these levels of protection are not readily available in EDs.110,111 Fortunately, most chemical exposures are known. For those that occur in the workplace, Material Safety Data Sheets can be obtained and either the local poison center or the Agency for Toxic Substances and Disease Registry (ATSDR) can be contacted for advice on what level of protection is appropriate.

Third, appropriate primary triage should take place (seeFig. 42.17,step 3). Contaminated patients should not enter the ED until proper decontamination has occurred to ensure that the hospital staff will not be subjected to secondary contamination. Appropriate triage should then take place, with experienced personnel performing an initial brief assessment of each patient. The triage and decontamination areas should be organized into several “zones” to prevent further contamination. The hot zone is the location with the highest level of contaminant or where the incident occurred. In most cases of hospital-based decontamination there is no hot zone because patients have been removed from the initial chemical insult. On average, patients arrive at the ED 20 minutes after the event and have had significant off-gassing by this time; however, the majority of patients will have transported themselves and will not have received any prehospital decontamination by emergency medical services/HAZMAT personnel. Basic lifesaving treatments, airway and hemorrhage control, antidote administration (e.g., for cyanide or nerve agents), and decontamination occur in the “warm” zone. The “cold” zone is safe from contaminant.111

Conclusion

Decontamination is an essential part of any infection prevention and control programme.15 As discussed throughout this chapter, it is very important that appropriate protocols be employed for the decontamination of areas at high risk of microbial contamination in the hospital environment. In particular, in reducing the incidence and prevalence of HCAI the correct decontamination of medical devices is fundamental. Of growing relevance to hospital cleanliness and effectiveness are the evidence of biofilms. Biofilms should always be considered significant as they have a role to play in influencing the effectiveness of decontamination procedures in hospitals.46 The reasons for this are discussed in further detail in Part 2 of this book.

Remediation (Decontamination)

One of the more controversial topics regarding bioterrorist-associated use of anthrax is the method and cost associated with making spore-contaminated areas safe. This is an additional advantage to the terrorist of using an agent that has the demonstrated persistence of the anthrax spore. As a result of the massive cleanup effort in the wake of the 2001 attacks, there has been increased understanding of decontamination of spores. The Environmental Protection Agency outlined eight steps in the remediation process of contaminated sites, and these are presented inTable 207.9.133

One of the least expensive and most commonly available compounds used to destroy anthrax spores is household bleach, and many of the high-tech remediation methods use bleach in some manner. Bleach, chlorine dioxide, ethylene oxide, hydrogen peroxide, peroxyacetic acid, methyl bromide, paraformaldehyde, and vaporized hydrogen peroxide all were used to some degree in the federal decontamination process in 2001 and 2002.176 As might be expected, one agent is not suitable for all applications. Chlorine dioxide gas and liquid were used extensively in the US Capitol Hart Senate Office Building but were not found to be very effective for porous surfaces such as carpeting, chairs, and fabric surfaces, which were subsequently decontaminated with other agents.

In the event of widespread contamination of individuals and households where the public will be expected to be performing much of the decontamination efforts, it is likely that household bleach in 1 : 10 dilution will be recommended because it is readily available. Contaminated individuals should be advised to remove clothing and place it in a bag either before entering their home or immediately after entering (to minimize spores coming off clothes into the home). They should shower using soap and water and shampoo their hair. Clothes can be decontaminated by washing in hot water with bleach and machine drying. Dry cleaning will also destroy spores.

How extensively remediation must be performed remains controversial. Because it is well known from studies of wool mill workers and nonhuman primates that the innate immune system can eradicate an as yet undefined number of spores, preventing the development of inhalational anthrax, must every spore be removed from every surface? There may be an acceptable level of contamination that will allow for a timelier and cost-effective remediation effort after a city-wide exposure without serious compromise to the public health of the community. The National Academy of Sciences reviewed remediation of buildings after anthrax contamination and addressed many of these controversial areas but concluded that it cannot be determined what lowest level of spore contamination is acceptably safe for exposure.178

Decontamination

Decontamination remains an area of intense research and development. Current best practices rely on physical removal of agents using soap and water. Use of 0.5% bleach solution has fallen out of favor. Several good consensus standards have been promulgated.52–55 There is evidence, however, to suggest these water-based techniques, if not performed immediately after exposure, may not be effective, and may even cause more harm.56 Others argue for a more-rational approach that considers high molecular weight solutions optimized for specific agent characteristics including solubilities.57 A comprehensive review of decontamination guidelines conducted by a joint effort by the DHS Office of Health Affairs and the DHHS PHEMCE provided the “Patient Decontamination in a Mass Chemical Exposure Incident: National Planning Guidance for Communities.” This multiyear effort included broad participation of stakeholders in government, the private sector, and the general public, and it should provide national planning guidance for communities on patient decontamination in mass chemical exposure incidents.58

Mass causalities requiring decontamination present major challenges to the resources, personnel, and efficiency of a community response. After a chemical attack, potentially contaminated patients may be injured and may remain at the scene, unable to extricate themselves or they may be ambulatory and remain at the scene or they may leave and self-triage to the hospital or leave and go home. Proper decontamination offers the benefit by decreasing exposure dose by diluting or removing chemicals preventing additional absorption and reducing contamination, preventing the spread of contaminants that could jeopardize critical infrastructure such as personnel, ambulances or hospitals. Since decontamination is a first aid procedure, every attempt to accomplish decontamination reduction should start as quickly as possible. A tiered approach provides a method of rapid contamination reduction for a large number of people and may decrease chemical exposure. This approach begins by quickly instructing exposed groups how to perform self-care, followed by rapid gross decontamination and subsequent technical decontamination. Each step along the way requires resource capabilities that are more intense.

For ambulatory patients, most systems essentially represent mass shower sequences through tents for set periods of time, with a range of shower times depending on various factors. Although it is commonly stated that disrobing may provide up to 90% decontamination in and of itself, some care to the process must be applied to prevent cross contamination. Decontamination of nonambulatory patients is time and manpower intensive. Even the most elaborate systems and experienced teams do not provide adequate throughput for true MCI. Roller systems that allow easier, rapid movement of patients through a “car wash”-like system take more than 2 to 5 minutes per patient. Set up times for different teams and systems vary and, if not prepositioned, provide additional challenges because of large footprints and time to set up. In addition, mass casualty decontamination setups require a significant reliable water source, and pose the inability to move easily if necessary.

There are several critical issues in the decontamination process. First, at least three separate lanes for processing people through should be recognized: a lane for ambulatory patients, a lane for nonambulatory patients, and a separate lane for responders. Each group will have different decontamination requirements and priorities and likely use different processes. The responder lane becomes especially critical for responders on supplied air who will usually be near the end of their air supply while processing out. Cutting clothes with “J knives” versus scissors may enhance the throughput capability and avoid hand fatigue. Second, controlling water temperature during the decontamination process can be a challenge given portability, sourcing, and volume requirements. Third, decontamination lanes are typically manned with nonmedical personnel, so medical oversight during the decontamination process needs to be provided with clear protocols for alerting medical providers of any medical issues in patients during the decontamination process. Finally, the environment in decontamination systems can become very hot and humid. The effect on personnel, as well as filter performance, must be considered. Finally, neutralizing solutions such as Reactive Skin Decontaminant Lotion (RSDL) are commercially available and offer significantly more favorable decontamination performance.59 However, further evaluation needs to be done, including FDA licensing as a medical drug if such solutions are to be used for full-body decontamination

Mechanisms of Action and Evidence

Charcoal is activated by the manufacturer by heating it to approximately 900°C and washing it in a stream of carbon dioxide gas or steam. This increases the surface area from 2 m2/g to greater than 2000 m2/g; consequently, a 50-g dose has the surface area of 10 football fields. When ingested, there is no modification of charcoal’s structure by digestive enzymes as it passes through the stomach and intestines, nor is it absorbed across the intestinal wall. Activated charcoal binds with toxins and then passes through the gastrointestinal tract to be eliminated in the stool as a sticky black substance. As the charcoal absorbs the toxin in the intestine and passes distally, it creates a diffusion gradient. This in turn causes already absorbed toxins to diffuse back across the intestinal membrane and into the lumen; it somewhat dialyzes the intestinal blood. Thus charcoal decreases systemic absorption of toxins by both its absorptive mechanism and its ability to form a diffusion gradient.

Charcoal has an excellent safety profile; it is even considered safe during pregnancy, in lactating women, and in the pediatric population. Although studies show a better safety profile and a more effective decrease in toxin absorption compared with lavage or ipecac-induced emesis, no significant decrease in mortality, length of hospital stay, or likelihood of clinical deterioration has been demonstrated with the use of activated charcoal. In studies using a single dose of at least 50 g of activated charcoal, there was a 47% to 21% reduction in toxin absorption when administered 30 to 180 minutes after toxin ingestion, respectively. According to the AACT (Position Statement 2004), the administration of activated charcoal may be considered if a patient has ingested a potentially toxic amount of a poison up to 1 hour following ingestion. Activated charcoal may be considered more than 1 hour after ingestion, but there are insufficient data to support or exclude its use.

Similarly, although studies have shown statistical significance for multidose charcoal’s effectiveness in removing toxins, it has not been shown to reduce morbidity or mortality. Therefore multidosing is usually not recommended except for a select list of drugs (see section on “Indications”). Although there is no evidence supporting their use, cathartics are added to activated charcoal by some experts to hasten elimination. This may be helpful when large doses of charcoal have been administered, which can be constipating. Sorbitol, which is used as a preservative and to decrease the grittiness of charcoal, also enhances the flavor of charcoal by making it slightly sweet. It is not absorbed and therefore encourages water secretion into the lumen, which in turn stimulates bowel peristalsis. However, it can cause severe cramping, hypotension, and vomiting and increase the risk of pulmonary aspiration. Sorbitol with activated charcoal may cause electrolyte imbalances and is not recommended in children. Magnesium, another cathartic, is contraindicated in patients with hypermagnesemia, myasthenia gravis, renal insufficiency, or cardiac arrhythmias. Sodium-based cathartics should be avoided in patients with severe hypertension, renal failure, or congestive heart failure. Mineral oil or other oil-based cathartics should not be used because of risk of aspiration. The concurrent use of a cathartic is not recommended with multidose activated charcoal due to the risk of diarrhea leading to fluid shifts and electrolyte imbalances.

Selective decontamination of digestive tract

Selective decontamination of the digestive tract (SDD) has been proposed as a prophylactic treatment to prevent serious infections in burn patients. There is considerable debate regarding the implementation of SDD as a standard preventative maneuver in burn patients. One study in which polymixin E, tobramycin and amphotericin B were administered to burned children showed no effect on the incidence of infections or the production of inflammatory cytokines.156 However, Mackie and colleagues reported that SDD reduced the incidence of infections with Pseudomonas species and Enterobacteriaceae in burn patients.157 de la Cal et al. reported that SDD, by the immediate administration of parenteral cefotaxime and intestinal non-absorbable antibiotics, significantly reduced mortality and the incidence of pneumonia in burned adults.158 Additionally, it was reported that enteral vancomycin reduces MRSA infections in burn patients.159 However, the American Burn Association does not encourage SDD because of concerns about emerging antibiotic resistance.15

Protozoa as Indicators of Soil Decontamination

Decontamination of polluted soils is a current challenge for scientists from various fields. Few data are available as concerns the soil fauna, and only one study included protozoa (Figure 9). Immediately after decontamination, active protozoa, nematodes, and collembola were not detected in treated soil. However, protozoan cysts survived treatment (5700 ± 4200 cysts per g dry soil). Following 1 week of exposure, no active protozoa were found. From the second sampling date onwards (after 3 weeks), protozoa were observed with significantly increasing biomass until the end of the experiment 12 weeks after exposition.

Decontamination (casualty hazard management)

Individual casualty decontamination must be carried out fully as soon as possible to enable initial resuscitation and in order to prevent further absorption of the chemical agent. Immediate decontamination may be life-saving in the case of chemical agents and should be concurrent with life-saving interventions (LSIs) see Box 5.7.

Decontamination must take place before the patient leaves the hot and warm zones and therefore is best performed at the border of the inner cordon upwind of the threat and in close proximity to the treatment facility. It should only be carried out by trained personnel wearing appropriate PPE. Ambulatory casualties should be directed to self-decontamination facilities, initially with ‘dry’ decontamination by removal of all clothing, which should be disposed of appropriately. If specialised decontamination units are initially unavailable, improvised methods may be utilised as outlined in Box 5.5. However, no attempt should be made to carry this out until appropriate PPE is available. Contaminated casualties may self-present to local hospitals and will require decontamination outside emergency departments.

The chief method of decontamination is dilution with copious quantities of water. Clothing and jewellery must be removed quickly but carefully and placed safely away or double-bagged to prevent exposure from off-gassing. A decontamination solution of 0.5% hypochlorite in water is effective against many substances although the HPA advises the use of detergent solutions for initial decontamination rather than bleach solutions. Bleach solutions are harmful to the eyes and must not be used if ammonia is thought to be one of the agents involved, as they will interact to produce chlorine gas. Generic decontamination guidance is shown in Box 5.6.

Laser Decontamination Appointment

The laser decontamination appointment is provided after thorough debridement of tooth structure, when continued decontamination of the tissue wall, impairment of epithelium, and maturation of connective tissue are required. Laser decontamination appointments continue until each pocket has had sufficient therapy to support healing to ideal resolution.

Again, for each millimeter of attachment gain desired, an additional laser decontamination session should be provided. These sessions are scheduled approximately 10 days apart after the last debridement plus lasing session. Sessions may be 30 to 60 minutes in length, depending on the number of sites and pocket depths to be treated. At completion of the last laser decontamination appointment, the definitive therapy appointment should be scheduled for 6, 8, or 12 weeks (a longer interval allows attachment to mature).

Selective Decontamination of the Digestive Tract

Selective decontamination of the digestive tract (SDD) involves the use of topical and oral nonabsorbable antimicrobial agents (polymyxin E, tobramycin, amphotericin B, and vancomycin in case of endemic methicillin-resistant Staphylococcus aureus), possibly in conjunction with parenteral antibiotics (usually cephalosporins) to control the overgrowth of potentially pathogenic microorganisms, as often occurs in critically ill patients. This prophylactic measure has been largely proven to reduce bloodstream and pulmonary infections and mortality rates in ICU patients. The effectiveness of SDD also has been investigated in surgical ICU patients, but evidence is not overwhelming. Until recently, a meta-analysis performed in 1999 including 11 RCTs was the only study showing a survival benefit with SDD in the postoperative setting. The authors found that SDD significantly reduced mortality rates among critically ill surgical patients (OR, 0.70; 95% CI, 0.52–0.93) because of reduced rates of bacteremia and pneumonia. Furthermore, the survival benefit was greater with the use of SDD regimens that included both oral and parenteral antimicrobial agents (OR, 0.60; 95% CI, 0.41–0.88). These findings seem to be confirmed by a recent (2017) individual patient data meta-analysis including six RCTs performed in countries with low levels of antibiotic resistance, which showed reductions in both hospital and ICU mortality rates regardless of the ICU admission type (medical or surgical).

Conversely, the perioperative use of SDD protocols outside the ICU setting has not been shown to reduce mortality rates, although it seemed to be a promising prophylactic measure, especially in patients undergoing upper GI tract surgical procedures.

The use of SDD is not widespread and not generally suggested, even in the critical care setting. The reason is probably multifactorial and mainly reflects concern about development of bacterial resistance to antibiotics, even if SDD seems to be safe from this point of view. A large, multicenter RCT in patients undergoing elective colorectal cancer operations that is evaluating the role of SDD in addition to standard antibiotic prophylaxis and that includes death among its endpoints is currently ongoing. Meanwhile, the role of SDD, both in the perioperative period and in postsurgical ICU patients, as a strategy to improve survival remains uncertain.