How Secondary Exposure Occurs

Persons contaminated with toxic cholinesterase inhibiting substances pose a risk to those around them (e.g., prehospital responders, hospital staff, visitors, other patients) that may become secondarily exposed. (Hammond, Merritt et al. 1989; Geller, Singleton et al. 2001; Horton, Berkowitz et al. 2003)

The first priority in managing patients is to prevent secondary exposure and injury to others.

This secondary exposure may occur from direct contact or off-gassing from

• Regurgitated stomach contents containing the ingested chemical. (Geller, Singleton et al. 2001; U.S. Occupational Safety and Health Administration 2005)
• The chemical on the victim's skin, hair, or clothing. (Okumura, Suzuki et al. 2000; Horton, Berkowitz et al. 2003)
• The contaminated vehicle (or its contents) in which the patient was transported.

Example of Secondary Exposure (Optional Reading)

A 40-year-old man was brought to the emergency department by a friend approximately 20 minutes after ingesting a concentrated solution of veterinary insecticide. (Geller, Singleton et al. 2001) The patient had profuse oral and bronchial secretions, vomiting, bronchospasm, and respiratory distress. The friend also was beginning to show symptoms. Neither had been decontaminated prior to hospital arrival, nor was either decontaminated in the emergency department.

Three emergency department staff exposed to the patient began to show symptoms typical of cholinesterase inhibitor toxicity within an hour of the patient's arrival. All required antidotal treatment. One sickened staff member had to be intubated, and was hospitalized for 9 days. The other two had to be kept in the hospital for 12 hours and overnight, respectively.

Misconception:

If patients have only been exposed to cholinesterase inhibitor vapor, there is no risk of secondary exposure.

Reality

Toxic vapors may become trapped in clothing. Subsequent off-gassing has been reported to expose healthcare workers. (Okumura, Takasu et al. 1996) At the very least, such patients should have their clothing removed and properly stored in sealed containers.

Five Tactics for Preventing Secondary Contamination

The five key strategies that can be used to control secondary contamination include:

1. Using personal protective equipment (PPE).
2. Carrying out initial assessment and decontamination outdoors or in a room with separate ventilation to the outside (This ventilation should be carried out in such a manner that it does not itself create an exposure risk. Filtering of ventilated air should be considered.).
3. Isolating the patient from other patients, staff, and visitors.
4. Removing the patient's clothing.
5. Decontaminating the patient.

These tactics are well explained in the document, OSHA Best Practices for Hospital-Based First Receivers of Victims from Mass Casualty Incidents Involving the Release of Hazardous Substances, (2005) U.S. Occupational Safety and Health Administration. It can be downloaded at no charge from: http://www.osha.gov/dts/osta/bestpractices/html/hospital_firstreceivers.html

Note: It has been said that removing clothing will remove up to 80% of chemical contaminants. However, it has been difficult to verify this, (McMullen 1996) and empirical evidence to support this assertion was not located during the literature search for this case study.

Controversy

There has been some diversity of opinion as to whether bleach solution (0.5% hypochlorite), water, or soapy water is the best decontamination fluid for use in cases of topical cholinesterase inhibitor exposure.

Some have recommended a 10:1 solution of household bleach (0.5% sodium hypochlorite). The reasoning for this is that this solution is alkaline and organophosphorus compounds hydrolyze faster at an alkaline pH. (Leikin, Thomas et al. 2002) One concern about the use of bleach is that it injures skin or eyes, facilitating absorption of the toxicant. Another issue is that bleach solution has to be freshly made daily or it loses its potency. (Levitin, Siegelson et al. 2003) Hurst warns against the use of hypochlorite in abdominal or open-chest wounds, on exposed nervous tissue, or in the eye. (Hurst 1997)

Others have reported that water or soapy water is very effective. (Trapp 1985)

PROBABLY MORE IMPORTANT THAN THE SPECIFIC DECONTAMINATION FLUID USED, IS THE RAPIDITY WITH WHICH IT IS APPLIED. (Trapp 1985), (Hurst 1997)

Most data on this subject appears to be derived from studies with chemical warfare nerve agents. See, for example, the table below.

Van Hooidonk et al. (van Hooidonk, Ceulen et al. 1983) in experiments found that in Guinea pigs dermally exposed to VX and Soman, survival was better with soapy water. Interestingly, salad oil was also effective if used promptly. However, mortality after decontamination with each of these solutions increased substantially if decontamination was delayed more than 4 minutes. See the table below.

Progress Check