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Cholinesterase Inhibitors: Including Insecticides and Chemical Warfare Nerve Agents
Part 4: The Cholinergic Toxidrome
Section 11: Management of the Cholinergic Toxidrome
Management Strategy 1: Prevention of Secondary Exposure

Course: WB 1098
CE Original Date: October 16, 2007
CE Renewal Date: October 16, 2010
CE Expiration Date: October 16, 2012
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Learning Objectives

Upon completion of this section, you should be able to

  • Describe five key strategies for preventing secondary exposure from patients contaminated with cholinesterase inhibitors.

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.

Affect of Decontamination Time Delay on Nerve Agent Survival with Dermal Exposure (Trapp 1985)
Time Delay between Exposure and Initiation of Decontaminationv
Estimated Survival Rate

2 minutes

80%

5 minutes

30%

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.

Mortality in Guinea Pigs Dermally Exposed to VX or Soman vs. Decontamination Fluid (van Hooidonk, Ceulen et al. 1983)

Decontamination Fluid
Delay Time (min.)
Mortality
VX (mg)
Soman (mg)

 

 

0.25

0.50

5.0

10.0

Bleaching-water*

4

0/8

6/8

6/8

-

Bleaching-water*

10

3/8

-

-

-

Bleaching-water*

30

8/8

-

-

-

Soapy water§

4

0/8

-

0/8

8/8

Soapy water§

10

3/8

-

-

-

Soapy water§

30

7/8

-

-

-

Salad-oil

4

0/8

-

0/8

2/8

Salad-oil

8

5/8

-

-

-

Salad-oil

30

8/8

-

8/8

-

* Concentration not specified

§ Authors indicated that plain water was as effective as soapy water

Key Points

  • Patients suffering from cholinesterase inhibitor poisoning can secondarily expose others in their proximity because of contaminated skin, clothing, hair, or emesis.
  • Caregivers should be prepared to protect themselves with appropriate personal protective equipment (PPE), isolate such patients, and decontaminate them.
  • Rapidity of decontamination can be a crucial determinant of survival in skin exposures.

   

Progress Check

31. Strategies helpful in reducing secondary exposure include (Choose ALL correct answers)

A. The use of personal protective equipment by healthcare workers coming into contact with the patient.
B. Isolating contaminated patients from other hospital patients.
C. Removing the patient's clothing.
D. None of the above.

Answer:

To review relevant content, see Five Tactics for Preventing Secondary Contamination in this section.

32. Which of the following statements is true about secondary exposure to hazardous substances such as cholinesterase inhibitors? (Choose ALL correct answers)

A. Healthcare workers can be secondarily exposed to cholinesterase inhibitor poisoning victims due to off-gassing of chemicals on the victims' skin, hair, and clothing.
B. Patients with skin exposure should be decontaminated with 0.5% hypochlorite (bleach) solution, rather than water.
C. Indoor decontamination rooms should have independent ventilation to the outside.
D. Secondary exposure can result from emesis after ingestion of cholinesterase inhibitors.
E. None of the above.

Answer:

To review relevant content, see Five Tactics for Preventing Secondary Exposures and Controversy in this section.

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