Case Definition: Nerve Agents or Organophosphates

Clinical description

Nerve agent or organophosphate toxicity might result from multiple routes of exposure. It consists of a cholinergic syndrome of excess respiratory and oral secretions, diarrhea and vomiting, diaphoresis, convulsions, altered mental status, miosis, bradycardia, and generalized weakness that can progress to paralysis, respiratory arrest and death (1-3).

In certain cases, excessive autonomic activity from stimulation of nicotinic receptors will predominate in the syndrome and will manifest as fasciculations, hypertension, mydriasis, and tachycardia.

Laboratory criteria for diagnosis

• Biologic: A case in which nerve agents in urine are detected, as determined by CDC or a LRN laboratory that has this capacity. Decreased plasma or red blood cell cholinesterase activity based on a specific commercial laboratory reference interval might indicate a nerve agent or organophosphate exposure; however, the reference intervals for cholinesterase activity are wide, which makes interpretation of these values difficult without a baseline measurement or repeat measurements over time.

- OR-

• Environmental: Detection of organophosphate pesticides in environmental samples (6-10). However, a confirmation test for nerve agents in environmental samples is not readily available.

Case classification

• Suspected: A case in which a potentially exposed person is being evaluated by health-care workers or public health officials for poisoning by a particular chemical agent, but no specific credible threat exists.
• Probable: A clinically compatible case in which a high index of suspicion (credible threat or patient history regarding location and time) exists for nerve agent or organophosphate pesticide exposure, or an epidemiologic link exists between this case and a laboratory-confirmed case.
• Confirmed: A clinically compatible case in which laboratory tests have confirmed exposure.

The case can be confirmed if laboratory testing was not performed because either a predominant amount of clinical and nonspecific laboratory evidence of a particular chemical was present or the etiology of the agent is known with 100% certainty.

Additional resources

1. Sidell FR. Soman and sarin: clinical manifestations and treatment of accidental poisoning by organophosphates. Clin Toxicol 1974;7:1-17.
2. Sidell FR. Nerve agents. In: Zajtchuk R, Bellamy RF, eds. Textbook of military medicine: medical aspects of chemical and biological warfare. Washington, DC: Office of the Surgeon General at TMM Publications, Borden Institute, Walter Reed Army Medical Center; 1997:129-79.
3. Holstege CP, Kirk M, Sidell FR. Chemical warfare: nerve agent poisoning. Crit Care Clin 1997;13:923-42.
4. Eddelston M, Buckley NA, Eyer P, Dawson AH. Management of acute organophosphorus poisoning. Lancet 2008; 371: 597-607.
5. Leikin JB, Thomas RG, Walter FG, Klein R, Meislin HW. A review of nerve agent exposure for the critical care physician. Crit Care Med. 2002 Oct;30(10):2346-54.
6. NIOSH. NIOSH manual of analytical methods [online]. 2003. [cited 2013 Apr 5]. Available from URL: http://www.cdc.gov/niosh/docs/2003-154/.
7. OSHA. Sampling and analytical methods [online]. 2010. [cited 2013 Apr 5]. Available from URL: http://www.osha.gov/dts/sltc/methods/index.html.
8. FDA. Food: Laboratory methods [online]. 2013. [cited 2013 Apr 5]. Available from URL: http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/default.htm.
9. EPA. Selected analytical methods: chemical methods query [online]. 2013. [cited 2013 Apr 5]. Available from URL: http://www.epa.gov/sam/searchchem.htm.
10. EPA. Selected analytical methods for environmental remediation and recovery (SAM) [online]. 2012. [cited 2013 May 8]. Available from URL: http://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryId=245280.