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CBRNE - Nerve Agents, Binary - GB2, VX2 Workup

  • Author: Larissa I Velez-Daubon, MD; Chief Editor: Duane C Caneva, MD, MSc  more...
 
Updated: Apr 28, 2015
 

Laboratory Studies

Many studies have related symptoms to laboratory parameters in cases of nerve agent exposures. A review of those studies is beyond the scope of this article but can be found in Chemical Warfare Agents: Toxicology and Treatment by Marrs, Maynard, and Sidell.

However, laboratory tests do not aid in the immediate treatment of patients exposed to nerve agents. Laboratory studies are most useful in observing long-term exposures over time when the individual's baseline measurement is known. Never withhold treatment while waiting for laboratory results. Nevertheless, laboratory analysis may be used to help document an exposure to a nerve agent, may help quantify the exposure, and may aid in the evaluation of the patient's recovery.

Red blood cell cholinesterase (RBC-ChE) levels: RBC-ChE is believed to be the most reliable indicator of the tissue cholinesterase status. However, baseline cholinesterase values vary significantly depending on age, ethnicity, nutritional status, and other individual factors. RBC-ChE levels are altered later in the course of the acute illness or with chronic exposures.

Plasma cholinesterase (butyrylcholinesterase [BuChE]) levels: This enzyme is also termed pseudocholinesterase. With organophosphate pesticide toxicity, this is the earliest enzyme to be inhibited and the earliest to be regenerated. However, sarin and VX preferentially bind RBC-ChE; thus, for these agents, the RBC cholinesterase is a more sensitive indicator of acute nerve agent exposure.

Blood concentrations of nerve agents are not available in clinical laboratories. The US Army Medical Research Institute of Chemical Defense can process blood samples and can be used as a reference laboratory.

Order basic laboratory studies in all but minimally symptomatic patients. Electrolytes and arterial blood gases aid in the evaluation of fluid status, oxygenation, and the acid/base balance. Observe the temperature in a serial fashion because patients can become hypothermic.

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Imaging Studies

See the list below:

  • Request chest radiography for any severely dyspneic or intubated patient.
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Other Tests

See the list below:

  • Additional tests do not provide information that aids in the treatment of patients with nerve agent poisoning. Presently, no information supports the use of tests to predict outcome.
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Procedures

See the list below:

  • Endotracheal intubation and mechanical ventilation may be needed for patients with ventilatory and/or respiratory failure.
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Contributor Information and Disclosures
Author

Larissa I Velez-Daubon, MD Professor, Program Director, Department of Surgery, Division of Emergency Medicine, University of Texas Southwestern Medical School, Parkland Memorial Hospital; Staff Toxicologist, Department of Surgery, Division of Emergency Medicine, North Texas Poison Center, Parkland Memorial Hospital

Larissa I Velez-Daubon, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Medical Toxicology, Society for Academic Emergency Medicine, American College of Emergency Physicians

Disclosure: Nothing to disclose.

Coauthor(s)

Daniel C Keyes, MD, MPH Associate Chair, Academic Affairs, Department of Emergency Medicine, St Joseph Mercy Hospital; Clinical Faculty, Emergency Medicine Residency, University of Michigan Medical School; Clinical Associate Professor, Department of Surgery, Division of Emergency Medicine and Toxicology, University of Texas Southwestern School of Medicine

Daniel C Keyes, MD, MPH is a member of the following medical societies: American College of Emergency Physicians, American College of Medical Toxicology, American College of Occupational and Environmental Medicine, American College of Physicians-American Society of Internal Medicine

Disclosure: Nothing to disclose.

Fernando L Benitez, MD Assistant Medical Director, Dallas Metropolitan BioTel (EMS) System; Associate Professor in Emergency Medicine, Department of Surgery, Division of Emergency Medicine, University of Texas Southwestern Medical Center and Parkland Health and Hospital

Fernando L Benitez, MD is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, National Association of EMS Physicians

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Duane C Caneva, MD, MSc Senior Medical Advisor to Customs and Border Protection, Department of Homeland Security (DHS) Office of Health Affairs; Federal Co-Chair, Health, Medical, Responder Safety Subgroup, Interagency Board (IAB)

Disclosure: Nothing to disclose.

Additional Contributors

Fred Henretig, MD Director, Section of Clinical Toxicology, Professor, Medical Director, Delaware Valley Regional Poison Control Center, Departments of Emergency Medicine and Pediatrics, University of Pennsylvania School of Medicine, Children's Hospital

Disclosure: Nothing to disclose.

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Table 1. Toxicity of Nerve Agents
Agent Chemical Name LCt50, mgXmin/m3 LD50,



mg



GA Ethyl N -dimethylphosphoramidocyanidate 400 1000
GB Isopropyl methylphosphonofluoridate 100 1700
GD Pinacolyl methylphosphonofluoridate 50 100
VX O-Ethyl S-2-diisopropylaminoethyl methylphosphonothioate 10 10
Table 2. Severity of Toxicity From Liquid and Vapor Exposures
Severity of Exposure Signs and Symptoms - Liquid* Signs and Symptoms - Vapor†
Minimal Localized sweating at site



Localized fasciculations at site



Miosis



Rhinorrhea



Slight dyspnea



Moderate Above-mentioned symptoms and the following:



Nausea, vomiting, and diarrhea



Generalized weakness



Above-mentioned symptoms and the following:



Moderate-to-marked dyspnea



(bronchorrhea and/or bronchoconstriction)



Severe Above-mentioned symptoms and the following:



Loss of consciousness



Seizures



Generalized fasciculations



Flaccid paralysis and apnea



Above-mentioned symptoms and the following:



Loss of consciousness



Seizures



Generalized fasciculations



Flaccid paralysis and apnea



* Onset possibly delayed



† Rapid onset of symptoms



Table 3. Drugs Used to Treat Patients With Nerve Agent Poisoning*
Drug Dose (Adult) Route Indications Contraindications
Atropine 2 mg q5-10min prn



Note: The MARK 1 kit contains 2 mg of atropine.



IV/IM/ETT Excessive muscarinic symptoms Relative: IV route in hypoxia has been associated with ventricular fibrillation.
Pralidoxime chloride (Protopam, 2-PAM) 15-25 mg/kg over 20 min; can be repeated after 1 h



Note: The MARK 1 kit contains 600 mg of pralidoxime.



IV/IM Symptomatic nerve agent poisoning Rapid infusion may result in hypertension; may worsen symptoms in carbamate poisoning
Diazepam (Valium) 2-5 mg IV



10 mg IM



IV/IM Moderate or severe signs of poisoning, seizures None
*Adapted from Sidell, 1992.[3]
Table 4. Summary of Treatment Modalities According to Severity of Exposure*
Severity/Route of Exposure Atropine (Adult Dose) Pralidoxime Diazepam Other
Suspected No No No Decontamination and 18-h observation for liquid exposures
Mild 2 mg for severe



rhinorrhea or



dyspnea; may be



repeated



Administer if dyspnea



is not improving



or if GI



symptoms occur



No Decontamination and 18-h observation for liquid exposures; oxygen
Moderate 6 mg; may need to repeat Administer with atropine Administer even in absence of seizures Decontamination; oxygen
Severe Start with 6 mg; may need to repeat Administer with atropine; should repeat once or twice Administer even in absence of seizures Airway, breathing, and circulation; decontamination
*Adapted from Sidell, 1992.[3]
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