Laboratory Studies
Exposure to VX in both the vapor and liquid forms has been studied since the 1950s. Laboratory tests do not aid in the acute treatment of patients exposed to nerve agents; however, measurement of acetylcholinesterase (AChE) levels for documentation and ongoing treatment is nevertheless prudent. Since there is a wide variability in baseline levels, AChE testing is most useful in treating chronic exposures when the clinician is able to compare values to an individual's baseline. Never withhold treatment while waiting for laboratory results.
AChE can be measured in red blood cells or plasma. The red blood cell cholinesterase (RBC-AChE) level is believed to be the most reliable indicator of the tissue cholinesterase status. Plasma cholinesterase (butyrylcholinesterase) levels also are referred to as pseudocholinesterase levels, because they are less predictive of central nervous system (CNS) cholinesterase activity. This often is the earliest enzyme to be inhibited by organophosphates, but that is not true for some nerve agents, particularly VX and GB.
In 2016, Schulze and colleagues released findings that accurate and precise quantitation of nerve agent metabolites can be obtained from serum, plasma, whole blood, lysed blood and postmortem blood. [12]
Order basic laboratory tests for all but minimally symptomatic patients. Measurement of electrolytes and arterial blood gases may aid in the evaluation of the patient's fluid status and the acid/base balance.
A number of new tests for the detection and quantification of chemical warfare agents are being developed. These include an active capillary dielectric barrier discharge plasma ionization (DBDI) technique for mass spectrometry, which may be useful in combination with hand-held instruments for on-site monitoring [13, 14] and a highly accurate method for detecting G- and V-series organophosphorus nerve agent adducts to butyrylcholinesterase in filtered blood, serum, or plasma. [15]
Other Tests
Electrocardiography - For palpitations or for any dysrhythmias noted on monitor
Procedures
Because a significant cause of morbidity and mortality of these patients relates to the airway and breathing, ensure that ventilation (which can be impaired from the respiratory muscle fatigue) and oxygenation (which can be impaired from the bronchorrhea and bronchoconstriction) are adequate. Endotracheal intubation may be needed for those with ventilatory and/or respiratory compromise.
Radiography
Typically, request a chest radiograph for dyspneic and intubated patients. A chest radiograph may also help in the diagnosis of noncardiogenic pulmonary edema.
Tables
Code Name |
Chemical Name |
VX |
O-Ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate |
VE |
O-Ethyl-S-[2-(diethylamino)ethyl] ethylphosphonothioate |
VG |
O,O-Diethyl-S-[2-(diethylamino)ethyl] phosphorothioate |
VM |
O-Ethyl-S-[2-(diethylamino)ethyl] methylphosphonothioate |
V-gas |
Russian equivalent of VX |
Agent |
LCt50 (mg ⋅ min/m3) |
LD50 (mg) |
Aging Half-Life |
Tabun (GA) |
400 |
1000 |
46 h |
Sarin (GB) |
100 |
1700 |
5.2-12 h |
Soman (GD) |
50 |
100 |
40 sec to 10 min |
VX |
10 |
10 |
50-60 h |
Receptor Involved |
Clinical Effect |
Acetylcholine, GABA, N -methyl-D -aspartate: Central (CNS) |
Anxiety, restlessness, seizures, failure to concentrate, depression, coma, apnea |
Acetylcholine: Muscarinic Postganglionic parasympathetic |
"DUMBELS" (commonly used mnemonic) D - Diarrhea U - Urination M - Miosis B - Bronchorrhea, bronchoconstriction E - Emesis L - Lacrimation S - Salivation Note: The other commonly used mnemonic "SLUDGE" is not used here, as it does not include an important sign and symptom: bronchorrhea and bronchoconstriction. |
Acetylcholine: Nicotinic Motor endplate Sympathetic and parasympathetic ganglia |
Pallor, tachycardia, hypertension, muscle weakness and/or paralysis, fasciculations Note: Some use the days of the week as an easy mnemonic for these: M - Mydriasis T - Tachycardia W - Weakness tH - Hypertension F - Fasciculations |
* Adapted from Marrs, Maynard, and Sidell. [10] |
|
Severity of Exposure |
Signs and Symptoms - Liquid |
Signs and Symptoms - Vapor |
Onset of symptoms |
Possibly delayed toxicity |
Rapidly manifesting toxicity |
Minimal |
Localized sweating at site Localized fasciculations at site |
Miosis Rhinorrhea Mild dyspnea |
Moderate |
Fasciculations Diaphoresis Nausea, vomiting, and diarrhea Generalized weakness |
Above symptoms and the following: Moderate-to-marked dyspnea (bronchorrhea and/or bronchoconstriction) |
Severe |
Above symptoms and the following: Loss of consciousness Seizures Generalized fasciculations Flaccid paralysis and apnea |
Above symptoms and the following: Loss of consciousness Seizures Generalized fasciculations Flaccid paralysis and apnea |
Drug |
Dose |
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 |
2-PAM Cl (pralidoxime chloride, Protopam) |
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 |
Diazepam (Valium) |
2-5 mg IV or 10 mg IM |
IV/IM |
Active seizures; administer as prophylaxis if moderate or severe signs of poisoning are present |
None |
*Adapted from Sidell. |
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Severity/Route of Exposure |
Atropine |
2-PAM Cl |
Diazepam |
Other |
Suspected |
No |
No |
No |
Decontamination and 18-h observation for liquid exposures |
Mild |
2 mg for severe rhinorrhea or dyspnea; may repeat prn |
Administer if patient has nonimproving dyspnea or GI symptoms |
No |
Decontamination and 18-h observation for liquid exposures; oxygen |
Moderate |
6 mg; may require repeat doses |
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 |
ABCs, decontamination |
*Adapted from Sidell. |
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