injuries poisoning
Nerve Chemical Warfare Agents
Treatment of Nerve Chemical Warfare Injuries
Anticholinergics (eg,atropine) Oxime reactivators (eg, 2-PAM, MMB-4) Benzodiazepines Respiratory support as needed is given (see table Symptoms and Treatment of Specific Poisons ). Airway, breathing, and circulation are addressed in standard fashion, as discussed in Decontaminate all suspicious liquid on skin as soon as possible using Reactive Skin Decontamination Lotion (RSDL®); a 0.5% hypochlorite solution may also be used, as may soap and water. Possibly contaminated wounds require inspection, removal of all debris, and copious flushing with water or saline. Severe symptoms and death may occur after skin decontamination because decontamination may not completely remove nerve agents that are passing through the skin. In the US two drugs are given: Atropine 2-pyridine aldoxime methyl chloride (2-PAM—also calledpralidoxime). Atropineblocks the action of acetylcholine (ACh) at muscarinic receptors. 2-PAM reactivates acetylcholinesterase (AChE) that has been phosphorylated by nerve agents (or organophosphate insecticides) but that has not yet undergone aging. Becauseatropineacts only at muscarinic ACh receptors, 2-PAM is also needed to reverse effects on skeletal muscles (eg, twitching, respiratory-muscle weakness, and paralysis). The oxime 1,1′-methylenebis[4-[(hydroxyimino)methyl]-pyridinium] dibromide, or MMB-4, appears to be more effective against a broader range of nerve agents than is 2-PAM and will replace 2-PAM for US military use in the next few years. For military, prehospital, and mass-casualty care, autoinjectors for intramuscular use are typically used; each contains 2.1 mg ofatropineand 600 mg of 2-PAM. The drugs are given into the belly of a large muscle (eg, thigh) before establishing IV access. Once IV access is obtained, subsequent doses are given IV. Adult patients with significant difficulty breathing or with systemic effects should promptly receive three 2.0-mg (if intravenous) or 2.1-mg (if an autoinjector is used) doses ofatropineand three 600-mg doses of 2-PAM followed immediately by a benzodiazepine.Midazolamhas replaceddiazepamas the preferred agent becausemidazolamis better absorbed when given intramuscularly, but either can be used based on availability. Both are administered as 10-mg doses when treating nerve agent toxicity. The newly developed 10-mgmidazolamautoinjector will eventually replace thediazepamautoinjector for treating seizures. Patients with less severe signs and symptoms can be given one combination autoinjector kit (atropineand 2-PAM) repeated in 3 to 5 minutes if symptoms have not resolved; a benzodiazepine is not automatically given unless 3 autoinjectors are required to be given all at once. Additional 2-mg doses ofatropineare given every 2 to 3 minutes until muscarinic effects (airway resistance, secretions) resolve. Additional 600-mg doses of 2-PAM may be given hourly as needed for the control of skeletal-muscle effects (twitching, fasciculations, weakness, paralysis). Additional doses of benzodiazepines are given as needed for seizures. Note that paralyzed patients may have seizures in the absence of visible convulsions. Transition to IV administration should be done at the first opportunity. Dosages are adjusted downward for children. A-series agents are difficult to treat once victims have gone into cholinergic crisis; aggressive treatment withatropineand an oxime is needed along withscopolamine1 mg IV. During the latent period, victims need to be decontaminated thoroughly as soon as possible, although decontamination, especially with RSDL®, may be effective even an hour or two after exposure. Heart rate, core temperature, and acetylcholinesterase (AChE) levels should be monitored. 