Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter VI: Chemical Injury

Nerve Agents

United States Department of Defense

Nerve agents inhibit the ability of choline esterase to hydrolyze acetylcholine (ACh) which in turn stimulates muscarinic and nicotinic receptors as well as the central nervous system (CNS) directly. As a result, the casualty will manifest a classic cholinergic syndrome that, depending on exposure and treatment, can span the range from simple miosis and "red eye" to a fulminanting cholinergic crisis progressing within minutes to respiratory arrest and death.

Diagnosis: The diagnosis of nerve agent exposure is readily made from physical signs: fasciculation of skeletal muscle (perhaps progressing to depolarization paralysis), smooth muscle contraction of airways, bladder, and bowel; intense miosis and cycloplegia; marked bradycardia (may be masked by excitement or atropine); copious secretions; convulsions; rapidly weakening respiratory effort; pale cyanosis; and terminal apnea.

Treatment: Immediate IM or IV injection with atropine to block muscarinic cholinergic receptors, and with 2-PAM (if given soon after exposure) to reactivate cholinesterase, is effective. Each U.S. soldier has in a pocket of his protective mask carrier three MARK I kits for intramuscular self-injection, each kit delivering 2 mg injections of atropine sulfate and 600 mg pralidoxime chloride (3-PAMCl). Additional 2 mg injections of atropine may need to be given by medical personnel until clear clinical evidence of atropinization is obtained (dry red skin, easier breathing, decreased wheezing, dry mouth and, less consistently, dilating pupils).

Airway obstruction requires the clearing of secretions (by suction, if possible, or else by prone turning for postural drainage), the placement of an oropharyngeal or nasopharyngeal airway, and supplementary oxygen, if available. Endotracheal intubation or cricothyrotomy may be required in conjunction with manual or mechanical ventilation. If the environment is chemically contaminated, a closed system or charcoal-filtered air must be used for ventilation.

Experimental evidence suggests that benzodiazepine anticonvulsants reduce the morbidity associated with organophosphate-induced convulsions. Suggested doses are 5 mg Valium (IM) repeated as needed, or 2.5 mg increments of (IV) Valium.

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Operational Medicine 2001

Health Care in Military Settings

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