Medical Aspects of Chemical Warfare (2008) - The Black Vault

Medical Management of Chemical Toxicity in PediatricsPediatric VulnerabilityA child’s smaller mass alone reduces the dose ofnerve agent needed to cause symptoms or lethality. Forvolatile nerve agents, children are especially at risk forrespiratory effects from toxicity. Their smaller airwayscan become compromised by copious secretions andby bronchospasm after nerve agent exposure. Also,a greater dose of nerve agent is inhaled by childrenthan adults because of their higher respiratory ratesand minute volumes.TreatmentThe overall approach to treating nerve agent exposurefocuses on airway and ventilatory support, aggressiveuse of antidotes (atropine and pralidoxime),prompt control of seizures, and decontamination, asnecessary. 70 Atropine is used for its antimuscariniceffects, and oxime is used to reactivate AChE. Thecombination of atropine and pralidoxime chloride(2-PAM Cl) is recommended for the prompt treatmentof all serious cases, and timing atropine and 2-PAMCl administration is critical; the faster these antidotesare given, the better the outcome. Oxime therapy isrendered ineffective if given after the enzyme agingprocess has been completed, 69 so autoinjectors havebeen developed to rapidly administer intramuscular(IM) doses of these medications. However, the US Foodand Drug Administration (FDA) has yet to approvea pediatric 2-PAM Cl autoinjector. Other administrationroutes and methods include intravenous (IV) orintraosseous administration for atropine, and slow IVor continuous infusion for 2-PAM Cl. Data show thatplasma concentrations of autoinjector medicationspeak in less than 5 minutes, as opposed to 25 minutesfor IM administration using a needle and syringe. 33Adult nerve intoxication therapy typically includes theuse of an autoinjector set that provides both antidotes,called the Mark I kit (Meridian Medical TechnologiesInc, Bristol, Tenn; see Chapter 5, Nerve Agents). TheMark I kit delivers 600 mg of 2-PAM Cl and 2 mg ofatropine (via an autoinjector called the AtroPen [MeridianMedical Technologies Inc, Bristol, Tenn]) inseconds. It was originally developed for administrationto soldiers. The autoinjector uses a spring-loadedneedle to disperse medication in an “all-or-nothing”fashion, so it is impossible to give partial doses of anautoinjector for children, but Mark I kits can be givenin their entirety to children beginning at age 3 (seeTable 21-2). Drug dosing of atropine and 2-PAM Clin pediatrics is primarily weight based, so a standarddose cannot be used. Pediatric versions of the Mark Ikit are available overseas but are not currently availablein the United States. 71 In June 2003 the FDA approvedpediatric doses of the AtroPen to respond tothe lack of pediatric-specific therapy. 72 The AtroPen isnow available in four dosages, 0.25 mg, 0.5 mg, 1 mg,and 2 mg (Figure 21-1). The autoinjector needle lengthis 0.8 inches, with a gauge of 22. Because the AtroPendelivers only atropine and not 2-PAM Cl, the prompttreatment of pediatric nerve agent casualties remainslimited. This has caused groups such as the pediatricexpert advisory panel from the National Center forDisaster Preparedness to recommend the adult MarkI kit (which contains atropine and 2-PAM Cl) beforeuse of the pediatric AtroPen alone. 71 Meridian MedicalTechnologies has recently received FDA approval fora dual-chambered autoinjector called the “ATNAA”(antidote treatment nerve agent autoinjector) for themilitary, and Duodote (Figure 21-2) for civilian emergencymedical technicians and first responders. Eachautoinjector contains 2 mg of atropine sulfate and 600mg of 2-PAM Cl, which are injected sequentially.In 1992 Amitai et al reviewed 240 instances of accidentalpediatric atropine injections using adult-dose–based autoinjectors. 73 The study authors found a lowincidence of toxicity and no seizures, arrhythmias,Fig. 21-1. The AtroPen pediatric autoinjector, manufacturedby Meridian Medical Technologies Inc, Bristol, Tenn. Dosesizes range from 0.25 mg for infants to 0.5 mg for children7–18 kg, 1 mg for children 18–41 kg, and 2 mg for adolescentsand adults.Reproduced with permission from: Meridian Medical TechnologiesInc, Bristol, Tenn.663