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

Medical Aspects of Chemical Warfareto protect those responding. The second is to rapidlyintervene to avoid unnecessary complications. Thethird is to provide supportive measures accordingto the extent of injury. And the fourth is to providespecific antidotes even in the absence of confirmatorylaboratory testing while controlling for undesirableside effects (Table 11-4). If these principles are followed,most persons arriving for medical care will recoverwithin hours to days. Once discharged, all seriouslyaffected persons should receive periodic follow-upto ensure that any underlying psychiatric problemsor delayed neurological and other consequences aredetected and managed (see below).Triage, Decontamination and Patient Transport(Evacuation)Triage is necessitated by the presence of overwhelmingdemands on the available medical system.It provides for a methodical and orderly approach tocasualties. Triage, decontamination, and timely transportto prepared medical receivers depend on a trained,prepared, and well-integrated organizational system.A coordinated system is at least as critical to casualtysurvival as are specific antidotes. 142 The remainderof this discussion will assume reader awareness ofgeneral principles of casualty rescue: protection ofworkers from exposure; reduction of contaminationby evacuation from the contamination source, undressing,and removal of obvious liquid cyanide; provisionof general life support including seizure ablation;and, finally, medical decontamination and definitivemedical care.Triage of a cyanide mass casualty event focuses onidentifying casualties who require emergent care tosurvive with the least possible consequence to laterfunction, including neurological function. Casualtiesabsent of heart rate are termed expectant or black. Comatose,seizing, hypotensive, or hypopneic casualtiesare classified immediate or red. These patients mustreceive immediate respiratory support, oxygen, circulatorysupport, and antiseizure medications in additionto having obvious cyanide removed. As soon as possible,specific cyanide antidotes must be administered.Thiosulfate may be the preferred antidote in mass casualtysituations because of its favorable safety profile. Ifpersonnel are available to monitor for nitrite-inducedhypotension and to adjust the rate of administration,then the addition of nitrites will enhance recovery.Because their condition can be expected to deterioraterapidly, persons who have ingested cyanide or whohave liquid contamination should be considered forearly intravenous access with possible initiation ofthiosulfate infusion even before overt signs develop.Remaining casualties are removed from furtherexposure and sorted into delayed (yellow) and minimal(green) categories. Minimal (green) is assignedto mildly affected, vapor-exposed persons. Thesecasualities experience nausea and dizziness, and maybe agitated or hyperventilating. They require onlyremoval from exposure, a calming environment, andreassurance. Once recovered, they may be asked to provideassistance to the response effort, because they willsustain no injury from their exposure and may benefitfrom early return to useful activity. Delayed (yellow)casualties are those who have received initial treatmentand are under observation during recovery. Casualtieswho are alive at the time of first medical contact shouldbe expected to survive given full care.Cyanide decontamination is straightforward. IfTABLE 11-4US APPROACH TO CYANIDE ANTIDOTESMechanism Natural Process of Elimination TreatmentUnload cyanide from cellular cytochrome Use methemoglobin 1%–2% (Fe 3+ ) Amyl nitrite ampules (inhaled),oxidasesodium nitrite (300 mg IV), orhydroxocobalamin (5 g, diluted, IV)Transfer CN – from stable, time-release Rhodanese conjugates CN – with Sodium thiosulfate (50 mL of 25%depot to excretable molecule thiocyanate ion g SCN + sulfite solution, IV)Remove from body renal excretion renal excretionPotentiate effects of nitrite and thiosulfate NoneReduce burden of ingested cyanide Vomit Gastric lavageSupplemental oxygen (100% humidified)CN – : cyanide anionSCN – : thiocyanate386