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

Medical Aspects of Chemical Warfare9 hours after ingesting boiled cassava. They were intubatedand put on ventilatory support, but antidotes(nitrite and thiosulfate) were given several hours laterupon the children’s arrival at a regional intensive careunit. Both received appropriate general support forcirculation and ventilation, including fluid loading anddobutamine for hypotension. The older child receivednitrite and thiosulfate at 19 hours after ingestion plusgastric decontamination and recovered fully. The otherchild received only general supportive care because hewas not sufficiently stable for transport to the regionalhospital until 23 hours after ingestion; by that time hewas alert and without cyanosis or serious acidosis. 183 Ina second report, eight Venezuelan boys between 8 and11 years of age consumed cyanogenic bitter cassava.Pigs that ate the remaining cassava died. On arrivalat the emergency room, all were critically ill with respiratoryfailure, bradycardia, and hypotension. Twoalso displayed generalized seizures. All the childrenreceived 100% oxygen and general supportive care.The four least ill children received in addition intramuscularhydroxocobolamin (500 mg). The four sickerchildren received nitrite and thiosulfate on a milligramper kilogram basis. Their blood was noted to be brightcherry red with identical arteriovenous Po 2values.All the children improved within a few minutes andwere discharged in good condition in 1 day. 184 A thirdcase suggests that methemoglobin formers should beused with particular care in children. Children havehigher oxygen demands than adults, and infants inparticular are unable to reduce methemoglobin efficientlybecause of immature methemoglobin reductasesystems. 185 This case reports that a 17-month-old childdied after receiving a double dose of sodium nitritefor sublethal cyanide ingestion. Antidotes were givenin the absence of serious illness and were repeatedwithout first assessing levels of methemoglobin. Furthermore,antidote dosing was not adjusted for bodyweight and hemoglobin. Toxicological estimates placethe child’s induced methemoglobin at 92%. 186These three case reports and principles of toxicologyand pediatrics demonstrate that young children whoare critically ill with cyanide overdose can be successfullyresuscitated with expectation of full recovery.As with adults, resuscitation of the poisoned childinvolves life support and stabilization measures, followedby identification of the toxin and detoxificationas appropriate. General measures include 100% oxygenand general life support, including gut decontaminationwith lavage and adsorbents. Antidotes should beadministered in accordance with local availability anddose adjusted for weight. General dosing guidelinesper package insert should be followed. In general,sodium nitrite should be dosed in the range of 4 mg/kg to 6.6 mg/kg. The former is equivalent to thestandard adult dose, and the latter is recommendedin the manufacturer’s package insert. These doses areconsiderably less than the often published 10 mg/kg dose. Figure 11-5 demonstrates how the 10-mg/kg dose is unacceptably high for young children inparticular. Children over approximately 40 kg bodyweight can receive an adult dose of sodium nitrite assumingabsence of anemia. Hemoglobin levels under12 g/100 mL dictate dose reductions. 186 It is appropriateto administer the nitrite slowly and considerpartial doses so that methemoglobin levels can becarefully monitored. Methemoglobin levels must bemonitored before retreatment; successful therapeuticlevels appear to be well under 20%, often under 10%.If a treated child becomes cyanotic despite adequateoxygenation during nitrite therapy, methylene blueshould be considered even if the methemoglobin levelis less than 30%. 187 Although repeat dosing with halfthe original dose of antidote may be required, it shouldnot be given until caregivers are confident that lethalexposure has occurred, that acidosis persists, that thecondition remains unstable, and that adequate oxygentransport capability remains. If poor clinical statepersists despite adequate methemoglobin levels, otherdiagnoses must be considered.PolyintoxicationsThe most likely cointoxications with cyanide arealcohol and carbon monoxide. Although alcohol isfrequently used before a cyanide suicide attempt andclearly complicates the clinical management of the cyanide-overdosedpatient, it is not understood to directlyinfluence outcomes of cyanide intoxication and willnot be further discussed here. Of greater concern is theextent to which HCN contributes to mortality and morbidityin fire victims. The pathophysiology of smokeinhalation is complex. Thermal conditions, as well asthe constituents of smoke vary not only from fire tofire, but also from one location to another within thesame fire. Morbidity and mortality result from a numberof interacting processes including thermal injury,carbon monoxide poisoning, trauma, reduced oxygentension in the heated atmosphere, and other toxicantspresent. Cyanide is one of those toxicants that might bepresent in significant amounts because of incompletecombustion in hypoxic conditions. 128,188,189 Although nosingle factor or group of factors reliably predicts theextent to which HCN intoxication contributes to theclinical picture of any single smoke inhalation casualty,severity of carbon monoxide illness and lactic acidemiagreater than 10 mmol/L are most closely associatedwith severe cyanide cotoxicity. 126,138,145,190–192390