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CBRNE - Cyanides, Hydrogen: Treatment & Medication
Updated: Mar 11, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Prehospital Care
- Appropriate prehospital measures include the following:
- Rescue from the cyanide source (assuming rescuers have the highest level of respiratory protection [Level A])
- Removal of contaminated clothing and decontamination of the skin as required with soap and water
- Administration of high-flow oxygen, airway management, and ventilatory support as required
- Establishment of intravenous access
- Continuous cardiac monitoring
- Advanced cardiac life support (ACLS) measures as indicated for dysrhythmias
- Administer cyanide antidotes as soon as possible. While generally not carried by emergency medical technicians, these may be available at certain industrial sites.
Emergency Department Care
- Continue hemodynamic support and monitoring, oxygenation, ventilatory support, and seizure control in the emergency department (ED).
- Administer cyanide antidotes (sodium nitrite and sodium thiosulfate) as soon as possible, taking care not to create toxic methemoglobinemia. Do not delay treatment for confirmatory RBC cyanide levels.
- Consider gastric lavage followed by the administration of activated charcoal in recent ingestions. The gastric aspirate may cause secondary contamination and should be viewed as hazardous.
Consultations
In any suspected terrorist attack, contact local law enforcement authorities and the Federal Bureau of Investigation. Consultation with a medical toxicologist and/or poison control center and intensivist may be useful.
Medication
The Taylor (formerly Lily or Pasadena) Cyanide Antidote Package contains amyl nitrite, sodium nitrite, and sodium thiosulfate. The nitrite components oxidize iron contained in hemoglobin to methemoglobin. This creates an additional site for cyanide binding and promotes dissociation from cytochrome oxidase. Resultant cyanomethemoglobin may then be converted to less toxic thiocyanate through enzymes such as rhodanese or other sulfurtransferases in the presence of sodium thiosulfate. Only use amyl nitrite perles as a temporizing measure if IV access has not been established, since administration of IV sodium nitrite is more effective in creating therapeutic methemoglobin levels.
The use of the nitrite-containing components of the cyanide antidote kit must be done with caution, as they may result in significant hypotension and cardiovascular collapse. Production of methemoglobin reduces oxygen-carrying capacity, which in excess can be life-threatening. In the setting of concomitant carbon monoxide poisoning, use of sodium nitrite must occur with particular caution if not abandoned altogether. Patients exposed to carbon monoxide have an underlying diminished oxygen-carrying capacity; further decreased by production of methemoglobinemia may be lethal. However, in cases of smoke inhalation where cyanide toxicity is suspected, administration of sodium thiosulfate is safe.
Unlike carbon monoxide, inhibition of cytochrome oxidase by cyanide is noncompetitive; therefore, oxygen has antidotal efficacy in cyanide poisoning through uncertain mechanisms. Treat patients with 100% oxygen. Hyperbaric oxygen use may be considered for patients with cyanide poisoning refractory to other antidotes; it is especially effective when concomitant carbon monoxide toxicity exists. However, its use in pure cyanide poisoning is controversial.
Hydroxocobalamin, used routinely in Europe for cyanide toxicity, can be administered when available. It functions by combining with cyanide to form cyanocobalamin, which is relatively nontoxic and cleared renally. It can be combined with sodium thiosulfate administration for accelerated detoxification.
Antidotes
Administration of antidotes, which counteract the toxic effects of cyanide, is critical for life-threatening intoxication. Hydroxocobalamin (vitamin B-12a) has been recognized as an antidote for cyanide toxicity for more than 40 years and is in active use in France for cyanide poisoning. It is FDA approved for the treatment of pernicious anemia and has an excellent safety profile. Hydroxocobalamin binds with cyanide on an equimolar basis to form cyanocobalamin (vitamin B-12) and thereby detoxifies the agent. However, US formulations are not sufficiently concentrated to make hydroxocobalamin a useful alternative treatment at this time.
Currently, the most concentrated formulation in the United States is 1,000 mcg/mL. The typical cyanide treatment dose used in Europe is 5 g, which would require 5 L of this formulation. Hopefully, the continuing threat of CW terrorism as well as industrial accidents/fires will result in greater future efforts to establish hydroxocobalamin as the treatment of choice for cyanide toxicity in the United States as well.
Amyl nitrite (Isoamyl Nitrate)
Ampules can be crushed and inhaled by a spontaneously breathing patient or ventilated into an apneic patient using a bag valve mask device; temporizing measure until IV access can be established.
Adult
1 ampule (0.2 mL) for 30-60 s administered by inhalation along with 100% oxygen
Pediatric
Not established
Coadministration with alcohol may cause severe hypotension and cardiovascular collapse; with calcium channel blockers, may produce symptomatic orthostatic hypotension; aspirin may increase nitrate serum concentrations
Documented hypersensitivity, cerebral hemorrhage
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Can cause severe methemoglobinemia in overdose or in those with G-6-PD deficiency; rarely may cause hemolytic anemia
Sodium nitrite
DOC once IV access is established; creates methemoglobinemia more effectively than amyl nitrite.
Adult
300 mg (10 mL of 3% solution) IV over 5-20 min; slow rate of infusion if hypotension develops; this dose assumes hemoglobin level of 12 mg/dL (dosage adjustment necessary in patients with anemia); may repeat up to half initial dose in 1 h if required
Pediatric
0.33 mL/kg of 3% solution IV over 5-20 min, not to exceed 300 mg; this dose assumes hemoglobin level of 12 mg/dL (dosage adjustment necessary in patients with anemia)
Coadministration with channel blockers may increase symptomatic orthostatic hypotension (adjust dose of either agent)
Documented hypersensitivity, concomitant severe carbon monoxide poisoning
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Excessive methemoglobinemia, hemolysis, or hypotension may occur, especially in patients with G-6-PD deficiency
Sodium thiosulfate (Tinver)
Acts as donor of sulfur, which is used as substrate by rhodanese and other sulfurtransferases for detoxification of cyanide to thiocyanate; DOC for treating cyanide toxicity with concomitant carbon monoxide poisoning.
Adult
12.5 g (50 mL) IV over 10 min; may repeat up to half dose at 1 h for patients with persistent symptoms
Pediatric
1.65 mL/kg of 25% solution over 10 min, not to exceed 12.5 g; may repeat up to half dose at 1 h for patients with persistent symptoms
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in asthma; rapid IV infusion may cause transient hypotension and ECG changes
Hydroxocobalamin (vitamin B-12)
Complexes with cyanide to form nontoxic cyanocobalamin (vitamin B-12); disadvantages are large dose required for antidotal efficacy and availability in US only in very dilute solutions.
Adult
4 g IV over 30 min, not to exceed 10 g; may be given more rapidly in cardiac arrest
Pediatric
Not established
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
None reported for this indication
Activated charcoal (Actidose-Aqua, Liqui-Char)
Emergency treatment in poisoning caused by drugs and chemicals. Network of pores present in activated charcoal adsorbs 100-1000 mg of drug per gram of charcoal. Does not dissolve in water.
For maximum effect, administer within 30 min after ingesting poison.
Adult
25-100 g PO; 1 g/kg PO; or 10 times weight of ingested poison; give as susp in 4-8 oz water
Pediatric
<1 year: Not recommended
>1 year: Administer as in adults
May inactivate ipecac syrup if used concomitantly; effectiveness of other medications decreases with coadministration; do not mix with sherbet, milk, or ice cream (decreases absorptive properties of activated charcoal)
Documented hypersensitivity; poisoning or overdosage of mineral acids and alkalies
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Not very effective in poisonings of ethanol, methanol, and iron salts; induce emesis before giving activated charcoal; after emesis with ipecac syrup, patient may not tolerate activated charcoal for 1-2 h; can administer in early stages of gastric lavage; without sorbitol, gastric lavage returns are black
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References
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Further Reading
Keywords
cyanides, AC, hydrocyanic acid, HCN, cyanide, chemical warfare agent, chemical weapon, cyanide exposure, hydrogen cyanide exposure, cyanogen chloride, cyanide poisoning, hydrogen cyanide poisoning, hydrogen cyanide exposure, terrorism
