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For further information, see CMDT Part 38-31: Cyanide Poisoning

Key Features

  • Cyanide is rapidly absorbed by inhalation, skin absorption, ingestion

  • In gaseous form, hydrogen cyanide is an important component of fire smoke

  • Cyanide-generating glycosides also found in the pits of apricots and other related plants

  • Cyanide is generated by breakdown of nitroprusside; poisoning can result from rapid high-dose infusions

  • Also formed by metabolism of acetonitrile, found in some over-the-counter fingernail glue removers

Clinical Findings

  • Onset of toxicity is nearly instantaneous after inhalation

  • However, it may be delayed for minutes to hours after ingestion of cyanide salts or cyanogenic plants or chemicals

  • Effects include

    • Headache

    • Dizziness

    • Nausea

    • Abdominal pain

    • Anxiety

    • Confusion

    • Syncope

    • Shock

    • Seizures

    • Coma

    • Death

  • "Bitter almond" odor may be detected on the victim's breath or in vomitus, although this is not a reliable finding

Diagnosis

  • The venous oxygen saturation may be elevated (> 90%) in severe poisonings because tissues have failed to take up arterial oxygen

Treatment

  • Remove the victim from exposure, taking care to avoid exposure to rescuers

  • Activated charcoal

    • Administer 60–100 g mixed in aqueous slurry orally or via gastric tube

    • Do not use for comatose or convulsing patients unless they are endotracheally intubated

  • Stop or slow the nitroprusside infusion rate for suspected cyanide toxicity

  • In the United States, there are prepackaged cyanide antidotes (eTable 38–1)

  • Nithiodote

    • Conventional cyanide antidote package

    • Contains

      • Sodium nitrite (to induce methemoglobinemia, which binds free cyanide)

      • Sodium thiosulfate (to promote conversion of cyanide to the less toxic thiocyanate)

    • Administer 3% sodium nitrite solution, 10 mL intravenously followed by 25% sodium thiosulfate solution, 50 mL intravenously (12.5 g)

    • Caution: Nitrites may induce hypotension and dangerous levels of methemoglobin

  • Hydroxocobalamin

    • A newer and potentially safer antidote

    • Adult dose: 5 g intravenously (children's dose is 70 mg/kg)

    • Note: Hydroxocobalamin causes red discoloration of skin and body fluids that may last several days and can interfere with some laboratory tests

eTable 38–1.Currently available cyanide (CN) antidote kits.

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