Toxicology 17: Cyanide Poisoning Portal
Cyanide poisoning can accompany carbon monoxide poisoning when the victim is overcome in a closed space with burning synthetic materials (as in many home fires). Cyanide poisoning can quickly be fatal. The physical findings of carbon monoxide poisoning and cyanide poisoning are similar. If the patient's COHgb level does not account for the severity of the symptoms, consider cyanide poisoning.1
Common Signs and Symptoms of Cyanide Poisoning
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The basic pathophysiology is a blockade of the enzyme systems enabling cellular use of oxygen. Arterial and venous blood is well oxygenated in the presence of severe systemic hypoxia and acidosis. The patient will not appear cyanotic. Laboratory studies are not useful in the diagnosis. The ingestion of fruit seeds and exposure to silver polish may also produce cyanide poisoning.
Management
- Administer oxygen and protect the airway.
- Rescuers should not apply mouth-to-mouth resuscitation because they themselves may grow to be overcome with cyanide poisoning.
- If the patient's COHgb level does not account for the
severity of the symptoms, a trial with a cyanide antidote kit may be
indicated. The cyanide antidote kit contains 1 NG tube, 1 60-mL
syringe, 1 tourniquet, and instructions. The kit also contains 2
ampules sodium nitrite injection, 2 ampules sodium thiosulfate
injection, 12 amyl nitrite inhalants, 1 10-mL syringe with 22-gauge
needle, 1 60-mL syringe, 1 20-gauge needle.
Crush 1 to 2 amyl nitrite perles in gauze and have the patient inhale 1 to 6 times. If the patient cannot do this, crush the perles and place them over the intake valve of the ambu bag. Have the patient inhale 1 to 6 times. Repeat this every 3 to 5 minutes until the IV is started.
- If an IV has been established, skip the step above. There is no advantage in using the ampule of amyl nitrate by inhalation. Give sodium nitrite 3% solution 300 mg (10 mL) over 15 to 20 minutes. (PEDS) Pediatric dosing depends on the hemoglobin (usually 6 to 10 mg/kg or 0.2 to 0.33 mL/kg). Refer also to the chart for pediatric dosing in the kit.
- Follow this with 25% (50 mL) solution of sodium thiosulfate given IV. (PEDS) give a dose of 1.65 mL/kg (412.5 mg/kg) for a child. The sodium nitrite produces methemoglobinemia. The sodium thiosulfate donates sulfur to enzyme systems that remove cyanide from met hemoglobin, allowing it to be excreted by the kidneys as thiocyanate.
- Consult your poison center or toxicologist for this complex problem.
- A newer, more expensive treatment, called the Cyanokit™ (containing the drug hydroxocobalamin) is now available in the United States. In the presence of cyanide, Cyanokit’s active drug takes up the cyanide and becomes a form of vitamin B12. The starting dose of hydroxocobalamin for adults is 5 g (ie, both 2.5 g vials) administered as an IV infusion over 15 minutes (approximately 15 mL/min or 7.5 min per vial).
- Reconstitute each 2.5 g vial of hydroxocobalamin for injection with 100 mL of diluent (not provided with Cyanokit) using the supplied sterile transfer spike. The recommended diluent is 0.9% sodium chloride injection (0.9% NaCl). Lactated Ringer’s injection and D5W are also compatible with hydroxocobalamin and may be used if NaCl is not readily available.
- The most frequently reported adverse reactions are red urine and skin redness (both from the drug’s coloration), temporary increase in blood pressure, headache, nausea, and injection site reactions. Allergic reactions have been observed in a small number of people but are relatively mild and respond to treatment.2
- Physical incompatibility (particle formation) has been
observed with hydroxocobalamin in solution and the following drugs:
diazepam, dobutamine, dopamine, fentanyl, nitroglycerin, pentobarbital,
propofol, and thiopental. These drugs should not be administered
through the same IV line.
Chemical incompatibility has been observed with sodium thiosulfate, sodium nitrite, and ascorbic acid, and should not be administered simultaneously though the same IV line with hydroxocobalamin.
Simultaneous administration of hydroxocobalamin and blood products (whole blood, packed RBCs, platelet concentrate, and/or FFP) through the same IV line is not recommended. Blood products and hydroxocobalamin can be administered simultaneously using separate IV lines (preferably on contralateral extremities, if peripheral lines are being used). - Prior to administration of Cyanokit, smoke inhalation
victims should have:
- Been exposed to smoke in an enclosed area
- Soot present around mouth, nose, or oropharynx
- Altered mental status
References
- Kerns WP, Kirk MA. Cyanide and Hydrogen Sulfide. In Goldfrank’s Toxicologic Emergencies, 6th ed. Goldfrank LR, Flomenbaum NE, Lewin NA, Weisman RS, Howland MA, Hoffman RS, eds. Stamford, Conn: Appleton & Lange, 1998.
- Uhl W, Nolting A, Golor G, Rost KL, Kovar A. Safety of hydroxocobalamin in healthy volunteers in a randomized, placebo-controlled study. Clin Toxicol. 2006;44(suppl 1):17-28.