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Toxicity, Cyanide: Differential Diagnoses & Workup

Author: Inna Leybell, MD, Staff Physician, Department of Emergency Medicine, North Shore University Hospital
Coauthor(s): Stephen W Borron, MD, MS, FACEP, FACMT, Professor of Emergency Medicine and Medical Toxicology, Division of Medical Toxicology, Department of Emergency Medicine, Paul L Foster School of Medicine, Texas Tech University Health Sciences Center; Associate Medical Director, West Texas Regional Poison Center; Carlos J Roldan, MD, FAAEM, Assistant Professor, Department of Emergency Medicine, University of Texas Health Science Center at Houston Medical School; Consulting Staff, Department of Emergency Medicine, Memorial Hermann Hospital and Lyndon Baines General Hospital
Contributor Information and Disclosures

Updated: Dec 14, 2009

Differential Diagnoses

Acute Coronary Syndrome
Pediatrics, Meningitis and Encephalitis
Anaphylaxis
Pediatrics, Tachycardia
Angina Pectoris
Physician Suicide
Anxiety
Plant Poisoning, Hemlock
Encephalitis
Pulmonary Embolism
Herpes Simplex Encephalitis
Sedation
Lactic Acidosis
Shock, Cardiogenic
Mesenteric Ischemia
Smoke Inhalation
Metabolic Acidosis
Stroke, Ischemic
Methemoglobinemia
Toxicity, Carbon Monoxide
Myocardial Infarction
Toxicity, Hydrogen Sulfide
Pediatrics, Apnea
Toxicity, Iron
Pediatrics, Gastroenteritis
Toxicity, Isoniazid
Pediatrics, Headache
Toxicity, Nonsteroidal Anti-inflammatory Agents

Other Problems to Be Considered

Strychnine poisoning
Methanol toxicity
Azide toxicity

Workup

Laboratory Studies

  • Arterial and venous blood gases
    • Metabolic acidosis, often severe, combined with reduced arterial-venous oxygen saturation difference (<10%) suggests diagnosis.
    • Apnea may result in combined metabolic and respiratory acidosis.
  • Blood lactate level
    • A plasma lactate concentration greater than 10 mmol/L in smoke inhalation or greater than 6 mmol/L after reported or strongly suspected pure cyanide poisoning suggests significant cyanide exposure.
  • Red blood cell and plasma cyanide concentration
    • Cyanide blood concentrations are not generally available in time to aid in the treatment of acute poisoning.
    • In cyanogen exposures, these tests provide documentation for therapeutic use, which may last several days.
    • Blood cyanide concentrations may artificially increase after sodium nitrite administration because of in vitro release of cyanide from cyanomethemoglobin during the analytical procedure by strong acid used in analysis.
  • Carboxyhemoglobin (HbCO) or blood carbon monoxide concentration (by infrared spectroscopy) may be obtained in patients with smoke inhalation to rule out concurrent exposure.
  • Blood concentrations of methanol, ethylene glycol, iron, ketones, and salicylates may be useful in evaluation of unexplained metabolic acidosis. Pending results should not delay the treatment if cyanide exposure is suspected.
  • Methemoglobin concentrations provide a guide for continued therapy after use of methemoglobin-inducing antidotes such as sodium nitrite.
    • Presence of methemoglobin suggests little or no free cyanide for binding because methemoglobin vigorously binds cyanide to form cyanomethemoglobin (not measured as methemoglobin).
    • Elevated levels of methemoglobin (>10%) indicate that further nitrite therapy is not indicated and, in fact, may be dangerous.

Imaging Studies

  • No imaging studies are indicated acutely for cyanide exposure.
  • MRI may be useful during evaluation of postexposure neurologic sequelae.

Other Tests

  • ECG may show nonspecific changes.
    • Atrioventricular (AV) blocks
    • Supraventricular or ventricular arrhythmias
    • Ischemic ECG changes and eventual asystole

More on Toxicity, Cyanide

Overview: Toxicity, Cyanide
Differential Diagnoses & Workup: Toxicity, Cyanide
Treatment & Medication: Toxicity, Cyanide
Follow-up: Toxicity, Cyanide
Multimedia: Toxicity, Cyanide
References
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References

  1. American Association of Poison Control Centers. Annual Reports of the Toxic Exposure Surveillance System. [Full Text].

  2. Bronstein AC, Spyker DA, Cantilena LR Jr, Green JL, Rumack BH, Heard SE. 2007 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 25th Annual Report. Clin Toxicol (Phila). Dec 2008;46(10):927-1057. [Medline]. [Full Text].

  3. National Cancer Institute. Cancer topics: Laetrile/Amygdalin. 11/21/2005;[Full Text].

  4. Hall AH, Saiers J, Baud F. Which cyanide antidote?. Crit Rev Toxicol. 2009;39(7):541-52. [Medline].

  5. Baud FJ, Barriot P, Toffis V, et al. Elevated blood cyanide concentrations in victims of smoke inhalation. N Engl J Med. Dec 19 1991;325(25):1761-6. [Medline].

  6. Beamer WC, Shealy RM, Prough DS. Acute cyanide poisoning from laetrile ingestion. Ann Emerg Med. Jul 1983;12(7):449-51. [Medline].

  7. Borron SW, Baud FJ. Acute cyanide poisoning: clinical spectrum, diagnosis, and treatment. Arh Hig Rada Toksikol. Sep 1996;47(3):307-22. [Medline].

  8. Borron SW, Baud FJ, Barriot P, et al. Prospective study of hydroxocobalamin for acute cyanide poisoning in smoke inhalation. Ann Emerg Med. Jun 2007;49(6):794-801, 801.e1-2. [Medline].

  9. Borron SW, Baud FJ, Megarbane B, et al. Hydroxocobalamin for severe acute cyanide poisoning by ingestion or inhalation. Am J Emerg Med. Jun 2007;25(5):551-8. [Medline].

  10. Clark CJ, Campbell D, Reid WH. Blood carboxyhaemoglobin and cyanide levels in fire survivors. Lancet. Jun 20 1981;1(8234):1332-5. [Medline].

  11. Forsyth JC, Mueller PD, Becker CE, et al. Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers. J Toxicol Clin Toxicol. 1993;31(2):277-94. [Medline].

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  15. Mannaioni G, Vannacci A, Marzocca C, et al. Acute cyanide intoxication treated with a combination of hydroxycobalamin, sodium nitrite, and sodium thiosulfate. J Toxicol Clin Toxicol. 2002;40(2):181-3. [Medline].

  16. Mueller M, Borland C. Delayed cyanide poisoning following acetonitrile ingestion. Postgrad Med J. May 1997;73(859):299-300. [Medline].

  17. O'Brien B, Quigg C, Leong T. Severe cyanide toxicity from 'vitamin supplements'. Eur J Emerg Med. Oct 2005;12(5):257-8. [Medline].

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Further Reading

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Keywords

cyanide toxicity, cyanide poisoning treatment, cyanide poisoning symptoms, smoke inhalation, hydroxocobalamin, cyanide poisoning, cyanide exposure, nitrile poisoning, prussic acid, hydrocyanic acid, hydrogen cyanide, cyanogens, HCN

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Contributor Information and Disclosures

Author

Inna Leybell, MD, Staff Physician, Department of Emergency Medicine, North Shore University Hospital
Inna Leybell, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Student Association/Foundation, and Phi Beta Kappa
Disclosure: Nothing to disclose.

Coauthor(s)

Stephen W Borron, MD, MS, FACEP, FACMT, Professor of Emergency Medicine and Medical Toxicology, Division of Medical Toxicology, Department of Emergency Medicine, Paul L Foster School of Medicine, Texas Tech University Health Sciences Center; Associate Medical Director, West Texas Regional Poison Center
Stephen W Borron, MD, MS, FACEP, FACMT is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology, American College of Occupational and Environmental Medicine, American Industrial Hygiene Association, and European Association of Poisons Centres and Clinical Toxicologists
Disclosure: Dey, L.P. Consulting fee Consulting; Merck Sante Grant/research funds Laboratory research; Dey, L.P. Honoraria Speaking and teaching

Carlos J Roldan, MD, FAAEM, Assistant Professor, Department of Emergency Medicine, University of Texas Health Science Center at Houston Medical School; Consulting Staff, Department of Emergency Medicine, Memorial Hermann Hospital and Lyndon Baines General Hospital
Carlos J Roldan, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Pain Society, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

David C Lee, MD, Research Director, Department of Emergency Medicine, Associate Professor, North Shore University Hospital and New York University Medical School
David C Lee, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Medical Toxicology, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

John T VanDeVoort, PharmD, Regional Director of Pharmacy, Sacred Heart & St. Joseph's Hospitals
John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists
Disclosure: Nothing to disclose.

Managing Editor

John G Benitez, MD, MPH, FACMT, FACPM, FAAEM, Associate Professor, Department of Medicine, Clinical Pharmacology Division, Vanderbilt University; Managing Director, Tennessee Poison Center
John G Benitez, MD, MPH, FACMT, FACPM, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine, American College of Medical Toxicology, American College of Preventive Medicine, Society for Academic Emergency Medicine, Undersea and Hyperbaric Medical Society, and Wilderness Medical Society
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Asim Tarabar, MD, Assistant Professor, Director, Medical Toxicology, Department of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital
Disclosure: Nothing to disclose.

 
 
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