Approach Considerations

The workup in patients with cyanide exposure may include the studies discussed below.

Arterial and venous blood gases

Cyanide toxicity is characterized by a normal arterial oxygen tension and an abnormally high venous oxygen tension, resulting in a decreased arteriovenous oxygen difference (< 10%). A high-anion-gap metabolic acidosis is a hallmark of significant cyanide toxicity.^{[10, 27]}Apnea may result in combined metabolic and respiratory acidosis.

Blood lactate level

Elevation in the blood lactate level is a sensitive marker for cyanide toxicity. A plasma lactate concentration of 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.^[28]

Red blood cell or plasma cyanide concentration

Cyanide blood concentrations are not generally available in time to aid in the treatment of acute poisoning, but may provide subsequent confirmation. In cyanogen exposures, these tests provide documentation for therapeutic use, which may last several days.

The preferred test is a red blood cell cyanide concentration. With this method, mild toxicity is observed at concentrations of 0.5-1.0 μg/mL. Concentrations of 2.5 μg/mL and higher are associated with coma, seizures, and death. Blood cyanide concentrations may artificially increase after sodium nitrite (antidote) administration, because of in vitro release of cyanide from cyanomethemoglobin during the analytical procedure by strong acid used in analysis.

Carboxyhemoglobin level or blood carbon monoxide concentration

Carboxyhemoglobin (HbCO) level (by co-oximetry) or blood carbon monoxide concentration (by infrared spectroscopy) may be obtained in patients with smoke inhalation to rule out concurrent exposure. HbCO measurements may be artificially elevated in blood samples drawn after hydroxocobalamin administration.^[29]

Methemoglobin level

A methemoglobin level is especially important in cyanotic patients. The presence of methemoglobin suggests that little or no free cyanide is available for binding, because methemoglobin vigorously binds cyanide to form cyanomethemoglobin (which is not measured as methemoglobin).

Methemoglobin concentrations provide a guide for continued therapy after the use of methemoglobin-inducing antidotes, such as sodium nitrite. Elevated levels of methemoglobin (> 10%) indicate that further nitrite therapy is not indicated and, in fact, may be dangerous.

Electrocardiogram (ECG)

On ECG, nonspecific findings predominate. Abnormalities may include the following^[30]:

Sinus bradycardia or tachycardia
Atrioventricular blocks
Supraventricular or ventricular arrhythmias
Ischemic changes

In some cases, shortening of the ST segment with eventual fusion of the T wave into the QRS complex has been observed.

Other

No imaging studies are indicated acutely for cyanide exposure, but magnetic resonance imaging (MRI) may be useful during the evaluation of postexposure neurologic sequelae.

Fluorescein staining and slit-lamp examination of the eyes may be necessary following decontamination, to assess corneal integrity.

Treatment & Management

Holstege CP, Kirk MA. Cyanide and Hydrogen Sulfide. Nelson LS, Howland MA, Lewin NA, Smith SW, Goldfrank LR, Hoffman RS, eds. Goldfrank's Toxicologic Emergencies. 11th ed. New York, NY: McGraw-Hill Education; 2019. 1684-93.
Abraham K, Buhrke T, Lampen A. Bioavailability of cyanide after consumption of a single meal of foods containing high levels of cyanogenic glycosides: a crossover study in humans. Arch Toxicol. 2016 Mar. 90 (3):559-74. [QxMD MEDLINE Link].
Akyildiz BN, Kurtoglu S, Kondolot M, Tunc A. Cyanide poisoning caused by ingestion of apricot seeds. Ann Trop Paediatr. 2010. 30(1):39-43. [QxMD MEDLINE Link].
Armstrong J. Chemical warfare. RN. 2002 Apr. 65 (4):32-9; quiz 40. [QxMD MEDLINE Link].
Brennan RJ, Waeckerle JF, Sharp TW, Lillibridge SR. Chemical warfare agents: emergency medical and emergency public health issues. Ann Emerg Med. 1999 Aug. 34(2):191-204. [QxMD MEDLINE Link].
Centers for Disease Control and Prevention. Chemical Emergencies Fact Sheets--Cyanide: Exposure, Deconatmination, Treatment. CDC.gov. Available at https://www.cdc.gov/chemicalemergencies/factsheets/cyanide.html. February 7, 2023; Accessed: August 26, 2023.
Baud FJ. Cyanide: critical issues in diagnosis and treatment. Hum Exp Toxicol. 2007 Mar. 26(3):191-201. [QxMD MEDLINE Link].
Greenfield RA, Brown BR, Hutchins JB, Iandolo JJ, Jackson R, Slater LN, et al. Microbiological, biological, and chemical weapons of warfare and terrorism. Am J Med Sci. 2002 Jun. 323(6):326-40. [QxMD MEDLINE Link].
Rosenbloom M, Leikin JB, Vogel SN, Chaudry ZA. Biological and chemical agents: a brief synopsis. Am J Ther. 2002 Jan-Feb. 9(1):5-14. [QxMD MEDLINE Link].
Baskin SI, Brewer TG. Cyanide poisoning. Cyanide poisoning. Medical Aspects of Chemical and Biological Warfare. 1997. 271-286.
Morocco AP. Cyanides. Crit Care Clin. 2005 Oct. 21(4):691-705, vi. [QxMD MEDLINE Link].
Sidell FR, Patrick WC, Dashiell TR. Cyanide. Jane's Chem-Bio Handbook. 1998. 79-88.
USACHPPM. Cyanide. USACHPPM Tech Guide 244: The Medical NBC Battlebook. 1999. V: 36-37.
Burda AM, Sigg T. Pharmacy preparedness for incidents involving weapons of mass destruction. Am J Health Syst Pharm. 2001 Dec 1. 58(23):2274-84. [QxMD MEDLINE Link].
Lynch EL, Thomas TL. Pediatric considerations in chemical exposures: are we prepared?. Pediatr Emerg Care. 2004 Mar. 20(3):198-208. [QxMD MEDLINE Link].
Zheng A, Dzombak DA, Luthy RG. Formation of free cyanide and cyanogen chloride from chloramination of publicly owned treatment works secondary effluent: laboratory study with model compounds. Water Environ Res. 2004 Mar-Apr. 76(2):113-20. [QxMD MEDLINE Link].
Schnepp R. Cyanide: sources, perceptions, and risks. J Emerg Nurs. 2006 Aug. 32(4 Suppl):S3-7. [QxMD MEDLINE Link].
Musshoff F, Schmidt P, Daldrup T, Madea B. Cyanide fatalities: case studies of four suicides and one homicide. Am J Forensic Med Pathol. 2002 Dec. 23(4):315-20. [QxMD MEDLINE Link].
Hendry-Hofer TB, Ng PC, Witeof AE, Mahon SB, Brenner M, Boss GR, et al. A Review on Ingested Cyanide: Risks, Clinical Presentation, Diagnostics, and Treatment Challenges. J Med Toxicol. 2019 Apr. 15 (2):128-133. [QxMD MEDLINE Link]. [Full Text].
National Cancer Institute. Cancer topics: Laetrile/Amygdalin. 6/14/2022. [Full Text].
Dang T, Nguyen C, Tran PN. Physician Beware: Severe Cyanide Toxicity from Amygdalin Tablets Ingestion. Case Rep Emerg Med. 2017. 2017:4289527. [QxMD MEDLINE Link]. [Full Text].
Gummin DD, Mowry JB, Beuhler MC, Spyker DA, Rivers LJ, Feldman R, et al. 2021 Annual Report of the National Poison Data System(©) (NPDS) from America's Poison Centers: 39th Annual Report. Clin Toxicol (Phila). 2022 Dec. 60 (12):1381-1643. [QxMD MEDLINE Link]. [Full Text].
Haden M, Wheatley N, Gray LA, Bradberry SM, Sandilands EA, Thanacoody RH, et al. Potential cyanide poisoning reported to the UK national poisons information service: 2008-2019. Clin Toxicol (Phila). 2022 Sep. 60 (9):1051-1058. [QxMD MEDLINE Link].
Alqahtani RM, Alyousef MY, AlWatban ZH, Ghandour MK. Long-Term Neuropsychiatric Sequelae in a Survivor of Cyanide Toxicity Patient With Arterialization. Cureus. 2020 Jun 3. 12 (6):e8430. [QxMD MEDLINE Link]. [Full Text].
Mao Q, Zhao X, Kiriyama A, Negi S, Fukuda Y, Yoshioka H, et al. A synthetic porphyrin as an effective dual antidote against carbon monoxide and cyanide poisoning. Proc Natl Acad Sci U S A. 2023 Feb 28. 120 (9):e2209924120. [QxMD MEDLINE Link]. [Full Text].
Department of the Army. Blood agents (Cyanogens). Field Manual 8-285: Treatment of Chemical Agent Casualties and Conventional Military Chemical Injuries. 1995. VI: 1-2.
Baud FJ, Borron SW, Mégarbane B, Trout H, Lapostolle F, Vicaut E, et al. Value of lactic acidosis in the assessment of the severity of acute cyanide poisoning. Crit Care Med. 2002 Sep. 30(9):2044-50. [QxMD MEDLINE Link].
Baud FJ, Barriot P, Toffis V, Riou B, Vicaut E, Lecarpentier Y, et al. Elevated blood cyanide concentrations in victims of smoke inhalation. N Engl J Med. 1991 Dec 19. 325(25):1761-6. [QxMD MEDLINE Link].
Lee J, Mukai D, Kreuter K, et al. Potential interference by hydroxocobalamin on co-oximetry hemoglobin measurements during cyanide and smoke inhalation treatments. Ann Emerg Med. 2007. 49(6):802-805. [QxMD MEDLINE Link].
Fortin JL, Desmettre T, Manzon C, Judic-Peureux V, Peugeot-Mortier C, Giocanti JP, et al. Cyanide poisoning and cardiac disorders: 161 cases. J Emerg Med. 2010 May. 38(4):467-76. [QxMD MEDLINE Link].
Sanders KN, Aggarwal J, Stephens JM, Michalopoulos SN, Dalton D, Lewis DE, et al. Cost impact of hydroxocobalamin in the treatment of patients with known or suspected cyanide poisoning due to smoke inhalation from closed-space fires. Burns. 2022 Sep. 48 (6):1325-1330. [QxMD MEDLINE Link]. [Full Text].
USAMRICD. Cyanide. Field Management of Chemical Casualties Handbook. 1996. 37-40.
USAMRICD. Cyanide. Medical Management of Chemical Casualties Handbook. 1999. 38-58.
Martin CO, Adams HP Jr. Neurological aspects of biological and chemical terrorism: a review for neurologists. Arch Neurol. 2003 Jan. 60(1):21-5. [QxMD MEDLINE Link].
Kirk MA, Gerace R, Kulig KW. Cyanide and methemoglobin kinetics in smoke inhalation victims treated with the cyanide antidote kit. Ann Emerg Med. 1993 Sep. 22(9):1413-8. [QxMD MEDLINE Link].
Borron SW, Baud FJ, Mégarbane B, Bismuth C. Hydroxocobalamin for severe acute cyanide poisoning by ingestion or inhalation. Am J Emerg Med. 2007 Jun. 25(5):551-8. [QxMD MEDLINE Link].
Borron SW, Baud FJ, Barriot P, Imbert M, Bismuth C. Prospective study of hydroxocobalamin for acute cyanide poisoning in smoke inhalation. Ann Emerg Med. 2007 Jun. 49(6):794-801, 801.e1-2. [QxMD MEDLINE Link].
Thompson JP, Marrs TC. Hydroxocobalamin in cyanide poisoning. Clin Toxicol (Phila). 2012 Dec. 50 (10):875-85. [QxMD MEDLINE Link].
Hall AH, Saiers J, Baud F. Which cyanide antidote?. Crit Rev Toxicol. 2009. 39(7):541-52. [QxMD MEDLINE Link].
Curry SC, Connor DA, Raschke RA. Effect of the cyanide antidote hydroxocobalamin on commonly ordered serum chemistry studies. Ann Emerg Med. 1994 Jul. 24(1):65-7. [QxMD MEDLINE Link].
Sutter M, Tereshchenko N, Rafii R, Daubert GP. Hemodialysis Complications of Hydroxocobalamin: A Case Report. J Med Toxicol. 2010 Mar 30. [QxMD MEDLINE Link].
Shepherd G, Velez LI. Role of hydroxocobalamin in acute cyanide poisoning. Ann Pharmacother. 2008 May. 42(5):661-9. [QxMD MEDLINE Link].

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Author

Inna Leybell, MD Clinical Assistant Professor, Department of Emergency Medicine, NYU Langone Medical Center

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, Phi Beta Kappa

Disclosure: Nothing to disclose.

Coauthor(s)

Stephen W Borron, MD, MS, FAAEM, FACEP, FAACT, 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, FAAEM, FACEP, FAACT, FACMT is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American Industrial Hygiene Association, American College of Occupational and Environmental Medicine, European Association of Poisons Centres and Clinical Toxicologists, American College of Medical Toxicology

Disclosure: Received consulting fee from Meridian Pharmaceuticals for consulting.

Carlos J Roldan, MD, FAAEM, FACEP Professor of Emergency Medicine, Department of Emergency Medicine, McGovern Medical School, University of Texas Health Science Center at Houston; Associate Professor of Pain Medicine, Department of Pain Medicine, MD Anderson Cancer Center

Carlos J Roldan, MD, FAAEM, FACEP is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Pain Society, American Society of Regional Anesthesia and Pain Medicine, International Association for the Study of Pain, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Colleen M Rivers, MD Senior Fellow in Medical Toxicology, New York City Poison Control Center, Bellevue Hospital Center

Colleen M Rivers, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Michael A Miller, MD Clinical Professor of Emergency Medicine, Medical Toxicologist, Department of Emergency Medicine, Texas A&M Health Sciences Center; CHRISTUS Spohn Emergency Medicine Residency Program

Michael A Miller, MD is a member of the following medical societies: American College of Medical Toxicology

Disclosure: Nothing to disclose.

Acknowledgements

Frederic J Baud, MD Director, Professor, Toxicological and Medical Intensive Care Unit, Hôpital Lariboisiere of Paris, France