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Cyanide Toxicity Treatment & Management

  • Author: Inna Leybell, MD; Chief Editor: Asim Tarabar, MD  more...
 
Updated: Dec 07, 2015
 

Approach Considerations

Administer a cyanide antidote if the diagnosis of cyanide toxicity is strongly suspected, without waiting for laboratory confirmation. Available antidotes are hydroxocobalamin (Cyanokit) and sodium thiosulfate and sodium nitrite (Nithiodote). Both are given intravenously.

Patients who present with more than minimal symptoms that resolve without treatment should be admitted for observation and supportive care. In patients with acute poisoning from hydrogen cyanide (HCN) gas or soluble salts, the principal acute care concerns are hemodynamic instability and cerebral edema. The continuous cardiac monitoring, respiratory and cardiovascular support, and frequent neurologic evaluation these patients require is generally best provided in an intensive care unit.

Conversely, acute poisoning from cyanogens (nitriles) or poorly soluble salts may not manifest or become life-threatening for several hours after exposure. These patients require a 24-hour observation period.[23, 24]

Oxygenation should be optimized and continuous cardiac monitoring provided. Depending on the severity of symptoms, endotracheal intubation may be necessary to optimize oxygen delivery and protect the airway. Serum lactate concentrations, chemistries, and arterial or venous blood gases should be monitored.

Patients should be reevaluated 7-10 days after discharge from the hospital.[25] Delayed onset of Parkinson-like syndrome or neuropsychiatric sequelae may be noted on followup.

Special concerns in pregnancy

Fetal demise is possible in cyanide poisoning. Aggressive support and antidotal treatment of the mother is paramount. An obstetric evaluation following stabilization of the mother is essential. Therapeutic abortion may be indicated in the presence of fetal demise.

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Prehospital Care

Use of personal protective equipment is essential at many cyanide exposure scenes. Respiratory protection against hydrogen cyanide gas may be needed at fires and industrial accidents. Certain cyanide compounds can be absorbed dermally; emergency services personnel should wear gloves and other forms of skin protection.

Appropriate prehospital measures may include the following[5, 6] :

  • Rescue from the cyanide source (on the assumption that 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 (IV) access
  • Continuous cardiac monitoring
  • Advanced cardiac life support (ACLS) measures as indicated for dysrhythmias

Aggressive airway management with delivery of 100% oxygen can be lifesaving. (Although theoretically useless, supportive care with administration of oxygen alone has proven effective in a number of poisonings.) It can also treat concomitant carbon monoxide exposure, pending measurement of blood levels.

Administer cyanide antidotes as soon as possible.[26, 23, 24] While not carried by all emergency medical technicians, some first responders do have protocols to administer hydroxocobalamin in the field. As a temporizing measure, amyl nitrite ampules can be crushed and their contents poured onto a gauze pad and placed in front of the patient's mouth, if the patient is breathing spontaneously, or ventilated into an apneic patient using a bag-valve-mask.

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Emergency Department Care

Initial emergency department care for patients with cyanide exposure is identical to that provided in the prehospital phase. Provide supportive care, including the following:

  • Airway control, ventilation, and 100% oxygen
  • Crystalloids and vasopressors, as needed, for hypotension
  • Sodium bicarbonate, titrated according to arterial blood gas (ABG) and serum bicarbonate level

Decontaminate the patient with removal of clothing/skin flushing and/or activated charcoal (1g/kg), as appropriate. Activated charcoal should be given after oral exposure in alert patients who are able to protect the airway or after endotracheal intubation in unconscious patients. In recent ingestions, activated charcoal may be preceded by gastric lavage. The gastric aspirate may cause secondary contamination and should be viewed as hazardous.

Administer hydroxocobalamin or sodium thiosulfate and sodium nitrite if the diagnosis is strongly suspected. Do not wait for laboratory confirmation.

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Cyanide Antidotes

Antidotes to cyanide include hydroxocobalamin and sodium nitrite and sodium thiosulfate. Sodium thiosulfate may be given in combination with sodium nitrite or hydroxocobalamin, or may be given alone. These agents are administered intravenously.

Hydroxocobalamin

Hydroxocobalamin, which is considered the drug of choice in continental Europe and Australia, is approved by the US Food and Drug Administration (FDA) for treating known or suspected cyanide poisoning.[27, 28] Coadministration of sodium thiosulfate (through a separate line or sequentially) has been suggested to have a synergistic effect on detoxification.

Hydroxocobalamin combines with cyanide to form cyanocobalamin (vitamin B-12), which is renally cleared.[29] Alternatively, cyanocobalamin may dissociate from cyanide at a slow enough rate to allow for cyanide detoxification by the mitochondrial enzyme rhodanese.

A review by Hall et al notes that hydroxocobalamin has not been associated with clinically significant toxicity in antidotal doses compared with other cyanide antidotes. Hydroxocobalamin has a rapid onset of action, neutralizes cyanide without interfering with cellular oxygen use, is conducive to prehospital use due to its tolerability and safety profiles, and is safe for use in patients with smoke inhalation.[30]

Adverse effects of hydroxocobalamin administration include transient hypertension (a benefit in hypotensive patients), reddish brown skin, mucous membrane and urine discoloration, and rare anaphylaxis and anaphylactoid reactions. Because of its bright red color, it also interferes with co-oximetry (about a 5% increase in carboxyhemoglobin levels) and blood chemistry testing (bilirubin, creatinine kinase and possibly liver enzymes, creatinine, phosphorus, glucose, magnesium, and iron levels).[31] It can also interfere with hemodialysis.[32]

Certain medications should not be administered simultaneously or through the same line as hydroxocobalamin. These include diazepam, dopamine, dobutamine, and sodium thiosulfate.

Sodium nitrite and sodium thiosulfate

Sodium nitrite and sodium thiosulfate are often used in combination and are currently considered second-line therapy after hydroxocobalamin. Sodium nitrite is rapidly effective but can cause life-threatening toxicity, whereas sodium thiosulfate has a somewhat delayed effect but is far safer.

Sodium nitrite induces methemoglobin in red blood cells, which combines with cyanide, thus releasing cytochrome oxidase enzyme. Sodium thiosulfate donates a sulfur atom necessary for the transformation of cyanide to thiocyanate by rhodanese, thus increasing the activity of the endogenous detoxification system. The thiocyanate is then renally excreted.

Sodium nitrite should not be used in patients with smoke inhalation unless their carboxyhemoglobin concentration is very low (< 10%). The induction of methemoglobinemia by sodium nitrite compounds the effect of any existing carboxyhemoglobinemia, significantly reduces the oxygen-carrying capacity of blood. In addition, vasodilation from sodium nitrite may result in significant hypotension and cardiovascular collapse.[26]

Appropriate dosing of sodium nitrite has not been established in children. Consequently, these patients are at increased risk for excessive methemoglobinemia, hypotension, or both.

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Inpatient Care

Optimize oxygenation. Monitor disease resolution by clinical criteria, serial plasma lactate concentrations, and arterial and venous blood gases. Perform serial electrocardiograms (ECGs) for patients with cardiac dysrhythmias or complaints of chest pain. Monitor for delayed onset of pulmonary edema in those presenting with evidence of respiratory irritation. Discharge the patient when neurologic status and cardiovascular status have normalized and acidosis and other metabolic abnormalities have resolved.

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Transfer

Avoid transfer of patients with acute cyanide toxicity. However, transfer the patient if antidotes and intensive care are unavailable and if rapid, appropriate medical transport can be assured. Ideally, transfer patients to a regional toxicology treatment center.

Provide medical stabilization (eg, airway, hemodynamic parameters) before transfer. Transfer with an advanced cardiac life support (ACLS) level of service under continuous cardiac monitoring with supplemental oxygen and intravenous access.

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Deterrence and Prevention

Smoke alarms significantly reduce the incidence of serious smoke inhalation injury. Workplaces using cyanides should have engineering controls in place to avoid inadvertent exposures. Workers should be provided with personal protective equipment and training; they should be instructed to avoid contact between cyanide salts and mineral acids or other compounds with low pH.

Patients receiving sodium nitroprusside at high doses or for more than 5 days should have monitoring of blood cyanide or thiocyanate concentrations. Alternatively, these patients can be treated prophylactically with sodium thiosulfate or hydroxocobalamin to reduce the risk of iatrogenic cyanide poisoning.

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Consultations

Consultation with a medical toxicologist or a poison control center is recommended. They should be contacted immediately upon consideration of cyanide as a diagnosis, given the critical nature of these cases.[5] They can provide recommendations regarding the most effective available antidotal therapy, as well as insight into potential sources of poisoning (eg, industrial) that may place others at risk. Online resources may also be consulted (see the chart below).

Chemical terrorism agents and syndromes: signs and symptoms (PDF) (Copyright University of North Carolina at Chapel Hill)

Consult with law enforcement authorities and the Federal Bureau of Investigation (FBI) in any suspected terrorist incident.

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Contributor Information and Disclosures
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 Associate Professor, Department of Emergency Medicine, University of Texas Health Science Center at Houston Medical School; Consulting Staff, Department of Emergency Medicine, Memorial Hermann Hospital Lyndon Baines General Hospital and 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

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.

Acknowledgements

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

Disclosure: Nothing to disclose.

John G Benitez, MD, MPH, FACMT, FAACT, FACPM, FAAEM, Associate Professor, Department of Medicine, Medical Toxicology, Vanderbilt University Medical Center; Managing Director, Tennessee Poison Center

John G Benitez, MD, MPH, FACMT, FAACT, FACPM, FAAEM, is a member of the following medical societies: American Academy of Clinical Toxicology, 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.

Robert S Hoffman, MD, FAACT, FACMT Associate Professor, Departments of Emergency Medicine and Medicine, Clinical Pharmacology, New York University School of Medicine, Consulting Staff, Department of Emergency Services, Bellevue and New York University Hospital

Robert S Hoffman, MD, FAACT, 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 Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

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.

Jorge A Martinez, MD, JD Clinical Professor, Department of Internal Medicine, Louisiana State University School of Medicine in New Orleans; Clinical Instructor, Department of Surgery, Tulane School of Medicine

Jorge A Martinez, MD, JD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Cardiology, American College of Emergency Physicians, American College of Physicians, and Louisiana State Medical Society

Disclosure: Nothing to disclose.

Heather Murphy-Lavoie, MD, FAAEM Assistant Professor, Assistant Residency Director, Emergency Medicine Residency, Associate Program Director, Hyperbaric Medicine Fellowship, Section of Emergency Medicine and Hyperbaric Medicine, Louisiana State University School of Medicine in New Orleans; Clinical Instructor, Department of Surgery, Tulane University School of Medicine

Heather Murphy-Lavoie, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Society for Academic Emergency Medicine, and Undersea and Hyperbaric Medical Society

Disclosure: Nothing to disclose.

Lewis S Nelson, MD, FACEP, FAACT, FACMT Professor, Department of Emergency Medicine, New York University School of Medicine; Attending Physician, Department of Emergency Medicine, Bellevue Hospital Center, New York University Medical Center

Lewis S Nelson, MD, FACEP, FAACT, FACMT is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Andre Pennardt, MD, FACEP, FAAEM, FAWM Clinical Associate Professor of Emergency Medicine, Georgia Health Sciences University; Assistant Professor of Military and Emergency Medicine, Uniformed Services University of the Health Sciences; Consulting Staff, Department of Emergency Medicine, Eisenhower Army Medical Center

Andre Pennardt, MD, FACEP, FAAEM, FAWM is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, Association of Military Surgeons of the US, International Society for Mountain Medicine, National Association of EMS Physicians, Special Operations Medical Association, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Erik D Schraga, MD Staff Physician, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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.

Suzanne White, MD Medical Director, Regional Poison Control Center at Children's Hospital, Program Director of Medical Toxicology, Associate Professor, Departments of Emergency Medicine and Pediatrics, Wayne State University School of Medicine

Suzanne White, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Clinical Toxicology, American College of Epidemiology, American College of Medical Toxicology, American Medical Association, and Michigan State Medical Society

Disclosure: Nothing to disclose.

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