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Cyanide Toxicity Workup

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

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.[7, 19] 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.[20]

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.[21]

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[22] :

  • Sinus bradycardia or tachycardia
  • Atrioventricular blocks
  • Supraventricular or ventricular arrhythmias
  • Ischemic electrocardiographic 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.

 
 
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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