Carbon Monoxide Poisoning (Clinical)

Etiology

• Fire-related smoke inhalation Smoke Inhalation Carbon Monoxide Poisoning:^[1–3,5]
  • Most common cause of carbon monoxide Carbon monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. Carbon Monoxide Poisoning (CO) poisoning
  • CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning is the most common cause of fire-related death in the United States.
• Other sources of CO include the following, especially in poorly ventilated areas:^[1–3,5]
  • Gas-powered generators within homes
  • Clogged vents from home heating
  • Wood-burning stoves
  • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology vehicle exhaust (may be associated with a suicide attempt Suicide attempt The unsuccessful attempt to kill oneself. Suicide)
  • Extensive water pipe or hookah smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
• Most common in the winter Winter Pityriasis Rosea months due to increased use of heating devices
• Multiple members of the household are usually affected and may present with similar symptoms.

Pathophysiology

• CO has an affinity for hemoglobin that is approximately 240 times greater than oxygen, causing a displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of oxygen from hemoglobin in the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy.^[1–3,5]
• CO binds to hemoglobin, forming carboxyhemoglobin Carboxyhemoglobin Carbon Monoxide Poisoning (COHb) and causing a configurational change in the hemoglobin that prevents oxygen from being released at  effective levels into the peripheral tissues.
• Causes a leftward shift in the oxygen-hemoglobin curve
• Inhibits oxidative phosphorylation Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Post-translational Protein Processing at the mitochondrial level, leading to anaerobic respiration Respiration The act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in. Nose Anatomy (External & Internal) and cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death
• Lipid peroxidation Lipid peroxidation Peroxidase catalyzed oxidation of lipids using hydrogen peroxide as an electron acceptor. Drug-Induced Liver Injury in the central nervous system Central nervous system The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges. Nervous System: Anatomy, Structure, and Classification is increased.
• CO also binds to cardiac myoglobin Myoglobin A conjugated protein which is the oxygen-transporting pigment of muscle. It is made up of one globin polypeptide chain and one heme group. Rhabdomyolysis, thereby increasing the risk of myocardial depression, hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension, and arrhythmias.
• CO induces re-oxygenation injury and the formation of oxygen free radicals Free radicals Highly reactive molecules with an unsatisfied electron valence pair. Free radicals are produced in both normal and pathological processes. They are proven or suspected agents of tissue damage in a wide variety of circumstances including radiation, damage from environment chemicals, and aging. Natural and pharmacological prevention of free radical damage is being actively investigated. Ischemic Cell Damage in the nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. Nervous System: Anatomy, Structure, and Classification.

Clinical Presentation

The symptoms of CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning are varied and nonspecific.

The severity of the clinical presentation of CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning depends on the amount of CO in the inhaled air, the duration of the exposure, and the general state of health of the affected individual.

Mildly to moderately CO-intoxicated individuals^[1–3,5]

• Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess (the most common presenting symptom)
• Malaise Malaise Tick-borne Encephalitis Virus
• Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics/ vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
• Dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome)
• Impaired judgment Judgment The process of discovering or asserting an objective or intrinsic relation between two objects or concepts; a faculty or power that enables a person to make judgments; the process of bringing to light and asserting the implicit meaning of a concept; a critical evaluation of a person or situation. Psychiatric Assessment and difficulty concentrating
• Confusion
• Shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea

Severely CO-intoxicated individuals^[1–3,5]

• Neurologic symptoms:
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • Syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope
  • Altered mental status Altered Mental Status Sepsis in Children
  • Loss of consciousness and/or coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma
• Cardiovascular symptoms:
  • Chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea (due to myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction)
  • Palpitations Palpitations Ebstein’s Anomaly and arrhythmias
  • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
• Respiratory symptoms:
  • Shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea
  • Pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema
  • Respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure
  • Concomitant airway Airway ABCDE Assessment injuries due to smoke inhalation Smoke Inhalation Carbon Monoxide Poisoning (in cases of house fires)
• Delayed neuropsychiatric syndrome: presents in 30% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship, usually within the first 30 days but sometimes up to 240 days after exposure
  • Personality changes
  • Cognitive and learning difficulties
  • Psychosis
  • Movement disorders (e.g., parkinsonism Parkinsonism West Nile Virus, paralysis, chorea Chorea Involuntary, forcible, rapid, jerky movements that may be subtle or become confluent, markedly altering normal patterns of movement. Hypotonia and pendular reflexes are often associated. Conditions which feature recurrent or persistent episodes of chorea as a primary manifestation of disease are referred to as choreatic disorders. Chorea is also a frequent manifestation of basal ganglia diseases. Huntington Disease)

Diagnosis

• Clinical suspicion is a key factor in establishing a diagnosis of CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning. 
• The wide variety and nonspecificity of the symptoms make misdiagnosis very common, especially in the absence of evident exposure. 
• A history of CO exposure is not always evident: Due to the lack of odor, color, and taste of the gas, individuals may not be aware of their exposure.
• Workup of suspected CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning:^[3,5–7,9]
  • Toxic levels of COHb measured in arterial or venous blood by cooximetry will show elevated levels of carboxyhemoglobin Carboxyhemoglobin Carbon Monoxide Poisoning (> 3% in nonsmokers and  > 10% in smokers).
    • COHb levels do not vary between arterial and venous blood because of the affinity of CO for hemoglobin.
    • Arterial blood gas Arterial blood gas Respiratory Alkalosis is better for diagnosing acid–base abnormalities.
  • Pulse oximetry is not useful and may appear normal because it cannot differentiate between COHb and oxyhemoglobin.
  • Electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) ( ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)) and/or cardiac enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes to rule out myocardial ischemia Myocardial ischemia A disorder of cardiac function caused by insufficient blood flow to the muscle tissue of the heart. The decreased blood flow may be due to narrowing of the coronary arteries (coronary artery disease), to obstruction by a thrombus (coronary thrombosis), or less commonly, to diffuse narrowing of arterioles and other small vessels within the heart. Coronary Heart Disease
  • Airway Airway ABCDE Assessment examination to assess for smoke inhalation Smoke Inhalation Carbon Monoxide Poisoning injury
  • Additional studies:
    • Complete blood count
    • Chemistries
    • Pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care test in female of childbearing age
    • Brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification imaging (e.g., CT): for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship presenting with acute neurologic symptoms
    • Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests: Obtain baseline study and evaluate for complications such as pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema.

Management

Management may vary based on practice location. The following information is based on US and UK guidelines.^[3,5–7,9]

Oxygen therapy

• Initial treatment with high-flow 100% oxygen 100% Oxygen Cluster Headaches: Oxygen therapy should begin immediately if clinical suspicion is high.
• Airway Airway ABCDE Assessment, breathing, circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment:
  • Assess whether the patient needs to be intubated (severe symptoms, altered mental status Altered Mental Status Sepsis in Children, Glasgow Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma Scale Scale Dermatologic Examination score < 8). 
  • O₂ therapy (as stated above)
  • IV access for fluid resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome and drug administration, if necessary
• Check blood CO-oximetry:
  • Note: COHb levels can confirm exposure, but cannot be used to judge the severity of exposure since they do not correlate well with the degree of poisoning (due to normal pulmonary clearance of CO). Therefore, only the patient’s signs and symptoms should be used to guide management.
  • If COHb is < 3% in a nonsmoker or < 10% in a smoker, CO intoxication is unlikely.
    • Continue workup for other causes of symptoms (alcohol/drug intoxication, intracranial pathology, infectious disease).
    • Continue supportive care.
    • Patient may be weaned off O₂ if it is not necessary.
  • If COHb is > 3% in a nonsmoker or > 10% in a smoker, treat for CO intoxication.
    • Non-rebreather mask 100% O₂ (definitive treatment), targeting SpO₂ of 100%.
    • Check ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) for signs of arrhythmia or ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage.
    • Check cardiac biomarkers if patient has a history of heart disease.
• Females of childbearing age should have a pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care test.
  • If pregnant, consider hyperbaric O₂  therapy (see below).
  • If not pregnant, continue with high-flow O₂ therapy and supportive care.
• Treatment with high-flow O₂ should last approximately 4‒6 hours.^[6,7,9]
  • Half-life Half-Life The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacologic, physiologic, or radiologic activity. Pharmacokinetics and Pharmacodynamics of COHb in a patient breathing room air is 300 minutes.
  • Half-life Half-Life The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacologic, physiologic, or radiologic activity. Pharmacokinetics and Pharmacodynamics of COHb in a patient breathing 100% O₂ is 40‒80 minutes.

Hyperbaric oxygen Hyperbaric oxygen The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Decompression Sickness (HBO) for certain conditions^[3,4,6]

• Administers 100% oxygen 100% Oxygen Cluster Headaches at pressures higher than atmospheric pressure Atmospheric pressure The pressure at any point in an atmosphere due solely to the weight of the atmospheric gases above the point concerned. Ventilation: Mechanics of Breathing
• HBO hastens the conversion of COHb to normal hemoglobin, so that the half-life Half-Life The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacologic, physiologic, or radiologic activity. Pharmacokinetics and Pharmacodynamics of COHb decreased to 30 minutes, thereby possibly decreasing the risk of DNS. 
• Consider hyperbaric oxygen Hyperbaric oxygen The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Decompression Sickness in the following conditions:
  • Failed initial treatment
  • COHb level > 25% with no clinical findings
  • COHb level > 15% in pregnant patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with fetal distress
  • Loss of consciousness
  • Seizure
  • Severe metabolic acidosis Acidosis A pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up. Respiratory Acidosis ( pH pH The quantitative measurement of the acidity or basicity of a solution. Acid-Base Balance < 7.1)  
  • Evidence of end-organ ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage (e.g., ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) changes, chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, altered mental status Altered Mental Status Sepsis in Children, respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure, or focal neurologic deficit Focal Neurologic Deficit Intracerebral Hemorrhage)
• Risks associated with hyperbaric oxygen Hyperbaric oxygen The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Decompression Sickness:^[9] 
  • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, myopia Myopia Refractive Errors
  • Ear, lung, sinus barotrauma Barotrauma Injury following pressure changes; includes injury to the eustachian tube, ear drum, lung and stomach. Invasive Mechanical Ventilation
  • Oxygen toxicity Oxygen Toxicity Invasive Mechanical Ventilation
• In the UK, hyperbaric oxygen Hyperbaric oxygen The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Decompression Sickness is not routinely used; the UK National Poisons Information Service (NPIS) does not recommend it, citing insufficient supporting evidence.^[8] 
• Additionally, even in the US, HBO is not widely available.
  • Appropriate referral to a toxicologist, poison center, or hyperbaric oxygen Hyperbaric oxygen The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. The list of treatment modalities includes stroke. Decompression Sickness specialist is highly encouraged in determining the use of HBO.
  • The risk of transfer to a facility with HBO should be considered, especially in unstable patients Unstable Patients Blunt Chest Trauma.
  • Extracorporeal membrane oxygenation (ECMO) has been used successfully as a substitute if it is available and HBO is not.

Additional considerations and follow-up^[7,9]

• Consider treating empirically for cyanide Cyanide Inorganic salts of hydrogen cyanide containing the -cn radical. The concept also includes isocyanides. It is distinguished from nitriles, which denotes organic compounds containing the -cn radical. Cyanide Poisoning poisoning if patient was found in a fire ( smoke inhalation Smoke Inhalation Carbon Monoxide Poisoning).^[3,4]
  • Empiric treatment with hydroxocobalamin 70 mg/kg IV
    • Can be administered by emergency medical services en EN Erythema nodosum is an immune-mediated panniculitis (inflammation of the subcutaneous fat) caused by a type IV (delayed-type) hypersensitivity reaction. It commonly manifests in young women as tender, erythematous nodules on the shins. Erythema Nodosum route to the hospital
    • Hospital staff should be notified if hydroxocobalamin was administered, as it can falsely lower the initial COHb level.
  • Sodium nitrite Sodium nitrite Nitrous acid sodium salt. Used in many industrial processes, in meat curing, coloring, and preserving, and as a reagent in analytical chemistry techniques. It is used therapeutically as an antidote in cyanide poisoning. The compound is toxic and mutagenic and will react in vivo with secondary or tertiary amines thereby producing highly carcinogenic nitrosamines. Nitrates should be avoided when also treating CO poisoning CO poisoning Carbon monoxide (CO) is an odorless, colorless, tasteless, nonirritating gas formed by hydrocarbon combustion (e.g., fires, car exhaust, gas heaters). Carbon monoxide has a higher affinity to hemoglobin than oxygen, forming carboxyhemoglobin (COHb). Increased levels of COHb lead to tissue hypoxia and brain damage. Carbon Monoxide Poisoning (impairs oxygen delivery).
• Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship found to have intentionally poisoned themselves should undergo psychiatric evaluation.
• Disposition:
  • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with severe symptoms should be admitted.
  • Discharge from the emergency department:
    • After at least 6 hours of 100% O₂ treatment
    • Symptoms have resolved.
    • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship should be warned of possible delayed neurologic complications. 
    • Follow-up should include a repeat medical and neurologic exam in 2 weeks.
    • Follow-up should occur sooner if symptoms return.
• Prevention:
  • Use CO monitors with alarms.
  • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with unintentional poisoning should have their home/work environment evaluated for ongoing exposure to CO.

Differential Diagnosis

• Respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure: results when there is inadequate oxygenation of blood or inadequate ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing/ elimination Elimination The initial damage and destruction of tumor cells by innate and adaptive immunity. Completion of the phase means no cancer growth. Cancer Immunotherapy of CO₂ or both. May be an acute condition that develops over hours or a chronic condition that takes months to years to develop. Management involves treating the underlying cause, oxygen administration, and, if necessary, mechanical ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing.
• Cyanide Cyanide Inorganic salts of hydrogen cyanide containing the -cn radical. The concept also includes isocyanides. It is distinguished from nitriles, which denotes organic compounds containing the -cn radical. Cyanide Poisoning poisoning: Hydrogen cyanide Cyanide Inorganic salts of hydrogen cyanide containing the -cn radical. The concept also includes isocyanides. It is distinguished from nitriles, which denotes organic compounds containing the -cn radical. Cyanide Poisoning (HCN) is a colorless, extremely poisonous, and flammable liquid used in multiple industries and products, including rubber, plastic, and household paints. Lethal complications of cyanide Cyanide Inorganic salts of hydrogen cyanide containing the -cn radical. The concept also includes isocyanides. It is distinguished from nitriles, which denotes organic compounds containing the -cn radical. Cyanide Poisoning poisoning occur in closed-space fires when plastics burn. Exposure is via inhalation, dermal, or intestinal. Symptoms develop within seconds to minutes and involve cardiovascular, respiratory, and neurologic changes. Management includes sodium thiosulfate Sodium Thiosulfate Cyanide Poisoning, nitrites, and hydroxocobalamin.
• Acute respiratory distress syndrome Acute Respiratory Distress Syndrome Acute respiratory distress syndrome is characterized by the sudden onset of hypoxemia and bilateral pulmonary edema without cardiac failure. Sepsis is the most common cause of ARDS. The underlying mechanism and histologic correlate is diffuse alveolar damage (DAD). Acute Respiratory Distress Syndrome (ARDS) (ARDS): a severe inflammatory reaction of the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy that is characterized by the presence of pulmonary infiltrates due to alveolar fluid accumulation. Systemic inflammatory response syndrome Systemic Inflammatory Response Syndrome Sepsis in Children and sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock are the major causes of ARDS. The main finding is respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure. Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests usually shows diffuse bilateral lung infiltrates (“butterfly opacity Opacity Imaging of the Lungs and Pleura”). 
• Acute ethanol Ethanol A clear, colorless liquid rapidly absorbed from the gastrointestinal tract and distributed throughout the body. It has bactericidal activity and is used often as a topical disinfectant. It is widely used as a solvent and preservative in pharmaceutical preparations as well as serving as the primary ingredient in alcoholic beverages. Ethanol Metabolism intoxication: This is a diagnosis of exclusion that is only made after excluding CO toxicity CO toxicity High-Risk Headaches and other serious conditions, such as head trauma Head trauma Head trauma occurs when external forces are directed to the skull and brain structures, resulting in damage to the skull, brain, and intracranial structures. Head injuries can be classified as open (penetrating) or closed (blunt), and primary (from the initial trauma) or secondary (indirect brain injury), and range from mild to severe and life-threatening. Head Trauma, hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage, hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, hypothermia Hypothermia Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Hypothermia, hepatic encephalopathy Encephalopathy Hyper-IgM Syndrome, and other metabolic disorders. Acute intoxication usually occurs after consuming ≥ 5 alcoholic Alcoholic Persons who have a history of physical or psychological dependence on ethanol. Mallory-Weiss Syndrome (Mallory-Weiss Tear) drinks (for males) and ≥ 4 drinks (for females) on a single occasion.
• Meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis: an infection of the meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges: Anatomy, the protective membranes around the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, most often caused by Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pneumoniae or Haemophilus Haemophilus Haemophilus is a genus of Gram-negative coccobacilli, all of whose strains require at least 1 of 2 factors for growth (factor V [NAD] and factor X [heme]); therefore, it is most often isolated on chocolate agar, which can supply both factors. The pathogenic species are H. influenzae and H. ducreyi. Haemophilus influenzae. Presents with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, stiff neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, and headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess. Diagnosis is by lumbar puncture Lumbar Puncture Febrile Infant for cerebrospinal (CSF) evaluation. Treatment consists of the rapid administration of antibiotics.
• Opioid toxicity Opioid Toxicity General Principles of Toxidromes: Opioids Opioids Opiates are drugs that are derived from the sap of the opium poppy. Opiates have been used since antiquity for the relief of acute severe pain. Opioids are synthetic opiates with properties that are substantially similar to those of opiates. Opioid Analgesics are central nervous system Central nervous system The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges. Nervous System: Anatomy, Structure, and Classification depressants used medically as a potent analgesic and commonly abused due to their euphoric effect. Features of opioid intoxication Opioid intoxication Opioid Use Disorder include drowsiness, respiratory depression, and pinpoint pupils, which can be managed by naloxone Naloxone A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors. Opioid Analgesics. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship may develop withdrawal symptoms (yawning, lacrimation, runny nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose Anatomy (External & Internal), piloerection, stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy cramps Cramps Ion Channel Myopathy) that can be managed by methadone Methadone A synthetic opioid that is used as the hydrochloride. It is an opioid analgesic that is primarily a mu-opioid agonist. Opioid Analgesics or buprenorphine Buprenorphine A derivative of the opioid alkaloid thebaine that is a more potent and longer lasting analgesic than morphine. It appears to act as a partial agonist at mu and kappa opioid receptors and as an antagonist at delta receptors. The lack of delta-agonist activity has been suggested to account for the observation that buprenorphine tolerance may not develop with chronic use. Opioid Analgesics.