II. Epidemiology

  1. Emergency Department visits per year: 50,000 in U.S.
  2. Leading cause of toxin related death in United States
    1. Accidental or Intentional (Suicide) deaths per year: 5000

III. Sources: Carbon Monoxide

  1. Gas powered engine
    1. Car with faulty exhaust system
    2. Passengers riding in back of a pickup truck
    3. Swimmers at back of a houseboat
    4. Propane fueled forklifts
    5. Ice skating rink Zamboni
    6. Indoor tractor pulls
  2. Home
    1. Indoor Heaters (most common cause)
      1. Furnace
      2. Home water heaters
      3. Gas heaters
      4. Pool heaters
      5. Kerosene heaters
    2. Indoor Flames
      1. Wood stoves
      2. Indoor charcoal fires
      3. Sterno fuel
    3. Tobacco smoke
      1. Tobacco Smokers
        1. Carboxyhemoglobin levels may reach 6-10%
      2. Hookah Smokers
        1. Carboxyhemoglobin levels may reach 15-20%
      3. Nonsmokers exposed to passive smoke
        1. Cigarette tip 2.5 fold greater CO than inhaled
  3. Industrial or Occupational
    1. Steel foundry
    2. Pulp paper mill
    3. Formaldehyde and coke producing plants
    4. Fire fighters
  4. Fire
    1. Building or structure fire
    2. Wilderness fire

IV. Pathophysiology

  1. Carbon Monoxide Properties (no warning features that gas is present until symptoms develop)
    1. Colorless
    2. Odorless
    3. Non-irritating gas
    4. Small molecule that crosses through some barriers into closed spaces (e.g. drywall)
  2. Exposures leading to Toxicity
    1. Carbon Monoxide toxicity occurs at Ambient levels >200-500 parts per million
    2. More severe illness occurs with longer exposure times
  3. Carbon Monoxide inhalation
    1. Carbon Monoxide has a high affinity for Hemoglobin (>200-250 times higher affinity than oxygen)
    2. Displaces Oxygen and produces Carboxyhemoglobin
      1. Shifts oxygen dissociation curve left with poor delivery of any residual oxygen to tissues
      2. Functional Anemia is however not responsible for Carbon Monoxide's lethal effects
  4. Direct toxin effects of Carbon Monoxide
    1. Sodium channel activation
    2. Nitric oxide levels increase
    3. Neurotoxic
      1. Basal Ganglia (Parkinsonism)
      2. Occiput (occipital blindness)
      3. Frontal cortex (personality change)
  5. Inflammatory cascade (responsible for neurologic toxicity)
    1. White Blood Cell response
    2. Glutamic acid (inflammatory)
    3. Free radicals

V. History

  1. Multiple persons (e.g. family, coworkers, pets) in the same environment with similar symptoms

VI. Symptoms

  1. Headache (88%)
  2. Dizziness (83%)
  3. Nausea (75%)
  4. Drowsiness (75%)
  5. Dry Mouth (44%)
  6. Syncope
  7. Chest Pain
  8. Shortness of Breath
  9. Myalgias
    1. Carbon Monoxide also binds myoglobin

VII. Signs

  1. Cherry-red skin and mucosa
    1. Late or post-mortem finding
  2. Bounding Pulse
  3. Hypertension
  4. Muscular fasciculations
  5. Stertorous breathing
  6. Dilated pupils
  7. Convulsions
  8. Altered Mental State to coma
  9. Do not rely on Oxygen Saturations (not accurate see below)

VIII. Findings: Carboxyhemoglobin level

  1. Carboxyhemoglobin: 10%
    1. Frontal Headache
  2. Carboxyhemoglobin: 20%
    1. Throbbing Headache
    2. Dyspnea on exertion
      1. Severe Hypoxemia requiring intubation may occur at this level
  3. Carboxyhemoglobin: 30%
    1. Impaired judgment
    2. Nausea or Vomiting
    3. Dizziness
    4. Visual disturbance
    5. Fatigue
  4. Carboxyhemoglobin: 40%
    1. Confusion
    2. Syncope
  5. Carboxyhemoglobin: 50%
    1. Coma
    2. Seizures
  6. Carboxyhemoglobin: 60%
    1. Hypotension
    2. Respiratory Failure
  7. Carboxyhemoglobin: 70%
    1. Death

IX. Labs

  1. Blood grossly appears abnormal red color
  2. Venous Blood Gas
  3. Carboxyhemoglobin
    1. Normal background Carboxyhemoglobin is 2-3%
    2. Carboxyhemoglobin elevated >25% is significant and associated with toxicity
      1. See above for findings related to Carboxyhemoglobin levels
  4. Complete Blood Count
    1. Leukocytosis

X. Precautions

  1. Oxygen Saturation (Pulse Oximeter) data is inaccurate
    1. Does not distinguish Carboxyhemoglobin from oxygenated Hemoglobin
  2. Drywall does not deter Carbon Monoxide
    1. Carbon Monoxide diffuses across drywall and may permeate separated rooms in multi-tenant housing
  3. Consider concurrent Cyanide toxicity in structure fires
    1. Smoke Inhalation and Lactic Acid >8 suggests cyanide Poisoning
    2. Especially with Altered Level of Consciousness
  4. Start oxygen while awaiting lab testing results if higher level of suspicion
    1. Start 100% oxygen via non-rebreather
  5. Hyperglycemia is a Neurotoxin and worsens outcomes
    1. Consider Insulin for Glucose >300 mg/dl

XI. Management: Mild Poisoning

  1. Criteria
    1. Carboxyhemoglobin <30%
    2. No Neurologic or Cardiovascular Impairment
  2. Management
    1. Oxygen 100% Non-Rebreathing Mask
      1. Continue until Carboxyhemoglobin <5%
      2. Carbon Monoxide decreases 50% in 6 hours on room air
      3. Carbon Monoxide decreases 50% in 60 minutes on Non-Rebreather Mask
      4. Carbon Monoxide decreases 50% in 30 minutes on 100% oxygen while intubated
    2. Continuous Positive Airway Pressure (CPAP) with oxygen lowers Carbon Monoxide faster than oxygen alone
      1. Bal (2020) Eur J Emerg Med 27(3):217-22 +PMID:31815874 [PubMed]
    3. Hyperbaric Oxygen Indications
      1. See Hyperbaric Oxygen below
      2. Carboxyhemoglobin >25% and associated factors (cardiac or neurologic findings, age >36 years old)
      3. Consider in Pregnancy
    4. Admission criteria
      1. All patients with Carboxyhemoglobin >25%
      2. Underlying heart disease

XII. Management: Moderate Poisoning

  1. Criteria
    1. Carboxyhemoglobin: 30-40%
    2. No Neurologic Impairment
  2. Management
    1. Oxygen 100% Non-Rebreathing Mask
      1. Continue until Carboxyhemoglobin <5% (see above)
    2. Admission to telemetry (cardiovascular monitor)
    3. Consider hyperbaric oxygen (see below)
      1. Cerebellar signs
      2. Focal neurologic deficit
      3. Persistent severe Headache
      4. Loss of consciousness, Seizure or coma
      5. Glasgow Coma Scale (GCS) <15
      6. Age >36 years old
      7. Prolonged Carbon Monoxide exposure
    4. Venous Blood Gas
      1. Determine acid-base status

XIII. Management: Severe Poisoning

  1. Criteria
    1. Carboxyhemoglobin: >40%
    2. Neurologic Impairment
  2. Management
    1. Oxygen 100% Non-Rebreathing Mask
      1. Continue until Carboxyhemoglobin <5% (see above)
    2. Admission to telemetry (cardiovascular monitor)
    3. Endotracheal Intubation may be required due to severe Hypoxemia
    4. Venous Blood Gas
      1. Follow acid-base status
    5. Extracorporeal Membrane Oxygenation (VA-ECMO)
      1. Indicated in refractory cardiovascular collapse
    6. Hyperbaric oxygen (see below)
      1. Ideally performed within 6 hours of presentation
      2. Chamber immediately available OR
      3. No improvement in 4 hours
        1. Cardiovascular status
        2. Neurologic status

XIV. Management: Hyperbaric oxygen chamber

  1. Mechanism
    1. Carbon Monoxide decreases 50% in 20-30 minutes on hyperbaric oxygen at 2.8 atm
    2. Allows oxygen to dissolve in blood at a much greater extent (beyond Hemoglobin binding)
    3. Decreases inflammatory cascade
    4. Decreases reperfusion injury
  2. Efficacy
    1. Decreases risk of delayed neuropsychiatric effects
      1. Reduces risk of personality change, Parkinsonism, cognitive effects
    2. Better short-term and long-term cognitive outcome
    3. Weaver (2002) N Engl J Med 347:1057-67 [PubMed]
    4. Rose (2018) Crit Care Med 46(7): e649-55 [PubMed]
  3. Indications
    1. Carboxyhemoglobin: >40%
    2. Carboxyhemoglobin: >25-30% and associated factors
      1. Neurologic Impairment
      2. Transient or prolonged loss of consciousness
      3. Severe acidosis
      4. Cardiac involvement
      5. Abnormal neuropsychiatric findings
      6. Age >36 years old
    3. Carboxyhemoglobin: <25%
      1. Consider hyperbaric oxygen for pregnant patients

XV. Complications

  1. Hypoxic Encephalopathy
    1. Cognitive effects may persist for weeks to months or even permanently (up to 15-40% of cases)
      1. Reduced risk with hyperbaric oxygen therapy (see above)
    2. Parkinsonism
    3. Occipital blindness
    4. Personality change
  2. Coronary ischemia or myocadial infarction
  3. Increased risk of Coronary Artery Disease
    1. Henry (2006) JAMA 295(4): 398-402 [PubMed]

XVI. Prevention

  1. Adequate Ventilation
  2. Carbon Monoxide detectors
    1. Alarm sounds when Ambient Carbon Monoxide levels are >50 parts per million
    2. Carbon Monoxide toxicity occurs at Ambient levels >200-500 parts per million

XVIII. References

  1. Kinker and Glauser (2021) Crit Dec Emerg Med 35(9): 19-27
  2. Moayedi and Swaminathan in Herbert (2016) EM:Rap 16(7): 13-14
  3. Nordt and Shoenberger in Herbert (2019) EM:Rap 19(1): 4-6
  4. Reisdorf (1996) in Tintinelli (1996)
  5. (1995) MMWR Morb Mortal Wkly Rep 44:765-7 [PubMed]

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Related Studies

Ontology: Carbon Monoxide (C0007018)

Definition (MSHCZE) CO, jedovatý plyn, který je produktem neúplného spalování uhlíku (svítiplyn, kouření, výfukové plyny). Váže se na krevní barvivo hemoglobin asi 250krát silněji než kyslík a narušuje tak významně jeho přenos. Organismus při otravě CO trpí výrazným nedostatkem kyslíku (hypoxií). V průběhu otravy se objevují bolesti hlavy, závratě, nevolnost a zvracení, později jsou v popředí poruchy vědomí až kóma. Typické je třešňově červené zbarvení kůže a sliznic. V léčbě je nutné co nejrychleji zabezpečit přívod kyslíku do organismu (vynesení postiženého na čerstvý vzduch, podávání kyslíku, v těžkých případech přetlakem). Těžší otrava může i po vyléčení zanechávat některé trvalé následky na činnosti mozku. CO vzniká v malém množství také v lidském organismu, a to zejm. při přeměně hemu na bilirubin. Takto vzniklý CO je přenášen hemoglobinem z tkání do plic, kde je z těla vylučován. I za běžných podmínek je proto asi 1% hemoglobinu obsazeno CO. Již po vykouření jediné cigarety se však toto množství zvýší na několikanásobek. (cit. Velký lékařský slovník online, 2013 http://lekarske.slovniky.cz/ )
Definition (NCI_NCI-GLOSS) A poisonous gas that has no color or odor. It is given off by burning fuel (as in exhaust from cars or household heaters) and tobacco products. Carbon monoxide prevents red blood cells from carrying enough oxygen for cells and tissues to live.
Definition (NCI) An odorless, tasteless, poisonous gas, CO, that results from the incomplete combustion of carbon. Inhalation causes central nervous system damage and asphyxiation.
Definition (MSH) 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. (From Merck Index, 11th ed)
Definition (CSP) colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion.
Concepts Hazardous or Poisonous Substance (T131) , Inorganic Chemical (T197)
MSH D002248
SnomedCT 51765001
English Carbon Monoxide, Monoxide, Carbon, CO, Carbon Monoxide [Chemical/Ingredient], co carbon monoxide, carbon monoxide, CARBON MONOXIDE, Carbon monoxide, CO - Carbon monoxide, Carbon monoxide gas, Carbon monoxide (substance)
French Monoxyde de carbone
Swedish Kolmonoxid
Czech oxid uhelnatý
Finnish Hiilimonoksidi
Italian Monossido di carbonio
Polish Tlenek węgla
Norwegian Kullos, Karbonmonoksid
Spanish gas monóxido de carbono, monóxido de carbono (sustancia), monóxido de carbono, Monóxido de Carbono
German Kohlenmonoxid
Portuguese Monóxido de Carbono

Ontology: Carbon Monoxide Poisoning (C0007020)

Definition (MEDLINEPLUS)

Carbon monoxide (CO) is a gas that has no odor or color. But it is very dangerous. It can cause sudden illness and death. CO is found in combustion fumes, such as those made by cars and trucks, lanterns, stoves, gas ranges and heating systems. CO from these fumes can build up in places that don't have a good flow of fresh air. You can be poisoned by breathing them in. The most common symptoms of CO poisoning are

  • Headache
  • Dizziness
  • Weakness
  • Nausea
  • Vomiting
  • Chest pain
  • Confusion

It is often hard to tell if someone has CO poisoning, because the symptoms may be like those of other illnesses. People who are sleeping or intoxicated can die from CO poisoning before they have symptoms. A CO detector can warn you if you have high levels of CO in your home.

Centers for Disease Control and Prevention

Definition (MSH) Toxic asphyxiation due to the displacement of oxygen from oxyhemoglobin by carbon monoxide.
Definition (CSP) toxic asphyxiation due to the displacement of oxygen from oxyhemoglobin by carbon monoxide.
Concepts Injury or Poisoning (T037)
MSH D002249
SnomedCT 17383000
English Carbon Monoxide Poisonings, Monoxide Poisoning, Carbon, Monoxide Poisonings, Carbon, Poisoning, Carbon Monoxide, Poisonings, Carbon Monoxide, POIS CARBON MONOXIDE, CARBON MONOXIDE POIS, carbon monoxide poisoning, CO poisoning, poisoning by carbon monoxide (diagnosis), poisoning by carbon monoxide, Carbon Monoxide Poisoning [Disease/Finding], carbon monoxide poison, carbon monoxide toxicity, Carbon Monoxide Poisoning, CO Poisoning, Carbon monoxide poisoning
Italian Intossicazione da monossido di carbonio, Avvelenamento da monossido di carbonio
Swedish Kolmonoxidförgiftning
Japanese イッサンカタンソチュウドク, 中毒-一酸化炭素, 照明用ガス中毒, 灯用ガス中毒, CO中毒, 一酸化炭素中毒
Finnish Häkämyrkytys
Czech Otrava oxidem uhelnatým, otrava kysličníkem uhelnatým, intoxikace oxidem uhelnatým, otrava oxidem uhelnatým, oxid uhelnatý - otrava
Polish Zatrucie gazem świetlnym, Zatrucie tlenkiem węgla
Hungarian Szén-monoxid mérgezés
Norwegian Karbonmonoksidforgiftning, Kullosforgiftning
Spanish Envenenamiento por Monóxido de Carbono, Envenenamiento por Gas del Alumbrado, intoxicación por monóxido de carbono, Intoxicación por monóxido de carbono, Intoxicación por Monóxido de Carbono
Portuguese Envenenamento por Monóxido de Carbono, Intoxicação por monóxido de carbono, Intoxicação por Monóxido de Carbono
Dutch koolmonoxidevergiftiging, Kolendampvergiftiging, Koolmonoxydevergiftiging, Vergiftiging, kolendamp-
French Intoxication par le monoxyde de carbone, Intoxication oxycarbonée, Intoxication au monoxyde de carbone, Intoxication par l'oxyde de carbone, Intoxication à l'oxyde de carbone, Oxycarbonisme
German Kohlenmonoxidvergiftung