Currently, in the Northern Hemisphere, it is cold (Yes, I know my cold intolerance has been worsening as my hair gets more grey… but objectively, it is freezing!). The time of year certainly affects what conditions we must consider when caring for children (ex, Traumas, Submersion Injuries, Bronchiolitis) and when it is cold outside, people do what they need can in order stay warm. This, unfortunately, may require us to put a tricking diagnosis on the top of our Ddx list. Let’s take a moment to digest a Morsel (hot, out of the oven) on a severe poisoning – Carbon Monoxide Poisoning in Children:

Carbon Monoxide Poisoning: Basics

• Carbon Monoxide Poisoning is the leading cause of poisoning deaths in children in the USA.[Mowry, 2015]
  • This is why it is still important to educate about this danger and also the benefit of CO detectors.
  • While accidental exposures are more common, use of Carbon Monoxide in suicide attempts is also an important consideration.
    • Mortality rate ~10 times higher for intentional CO exposure compared to accidental.

• Carbon Monoxide is generated by incomplete combustion of hydrocarbon containing compounds.
  • It is a colorless, odorless, and tasteless gas.
  • It is toxic to animals with hemoglobin (both vertebrates and invertebrates).

• Carbon Monoxide Toxicity
  • Carbon Monoxide binds to hemoglobin with an affinity 210 times that of oxygen. [Yildiz, 2018]
  • Results in: [Yildiz, 2018]
    • Hypoxic Injury
      • Carboxyhemoglobin (COHb) leads to reduced oxygen delivery capacity to tissues.
      • Tissue hypoxia is most prominently expressed in organs with high metabolic demand (ex, Brain, Heart).
    • Inflammatory Injury
      • Various mechanisms lead to inflammatory changes.
      • Can lead to nervous system damage – which may resolve or can be permanent.
  • After acute Carbon Monoxide Poisoning, those who survive can have lasting consequences: [Chang, 2017]
    • Symptoms = chronic headache, mood disorders, personality changes, memory loss, focal neurologic deficits, hypoxic brain injury.
    • Permanent Neurologic Sequelae (symptoms persist for >3 months)
    • Delayed Neurologic Sequelae (symptoms develop abruptly after a period of days to weeks)

• Children are more susceptible to the effects of Carbon Monoxide Toxicity. [Yildiz, 2018]
  • Higher metabolic rate (high heart and respiratory rates) and immature central nervous systems.
  • Initial exposure may be underestimated by using Carboxyhemoglobin level alone.
    • Higher minute ventilation rates may help reduce blood levels once removed from environment. [Sethuraman, 2017]
    • Obtaining blood can be more difficult in smaller children… prolonging blood draw and leading to reduced measured level.

Carbon Monoxide Poisoning: Presentation

• Clinical picture is variable and symptoms do not necessarily correlate with COHb level. [Sethuraman, 2018; Yildiz, 2018]
• Common Symptoms are not specific for Carbon Monoxide Poisoning and a high index of suspicion is required. [Sethuraman, 2018; Yildiz, 2018]
  • Nausea and Vomiting (the most frequent symptoms reported)
  • Headache (also commonly reported)
  • Fatigue
  • Dyspnea
  • Confusion
  • Abdominal Pain
  • Visual Changes
  • Chest Pain
  • Loss of Consciousness

• Severe Clinical Course associated with: [Yildiz, 2018]
  • Clinical Features:
    • Low GCS (<8)
    • Altered Mental Status
    • Being Found Unresponsive
    • Seizures
  • Laboratory Features:
    • Elevated Cardiac Enzymes
      • CO Poisoning causes transient, and even permanent, myocardial injury.
      • There may be ECG or Echo abnormalities also, but not necessarily. [Yildiz, 2018]
    • High WBC Count (ok, you know how I feel about the WBC Count, but this may be related to the CO-related inflammatory process)
    • Carboxyhemoglobin level >25% is deemed to be consistent with a “Severe Poisoning,” but, …
      • the COHb level has not been found to be an independent factor in predicting clinical course. [Yildiz, 2018]
    • Lactate may prove to be more useful in predicting clinical course than COHb levels, but results are conflicting. [Yildiz, 2018; Damlapinar, 2016]

Carbon Monoxide Poisoning: Management

• ABCs – as always, stabilize the unstable!
  • For the unresponsive, ask about potential Carbon Monoxide exposure.
  • Inquire about other family members who may have also been exposed.

• Displace the Carbon Monoxide from the Hemoglobin
  • Half-life of CO is ~300 minutes in Room Air.
  • On a Non-rebreather facemask, half-life of CO is ~90 min.
  • Using Hyperbaric oxygen therapy, the half-life can be reduced to 30 min.
  • So… children with concern for CO poisoning should be getting supplemental oxygen by facemask at least.
  • The actual decision about when to use Hyperbaric oxygen therapy is difficult.
    • Most places don’t have access to Hyperbaric therapy (so transfer would be needed).
    • True benefit of Hyperbaric therapy has not be demonstrated in children. [Chang, 2017]
    • Hyperbaric therapy did not affect the rate of delayed neurologic symptoms in children. [Chang, 2017]
    • A pregnant patient is often considered high risk (as the fetus inside has Fetal Hgb which has even high affinity for the CO than the mother’s adult Hgb) and may benefit from Hyperbaric therapy.

• For the critically ill, ECMO may be an option! [Baran, 2016]
  • May be useful in patient with severe poisoning, but too unstable for hyperbaric therapy (or no easy access to it).
  • Start this process early… as it takes a while to coordinate.
  • V-V ECMO if the heart is performing well.
  • V-A ECMO is more complicated, but can help if myocardium is suffering.

• Check the ECG!
  • Myocardial injury is a well known complication of CO poisoning. [Ozyurt, 2017; Boztepe, 2014]
  • Arrhythmias may be contributing factor to deaths from CO poisoning.
  • Even in asymptomatic patients, CO poisoning has been shown to have negative effects on ECG and Echo. [Ozyurt, 2017]

• Labs Levels may be helpful…
  • Again your lactate and carboxyhemoglobin levels should be drawn, but take care in interpreting them and basing all decisions upon them.
  • Check the cardiac enzymes! [Ozyurt, 2017; Boztepe, 2014]

• Don’t forget Cyanide.
  • If the CO exposure was due to a significant fire, Cyanide may also be the cause of the patient’s critical state.
  • Consider empiric therapy for Cyanide.

Moral of the Morsel

• “Flu-like” might not be the Flu. Headache, nausea, vomiting and fatigue can be due to a viral illness, but we should consider asking about risk for carbon monoxide exposure.
• Winter Ddx of Change in Mental Status is Different! In the summer, we may need to consider RMSF, but in the Winter we have to think of CO poisoning as the cause for our unresponsive patient.
• Don’t forget the heart! While focusing on displacing the Carbon Monoxide, check that ECG and consider troponin levels.

References