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Risk Management Pitfalls For Carbon Monoxide Poisoning

  1. “The hyperbaric fellow is reluctant to treat my patient who had syncope because his COHb level is normal. Can I send the patient home?” All patients with CO poisoning must be questioned about syncope. There is no clear relationship between the severity of poisoning and the presenting COHb level. Syncope or loss of consciousness is a surrogate for more severe poisoning, and patients with syncope should be considered for advanced therapies and hospital admission.
  2. “My patient says he was just out working on his car in the garage with the engine running. This seems suspicious to me.” Intentional CO poisoning comprises a large share of fatal cases. All patients with CO poisoning should be questioned directly about suicidal ideation and plan.
  3. “The nurse is sending an arterial blood gas to assess the patient’s degree of poisoning. Do I need to request any special testing?” Carboxyhemoglobin level by co-oximetry is not part of routine blood gas analysis in most hospital laboratories and should be specifically requested by name. Arterial blood gas analysis with co-oximetry is the ideal means for obtaining COHb level because it also provides important information about the patient’s acid-base status, which helps quantify the severity of poisoning.
  4. “My 18-year-old previously healthy patient with CO exposure has an abnormal ECG. Isn’t this most likely a normal variant?” Carbon monoxide impairs oxygen delivery and cellular respiration and can cause myocardial ischemia and infarction even in patients without native coronary artery disease. Those with symptoms such as syncope, chest pain, or shortness of breath and/or an abnormal ECG warrant cardiac biomarker testing.
  5. “My senior resident is telling me that there is no benefit from hyperbaric treatment in CO poisoning. What does the best available evidence tell us?” Taking all RCTs into account, systematic reviews have found insufficient evidence to demonstrate improvement in delayed neuropsychological sequelae following CO poisoning in patients who receive hyperbaric therapy.32
  6. “My pregnant patient is asymptomatic and had a normal COHb level. She is asking me about the risks to her baby. What can I tell her?” Multiple studies have shown that pregnant women with normal mental status and no history of loss of consciousness have good outcomes in terms of normal delivery and future development of their children.52,53,54
  7. “I have a pregnant patient who lost consciousness and has ongoing chest pain after a CO exposure. She is nervous about undergoing hyperbaric therapy and wants to know the risks to her fetus associated with this treatment.” Pregnant patients were, unfortunately, excluded from all RCTs testing hyperbaric therapy. Animal and human studies on hyperbaric therapy in pregnant subjects show conflicting results in terms of fetal risk. Results range from no apparent effects of HBO therapy on the fetus to adverse effects on fetal development; however, case series and a literature review of severely poisoned pregnant patients who did not receive HBO therapy demonstrated poor fetal outcomes, including stillbirth, limb and cranial malformations, mental retardation, and cerebral palsy.54 Current consensus among major texts in the field of toxicology is to treat pregnant patients the same as other patients meeting clinical criteria for HBO therapy, as well as considering HBO therapy for signs of fetal distress.10,16,36 Further, pregnant patients treated with NBO should be treated for longer times due to prolonged elimination of CO from the fetal circulation.45
  8. “My pregnant patient has no symptoms, but her COHb level is 22%. Is the threshold level for HBO treatment different in pregnancy?” The widely held belief that pregnant patients with CO poisoning should have a lower threshold to undergo HBO therapy is not supported by current evidence. Levels of COHb recommended as treatment thresholds vary and have been arbitrarily chosen. As above, clinical markers of poisoning severity should guide therapy for all patients, regardless of pregnancy status.
  9. “My patient was stripping furniture in his basement and has an unexplained COHb level of 15%.” Methylene chloride, a common ingredient in commercial paint removers, is metabolized to CO in the liver. Exposure to this agent via ingestion or inhalation can cause CO poisoning. Remember that the endogenous production of CO in this case continues long after removal from the source, and therefore treatment should be prolonged.
  10. “I won’t bother calling the hyperbaric chamber about this patient; he’s intubated.” Most chambers are capable of handling patients who are endotracheally intubated. This alone should not disqualify your patient. Ventilators have been adapted to function in the hyperbaric chamber. The endotracheal tube’s cuff, interestingly, will have to be filled with saline instead of air to avoid its deflation under the higher pressure. The only absolute contraindication to hyperbaric therapy is untreated pneumothorax, although previous exposure to bleomycin is a strong relative contraindication, because it sensitizes the lung to the toxic effect of oxygen at higher concentrations.

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Last Modified: 11/23/2017
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