In October 2016, the ACEP Board of Directors approved a clinical policy on the evaluation and management of adult patients presenting to the emergency department with acute carbon monoxide (CO) poisoning. Developed by ACEP’s Clinical Policies Committee, this clinical policy can also be found on ACEP’s website and has been submitted for inclusion on the National Guideline Clearinghouse website.

There are approximately 50,000 ED visits per year as a result of CO poisoning. Acute poisonings have extremely varied presentations, from minimal symptomatology to unresponsiveness, hypotension, severe acidemia, or acute respiratory failure. CO poisoning is also known to be associated with longer-term morbidity and mortality. Neurologic sequelae have been described in 12 percent to 68 percent of poisoned patients, and mortality rates increase threefold compared with matched unexposed individuals at a median follow-up of 7.6 years after exposure.

Based on feedback from the ACEP membership, the committee focused on three clinical questions about the evaluation and management of acute CO poisoning in the emergency department. A systematic review of the evidence was conducted, and the committee made recommendations (Level A, B, or C) based on the strength of evidence available (see Table 1). This clinical policy underwent internal and external review from emergency physicians, medical toxicologists, hyperbaric medicine specialists, the Council of Undersea and Hyperbaric Medicine Fellowship Directors, and the ACEP Undersea and Hyperbaric Medicine Section leadership during the 60-day open-comment period. These responses were used to refine and enhance the final policy but do not imply endorsement of the clinical policy.

Critical Questions and Recommendations

Question 1: In ED patients with suspected acute CO poisoning, can noninvasive carboxyhemoglobin (COHb) measurement be used to accurately diagnose CO toxicity?

Patient Management Recommendations

* Level A: None specified.

* Level B: Do not use noninvasive COHb measurement (pulse CO oximetry) to diagnose CO toxicity in patients with suspected acute CO poisoning.

* Level C: None specified.

Recommendations for this critical question are intended specifically to apply to the accurate diagnosis of CO toxicity using noninvasive COHb measurement in patients in the emergency department with suspected exposure, which is a separate clinical question from the utility of noninvasive CO oximetry to screen for CO exposure in undifferentiated populations of ED patients or in the prehospital setting. The latter was not addressed in this policy.

Question 2: In ED patients diagnosed with acute CO poisoning, does hyperbaric oxygen (HBO2) therapy, as compared with normobaric oxygen therapy, improve long-term neurocognitive outcomes?

Patient Management Recommendations

* Level A: None specified.

* Level B: Emergency physicians should use HBO2 therapy or high-flow normobaric therapy for acute CO-poisoned patients. It remains unclear whether HBO2 therapy is superior to normobaric oxygen therapy for improving long-term neurocognitive outcomes.

* Level C: None specified.

Five original trials looking at the utility of HBO2 for prevention of neurologic sequelae in CO-poisoned patients now exist. While three studies found no benefit and two found benefit, wide variability of methods and study biases make drawing definitive conclusions about the benefit or harm of using HBO2 versus normobaric therapy for the treatment of acute CO poisoning difficult. Either may be used in the treatment of CO-poisoned patients.

Question 3: In ED patients diagnosed with acute CO poisoning, can cardiac testing be used to predict morbidity or mortality?

Patient Management Recommendations

* Level A: None specified.

* Level B: In ED patients with moderate to severe CO poisoning, obtain an ECG and cardiac biomarker levels to identify acute myocardial injury, which can predict poor outcome.

* Level C: None specified.

CO is known to be cardiotoxic by inducing both tissue-level hypoxia and cellular-level damage. In CO-poisoned patients, acute myocardial injury was found to be the only independent predictor of poor outcome and, when present on presentation, conferred significantly higher long-term all-cause and cardiac-cause mortality.

Dr. Wolf is an associate professor and vice chair for academic affairs in emergency medicine at the University of Virginia School of Medicine in Charlottesville.