Is Hyperbaric Oxygen Therapy Beneficial in Carbon Monoxide Poisoning?
HBO therapy did not add benefit to normobaric oxygen therapy in these studies.
In two parallel prospective randomized studies, researchers evaluated the effectiveness of hyperbaric oxygen therapy (HBOT) in patients (age, ≥15 years) with acute isolated carbon monoxide (CO) poisoning who presented to an academic hospital in France between 1989 and 2000. In trial A (mild poisoning), 179 patients with transient loss of consciousness received normobaric oxygen therapy (NBOT) for 6 hours or NBOT for 4 hours plus one session of HBOT. In trial B (severe poisoning), 206 comatose patients (Glasgow Coma Scale score below 8) received NBOT for 4 hours plus either one or two HBOT sessions. Each HBOT session lasted 2 hours in a multiplace chamber at 2.0 atmospheres absolute; interval between sessions was 6 to 12 hours. At baseline, 82% of patients in trial A and 65% in trial B had headaches, and 4% and 10%, respectively, had seizures.
At 1 month, patients completed a symptom questionnaire and were evaluated by an intensivist with neurology training who was blinded to treatment group. Complete recovery was defined as absence of patient-reported symptoms and normal physical and neuropsychological exam, "moderate sequelae" was defined as one or more self-reported symptoms, and "severe sequelae" was defined as any objective physical exam finding. In trial A, complete recovery rates were similar in the two groups (approximately 60%), and no patient in either group had severe sequelae. In trial B, complete recovery rates were significantly lower in the group that received two HBOT sessions than in the group that received one session (47% vs. 68%; unadjusted odds ratio, 0.42).
The trial A findings support the teaching that most patients with mild CO poisoning will improve after removal from the exposure and treatment with high-flow oxygen. The trial B finding is surprising and suggests that HBOT might not benefit even those patients with severe toxicity. Pending a larger trial with clearer toxicity definitions, physicians should contact a regional poison center or HBOT referral center to discuss with consultants the best approach for an individual patient with known CO poisoning, particularly when the treatment might involve transfer of an unstable patient.
Kristi L. Koenig, MD, FACEP
Published in Journal Watch Emergency Medicine January 28, 2011
Annane D et al. Hyperbaric oxygen therapy for acute domestic carbon monoxide poisoning: Two randomized controlled trials. Intensive Care Med 2010 Dec 2; [e-pub ahead of print]. (http://dx.doi.org/10.1007/s00134-010-2093-0)