Delayed Neuropsychologic Sequelae After Carbon Monoxide Poisoning: Prevention by Treatment With Hyperbaric Oxygen☆,☆☆,★,★★
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INTRODUCTION
Carbon monoxide (CO) is a major environmental toxicant that frequently causes death or neurologic morbidity.1 Since the pioneering studies of Haldane2, the principal cause of acute mortality has been attributed to hypoxic stress due to formation of carboxyhemoglobin (COHb) with an associated decrease in blood oxyhemoglobin. However, the pathophysiology of delayed neuropsychologic sequelae (DNS) cannot be explained simply by an acute hypoxic stress; symptoms appear after the COHb level has
MATERIALS AND METHODS
This study was a prospective, randomized, nonblinded comparative trial of HBO and normobaric oxygen therapy. Patients were referred from emergency departments in our region. Informed consent involved having the patient read or be read a form outlining the two possible oxygen treatments and clearly stating that neither treatment has been proved effective in preventing neurological sequelae following CO poisoning. The study was approved by our institutional review board.
Patients were randomly
RESULTS
Between September 18, 1989 and December 20, 1993, 65 patients were enrolled; 32 patients were treated with ambient-pressure oxygen, and 33 patients received HBO. Two patients in the ambient-pressure group and three in the HBO group were lost to follow-up. Two patients in each treatment group refused formal neuropsychologic retesting but denied symptoms of DNS during telephone interviews conducted over the next 3 months.
Patients in the two treatment groups were similar, and their signs and
DISCUSSION
We found a 23% incidence of DNS, similar or slightly lower than those reported in several studies in which treatment did not include HBO.9, 13, 16 HBO treatment was associated with significant reduction in the incidence of DNS in our study. This differs from Raphael et al.17 Assuming that the questionnaire responses in that study did indeed reflect DNS, we believe the success of HBO treatment may require its administration within 6 hours after CO poisoning. Patients in the Raphael study17 were
CONCLUSION
Treatment with HBO reduced the incidence of DNS in our study population. The results also demonstrate that neither clinical history nor the COHb level predicts which patients may show DNS after CO poisoning.
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Cited by (0)
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From the University of Pennsylvania Medical Center, Institute for Environmental Medicine* and Departments of Emergency Medicine‡, Pharmacology §, and Medicine∥, Philadelphia, Pennsylvania.
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Supported in part by grant 05211 from the Environmental Health Sciences Division of the National Institutes of Health.
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Address for reprints: Stephen R Thom, MD, PhD, University of Pennsylvania, Institute for Environmental Medicine, 36th Street and Hamilton Walk, Philadelphia, Pennsylvania 19104-6068, 215-898-9095, Fax 215-898-0868,
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Reprint no. 47/1/62318