Delayed Neuropsychologic Sequelae After Carbon Monoxide Poisoning: Prevention by Treatment With Hyperbaric Oxygen,☆☆,,★★

Presented at the American College of Emergency Physicians Research Forum in San Diego, California, March 1994.
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Abstract

See related editorial, "Hyperbaric Oxygen for Carbon Monoxide Poisoning: Does It Really Work?"

Study objective: Carbon monoxide (CO) poisoning is a major clinical problem. The risk of morbidity and the most effective treatment have not been clearly established. We measured the incidence of delayed neurologic sequelae (DNS) in a group of patients acutely poisoned with CO and tested the null hypothesis that the incidence would not be affected by treatment with hyperbaric oxygen (HBO).

Design: We conducted a prospective, randomized study in patients with mild to moderate CO poisoning who presented within 6 hours. Patients had no history of loss of consciousness or cardiac instability. Interventions: The incidence of DNS was compared between groups treated with ambient pressure 100% oxygen or HBO (2.8 ATA for 30 minutes followed by 2.0 ATA oxygen for 90 minutes). DNS were defined as development of new symptoms after oxygen treatment plus deterioration on one or more subtests of a standardized neuropsychologic screening battery. Results: In 7 of 30 patients (23%), DNS developed after treatment with ambient-pressure oxygen, whereas no sequelae developed in 30 patients after HBO treatment (P<.05). DNS occurred 6±1 (mean±SE) days after poisoning and persisted 41±8 days. At follow-up 4 weeks after poisoning, patients who had been treated with ambient pressure oxygen and had not sustained DNS exhibited a worse mean score on one subtest, Trail Making, compared with the group treated with HBO and with a control group matched according to age and education level. There were no differences in scores between the control group and the hyperbaric oxygen group. Conclusion: DNS after CO poisoning cannot be predicted on the basis of a patient's clinical history or CO level. HBO treatment decreased the incidence of DNS after CO poisoning. [Thom SR, Taber RL, Mendiguren II, Clark JM, Hardy KR, Fisher AB: Delayed neuropsychologic sequelae after carbon monoxide poisoning: Prevention by treatment with hyperbaric oxygen. Ann Emerg Med April 1995;25:474-480.]

Section snippets

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.

References (28)

  • FH Shillito et al.

    The problem of nervous and mental sequelae in carbon monoxide poisoning

    JAMA

    (1936)
  • CA Simpson

    Carbon monoxide poisoning in New Castle-upon-Tyne

    N Castle Med J

    (1963)
  • H Bour et al.

    Le coma oxycarbone

    Semaine des Hôpitaux de Paris

    (1966)
  • JS Smith et al.

    Acute carbon monoxide poisoning: Three years' experience in a defined population

    Postgrad Med J

    (1970)
  • Cited by (0)

    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.

    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

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