Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen

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).

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.

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.

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.

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.