Apolipoprotein E genotype and response of carbon monoxide poisoning to hyperbaric oxygen treatment

Hyperbaric oxygen (HBO2) reduced the incidence of cognitive sequelae 6 weeks after carbon monoxide (CO) poisoning compared with normobaric oxygen (NBO2). The apolipoprotein (APOE) epsilon4 allele predicts unfavorable neurologic outcome after brain injury and stroke.

To assess the effects of the epsilon4 allele on 6-week cognitive sequelae after CO poisoning.

We tested APOE genotypes in 86 of 152 CO-poisoned patients from our randomized trial. Logistic regression was used to control for risk factors while testing for effects with the epsilon4 allele or interactions with epsilon4 and treatment on 6-week and 6- and 12-month cognitive sequelae.

We enrolled 86 patients: 44 received HBO2 and 42 NBO2 therapy. A total of 31 (36%) patients had at least one epsilon4 allele. Six-week cognitive sequelae rates for patients treated with HBO2 and NBO2, respectively: epsilon4 allele absent, 11% (3/27) and 43% (12/28); epsilon4 allele present, 35% (6/17) and 29% (4/14). The epsilon4 allele was not associated with 6-week cognitive sequelae, 27% (15/55) without and 32% (10/31) with the epsilon4 allele (P = 0.323). The interaction between the epsilon4 allele and treatment was significantly associated with 6-week cognitive sequelae (P = 0.048). The interaction between the epsilon4 allele and treatment was not associated with 6- and 12-month cognitive sequelae.

HBO2 therapy reduces cognitive sequelae after CO poisoning in the absence of the epsilon4 allele. Because apolipoprotein genotype is unknown at the time of poisoning, we recommend that patients with acute CO poisoning receive HBO2.