[abstract] RANDOMIZED PROSPECTIVE STUDY COMPARING THE EFFECT OF HBO VERSUS 12 HOURS NBO IN NON COMATOSE CO POISONED PATIENTS: RESULTS OF THE INTERIM ANALYSIS

Abstract

BACKGROUND: Hyperbaric oxygen therapy has long been proposed as the treatment of choice of Carbon Monoxide (CO) poisoning but Raphael's study (Lancet, 1989, 1:414) has raised some controversy concerning the treatment of non comatose CO poisoned patients. METHODS: The study was implemented in 4 French University Hospitals after Ethic Committee Review and approval. Patients are included if CO poisoned (HbCO over 10 percent), admitted in the hyperbaric center within 12 hours from poisoning termination, and non comatose on hospital admission. Mixed poisoning, pregnancy or HBO contra-indications were exclusion criteria. After randomization patients were treated either by a HBO session (2.5 ATA, 90 min) or by 12 hours normobaric pure oxygen. Close follow up was made at 1, 3, 6, and 12 months. Statistical analysis was done by ANOVA or chi-square test. An interim analysis was planned at the end of the third year. RESULTS: In 3 years, 575 patients were treated, 299 in the HBO arm, 276 to the NBO arm. No significant difference existed in age, sex ratio, CO origin, poisoning severity, HbCO on admission, frequency and duration of oxygen treatment prior to admission. Patients were all discharged from the hospital with a normal neurological examination. At 1 month, follow up showed fewer (although not statistically significant) persistent neurologic manifestations in the HBO group than in the NBO (23percent vs. 26percent). At 3 months, a large significant difference existed (HBO: 9.5percent vs. NBO 15percent; p = 0.016). The difference became less important at 6 months (6.4percent vs. 9.5percent; p = 0.09) and disappeared at 1 year (4.3percent vs. 5percent). CONCLUSION: HBO-treated patients suffered from fewer CO-induced persistent neurological manifestations at 3-month follow-up than NBO-treated patients, even though this difference disappeared at 1 year. The study will be continued to allow proper subgroup analysis.