3 hyperbaric oxygen treatments reduced cognitive sequelae of acute carbon monoxide poisoning.

Weaver LK, Hopkins RO, Chan KJ, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. QUESTION: In patients with carbon monoxide poisoning, is hyperbaric oxygen (HBO) more effective than normobaric oxygen for reducing cognitive sequelae? Design Randomised (allocation concealed*), blinded (patients, outcome assessors, and statisticians),* controlled trial with follow up at 6 weeks, 6 months, and 1 year. Patients 152 patients (mean age 36 y, 62% men) with documented or obvious exposure to carbon monoxide and any of 11 predetermined symptoms. Patients were excluded if they were < 16 years of age, moribund, or pregnant or if > 24 hours had elapsed since exposure. Follow up at 6 weeks was 97%. Intervention All patients had 3 hyperbaric chamber sessions at intervals of 6–12 hours starting within 24 hours after carbon monoxide exposure. All non-intubated patients received oxygen, 15 l/min via a non-rebreathing face mask and reservoir. Intubated patients were mechanically ventilated with 100% oxygen. 76 patients were allocated to HBO and exposed to 100% oxygen at 3 atmospheres (304 kPa) and then 2 atmospheres absolute (203 kPa) during the first chamber session and 100% oxygen at 2 atmospheres absolute for sessions 2 and 3. 76 patients were allocated to normobaric oxygen and exposed to air at 1 atmosphere absolute (101.3 kPa, or sea level pressure) for all 3 chamber sessions. Cognitive sequelae at 6 weeks were measured using a battery of neuropsychological tests and were considered present if any subtest score was > 2 standard deviations (SDs) below the mean of demographically corrected standardised scores or if ≥ 2 scores were > 1 SD below the mean. Analysis was by intention to treat. The trial was stopped early after 3 of 4 planned interim analyses were completed. At 6 weeks, 6 months, and 12 months, patients in the HBO group had fewer cognitive sequelae than did patients in the normobaric group (table). The analysis was adjusted for cerebellar dysfunction because it was not equally distributed (4 HBO v 15 normobaric group patients), with no change in results. Conclusion In patients with acute carbon monoxide poisoning, 3 hyperbaric oxygen treatments within 24 hours of exposure reduced cognitive sequelae at 6 weeks, 6 months, and 1 year. at 1 year 18% 33% 44% (2.2 to 68) 7 (4 to 182) †Abbreviations defined in glossary; RRR, NNT, and CI calculated from data in article. Analysis includes all patients. Those with missing data at …