Carbon Monoxide Poisoning: Risk Factors for Cognitive Sequelae and the Role of Hyperbaric Oxygen

Abstract

RATIONALE: Carbon monoxide poisoning is common and causes cognitive sequelae. Hyperbaric oxygen (HBO(2)) reduces cognitive sequelae incidence, but which patients may benefit from HBO(2) is unclear. OBJECTIVES: Risk factor determination for 6-wk cognitive sequelae from CO poisoning and risk modification with HBO(2). METHODS: Patients were from a randomized controlled trial, enrolling acutely CO-poisoned patients more than 15 years of age. Patients eligible but not enrolled in the randomized trial, and not receiving HBO(2), were followed during the study interval. In patients not receiving HBO(2), we performed univariate analyses including risk factors identified by randomized trial subgroup analyses. A multivariable analysis was performed using univariate results with and without HBO(2). MEASUREMENTS AND MAIN RESULTS: In 163 patients not receiving HBO(2), 68 (42%) manifested sequelae. Risk factors for sequelae from subgroup analyses were loss of consciousness, age of 36 years or more, and carboxyhemoglobin levels greater than or equal to 25%. By univariate analyses, risks for sequelae were age of 36 years or more (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.3-4.9; P = 0.005), and exposure intervals greater than or equal to 24 hours (OR, 2.4; 95% CI, 1.2-4.8; P = 0.019). Including 75 patients receiving HBO(2), cognitive sequelae was reduced in patients age of 36 years or more (OR, 0.3; 95% CI, 0.2-0.6; P < 0.001). Exposure intervals greater than or equal to 24 hours are an independent risk factor for sequelae (OR, 2.0; 95% CI, 1.0-3.8; P = 0.046). CONCLUSIONS: HBO(2) oxygen is indicated for patients with acute CO poisoning who are 36 years or older or have exposure intervals greater than or equal to 24 hours. In addition, subgroup analyses support that patients with loss of consciousness or higher carboxyhemoglobin levels warrant HBO(2).