Lactate as a prognostic factor in carbon monoxide poisoning: a case report

Carbon monoxide (CO) poisoning results in various neuropsychological impairments, including delayed encephalopathy (DE) and death. However, factors related to these outcomes are unknown. A group suicide was attempted by 3 young people--a 31-year-old man (patient 1), a 21-year-old woman (patient 2), and a 20-year-old man (patient 3)--by burning charcoal in a closed car. At the emergency department, hypotension and hyperthermia were severe in patient 1, moderate in patient 2, and absent in patient 3, although all the patients were comatose. The initial serum lactate levels were 75.1 mg/dL in patient 1, 41.9 mg/dL in patient 2, and 26.3 mg/dL in patient 3, although the carboxyhemoglobin levels were approximately equal in all the patients. Hyperbaric oxygen therapy (HBOT) was immediately initiated and continued for 10 days in all the cases; however, the outcomes of these patients varied considerably. Patient 1 remained comatose and died on day 31 because of central diabetes insipidus after shock. Patient 2 recovered from coma and was discharged; however, she was rehospitalized for DE on day 45 and recovered completely after another 10-day HBOT. Patient 3 gained consciousness and recovered completely with no sequelae during the 1-year follow-up. From these cases, we can consider that the initial blood lactate may correlate with the patient outcomes and prove to be a useful prognostic factor. Thus, we should particularly consider elevated lactate levels in CO poisoning.