Is hyperbaric oxygen therapy more effective than normobaric oxygen therapy for improving acute neuropsychologic status due to carbon monoxide poisoning?

ABSTRACT

OBJECTIVE: The evidence that hyperbaric oxygen (HBO) therapy is more effective for improving the acute neuropsychological status (ANS) of carbon monoxide poisoning than normobaric oxygen (NBO) therapy is not convincing. This is because the levels of carboxyhemoglobin (COHb) do not correlate with the clinical severity of carbon monoxide poisoning and there is no universally accepted severity scale of carbon monoxide poisoning. This paper suggests a new scale for the clinical and neurological severity of carbon monoxide poisoning, called the ANS, and assesses the effect of HBO therapy for each level of ANS compared to NBO therapy. METHODS: A total of 217 patients who had been hospitalized because of carbon monoxide poisoning from January 2009 to July 2013 were studied. ANS was suggested as a new severity scale of carbon monoxide poisoning considered in the Glasgow Coma Scale, acute neuro-psychologic signs and symptoms, or cardiac ischemia on the initial medical contact. HBO therapy is indicated in those who have a loss of consciousness, seizure, coma, abnormal findings on a neurological examination, pregnancy, persistent cardiac ischemia, level of COHb >25%, or severe metabolic acidosis (pH < 7.2). The end point is the day of discharge, and recovery is defined as a normal neuro-psychological status without any sequelae. RESULTS: The levels of troponin T and creatinine increased significantly with increasing ANS score. In the moderate to severe group (ANS 2 and 3), the recovery rate was significantly higher when treated with HBO therapy than with NBO therapy (P=0.030). On the other hand, the development of delayed neuro-psychological sequelae (DNS) did not correlate with any level of ANS, type of oxygen therapy, or recovery on discharge. CONCLUSION: In the moderate to severe poisoned group, HBO therapy is more effective for improving the ANS from carbon monoxide poisoning than NBO therapy. On the other hand, the development of DNS of HBO therapy is no more preventable than with NBO therapy. Although the level of ANS is low, the patient needs to be provided with sufficient information and a follow-up visit is recommended for any abnormal symptoms because the ANS does not correlate with the development and degree of DNS.