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Open Access Research article

Predictors for delayed encephalopathy following acute carbon monoxide poisoning

Kaoru Kudo1*, Kotaro Otsuka12, Junko Yagi1, Katsumi Sanjo1, Noritaka Koizumi1, Atsuhiko Koeda1, Miki Yokota Umetsu1, Yasuhito Yoshioka3, Ayumi Mizugai1, Toshinari Mita1, Yu Shiga1, Fumito Koizumi1, Hikaru Nakamura2 and Akio Sakai1

Author Affiliations

1 Department of Neuropsychiatry, Iwate Medical University, school of Medicine, Morioka, Iwate, Japan

2 Department of Disaster & Community Psychiatry, Iwate Medical University, school of Medicine, Morioka, Iwate, Japan

3 Department of Critical Care Medicine, Iwate Medical University, school of Medicine, Morioka, Iwate, Japan

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BMC Emergency Medicine 2014, 14:3  doi:10.1186/1471-227X-14-3

Published: 31 January 2014



In Japan, many carbon monoxide (CO) poisoning cases are transported to emergency settings, making treatment and prognostic assessment an urgent task. However, there is currently no reliable means to predict whether “delayed neuropsychiatric sequelae (DNS)” will develop after acute CO poisoning. This study is intended to find out risk factors for the development of DNS and to characterize the clinical course following the development of DNS in acute CO poisoning cases.


This is a retrospective cohort study of 79 consecutive patients treated at a single institution for CO poisoning. This study included 79 cases of acute CO poisoning admitted to our emergency department after attempted suicide, who were divided into two groups consisting of 13 cases who developed DNS and 66 cases who did not. The two groups were compared and analyzed in terms of clinical symptoms, laboratory findings, etc.


Predictors for the development of DNS following acute CO poisoning included: serious consciousness disturbance at emergency admission; head CT findings indicating hypoxic encephalopathy; hematology findings including high creatine kinase, creatine kinase-MB and lactate dehydrogenase levels; and low Global Assessment Scale scores. The clinical course of the DNS-developing cases was characterized by prolonged hospital stay and a larger number of hyperbaric oxygen (HBO) therapy sessions.


In patients with the characteristics identified in this study, administration of HBO therapy should be proactively considered after informing their family, at initial stage, of the risk of developing DNS, and at least 5 weeks’ follow-up to watch for the development of DNS is considered necessary.

Delayed encephalopathy; Carbon monoxide poisoning; Delayed neuropsychiatric sequelae; Suicide attempt; Psychiatric emergency