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January Mine Blasts Are A Deadly Reminder of Carbon Monoxide Risks, Neurological Complications for Survivors – Neurology today 1998 55 - Samson, Kurt

 January has not been a good month for miners - what with the tragic deaths of 12 miners at the Sago Mine in West Virginia on Jan. 2, and then two more deaths on Jan. 21, in another blast at the Alma Mine in the same state. These deaths and the efforts to save the lone survivor of the Sago blast, 26-year-old Randal McCloy Jr., serve as a sobering reminder of the risks of carbon monoxide (CO) asphyxiation - not only in traditionally hazardous work environments but also in homes, motor vehicles, and other enclosed spaces - especially in colder weather.

At press time, Mr. McCloy Jr. was emerging from a coma, but physicians did not know - or were not reporting - the extent of the neurological damage. His heart and liver functions had returned to normal, but he remained on dialysis. In an interview with The New York Times, Julian Bailes, MD, Chair of Neurosurgery at West Virginia University Hospital in Morgantown, noted that Mr. McCloy may be the longest known survivor of carbon monoxide poisoning. He added that physicians were in many ways in uncharted territory in terms of predicting his recovery, but we remain cautiously optimistic.

CO is the leading cause of injury and death by poisoning worldwide, with an estimated 15,000 people treated in US emergency rooms each year, according to the Centers for Disease Control and Prevention (CDC) in Atlanta. Brain damage occurs - days to weeks later - in up to one-half of patients with serious poisoning, according to the CDC.

Lower-level toxic exposure can cause neurological symptoms that are often misdiagnosed or overlooked. The National Institute for Occupational Safety and Health has set a ceiling limit for maximum CO exposure at 200 ppm, an eight-hour workday limit of 50 ppm, and a maximum carboxyhaemoglobin level of 5 ppm; however, neuropsychologic impairment has been reported in subjects breathing up to 100 ppm CO for 1.5 to 2.5 hours

Further, neurological complications of CO intoxication often emerge long after the patients recover from the acute effects of exposure. Up to 10 percent of survivors show gross neurological or psychiatric impairment, such as parkinsonism, persistent vegetative state, akinetic mutism, agnosia, apraxia, visual impairment, amnesia, or psychosis. Other survivors may develop persistent and subtle neuropsychiatric deficits.

In a three-year follow-up of 63 CO poisoning survivors, researchers reported that 33 percent of patients showed evidence of personality deterioration and 43 percent reported memory impairment (Br Med J 1973;1:318-321).

Carbon monoxide binds to hemoglobin with an affinity 210 to 280 times greater than oxygen, inhibiting delivery of oxygen to the brain and other tissues and causing hypoxia.

Oxygen is the first-line treatment for CO exposure. The half-life of COHb in normal air is 320 minutes, while administration of 100 percent cuts the half-life to about 60 minutes - 23 minutes if administered in a hyperbaric chamber.