Traumatic brain injury victims who have been drinking moderately may be less likely to die after arriving at the hospital than those with no alcohol in their bloodstream, according to a surprising new report.

Those with the highest alcohol levels, however, appear to have an increased risk of dying.

Alcohol use is a major risk factor for trauma, with about one-third to one-half of all patients hospitalized with trauma intoxicated at the time of injury. Once an injury has occurred, however, some human and animal studies have suggested that alcohol may be neuroprotective, keeping the injury from worsening once it has occurred.

Homer C. N. Tien, M.D. of Sunnybrook Health Sciences Centre, University of Toronto, and colleagues studied more than 1,000 consecutive patients who were evaluated at a trauma center for severe brain injury between 1988 and 2003. Patients' blood alcohol concentration (BAC) was tested upon admission.

The researchers found that those with a low to moderate BAC were less likely to die than those with no BAC (27.9 percent vs. 36.3 percent). After adjusting for other factors that could influence the risk of death-including injury severity, blood transfusions and whether the trauma occurred in a motor vehicle crash- the effect remained. Those with a low to moderate BAC had 24 percent lower chance of dying in the hospital than those with no BAC. In contrast, those with a high BAC had 73 percent higher odds of dying than those with no BAC.

Writing in the December 2006 issue of Archives of Surgery, the authors speculate that low to moderate doses of alcohol may protect the brain by stopping the mechanisms that contribute to secondary brain injury, which occurs when injured brain cells continue to be deprived of oxygen.

"There are major sociologic implications from implying that intoxicated patients with severe traumatic brain injury have better outcomes than non-intoxicated patients," the authors write. "We stress that our study only examined the role of alcohol on outcome in the post-injury phase because we examined only in-hospital deaths." About half of all individuals who die from trauma do so before they arrive at the hospital, they continue. Because alcohol use increases the likelihood of a severe injury, alcohol-related deaths comprise a large percentage of those who die before they have a chance to get to the hospital.

"Overall, people are still at much greater risk of dying if they drive while intoxicated," the authors conclude. "What our study implies is that there may be a role for an alcohol-based resuscitation fluid in improving outcomes in adequately resuscitated patients with severe head injury."