Wednesday, November 4th 2009

Serum Ethanol Levels: Predictor of Survival

Anyone who has spent any time at a major trauma center knows the nearly comical tragedy of alcohol associated motor vehicle accidents where the inebriated driver survives and the fourteen-year-old in the other car somehow doesn’t. It tugs at our sense of fairness. I have a particular interest in trauma and while going through a feed of major trauma and neurosurgical journals came across this paper from a mixed group out of Los Angeles.

Salim, Ali, Pedro Teixeira, Eric Ley, Joseph DuBose, Kenji Inaba, and Daniel Marguiles. “Serum Ethanol Levels: Predictor of Survival After Severe Traumatic Brain Injury.” Journal of Trauma 67.4 (2009): 697-703.

It’s a retrospective study from a single institution mining the SICU/trauma database from one of the nation’s larger trauma centers, LAC+USC, for severe traumatic brain injury whose EtOH level at the time of admission was documented. Severe TBI was defined as a head AIS >= 3. Their question focused on outcome differences between those with serum ethanol levels at the time of their accidents and those without; their primary outcome being in-hospital mortality.

Over a five year period they found 482 patients with head AIS >= 3 and EtOH serum levels drawn on admission. That’s from nearly 3,000 in the trauma database over the five year range the group was searching.

The question was certainly answered in the affirmative. Any EtOH on board seemed to convey an in-hospital survival benefit.

Indeed the serum EtOH level correlated with survival.

The mean serum ETOH level was significantly higher for survivors than for nonsurvivors (0.11 +/- 0.21 g/dL vs. 0.05 +/- 0.10 g/dL, p = 0.001). The serum ETOH levels
significantly correlated with the probability of survival (r = 0.21, p = 0.001), but this correlation was not strong as shown by the low r-value.

As can be imagined with that primary outcome, in hospital complication rates were pretty much lower across the board for those with positive EtOH levels on admission.

These findings aren’t shocking, merely confirmatory. Studies by Tien [1] and O’Phelan [2] and Kraus [3] and Tate [4], as cited by the authors of this paper had documented better outcomes for those who are inebriated at the time of their head injury as compared to those who aren’t. And indeed this isn’t even Dr. Salim’s only publication from this data mining effort. He is lead author of another broader retrospective study recently in the Archives of Surgery looking at the NTDB.

Salim, Ali, Eric Ley, H. Gill Cyer, Daniel Marguiles, Emily Ramicone, and Areti Tillou. “Positive Serum Ethanol Level and Mortality in Moderate to Severe Traumatic Brain Injury.” Archives of Surgery 144.9 (2009): 865-71. Print.

There are obvious limitations to this study. It is retrospective, as likely all in vivo studies of alcohol and trauma are likely to be. As well there were a limited number of TBIs presenting to LAC+USC who actually had serum EtOH levels tested. Formal serum EtOH testing of all trauma patients as a standard is becoming more and more frequent but likely wouldn’t have changed the findings of this study seeing as there weren’t major demographic discrepancies between those who had their serum EtOH drawn and those who didn’t (as the paper goes over). It was a single institution as well, but of course I feel safe in assuming that LAC+USC has a pretty heterogeneous population as might be seen elsewhere in the United States and most of the world.

These well documented results seem to be one of those sad, ironic, situations in life if I can prognosticate. Obviously these studies have limited clinical value at present, but perhaps if there’s some true protective pathophysiology in EtOH consumption before trauma then future bench top work may elucidate that and open some doors on acute measures that might be taken for those with traumatic brain injury early following injury.

[1] Tien HC, Tremblay LN, Rizoli SB, et al. Association between alcoholand mortality in patients with severe traumatic head injury. Arch Surg. 2006;141:1185–91

[2] O’Phelan K, McArthur DL, Chang CW, Green D, Hovda DA. Theimpact of substance abuse on mortality in patients with severe traumaticbrain injury. J Trauma. 2008;65:674–677

[3] Kraus JF, Morgenstern H, Fife D, Conroy C, Nourjah P. Blood alcoholtests, prevalence of involvement, and outcomes following brain injury. Am J Public Health. 1989;79:294–299

[4] Tate PS, Freed DM, Bombardier CH, Harter SL, Brinkman S. Traumaticbrain injury: influence of blood alcohol level on post-acute cognitive function. Brain Inj. 1999;13:767–784