Serum melatonin levels in predicting mortality in patients with severe traumatic brain injury.

Purpose: A secondary brain injury could appear after traumatic brain injury (TBI) due to neuroinflammation, oxidation and apoptosis. Higher levels of serum melatonin have been found on admission for TBI in non-surviving than in surviving patients. Thus, the objective of this study was to know serum melatonin levels during the first week of TBI in surviving and non-surviving patients, and to know if serum melatonin levels during the first week of TBI can be used to predict mortality.

Methods: Patients with an isolated and severe TBI were included; that is, if they scored < 10 points in non-cranial aspects of Injury Severity Score and < 9 points in the Glasgow Coma Scale. We measured serum melatonin concentrations at days 1, 4 and 8 of TBI. Thirty-day mortality was the end-point study.

Results: Lower serum melatonin levels were found in the surviving patients (n = 90) than in the non-survivors (n = 34) on days 1 (p < 0.001), 4 (p < 0.001), and 8 (p = 0.02) of TBI. Serum melatonin concentrations on days 1, 4, and 8 of TBI had an area under curve (95% Confidence Interval) for the prediction of 30-day mortality of 0.85 (0.77-0.91; p < 0.001), 0.82 (0.74-0.89; p < 0.001) and 0.71 (0.61-0.79; p = 0.06) respectively.

Conclusions: The new findings of this study were the presence of higher levels of serum melatonin on days 1, 4 and 8 of TBI in non-survivors than in survivors, and the ability to predict 30-day mortality for serum melatonin levels measured at these time points. However, more research is necessary to confirm our results.