Metabolic Response and Nutritional Support in Traumatic Brain Injury: Evidence for Resistance to Renutrition

Traumatic brain injury (TBI) is one of the most severe injuries encountered in intensive care units. TBI patients exhibit protein wasting and gastrointestinal dysfunction, which may be risk factors for a septic state. Specific nutritional support may be required for these patients, and we hypothesize that standard nutritional support does not allow restoration of the nutritional state of TBI patients. A well-validated rat model of TBI by fluid percussion was used. Rats were randomized into three groups: healthy rats receiving standard chow diet ad libitum (AL), rats sustaining TBI and receiving standard chow diet (TBI), and rats sustaining TBI and receiving a standard enteral diet (TBI-EN) for 4 days. TBI in rats was characterized by anorexia, body weight loss (AL: +15 +/- 5 g versus TBI: -11 +/- 4 g and TBI-EN: -8 +/- 4g; p < 0.05), decrease in nitrogen balance (AL: 2.9 +/- 0.2 g versus TBI: 1.0 +/- 0.2 g and TBI-EN: 0.2 +/- 0.2 g, p < 0.05) associated with decrease in muscular protein content (extensor digitorum longus [EDL]: AL: 36 +/- 2 mg versus TBI: 26 +/- 3 mg and TBI-EN: 28 +/- 2 mg; p < 0.05), and intestinal atrophy (ileum: AL: 673 +/- 42 mg versus TBI: 442 +/- 23 mg and TBI-EN: 377 +/- 27 mg; p < 0.05). Interestingly, standard enteral nutrition was not effective in restoring any of these parameters. This work confirms that TBI is associated with profound nutritional alterations and has a major impact on nitrogen metabolism and on intestinal trophicity. It also demonstrates that using standard enteral nutrition cannot reverse this phenomenon. Thus, developing new nutritional strategies to cover TBI patients' specific nutritional requirements appears mandatory.