The purpose of this study is to determine whether hydrocortisone associated with fludrocortisone decreases rate of hospital-acquired pneumonia on day-28 in TBI patients with glucocorticoid insufficiency. Glucocorticoid function will be assessed by a corticotropin test (ACTH 0.25 mg). The study treatment will be started before reception of the results of these test. Patients with glucocorticoid insufficiency (basal cortisolemia < 15 mcg/dl or post ACTH raise < or = 9 mcg/dl) will be treated for 10 days. Patients with adapted glucocorticoid function will no longer be treated till the results of corticotropin test are known.