Incidence of adrenal insufficiency after severe traumatic brain injury varies according to definition used: clinical implications

Background. Adrenal insufficiency impacts on the haemodynamic management of patients in intensive care. Very little is known about the incidence of adrenal insufficiency in the first 10 days after traumatic brain injury. Methods. We retrospectively reviewed the charts of 113 traumatic brain injury patients within 10 days of their injury. They all had a high-dose corticotropin stimulation test performed because of haemodynamic instability. Blood cortisol concentrations were measured at baseline, 30 and 60 min after the administration of high-dose corticotropin. The incidence of adrenal insufficiency was determined according to various definitions used in the literature. Results. The baseline cortisol concentration was < 414 nmol litre(-1) (15 mu g dl(-1)) in 78% of patients and < 690 nmol litre(-1) (25 mu g dl(-1)) in all patients. The cortisol concentration did not rise above 500 nmol litre(-1) (18 mu g dl(-1)) at 30 and 60 min in 49 and 22% of patients, respectively. The cortisol concentration did not rise by 250 nmol litre(-1) (9 mu g dl(-1)) at 30 and 60 min in 48 and 25% of patients respectively. Primary adrenal insufficiency defined by an abnormal baseline cortisol concentration and an abnormal response to the high-dose corticotropin stimulation test was present in 13-28% of patients according to the cut-off values used. Conclusions. The incidence of adrenal insufficiency varies from 25 to 100% in the first 10 days after traumatic brain injury. The range of incidences reported illustrates the need for standardization of the definition of adrenal insufficiency. This has a direct impact on treatment. Sampling at 60 min after the high-dose corticotropin stimulation test seems to correlate better with the maximum secreting capacity of the adrenal glands.