Diurnal salivary cortisol measurement in the neurosurgical-surgical intensive care unit in critically ill acute trauma patients

Acute trauma patients represent a specific subgroup of the critically ill population due to sudden and dramatic changes in homeostasis and consequently extreme demands on the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis. Salivary cortisol is an accepted surrogate for serum free cortisol in the assessment of HPA axis function. The purpose of this study was (1) to establish the feasibility of salivary cortisol measurement in acute trauma patients in the neurosurgical-surgical intensive care unit (NSICU), and (2) to determine the diurnal pattern of salivary cortisol in the acute phase after injury. Saliva from 50 acute trauma patients was prospectively collected twice a day at 6AM and 4PM during the first week after injury in the NSICU. Mean PM cortisol concentrations were significantly higher in subjects versus controls (p<0.001). Subjects failed to develop the expected PM versus AM decrease in cortisol concentration seen in controls (p=0.005). Salivary cortisol did not vary significantly with baseline Glasgow Coma Scale (GCS), Injury Severity Score, sex, injury type, ethnicity, or age. When comparing mean AM and PM salivary cortisol by GCS severity category (GCS ⩽8 and GCS >8) the AM salivary cortisol was significantly higher in patients with GCS ⩽8 (p=0.002). The results show a loss of diurnal cortisol variation in acute trauma patient in the NSICU during the first week of hospitalization. Patients with severe brain injury had higher morning cortisol levels than those with mild/moderate brain injury.