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Objectives: The "neurological wake-up test" is needed to evaluate the level of consciousness in patients with severe traumatic brain injury. However, the neurological wake-up test requires interruption of continuous sedation and may induce a stress response and its use in neurocritical care is controversial. We hypothesized that the neurological wake-up test induces an additional biochemical stress response in patients with severe traumatic brain injury.

Patients: Twenty-four patients who received continuous propofol sedation and mechanical ventilation after moderate to severe traumatic brain injury (Glasgow Coma Scale score <= 8; patient age 18-71 yrs old) were analyzed. Exclusion criteria were age <18 yrs old, ongoing pentobarbital infusion, or markedly increased intracranial pressure on interruption of continuous sedation.

Design: Single-center prospective study. During postinjury days 1-8, 65 neurological wake-up tests were evaluated. Adrenocorticotrophic hormone, epinephrine, and norepinephrine levels in plasma and cortisol levels in saliva were analyzed at baseline (during continuous intravenous propofol sedation) and during neurological wake-up test. Data are presented using medians and 25th and 75th percentiles.

Setting: The study was performed in a university hospital neurocritical care unit.

Interventions: None.

Measurements and Main Results: At baseline, adrenocorticotrophic hormone and cortisol levels were 10.6 (6.0-19.4) ng/L and 16.0 (10.7-31.8) nmol/L, respectively. Immediately after the neurological wake-up test, adrenocorticotrophic hormone levels increased to 20.5 (11.1-48.4) ng/L (p < .05) and cortisol levels in saliva increased to 24.0 (12.3-42.5) nmol/L (p < .05). The plasma epinephrine and norepinephrine levels increased from a baseline of 0.3 (0.3-0.6) and 1.6 (0.9-2.3) nmol/L, respectively, to 0.75 (0.3-1.4) and 2.8 (1.28-3.58) nmol/L, respectively (both p < .05).

Conclusions: The neurological wake-up test induces a biochemical stress response in patients with severe traumatic brain injury. The clinical importance of this stress response remains to be established but should be considered when deciding the frequency and use of the neurological wake-up test during neurocritical care.