The neurological wake-up test does not alter cerebral energy metabolism and oxygenation in patients with severe traumatic brain injury

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BACKGROUND: The neurological wake-up test (NWT) is used to monitor the level of consciousness in patients with traumatic brain injury (TBI). However, it requires interruption of sedation and may elicit a stress response. We evaluated the effects of the NWT using cerebral microdialysis (MD), brain tissue oxygenation (PbtiO2), jugular venous oxygen saturation (SjvO2), and/or arterial-venous difference (AVD) for glucose, lactate, and oxygen in patients with severe TBI.

METHODS: Seventeen intubated TBI patients (age 16-74 years) were sedated using continuous propofol infusion. All patients received intracranial pressure (ICP) and cerebral perfusion pressure (CPP) monitoring in addition to MD, PbtiO2 and/or SjvO2. Up to 10 days post-injury, ICP, CPP, PbtiO2 (51 NWTs), MD (49 NWTs), and/or SjvO2 (18 NWTs) levels during propofol sedation (baseline) and NWT were compared. MD was evaluated at a flow rate of 1.0 μL/min (28 NWTs) or the routine 0.3 μL/min rate (21 NWTs).

RESULTS: The NWT increased ICP and CPP levels (p < 0.05). Compared to baseline, interstitial levels of glucose, lactate, pyruvate, glutamate, glycerol, and the lactate/pyruvate ratio were unaltered by the NWT. Pathological SjvO2 (<50 % or >71 %; n = 2 NWTs) and PbtiO2 (<10 mmHg; n = 3 NWTs) values were rare at baseline and did not change following NWT. Finally, the NWT did not alter the AVD of glucose, lactate, or oxygen.

CONCLUSIONS: The NWT-induced stress response resulted in increased ICP and CPP levels although it did not negatively alter focal neurochemistry or cerebral oxygenation in TBI patients.


  • Karin Skoglund
  • Lars Hillered
  • Karlis Purins
  • Parmenion P Tsitsopoulos
  • Johanna Flygt
  • Henrik Engquist
  • Anders Lewén
  • Per Enblad
  • Niklas Marklund
External organisations
  • Uppsala University
Research areas and keywords


  • Adolescent, Adult, Aged, Arousal, Brain, Brain Injuries, Consciousness Disorders, Critical Care, Energy Metabolism, Female, Humans, Hypnotics and Sedatives, Intracranial Pressure, Jugular Veins, Male, Microdialysis, Middle Aged, Neurologic Examination, Oxygen, Stress, Physiological, Trauma Severity Indices, Young Adult, Journal Article, Research Support, Non-U.S. Gov't
Original languageEnglish
Pages (from-to)413-26
Number of pages14
JournalNeurocritical Care
Issue number3
Publication statusPublished - 2014 Jun
Publication categoryResearch