The Neurological Wake-up Test Does not Alter Cerebral Energy Metabolism and Oxygenation in Patients with Severe Traumatic Brain Injury

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 (Pb ti O 2 ), jugular venous oxygen saturation (SjvO 2 ), 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, Pb ti O 2 and/or SjvO 2 . Up to 10 days post-injury, ICP, CPP, Pb ti O 2 (51 NWTs), MD (49 NWTs), and/or SjvO 2 (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 SjvO 2 (<50 % or >71 %; n = 2 NWTs) and Pb ti O 2 (<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.