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Filter by:Introduction Both Mental Fatigue (MF) and hypoxia impair multiple aspects of cognitive functioning. The decline in cognitive functioning in hypoxic conditions is associated with alterations in brain oxygenation and hemodynamic responses. These hemodynamic responses are preferably measured at the prefrontal cortex, an area of the brain that is known for its executive function and role in decision making, planning, attention and (short-term) memory. This study will investigate the role of prefrontal cortex oxygenation during the development of mental fatigue and during cognitive performances by altering the ambient oxygen availability through normobaric hypoxia (3800m; 12,9% O2) and normoxia. Methods Subjects will perform four trials in a sound-insulated climate chamber (20°C and 40% RH). Upon entry in the climatic chamber participants will adapt to the environment for 30 minutes. Next, they will perform a modified cognitive test battery "cognition", a fine motor task "Motor Performance Series" and a visuomotor-fitlight task before and after a 60-minute individualized Stroop task or control task (randomized. blinded, placebo controlled, counter-balanced, cross-over design). Nearinfrared spectroscopy (NIRS) will be used to assess hemodynamic changes (oxygenated hemoglobin (O2Hb), deoxygenated-hemoglobin (HHb) and total hemoglobin (tHb)) at the PFC. Hypotheses 1) MF will lead to earlier changes in the prefrontal NIRS-parameters (O2Hb, HHb, tHb) with lower oxygen availability. 2) The effects of MF on cognitive performance manifest itself to a greater extent with lower oxygen availability.3) Visuomotor performance declines to a greater extent due to MF with lower oxygen availability.
During open surgery of a thoraco-abdominal aortic aneurysma (TAAA), diminished blood flow to the myelum can result in hypoxia, compromising proper function of the spinal cord. Intraoperatively, motor evoked potentials (MEP) are elicited to measure the functional integrity of the spinal cord. MEPs have proven to be a reliable marker of spinal cord ischemia. Moreover, these potentials react within minutes, which facilitates interventions to restore the blood flow. Monitoring intraoperatively with this ancillary test has reduced the rate of paraparesis to < 5%. Unfortunately, in the early postoperative period, spinal cord vulnerability is high. Therefore, some patients develop paraparesis, not during the surgical procedure, but after the surgical procedure. Postoperatively, suboptimal blood flow may lead to critical loss of function. This inadequate perfusion results in "delayed paraparesis". In the postoperative patient, it is not possible to measure MEPs when sedation is decreased, due to the high intensity of the electrical stimulus, which is unacceptably painful in the unanesthetized or partially anesthetized patient. Therefore ancillary tests are needed which can detect spinal cord ischemia postoperatively early, thus preceding the phase with clinically overt paraparesis. The test should be reliable and easy to perform for an extended period of time (up to several days). The purpose of this study is to explore the usefulness of various neurophysiological tests regarding accuracy and feasibility for the detection of spinal cord ischemia. In particular, to find a diagnostic test which is acceptable for the unanesthetized or partially anesthetized patient and therefore can also be performed postoperatively. These tests will be examined in fully sedated as well as partially sedated patients. The following candidate tests will be examined: 1. Long loop reflexes (LLR) consisting of F-waves. 2. Oxygenation measurements of the paraspinal muscles using Near-infrared spectroscopy (NIRS).
Aim oft he study is to compare two different devices for cerebral oximetry (FORE-SIGHTTM Monitor (CAS Medical Systems, Branford, Connecticut, USA and INVOSTM Somanetics, Troy, Michigan, USA) in patients undergoing surgical carotid thrombendarterectomy (cTEA) with crossclamped internal carotid artery (ACI). All procedures will be performed in regional anesthesia, therefore the patients will be awake and direct neurological examination during the procedure will be possible, giving information how the drop in cerebral saturation (measured with INVOS and FORESIGHT both on the same patient) correlates with any clinical symptoms. We expect to see a difference in the total drop and in the delay of the drop of cerebral oxygen saturation, making it possible to detect varieties in specificity and sensitivity of both devices compared to neurologic examination in the awake patient.