Changes in cerebral blood volume with changes in position in awake and anesthetized subjects.
ANESTHESIA AND ANALGESIA
372 - 376.
Changes in posture affect cerebral blood volume (CBV), and moderate head-up tilt is used as a therapeutic maneuver to reduce CBV and intracranial pressure. However, CBV is rarely measured in the clinical setting. Near-infrared spectroscopy allows real-time bedside monitoring of cerebral hemodynamics, and we have used this technique to measure changes in CBV with changes in posture in 10 normal subjects and 10 propofol-anesthetized patients. In the awake subjects, changes in CBV were correlated with the degree of table tilt. CBV decreased with 18 degrees head-up tilt and increased with 18 degrees head-down tilt (P < 0.0001, r = -0.924). In anesthetized patients, there were differences between head-up and head-down tilt. In the head-down position, CBV was also correlated with the degree of table tilt (P < 0.001, r = -0.782), whereas there was a clinically insignificant reduction in CBV in the head-up position. Near-infrared spectroscopy allows continuous, real time measurement of changes in CBV at the bedside. Implications: Near-infrared spectroscopy, a bedside technique, has been used to measure changes in cerebral blood volume in normal subjects. We have used the same technique in anesthetized patients and have shown that,when a patient is placed in the head up position, the decease in cerebral blood volume is attenuated, relative to normal subjects.
|Title:||Changes in cerebral blood volume with changes in position in awake and anesthetized subjects|
|Keywords:||NEAR-INFRARED SPECTROSCOPY, NEWBORN-INFANTS, CARBON-DIOXIDE, HEMODYNAMICS, OXYGENATION, METABOLISM, VOLUNTEERS, SPECTROPHOTOMETRY, QUANTIFICATION, TOMOGRAPHY|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Medical Physics and Bioengineering|
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