Postural influence on intracranial and cerebral perfusion pressure in ambulatory neurosurgical XXXX .

@entity1 @entity4 @entity1211 @entity428
UNASSIGNED: We evaluated postural effects on @entity428 ( @entity428 ) and cerebral perfusion pressure (CPP: mean arterial pressure (MAP) - @entity428 ) in neurosurgical @entity1 undergoing 24-hour @entity428 monitoring as part of their diagnostic workup. We identified 9 @entity1 (5 @entity1 , age 44  20 yrs.; mean  SD) who were "as normal as possible" i.e. without indication for neurosurgical intervention (e.g. focal lesions, global @entity4 , @entity428 or cerebrospinal fluid dynamics). @entity428 (tip-transducer probe, Raumedic) in the brain parenchyma (N=7) or in the lateral ventricles (N=2) and cardiovascular variables (Nexfin) were determined from 20   head-down tilt to standing up. Compared to the supine position, @entity428 increased during 10   and 20   of head-down tilt (from 9.4  3.8 to 14.3  4.7 and 19  4.7 mmHg, P<0.001). Conversely, 10   and 20   head-up tilt reduced @entity428 to 4.8  3.6 and 1.3  3.6 mmHg and @entity428 reached -2.4  4.2 mmHg when standing up (P<0.05). Concordant changes in MAP maintained CPP at 77  7 mmHg regardless of body position (P=0.95). During head-down tilt, the increase in @entity428 corresponded to a hydrostatic pressure gradient with reference just below the heart, likely reflecting the venous hydrostatic indifference point. When upright, the decrease in @entity428 was attenuated, corresponding to formation of a separate hydrostatic gradient with reference to the base of the skull, likely reflecting the site of @entity1211 . @entity428 therefore seems to be governed by pressure in the draining veins and collapse of neck veins may protect the brain from being exposed to a large negative pressure when upright. Despite positional changes in @entity428 , MAP keeps CPP tightly regulated.
