AUTHOR=Bronzwaer Anne-Sophie G. T. , Stok Wim J. , Westerhof Berend E. , van Lieshout Johannes J. 

TITLE=Arterial pressure variations as parameters of brain perfusion in response to central blood volume depletion and repletion

JOURNAL=Frontiers in Physiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2014.00157

DOI=10.3389/fphys.2014.00157

ISSN=1664-042X

ABSTRACT=<p><bold>Rationale:</bold> A critical reduction in central blood volume (CBV) is often characterized by hemodynamic instability. Restoration of a volume deficit may be established by goal-directed fluid therapy guided by respiration-related variation in systolic- and pulse pressure (SPV and PPV). Stroke volume index (SVI) serves as a surrogate end-point of a fluid challenge but tissue perfusion itself has not been addressed.</p><p><bold>Objective:</bold> To delineate the relationship between arterial pressure variations, SVI and regional brain perfusion during CBV depletion and repletion in spontaneously breathing volunteers.</p><p><bold>Methods:</bold> This study quantified in 14 healthy subjects (11 male) the effects of CBV depletion [by 30 and 70 degrees passive head-up tilt (HUT)] and a fluid challenge (by tilt back) on CBV (thoracic admittance), mean middle cerebral artery (MCA) blood flow velocity (V<sub>mean</sub>), SVI, cardiac index (CI), PPV, and SPV.</p><p><bold>Results:</bold> PPV (103 ± 89%, <italic>p</italic> &lt; 0.05) and SPV (136 ± 117%, <italic>p</italic> &lt; 0.05) increased with progression of central hypovolemia manifested by a reduction in thoracic admittance (11 ± 5%, <italic>p</italic> &lt; 0.001), SVI (28 ± 6%, <italic>p</italic> &lt; 0.001), CI (6 ± 8%, <italic>p</italic> &lt; 0.001), and MCAV<sub>mean</sub> (17 ± 7%, <italic>p</italic> &lt; 0.05) but not in arterial pressure. The reduction in MCAV<sub>mean</sub> correlated to the fall in SVI (<italic>R</italic><sup>2</sup> = 0.52, <italic>p</italic> &lt; 0.0001) and inversely to PPV and SPV [<italic>R</italic><sup>2</sup> = 0.46 (<italic>p</italic> &lt; 0.0001) and <italic>R</italic><sup>2</sup> = 0.45 (<italic>p</italic> &lt; 0.0001), respectively]. PPV and SPV predicted a ≥15% reduction in MCAV<sub>mean</sub> and SVI with comparable sensitivity (67/67% vs. 63/68%, respectively) and specificity (89/94 vs. 89/94%, respectively). A rapid fluid challenge by tilt-back restored all parameters to baseline values within 1 min.</p><p><bold>Conclusion:</bold> In spontaneously breathing subjects, a reduction in MCAV<sub>mean</sub> was related to an increase in PPV and SPV during graded CBV depletion and repletion. Specifically, PPV and SPV predicted changes in both SVI and MCAV<sub>mean</sub> with comparable sensitivity and specificity, however the predictive value is limited in spontaneously breathing subjects.</p>