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Hemodilution Improves Shear‐Mediated Transduction of Vasodilatory Signals in Human Cerebral and Systemic Circulations
Author(s) -
Hoiland Ryan Leo,
Tremblay Josh,
Flück Daniela,
Willie Chris,
Smith Kurt J,
Tymko Mike M,
Howe Connor A,
Donnelly Joseph,
Stembridge Mike,
Patrician Alex,
Rieger Matt,
Hansen Alex,
Coombs Geoff,
Santoro Antoinette,
Green Daniel,
MacLeod David,
Ainslie Philip
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.lb293
Subject(s) - hematocrit , brachial artery , medicine , vasodilation , endocrinology , cerebral blood flow , blood flow , cardiology , blood pressure
Shear stress (SS) regulates blood flow within the systemic and cerebral circulation. For example, in clinical populations (e.g. hemochromatosis), endothelium‐dependent flow‐mediated dilation (FMD) is improved and impaired by increases and decreases in whole blood viscosity (WBV), respectively. We tested the hypothesis that reductions in WBV would attenuate both cerebrovascular CO 2 reactivity and brachial FMD in healthy males (n=9). Internal carotid (ICA) and brachial artery (BA) blood flow, as well as cerebrovascular CO 2 reactivity and FMD, were measured prior to and following isovolumic hemodilution with 5% human serum albumin (20% removal/replacement of blood volume). Hemodilution reduced hematocrit (42.7±2.5 vs. 34.7±2.0 %; P<0.01) and WBV (3.6±0.2 vs. 2.7±0.2 cP; P<0.01). Resting ICA blood flow increased by 19% (328.7±66.3 vs. 389.9±91.0 mL · dL − 1 ; P<0.01) while SS was unaltered (13.4±3.2 vs. 12.5±2.6 dyn · cm − 2 ; P=0.17). BA blood flow (41.0±18.9 vs. 54.6±34.1 mL · min − 1 ; P=0.31) and SS (2.54±1.15 vs. 3.00±2.83 dyn · cm − 2 ; P=0.66) were unaltered following hemodilution. Despite a similarly unaltered SS area under the curve stimulus (733.4±296.6 vs. 996.1±571.1 au 3 ; P=0.20), BA FMD increased by 130% (3.9±2.3 vs. 9.0±4.3%; P=0.02). In contrast, however, neither absolute [24.3±7.4 vs. 30.1±13.5 ΔCBF (mL/dL) · ΔmmHg PaCO 2 ; P=0.10] or relative [7.6±3.1 vs. 8.5±4.1 %ΔCBF · mmHg PaCO 2 ; P=0.28) CO 2 reactivity were altered following hemodilution despite a reduced SS stimulus throughout the reactivity test (main effect, P<0.01). Therefore, despite the differing influence of hemodilution on cerebral and systemic circulations, both were more responsive for a given SS stimulus following hemodilution. Support or Funding Information Ryan L. Hoiland was supported by a Natural Sciences and Engineering Research Council of Canada Post Graduate Scholarship. Dr. David MacLeod is supported through the Duke University Human Physiology & Pharmacology Laboratory. Prof. Philip Ainslie is supported by the Natural Sciences and Engineering Research Council of Canada and Canada Research Chairs. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .