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Blood volume redistribution during hypovolemia.
MedLine Citation:
PMID:  23305001     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
BACKGROUND: The goal of this study was to investigate the contribution of splanchnic volume redistribution and lower limb vasoconstriction in the maintenance of blood pressure during progressive central hypovolemia induced by graded lower body negative pressure (LBNP). It was hypothesized that splanchnic blood volume loss during LBNP would buffer decreases in thoracic blood volume.
METHODS: There were 15 healthy subjects (8 men, 7 women) who participated in the study. We used LBNP of -10, -20, -30, and -40 mmHg with segmental impedance analysis to determine central and splanchnic volume changes, and near infrared spectroscopy (NIRS) to assess calf venous volume changes and vasoconstrictor tone.
RESULTS: In relation to baseline, LBNP to -40 mmHg resulted in a 57% increase in deoxygenated blood in the calf, indicating venous pooling in the lower limbs. These events led to a decrease in venous return and a 28% decline in cardiac output. Total upper body impedance increased by 6.6% with a 2.4% change in thoracic and a 13.1% increase in splanchnic impedance with progressive LBNP. Splanchnic blood volume contributed to more than 50% of the volume redistribution to the thoracic compartment during hypovolemia. Both men and women increased their heart rate, but only men vasoconstricted (4.4%) with increasing LBNP. The net result of these events was the maintenance of mean arterial blood pressure with no presyncopal symptoms in these subjects.
DISCUSSION: Our results suggest that splanchnic blood volume redistribution--rather than leg vasoconstriction--plays an important role in blood pressure regulation during central hypovolemia.
Authors:
Andrew P Blaber; Helmut Hinghofer-Szalkay; Nandu Goswami
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  84     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  59-64     Citation Subset:  IM; S    
Affiliation:
School of Kinesiology, Simon Fraser University, Burnaby, B.C., Canada.
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