These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Blood volume distribution during head-up tilt induced central hypovolaemia in man.
    Author: Matzen S, Perko G, Groth S, Friedman DB, Secher NH.
    Journal: Clin Physiol; 1991 Sep; 11(5):411-22. PubMed ID: 1934937.
    Abstract:
    We evaluated regional electrical impedance (Z degree) at 2.5 and 100 kHz to separate intra- and extracellular fluid changes and correlated Z degree over the thorax (TI) to relative changes in the central blood volume (CBV) induced by head-up tilt. In nine experiments head-up tilt resulted in normotensive central hypovolaemia associated with a 3.7 +/- 0.4 Ohm (mean +/- SE) increase in TI100 kHz after 60 min. In 24 experiments pre-syncopal symptoms were induced after 43 +/- 2 min, when TI100 kHz had increased 4.2 +/- 0.2 Ohm. Head-up tilt instantly decreased the activity of technetium labelled erythrocytes (99Tcm) over the thorax by 24 +/- 2%, and increased 99Tcm over the thigh by 68 +/- 10% (P less than 0.01, n = 8) with no further changes during the sustained tilt. Haematocrite increased during head-up tilt from 43.1 +/- 0.3 to 47.9 +/- 0.6% (P less than 0.01, n = 8). Accordingly, the increase in TI (6.3 +/- 0.6 vs. 4.5 +/- 0.4 Ohm, n = 6) and the decrease in Z degree through one leg (7.2 +/- 1.2 vs. 2.8 +/- 0.5 Ohm, n = 6) at 2.5 kHz was more pronounced than at 100 kHz. Also the changes in TI were correlated to CBV as calculated from 99Tcm and haematocrite (r = 0.90, P less than 0.01). The results suggest that: (1) Hypovolaemic shock is associated with a faster increase of TI than normotensive head-up tilt. (2) Head-up tilt is characterized by an initial decrease in CBV followed by a further decrease in plasma volume, which eventually leads to hypovolaemic shock. (3) Blood volume changes during head-up tilt are reflected in regional Z degree.
    [Abstract] [Full Text] [Related] [New Search]