Isovolemic hemodilution increases retinal tissue oxygen tension |
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| Authors: | Kimberly A Neely J Terry Ernest Thomas K Goldstick Robert A Linsenmeier Jonathan Moss |
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| Institution: | (1) Department of Ophthalmology, The University of Minnesota, 516 Delaware St. SE, 55455 Minneapolis, MN, USA;(2) Visual Sciences Center, Department of Ophthalmology and Visual Science, The University of Chicago, 939 East 57th Street, 60637 Chicago, IL, USA;(3) Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd., 60208 Evanston, IL, USA;(4) Department of Anesthesiology and Critical Care, The University of Chicago, 939 East 57th St., 60637 Chicago, IL, USA |
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| Abstract: |  Background: Therapeutic isovolemic hemodilution has been reported to improve blood flow and oxygen delivery. Few reliable measurements have been made, however, showing the effect of hemodilution on tissue oxygen tension. Methods: We measured retinal oxygen tension during experimental isovolemic hemodilution in normal cats. Polarographic oxygen microelectrodes were placed in the vitreous humor within 100–200  m of the retinal surface.Results: Tissue oxygen tension increased initially during isovolemic hemodilution to a maximum approximately 50% above baseline at approximately two thirds of the original hematocrit level. Hemodilution beyond this point to lower hematocrits caused a steady decline in tissue oxygen tension. Cardiac output measured in one cat undergoing isovolemic hemodilution increased as hematocrit was lowered, but the cardiac erythrocyte flux actually decreased steadily.Conclusion: The observed increase in tissue oxygen tension with hemodilution appears to be explained by a lesser reduction in capillary than in systemic hematocrit, coupled with an increased capillary blood flow. The increase in tissue oxygen tension we observed could in part explain the clinically beneficial effects of hemodilution. |
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