Isovolemic hemodilution increases retinal tissue oxygen tension. 1996

K A Neely, and J T Ernest, and T K Goldstick, and R A Linsenmeier, and J Moss
Department of Ophthalmology, University of Minnesota, Minneapolis 55455, USA.

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 microns 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. CONCLUSIONS 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.

UI MeSH Term Description Entries
D008297 Male Males
D008839 Microelectrodes Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed) Electrodes, Miniaturized,Electrode, Miniaturized,Microelectrode,Miniaturized Electrode,Miniaturized Electrodes
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D012160 Retina The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent. Ora Serrata
D001783 Blood Flow Velocity A value equal to the total volume flow divided by the cross-sectional area of the vascular bed. Blood Flow Velocities,Flow Velocities, Blood,Flow Velocity, Blood,Velocities, Blood Flow,Velocity, Blood Flow
D001794 Blood Pressure PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS. Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D001809 Blood Viscosity The internal resistance of the BLOOD to shear forces. The in vitro measure of whole blood viscosity is of limited clinical utility because it bears little relationship to the actual viscosity within the circulation, but an increase in the viscosity of circulating blood can contribute to morbidity in patients suffering from disorders such as SICKLE CELL ANEMIA and POLYCYTHEMIA. Blood Viscosities,Viscosities, Blood,Viscosity, Blood
D002302 Cardiac Output The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat). Cardiac Outputs,Output, Cardiac,Outputs, Cardiac
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D005260 Female Females

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