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Effects of Albumin Administration (I.V.) on Plasma Volume Expansion in the Heat,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
Pagination or Media Count:
To develop a reliable procedure for the acute expansion of plasma volume PV, 27 male volunteers were randomly assigned to either a thermoneutral 25degrees C and 40 RH or hotdry 37degrees C and 25 RH environment subsequently, each subject was seated for at least one hour and then infused I.V. with either 100 or 200 ml or a 25 albumin solution or 0.9 saline. On the day before each infusion, PV was estimated by dye dilution using indocyanine green. The net change in PV using Hct and Hb values was calculated at 1, 3, 6, 9, 12 and 24 hours post-infusion. The PV of subjects residing in the heat after a 100 ml saline infusion increased significantly over 1 hr values at 6,9 and 12 h, post infusion but not at 24 h. The same trend, although not significant was apparent at room temperature. The data suggest a slow, isooncotic, circadian pattern of PV expansion and contraction amplified significantly by heat exposure. The infusion of hyperoncotic albumin 25 g produced a rapid expansion of plasma volume. The expansion due to albumin alone was maximum at 1 hr post-infusion but accounted for only 44 of the expansion at 12 h. The absolute volume increase was greater and more persistent with the larger 50 g albumin dose. Heat exposure did not enhance the rapid, albumin-induced expansion but did result in a longer half-life of infused protein and a more consistent increase in oncotic pressure. The data suggest a mechanism for the retention of fluid during heat acclimatization and a useful procedure for plasma volume expansion in humans.
APPROVED FOR PUBLIC RELEASE