Effects of Albumin Administration (I.V.) on Plasma Volume Expansion in the Heat.

摘要

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 hot/dry (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.