Mechanism of Plasma Protein Changes Following Saline Infusions

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Abstract
Dogs, anesthetized with Na Pentothal, were infused with volumes of physiological saline soln. amounting to 1/3 to 3.5 times their plasma volumes at a rate of 30 ml./min. The actual percentage increase in plasma volume remains the same throughout this range of infusion volumes (250-2000 ml.). In terms of immediate plasma volume expansion, the most efficient infusion volumes are those which are less than 75% of the plasma volume. Judged by changes in the rates of disappearance of intraven. injd. radioactive iodinated albumin, these infusions increase the transudation of albumin from the circulation as much as 3-5 times. Concomitantly there is an increased rate of albumin return via lymph which is 3-6 times greater than that of the pre-infusion period. This increased albumin return masks the true loss of albumin from the plasma, and in many cases, actually exceeds the loss and results in increased levels of total circulating albumin. If the thoracic lymph is not returned to the circulation or if the thoracic lymph is replaced by saline, the total circulating plasma protein is decreased by as much as 15-30% in 3 hrs. Specific activity data indicate that no new albumin is involved in the process but that the infusion serves to mobilize interstitial protein for return via lymph to the blood stream.