Behaviour of Isotonic and Hypertonic Solutions in Blood Stream of Normal and Dehydrated Animals

The mode of regulation of the blood volume remains still an unsolved problem in spite of the efforts of many investigators. 1 - 4 It has been pointed out recently that the blood stream does act to some extent as a reservoir in the normal animal. 5 This study was undertaken to evaluate the rôle played by this reservoir action in the regulation of the blood at a constant volume and the effects of dehydration and protein loss. The investigation was divided into 2 parts, the first dealing with effects produced by isotonic solutions introduced in large amounts into the blood stream of normal and dehydrated animals. The second part concerns the results produced by hypertonic solutions.

The effects of isotonic solutions.

Material used—10 normal healthy dogs. Five dogs were used as controls and were allowed free access to water and food. Five were dehydrated by deprivation of water for a standard period of 10 days but food was permitted freely.

Method. 970-980 cc. of 0.9% sodium chloride solution or of 5% glucose solution were injected into the blood stream at a constant rate of 330 cc. per 5 min. Five cc. of blood were withdrawn from the femoral vein before and immediately after injection and at intervals of 15, 60, 180, and 300 minutes. The hemoglobin was determined by the Newcomer method, the plasma volume by the hematocrit method and erythrocyte counts were performed.

Results. The blood vascular system does act as a reservoir, the blood remaining diluted for a period of 5 hours, at which time it has almost returned to its normal state. With isotonic glucose solutions, the blood dilution shows a progressive diminution to the normal, i. e., there is a uniphasic response. With isotonic sodium chloride solutions, the response is polyphasic, e. g., the maximum dilution may not be reached until one hour after the injection or the initial dilution is followed by concentration and later by a further dilution.