The effect of increase of blood pressure on the concentration of colloidal dyes in the plasma

Abstract

Great changes in the number or volume of the corpuscles, or in the haemoglobin content of the blood may occur in a very short time. In using corpuscles or their derivatives as the indicator of the concentration of the blood one meets with the objection that there might be hidden masses of corpuscles ready to be put into the circulation in times of stress. No evidence exists for such masses of corpuscles and it is well known that dilution of the blood may take place equally as rapidly as concentration. In the case of the dilution caused by haemorrhage one of the authors 1 showed the fluid coming in from the tissue spaces was almost pure salt solution having a protein content of only 0.6 to 2 per cent. If changes in the concentration of the plasma could be shown when the blood becomes concentrated in corpuscles, it would get away from all objections of hidden masses of corpuscles.

In the experiments recorded here the concentration of injected congo red has been followed in the plasma. This method is not ideal for all phases of this problem because there is normally a gradual decrease in its concentration. Thus, according to Harris, 2 considering 100 as the percentage after the dye has been uniformly mixed with the plasma there is a fall of about 4 per cent. in five minutes. This is however, slower than with vital red. This figure is not fixed and sometimes we found larger figures than that and sometimes less. If, after this second sample of blood has been taken, the blood pressure be raised by the injection of adrenalin or by section of the vagi and a third sample taken after a few minutes, one finds the concentration of congo increased.