Studies of the circulation in haemorrhagic shock by means of erythrocytes labelled with radio-phosphorus.

Abstract

1. In any form of oligæmic shock, blood volume measurement by the labelled cell method measures only the circulating blood volume.2. In established hæmorrhagic shock, the injection of labelled red cells is followed by a fall in the concentration of labelled cells in the circulating blood, which suggests that there is a delay in complete mixing of the circulation. This is believed to be due to the presence of peripheral stasis, which acts as a source of unmixed unlabelled cells.3. When labelled cells are injected and allowed to mix thoroughly in the circulation of normal animals, a similar fall in the concentration of labelled cells occurs within two hours of bleeding. This cannot be explained by a delay in mixing which is already complete, and it has been postulated that sequestered red cells are released from some blood depot. The spleen and probably the lung and liver have been excluded as sources of these cells.4. Evidence is given that these dilution effects are not due to changes in cell‐plasma ratio, increased rate of loss of phosphorus from the cell under anoxic conditions, change in pH in the blood, selective destruction of labelled cells or to changes in circulation time.5. The closed sinusoidal system of the bone marrow is considered to be the most likely source of these cells, and this is in keeping with the known stimulant effect of chronic anoxæmia upon hæmatopoietic tissue, although rapid responses of this nature have not hitherto been demonstrated.