Blood Volume Changes in Cyanotic Congenital Heart Disease and Polycythemia Rubra Vera

The blood volume has been measured in 12 adult patients with cyanotic congenital heart disease and in 12 patients with polycythemia rubra vera by radioactive isotopes. In congenital heart disease the total blood volume was found to be within normal limits provided the red cell volume had not risen so high as to make an increase in total blood volume inevitable. In polycythemia rubra vera the total blood volume increased rapidly once a hematocrit level of 55 per cent had been exceeded. Increasing polycythemia in congenital heart disease was found to be associated with the predictable fall in plasma volume, and a formula for estimating the plasma volume from the predicted normal blood volume and the hematocrit is presented. It is suggested that the low plasma volume that may be found in very polycythemic patients may be partly responsible for their known tendency to postoperative hemorrhage.