[Relationship of haematocrit and plasma protein concentration pre- and postoperatively under "isotonic" haemodilution and haemoconcentration, and during laparatomy (author's transl)].

An increase or a decrease in blood volume caused by adding or subtracting isotonic but protein-free fluid to or from whole blood theoretically will result in disproportionate percentage changes of haematocrit and plasma protein concentration. Percentage changes of plasma protein concentration are larger than those of haematocrit and depend upon the initial haematocrit. It could be demonstrated that the theoretical rules of "isotonic" haemodilution and haemoconcentration do hold in vivo in patients pre- and postoperatively under isotonic volume expansion and furosemide diuresis, respectively. However, during laparotomy with moderate blood loss and infusion of crystalloids only we observed a definite decrease of intravascular protein mass. This seemed to be only partly due to surgical blood loss. We suppose that during laparotomy considerable amounts of intravascular protein, besides those with surgical blood loss, are lost in the area of the wound and into the peritoneal cavity.