B. Lisander et A. Enqvist, THE GAIN OF RED-CELLS FROM PREOPERATIVE HEMODILUTION EVALUATION OF BENEFIT USING A MATHEMATICAL-MODEL, Theoretical surgery, 9(3), 1994, pp. 142-147
To avoid tranfusions with homologous blood, surgical losses are routin
ely replaced with a plasma substitute until a predetermined minimal al
lowable haematocrit has been reached (intraoperative haemodilution, IH
D). On the other hand, in preoperative haemodilution (PHD) part of the
the blood volume is replaced with a cell-free fluid before surgery an
d the operation starts at the minimum haematocrit level. The harvested
blood is used to replace the surgical bleeding and raises the haemato
crit. Thus, for a given minimum haematocrit and for the same surgical
bleeding, PHD gives a higher final haematocrit than that obtained with
IHD. This gain, defined as the red cell mass after PHD minus that aft
er IHD, has been studied in a mathematical model, and the outcome of a
wide range of degrees of PHD is presented. The general conclusion fro
m the study is that the gain from PHD is minor if the surgical bleedin
g is compensated with the harvested blood only. On the other hand, if
after dilution the surgical bleeding is initially compensated by a pla
sma substitute and the major part of the stored red cells are not infu
sed until after successful haemostasis, more blood can be saved, justi
fying PHD as a blood-saving method.