CONTROL OF THE SUBSTITUTION FLUID INFUSION BY THE BLOOD REMOVAL RATE DURING PREOPERATIVE NORMOVOLEMIC HEMODILUTION

Twenty-one patients (mean age 46 +/- 13 years) due to undergo abdomina l or ENT surgery, presumed to give rise to an important blood loss wer e included in this study. None had any contraindication to the use of normovolaemic haemodilution (NH). Mean initial haemocrit was 40.3 +/- 1.8%. Their estimated total blood volume was 4,867 +/- 857 ml. The pat ients were anaesthetized with thiopentone, fentanyl, vecuronium or atr acurium. Maintenance was carried out with isoflurane (0.5 % during NH) . Usual haemodynamic monitoring was used throughout. The required haem atocrit was decided on before starting NH. The amount of blood to be r emoved was calculated with usual mathematical formulae. A radial arter y cannula (n = 7), or a subclavian or femoral venous cannula (n = 14) was used to remove blood, which was collected within a bag containing CPC-adenine. Six % hydroxyethyl starch (Elohes (R)) was given through a short venous cannula some distance from the first one. An antiparall el double line set in a roller pump was used to carry out the NH. A me an 1,341 +/- 405 ml of blood were withdrawn so as to reach a mean haem atocrit of 30.6 +/- 2.4 %. NH was completed within 17 +/- 6 min. No ma jor haemodynamic changes occurred during the procedure. No significant differences were observed between expected and observed final haemato crits. There was no effect of the volume of blood withdrawn on the err or of haematrocrit prediction (0.5 +/- 0.3 %). However, a higher rate of blood removal could increase this error. This easy-to-use device se ems to provide fast and identical rates of blood removal and replaceme nt. The expected haematocrit may thus be reached reliably, even if thi s must be checked for the sake of safety.