Effects of preoperative intentional hemodilution on the extravasation rate of albumin and fluid

Objective: To evaluate the effects of preoperative intentional hemodilution with 4% albumin solution on the extravasation rate of intravascular albumin and fluid in surgical patients. Design: A prospective, randomized, clinical study. Setting: University teaching hospital. Patients: Two groups (control group [group 1] and hemodiluted group [group 2]) of 13 healthy patients were studied during a longterm (>4 hrs) surgical procedure. Interventions: Autologous technetium-99m ( 99m Tc)-labeled red blood cells and indium-oxine ( 111 ln)-labeled human serum albumin were injected intravenously during anesthesia at T= 0 min in the two groups for the determination of total blood volume and albumin diffusion space, respectively. In addition, body tetrapolar electrical impedance was used to assess extracellular fluid volume. In the hemodiluted group (group 2), 15 mUkg of blood was withdrawn over 30 mins (T = 20 mins to T = 50 mins) and simultaneously replaced by an equal volume of 4% albumin solution (0.6 g/kg). Measurements and Main Results: The albumin diffusion space, the colloid oncotic pressure, the plasma albumin concentration and the electrical impedance were measured before (T = 10 mins) and after (T = 60, 120, and 240 mins) hemodilution. Urine was collected from T = 10 mins to T = 240 mins. The total blood volume was calculated at T = 10 mins. No differences in the initial values were found between the two groups. In group 2, hemodilution (hematocrit 30 ± 3%) resulted in a steeper increase in the albumin diffusion space (p 3 mUkg. Urine output was significantly lower in group 2 than in group 1 (0.7 ± 0.4 vs. 1.4 ± 1.0 mL/min, respectively; p <.05). A comparable decrease in colloid oncotic pressure and in plasma albumin concentration was observed in both groups. Conclusions: These results suggest that preoperative hemodilution using 4% albumin on a 1:1 volume basis for blood substitution during a prolonged surgical procedure with reduced blood losses enhances the extravasation rate of albumin and fluid to the interstitial tissues, impeding the maintenance of isovolemia. These findings support the use of a volume of infused colloid solution higher than that of withdrawn blood during preoperative hemodilution.