Influence of Fluid Infusion Associated with High-volume Blood Loss on Plasma Propofol Concentrations

Background It is common clinical practice to use fluid infusion to manage high-volume blood loss until a blood transfusion is performed. The authors investigated the influence of fluid infusion associated with blood loss on the pseudo-steady state propofol concentration. Methods Twenty-seven swine were assigned to a lactated Ringer's solution group, a hydroxyethyl starch group, or a threefold lactated Ringer's solution group (n = 9 in each group). After 180 min of steady state infusion of propofol at a rate of 2 mg.kg(-1).h(-1), hemorrhage and infusion were induced by stepwise bleeding followed by fluid infusion every 30 min. In each of the first two steps, 400 ml blood was collected; thereafter, 200 ml was collected at each step. Just after each bleeding step, fluid infusion was rapidly performed using a volume of lactated Ringer's solution or hydroxyethyl starch equivalent to the blood withdrawn, or a threefold volume of lactated Ringer's solution. Hemodynamic parameters and the plasma propofol concentration were recorded at each step. Results Although the plasma propofol concentration in the lactated Ringer's solution group increased with hemorrhage and infusion, it decreased in both the hydroxyethyl starch and the threefold lactated Ringer's solution groups. The propofol concentration in the hydroxyethyl starch group could be expressed by the following equation: Plasma Propofol Concentration Decrease (%) = 0.80 x Hematocrit Decrease (%) (r2 = 0.83, P < 0.0001). Conclusions When high-volume blood loss is managed by isovolemic hemodilution, the plasma propofol concentration during continuous propofol infusion decreases linearly with the hematocrit decrease.