Effects of anesthesia on fluid volume kinetics after infusion of colloid solution during blood donation

Background: The fluid kinetics of intravenously infused colloid during inhalation anesthesia and hemorrhage have not been investigated. We therefore assessed fluid space changes during infusion of hydroxyethyl starch solution after hemorrhage in conscious and desflurane-anesthetized individuals. Methods: Following the donation of 400 ml of blood, 500 ml of hydroxyethyl starch solution was infused over 20 minutes into wakeful and desflurane-anesthetized volunteers. Blood was repeatedly sampled to measure hemoglobin concentration, a marker of plasma dilution, and fluid kinetic analysis was performed to evaluate changes in fluid space. Results: Using a fluid kinetic model, we found that the mean volume of fluid space was 7,724 +/- 1,788 ml in wakeful volunteers and 6,818 +/- 4,221 ml in anesthetized volunteers, and the elimination rate constants were 7.1 +/- 3.5 ml/min and 19.4 +/- 4.6 ml/min, respectively. Conclusions: Infusion of colloid after mild hemorrhage resulted in similar expansions of plasma volume in desflurane-anesthetized and conscious individuals. During anesthesia, however, the expansion of plasma volume by colloid was decreased and of shorter duration than observed in conscious patients.