RESUMEN
OBJECTIVE: To study the changes in blood volume and hormones controlling sodium and water homeostasis after infusions of 0.9% saline, Gelofusine (4% succinylated gelatin in 0.7% saline, weight-average molecular weight 30 kD), and Voluven (6% hydroxyethyl starch in 0.9% saline, weight-average molecular weight 130 kD) in healthy volunteers. DESIGN: Randomized, three-way crossover study. SETTING: University teaching hospital. SUBJECTS: Ten healthy adult male volunteers. INTERVENTIONS: Volunteers received 1-L infusions of 0.9% saline, Gelofusine, and Voluven over 1 hr on three occasions. Body weight, hematocrit, serum biochemistry, and plasma concentrations of vasopressin, aldosterone, brain natriuretic peptide, and total renin were measured before infusion and hourly thereafter for 6 hrs. Changes in body water, blood volume, and extravascular fluid volume were calculated. MEASUREMENTS AND MAIN RESULTS: Although changes in body weight (total body water) after the infusions were similar, blood volume expansion by the two colloids was significantly greater than that produced by 0.9% saline (p < .01). At the end of infusions, 68%, 21%, and 16% of the infused volumes of 0.9% saline, Gelofusine, and Voluven, respectively, had escaped from the intravascular space to the extravascular space. Over the 6 hrs, the magnitude and duration of blood volume expansion by the two colloids were similar (p = .70). There were no significant differences in urinary volume, osmolality, and sodium content after the three infusions. Hormonal changes were similar after the three infusions, with the increase in natriuretic peptide being transient. The reduction in aldosterone and total renin concentrations was more sustained. CONCLUSIONS: The effects of Gelofusine and Voluven were similar despite the 100 kD difference in weight-average molecular weight. Excretion of an acute fluid load containing sodium and chloride may be dependent on a sustained suppression of the renin-angiotensin-aldosterone system rather than on natriuretic peptides.