Pharmacocinétique et modifications des propriétés physiques du sang et des urines après administration d'un dextran 60 000

Abstract

A study was carried out to assess the changes induced by an infusion of dextran, molecular weight 60 000 daltons, in blood and urine. Plasma and urine dextran and serum protein concentrations, haematocrit, blood and urine viscosities, and blood oncotic pressure were measured in 10 consecutive male patients. Fifteen min after administration of 20 ml dextran 1000 (Promit®), they were each given 500 ml (30 g) dextran 60 (Hemodex®) over 30 min for plasma volume expansion. The measurements were carried out at the end of the infusion, and then at regular intervals over a 48 h period. The highest dextran blood concentrations were found at the end of the infusion, decreasing thereafter with a distribution half-life of 1.83 ± 0.64 h, and an elimination half-life of 25.5 ± 7.6 h. Haematocrit values decreased by 12 %, and serum protein concentrations by 9.5 %, after the end of the infusion. These changes remained significant for 9 h ; they were probably due to the dilution effect of 500 ml of dextran. Colloid osmotic pressure was not significantly altered (20.7 ± 4.7 mmHg vs. 23.1 ± 5.1 mmHg 48 h after the end of the infusion). The colloid osmotic pressure due to dextran 60 compensated for the fall in protein concentration. A decrease in blood viscosity was found at different shear rates, despite dextran 60 being highly viscous. This could also be explained by a dilution effect. The highest degree of urinary excretion occurred 30 min after the end of the infusion, and lasted for 3 h. Forty-five percent of the total dextran dose had been excreted by the 48 th hour. Urinary viscosity reached a maximum 30 min after the end of the infusion, and remained significantly increased for 9 h (0.84 ± 0.07 mPa.s baseline vs. 1.96 ± 0.97 mPa.s). This latter effect suggests that dextran 60 should be given with caution to patients who have a reduced glomerular filtration rate.