[Changes in the colloid-osmotic pressure by a foreign colloid (dextran 70)].

In 55 patients undergoing elective surgery (general or urological) the colloid osmotic pressure (COP) of serum was followed up until the sixth postoperative day. The patients were divided into two groups, one receiving intra- and postoperative administration of dextran 70 and the other as a control group with no dextran. COP was measured at an artificial membrane (M = 10000) by a transducer; at the same time the concentrations of total protein, albumin and globulin were determined in order to calculate the COP by the formula of Keys. The dextran group and control group showed no difference in the measured COP. This variable reached the lowest value (which was not below 20 mm Hg) on the first postoperative day. The control patients showed close agreement of measured and calculated COP, while the calculated COP of dextran patients was significantly lower than the measured COP until the sixth postoperative day; the artificial membrane thus registered the action of dextran for this length of time. After each dextran infusion the serum proteins fell to a lower level than in the control group. Three possible explanations are discussed: an increase in intravascular volume, accelerated passage of macromolecules through the capillary wall, and a decrease in albumin synthesis.