Hydroxyethyl starch 120, dextran 70 and acetated Ringer's solution: hemodilution, albumin, colloid osmotic pressure and fluid balance following replacement of blood loss in pigs.

Twenty healthy pigs weighing 12-17 kg were anesthetized and the small intestines were exteriorized into saline-moistened gauze. During a 2-h period 4% of the animals' body weight was bled through an arterial cannula in six increments and replaced immediately by the fluid tested: hydroxyethyl starch 120 (HES, Plasmafusin, Orion Corp., Mw 120,000), dextran 70 (DEX) and Ringer's acetate (RA). The amount of fluid infused for replacement of blood loss was equal to the amount of blood withdrawn in the colloid groups but fourfold in the RA group. Five non-bled pigs served as controls. After the hemodilution the laparotomy was closed and the animals received only 5% dextrose (2 ml/kg/min) during a 5-h follow-up period. The synthetic colloids caused a more effective dilution of hemoglobin and albumin than did RA. The colloid osmotic pressure (COP) was well maintained by the plasma substitutes but decreased in the RA group to 64% of the initial values. A stable urinary output and no edema formation was found in the HES and DEX groups. The RA animals were unable to excrete the excess crystalloid, which resulted in a strikingly positive fluid balance persisting throughout the study. Thus, the synthetic colloids were superior to RA in expansion of the plasma volume, maintenance of the COP and prevention of fluid accumulation. The effect of the two colloids was similar except that COP was slightly better maintained during the follow-up period in animals which received HES 120.