Selection of optimal quantity of hydroxyethyl starch in the cardiopulmonary bypass prime.

Ringer's solution prime reduces colloid osmotic pressure and causes edema during cardiopulmonary bypass, while hydroxyethyl starch (HES) can be used to attenuate this effect. Fifty patients were classified into five equal groups: Group I (preoperative patients) is the control group and the other four groups (II, III, IV, V) received different volume ratios of Ringer's solution to HES (1:0, 2:1, 1:2, 0:1, respectively). This study was aimed at evaluating the optimal quantity of HES regarding body fluids expansion, ventilation and recovery time, blood rheologic properties, clotting parameters, platelet counts, blood loss and red blood cell membrane properties. The results showed a reduction in interstitial fluid (ISF) expansion, changes in blood rheologic properties with the increase in HES quantity and shorter ventilation and recovery times in Groups IV and V. We concluded that the optimal HES quantity in the prime is two thirds, which insures an 85% reduction of ISF relative to Group II, shorter ventilation and recovery times and avoidance of the hazards of high levels of HES.