The effect of volume replacement on serum protein concentration during cardiopulmonary bypass

Although controversy exists concerning the optimal total protein and colloid osmotic pressure that should be maintained during cardiopulmonary bypass (CPB), the primary volume expanders remain albumin and 6% hetastarch. The purpose of this study was to quantify the effect of adding boluses of volume replacement agents under various conditions to total serum protein values during CPB. A standard CPB circuit was utilized in eight 45-kg swine that had a priming volume (physiologic saline solution) of 2309 +/- 245 mL. Volumetric alterations occurred throughout the CPB period by the addition of combinations of physiologic saline solution, 6% hetastarch or 5% swine albumin. Pre- and postadministration samples were assayed for total serum protein, total protein, and albumin throughout the CPB period and at pre- and postvolume administration times. There was a significant decline in total serum protein with the initiation of CPB (6.14 +/- 0.49 g/dL vs. 3.40 +/- 0.43 g/dL, p < .0001). Addition of 12.5 g of swine albumin (N = 5) to two different swine increased total serum protein significantly when compared to adding 500 mL of 6% hetastarch (N = 6) (swine albumin 12.4 +/- 6.3% vs. hetastarch 3.3 +/- 2.1%, p < .005). A reduction in total serum protein occurred after hemodilution with varying amount of physiologic saline solution: 250-450 mL (7.4 +/- 4.5%), 451-650 mL (9.6 +/- 5.6%), and 651-1050 mL (19.4 +/- 4.0%). In summary, knowledge of total serum protein concentration and estimated circulating blood volume can be used to guide albumin and hetastarch administration following hemodilution.