Plasma Colloid Osmotic Pressure During Open-Heart Surgery Using Non-Colloid or Colloid Priming Solution in the Extracorporeal Circuit

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Abstract
Two different priming solutions for the heart-lung machine were compared in 14 patients during aortic valve replacement. Colloid osmotic pressure (COP) and albumin in plasma, blood erythrocyte volume fraction (B-EVF) and arterial O2 tension (PaO2) (FIO2 [fraction of inspired O2] = 1.0) were followed before, during and after perfusion. The 2 priming solutions were 2000 ml Ringerdex (7 patients) or 1800 ml Ringerdex + 200 ml 20% albumin (7 patients). COP and B-EVF were normal before bypass. After 10 min on bypass, when .apprx. 1000 ml of crystalloid cardioplegic solution had been given, COP was reduced by .apprx. 50% and B-EVF fell to 23%, indicating a small loss of water from the circulation when compared with in vitro dilution curves. COP was slightly lower in the noncolloid group (P < 0.02). Both COP and B-EVF remained unchanged during perfusion, despite transfusion from the heart-lung machine of a mixture of blood and crystalloid solution with a calculated very low COP (6 mm Hg) and B-EVF (15%). After perfusion, the restitution of COP and B-EVF was rapid and parallel. Both returned to normal levels after 2 h. There was a good correlation between COP and albumin measured in the same plasma samples (r = 0.83, P < 0.001). At 1 h after bypass, PaO2 (FIO2 = 1.0) tended to decrease in the noncolloid group, compared with the preperfusion level. Forty grams of albumin were too small of an amount of colloid to diminish substantially the reduction of COP during perfusion. The unchanged levels of COP and B-EVF during perfusion, despite further dilution and the parallel normalization after perfusion, can only be explained by loss of water from the circulation.