Changes in colloid osmotic pressure with plasma albumin concentration associated with extracorporeal circulation.

Colloid pressure (COP), plasma albumin concentration, haematocrit, and blood-gas tensions were measured in 16 patients undergoing open-heart surgery with cardiopulmonary bypass. The use of crystalloid priming and cardioplegia solutions resulted in a 60% decrease in COP, a 48% decrease in plasma albumin concentration and a 35% decrease in haematocrit. These measurements had returned to pre-perfusion values 6 h after the end of surgery. The alveolar-arterial PO2 difference increased significantly after by-pass and returned to pre-perfusion values within the same time scale. Right-to-left shunt increased from 7.9 to 10.3% 30 min after the end of by-pass. It is concluded that, in the absence of an increase in left atrial pressure, marked decreases in COP can be tolerated without the occurrence of pulmonary oedema.