Blood viscosity and open heart surgery. A comparison of values in systemic and pulmonary blood vessels.

Blood viscosity, haematocrit and plasma protein concentrations were determined simultaneously in five different vessels of the systemic and pulmonary circulations, before and immediately after cardiopulmonary bypass and again after surgery. There was a reduction in all these measurements after bypass and a lesser reduction one day after operation. At any one stage, however, values in the pulmonary artery and pulmonary vein were not significantly different from those in the superior vena cava, radial artery and a peripheral vein.