Postbypass plasma surface tension and its role in bubble filtration

Plasma samples from patients undergoing open-heart surgery were obtained at the end of cardiopulmonary bypass for surface tension analysis. The samples were measured with a Du Nouy tensiometer for true static surface tension. The surface tension values from 40 patients were analysed and correlated with plasma free haemoglobin levels, cardiopulmonary bypass time and oxygenator type. The mean surface tension value for the plasma samples was 49·96 ± 2·98 dynes/cm. No statistical correlation was found between the surface tension and the three variables. Surface tension phenomena have important implications in the removal of gaseous microemboli by screen filtration of arterial blood as it is applied to the bubble point concept. Another aspect of surface tension involves the concept of capillarity which considers the forces tending to push a bubble through a blood vessel thus preventing the obstruction of blood flow. The results of this study provide actual values of plasma surface tension from patients undergoing cardiopulmonary bypass.