Surface tension changes of perfusates: Implications for gaseous microemboli during cardiopulmonary bypass

Surface tension (ST) analysis was performed on solutions used to prime bubble oxygenators in order to determine what changes, if any, took place during preparation and clinical use of the cardiopulmonary bypass (CPB) circuit. Samples were taken as follows: crystalloid solution prior to its addition to the circuit; after 5 and 20 minutes of pre-CPB recirculation; after addition of albumin; and post-CPB. ST values, as measured with a Du Nouy tensiometer dropped from 71 dynes/cm to values in the mid 60s, with additional decreases (mid 50s) following the albumin. Post-CPB values of plasma derived from centrifugation of perfusate were in the upper 40 dynes/cm range. This pre-CPB drop in ST raises the question of wash-off of defoamer and its possible effect on gaseous microemboli (GME) removal by arterial screen filters. Removal of GME by filtration is dependent, in part, upon ST phenomenon according to the 'bubble point' concept and the equation of capillarity. Another concern is the potential removal of defoamer during pre-CPB filtration with subsequent inadequate oxygenator debubbling.