Lymphocyte's activation and apoptosis after coronary artery bypass graft: a comparative study of two membrane oxygenators--one with and another without a venous-arterial shunt.

Newer oxygenators with the latest technologies are designed to attenuate the immune response, including lymphopenia, prompted by cardiopulmonary bypass (CPB) in cardiac surgery. We evaluated the effect of CPB, comparing an oxygenator with a venous-arterial shunt and a conventional oxygenator with regard to lymphocyte's early activation and apoptosis induction and its implications in post-CPB lymphopenia. Patients undergoing coronary artery bypass graft surgery with CPB, using either a conventional oxygenator or one with a venous-arterial shunt, had blood samples drawn at anesthetic induction (baseline); the beginning and end of the CPB; and at 6, 12, and 24 hours after surgery. Analysis by flow cytometry was undertaken to assess the expression of lymphocyte surface markers (CD3+, CD25+, CD26+, CD69+) and apoptosis (annexin V). Twenty patients were studied; 10 used a conventional oxygenator, and 10 used an oxygenator with venous-arterial shunt. Postoperative lymphopenia (50% decrease), 35% increased expression of CD69+, and 56% decrease in annexin V were significant comparing baseline to 24 hour value, similarly in both groups. Early activation (expression of CD69+) and degree of apoptosis (expression of annexin V) of lymphocytes after CBP in cardiac surgery was similarly observed in both types of oxygenators. The observed lymphopenia after CPB does not appear to be secondary to apoptosis.