ObjectiveTo examine intraoperative and postoperative lymphocyte adenylyl cyclase activities in children undergoing repair of congenital cardiac defects with hypothermic cardiopulmonary bypass.DesignA prospective study.SettingTertiary university pediatric hospital.PatientsTwelve children were enrolled into the study to examine intraoperative lymphocyte adenylyl cyclase activities and 12 children were enrolled to examine postoperative lymphocyte adenylyl cyclase activities.InterventionsNone.Measurements and Main ResultsBasal (unstimulated), isoproterenol, and prostaglandin E-1 stimulated adenylyl cyclase activities, and plasma norepinephrine and epinephrine concentrations were measured.Intraoperative basal (unstimulated), beta-adrenergic receptor-stimulated (in response to isoproterenol), and prostaglandin E1(PGE1)-stimulated lymphocyte adenylyl cyclase activities all increased during cardiopulmonary bypass, then decreased immediately after cardiopulmonary bypass. In the postoperative group, a significant decrease in basal (unstimulated), beta-adrenergic receptor- and PGE1-stimulated adenylyl cyclase activities were observed on postoperative day 1 as compared with precardiopulmonary bypass values.ConclusionsIn the pediatric cardiac surgical patient, there was an intraoperative enhancement of lymphocyte adenylyl cyclase activities. This increase in adenylyl cyclase activities was followed by reduced lymphocyte adenylyl cyclase activities, including beta-adrenergic receptor desensitization, postoperatively, as we have previously documented in adults.(Crit Care Med 1996; 24:1654-1659)