The adrenergic response to cardiopulmonary bypass

12 out of 13 patients who underwent cardiac surgery requiring extracorporeal circulation survived the operation. Arterial and venous catecholamines were measured throughout the operation. Larges rises in catecholamine levels were not seen although significant changes did occur in arteriovenous differences and also between samples at certain points in the operation. These facts do not agree with Lillehei's findings (3) and may reflect improvements in surgical technique, anaesthesia and the reduced time on bypass. However the lack of an overall measurable adrenergic response in terms of plasma catecholamine levels does agree with similar findings after open heart surgery (4) and during other surgical procedures (5).