Changes of kallikrein and serotonin in plasma during and after open-heart surgery

Plasma kallikrein activity and plasma serotonin were studied during and after open-heart surgery in 15 patients with extracorporeal circulation and in 15 patients with surface-induced deep hypothermia. Following results were obtained: 1) Plasma kallikrein activity which reflects the activation of the kinin system, showed no significant change during extracorporeal circulation, and significantly increased three hours after the termination of perfusion. However, there was no significant difference in plasma kallikrein activity between the patients with and without low cardiac output syndrome (LOS). In surface-induced deep hypothermia, plasma kallikrein activity showed no significant change during and after operation. 2) Plasma serotonin significantly decreased during both extracorporeal circulation and hypothermia. Moreover, there was no significant difference in plasma serotonin between the patients with and without postoperative LOS or pulmonary hypertension. It is assumed that plasma serotonin may not play an important role in regulating blood pressure during or after open-heart surgery with either extracorporeal circulation or surface-induced deep hypothermia.