Role of endogenous adenosine as a predictive marker of vasoplegia during cardiopulmonary bypass and postoperative severe systemic inflammatory response

Objective: Systemic inflammatory response (SIRS) and severe SIRS (SIRS with organ dysfunction) occurring after cardiopulmonary bypass (CPB) are common causes of morbidity and mortality among cardiac surgical patients. These syndromes are often preceded by a profound vasodilation, characterized by vasoplegia occurring during surgery. Many substances have been implicated in their pathophysiology. Adenosine is a strong endogenous vasodilating agent released by endothelial cells and myocytes under metabolic stress and may be involved in blood pressure failure during CPB induced by severe SIRS. Design: A prospective comparative observational study. Setting: The operating room and intensive care unit of a tertiary care university hospital. Patients: Adenosine plasma levels (mean +/- SD; APLs) were measured before (baseline), during, and immediately after surgery in 35 patients who underwent aortic valve replacement involving CPB. APLs were correlated to operative and postoperative clinical courses. Measurements and Main Results. APLs were significantly higher in seven patients with vasoplegia and postoperative severe SIRS (1.6 mu mol.L-1 [0.2-2.6] vs. 0.4 mu mol.L-1 [0.1-1.0]) at baseline and during surgery. The duration of mechanical ventilation and stay in the intensive care unit were significantly longer for patients with higher APLs. Mean arterial pressure was inversely correlated with mean arterial APLs (Pearson's correlation coefficient: R = -0.66; p <.001). Conclusions: High APLs were found in patients with operative vasoplegia and postoperative severe SIRS occurring after cardiopulmonary bypass. This suggests that adenosine release is involved in vasoplegia that occurs during the systemic inflammatory response to cardiac surgery. Further studies are needed to clarify the association between cytokine production and adenosine release in severe SIRS following cardiac surgery.