Effect of Postoperative Hydrocortisone on Cardiovascular and Respiratory Function in Neonates Undergoing Cardiopulmonary Bypass

Open-heart surgery with cardiopulmonary bypass (CPB) induces an acute systemic inflammatory response (SIRS) via synthesis and release of inflammatory mediators. These inflammatory cascades may result in the development of capillary leak and generalized tissue edema, which are associated with multiorgan dysfunction involving the myocardium, lungs, kidneys, pancreas, and central nervous system. Neonates are especially susceptible to the injurious effects of SIRS. In attempt to blunt post-bypass SIRS, most neonatal heart programs have protocols in which patients receive preoperative and/or intraoperative steroids. Despite this widespread use, studies have not demonstrated consistent benefit in this therapy, and neonates often continue to suffer the deleterious effects of SIRS postoperatively. Only one study was designed to evaluate the impact of prophylactic postoperative steroid administration on outcomes after neonatal CPB. The early postoperative periods is a crucial time during which attenuation of CPB-induced SIRS by exogenous steroids may lead to improved clinical outcomes.

Adrenal insufficiency in neonates post-CPB may accentuate the harmful effects of SIRS by diminishing the anti-inflammatory and hemodynamic stabilization benefits of endogenous cortisol. Evidence suggests that neonates may suffer from inadequate cortisol activity relative to the severity of illness post-CPB, in part related to immaturity of their hypothalamic-pituitary-adrenal (HPA) axis. This so-called critical illness-related corticosteroids insufficiency (CIRCI) may contribute to low cardiac output syndrome (LCOS), respiratory dysfunction, and capillary leak in the postoperative period.

Much of the support for CIRCI as a contributor to LCOS after CPB originates from small clinical studies that demonstrate benefit of exogenous steroid supplementation on various short term clinical outcomes in patients with shock. Yet it is not clear if benefit from exogenous steroids suggests by dysregulation of the HPA axis or whether these are merely alternative effects of steroids. Investigators have recently begun to describe the cortisol response in neonates post-CPB, but there is no consensus regarding the incidence of clinically important adrenal insufficiency, its identification, or who should receive exogenous steroids.