Brain monitoring techniques near-infrared spectroscopy (NIRS) and transcranial Doppler (TCD) ultrasound were used in pediatric patients undergoing cardiopulmonary bypass for congenital heart defect (CHD) repair to analyze the effect of pulsatile or nonpulsatile flow on brain protection. Regional cerebral oxygen saturation (rSO 2 ) and cerebrovascular pulsatility index (PI) were measured by NIRS and TCD, respectively, in 111 pediatric patients undergoing bypass for CHD repair randomized to pulsatile (n ϭ 77) or nonpulsatile (n ϭ 34) perfusion. No significant differences in demographic and intraoperative data, including surgical risk stratification, existed between groups. Patients undergoing pulsatile perfusion had numerically lower decreases in rSO 2 from baseline for all time points analyzed compared with the nonpulsatile group, with significant ϳ12% lower decreases at 40 and 60 min after crossclamp. Patients undergoing pulsatile perfusion had numerically lower decreases in PI from baseline for the majority of time points compared with the nonpulsatile group, with significant ϳ30% lower decreases between 5 and 40 min after crossclamp. Pulsatile flow has advantages over nonpulsatile flow as measured by NIRS and TCD, especially at advanced time points, which may improve postoperative neurodevelopmental outcomes. A dvances in intraoperative surgical techniques and postoperative intensive care have substantively improved patient outcomes and decreased mortality rates in pediatric cardiac surgery for the repair of congenital heart defects (CHDs). With in-hospital mortality reported to be below 3% for categorized operations in a recent study despite an increase in case complexity (1), there is a growing need to address the paradoxical increased incidence of adverse neurological outcomes in the survivors of surgery. Cardiopulmonary bypass (CPB) presents unique challenges in this regard, with the extreme conditions encountered during extracorporeal support coupled with requisite surgical techniques that place severe stress on the patient acting in tandem to cause insult and injury to the brain. With increased incidence of postoperative neurologic complications reported in pediatric patients undergoing CPB, including neuromotor disabilities, learning disabilities, and behavioral abnormalities (2,3), there is increasing relevance for intra-and early postoperative brain monitoring techniques, which may predict neurologic outcomes and provide medical professionals actionable information to aid in the minimization of adverse sequelae (4).The debate between pulsatile and nonpulsatile perfusion modes further complicates considerations of best practices during pediatric CPB with the aim of minimizing neurological morbidity (5). Although current findings suggest that pulsatile flow imparts distinct advantages including increased hemodynamic energy leading to better blood flow to major organs such as brain, movement of lymph that prevents edema and sludging in microcapillaries, maintained microcirculatory flow, improve...