A randomized controlled trial comparing controlled reoxygenation and standard cardiopulmonary bypass in paediatric cardiac surgery

Normoxic Management during Cardiopulmonary Bypass Does Not Reduce Cerebral Mitochondrial Dysfunction in Neonatal Swine

Optimal oxygen management during pediatric cardiopulmonary bypass (CPB) is unknown. We previously demonstrated an increase in cortical mitochondrial reactive oxygen species and decreased mitochondrial function after CPB using hyperoxic oxygen management. This study investigates whether controlled oxygenation (normoxia) during CPB reduces cortical mitochondrial dysfunction and oxidative injury. Ten neonatal swine underwent three hours of continuous CPB at 34 °C (flow > 100 mL/kg/min) via cervical cannulation targeting a partial pressure of arterial oxygen (PaO2) goal < 150 mmHg (normoxia, n = 5) or >300 mmHg (hyperoxia, n = 5). The animals underwent continuous hemodynamic monitoring and serial arterial blood sampling. Cortical microdialysate was serially sampled to quantify the glycerol concentration (represents neuronal injury) and lactate-to-pyruvate ratio (represents bioenergetic dysfunction). The cortical tissue was analyzed via high-resolution respirometry to quantify mitochondrial oxygen consumption and reactive oxygen species generation, and cortical oxidized protein carbonyl concentrations were quantified to assess for oxidative damage. Serum PaO2 was higher in hyperoxia animals throughout CPB (p < 0.001). There were no differences in cortical glycerol concentration between groups (p > 0.2). The cortical lactate-to-pyruvate ratio was modestly elevated in hyperoxia animals (p < 0.03) but the values were not clinically significant (<30). There were no differences in cortical mitochondrial respiration (p = 0.48), protein carbonyls (p = 0.74), or reactive oxygen species generation (p = 0.93) between groups. Controlled oxygenation during CPB does not significantly affect cortical mitochondrial function or oxidative injury in the acute setting. Further evaluation of the short and long-term effects of oxygen level titration during pediatric CPB on cortical tissue and other at-risk brain regions are needed, especially in the presence of cyanosis.

Reducing Hyperoxia Exposure in Infants Requiring Veno-Arterial Extracorporeal Membrane Oxygenation after Cardiac Surgery

Recent studies have suggested worse outcomes in patients exposed to hyperoxia while supported on veno-arterial extracorporeal membrane oxygenation (VA-ECMO). However, there are no data regarding the effect of reducing hyperoxia exposure in this population by adjusting the fraction of inspired oxygen (FiO2) of the sweep gas of the ECMO circuit. A retrospective review of 143 patients less than 1 year of age requiring VA-ECMO following cardiac surgery from 2007 to 2018 was completed. 64 patients had a FiO2 of the sweep gas < 100% with an average PaO2 of 210 mm Hg in the first 48 h of support [vs 405 mm Hg in the group with a FiO2 = 100% (p < 0.0001)]. There was no difference in mortality at 30 days after surgery or other markers of end-organ injury with respect to whether the FiO2 was adjusted. At least one PaO2 value < 200 mm Hg in the first 24 h on ECMO in patients with a FiO2 < 100% trended toward a significant association (OR = 0.45, 95% CI = 0.21-1.01) with decreased risk of 30-day mortality when compared to those patients with a FiO2 = 100% and all PaO2 values > 200 mm Hg. Only 47% of patients with a FiO2 < 100% had an average PaO2 less than 200 mm Hg which indicates that the intervention of reducing the FiO2 of the sweep gas was not entirely effective at reducing hyperoxia exposure. Future research is needed for developing clinical protocols to avoid hyperoxia and to identify mechanisms for hyperoxia-induced injury on VA-ECMO.

From Other Journals: A Review of Recent Articles by Our Editorial Team

In this review, we provide a brief description of recently published articles addressing topics relevant to pediatric cardiologists. Our hope is to provide a summary of the latest articles published recently in other journals in our field. The articles reviewed in this manuscript address (1) long-term fate of the truncal valve, (2) comparison of combined heart‒liver vs heart-only transplantation in pediatric and young adult Fontan recipients showing non-inferior survival of heart-liver transplant in a small sample, (3) impact of palliation strategy on interstage feeding and somatic growth for infants with ductal-dependent pulmonary blood flow showing no difference in growth between ductal stenting and Blalock-Taussig shunt, (4) biventricular repair in interrupted aortic arch and ventricular septal defect with a small left ventricular outflow tract, (5) a randomized controlled trial comparing controlled reoxygenation and standard cardiopulmonary bypass in pediatric cardiac surgery, and (6) tricuspid valve and right ventricular function throughout the hybrid palliation strategy for hypoplastic left heart syndrome and variants.