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Purpose: Cardiopulmonary bypass induces an ischaemia-reperfusion injury and systemic inflammatory response, which contributes to low cardiac output syndrome following cardiac surgery. Exogenous nitric oxide during cardiopulmonary bypass has shown potential to ameliorate such injury. We undertook a large randomised controlled trial to investigate the clinical effects of administering nitric oxide to the cardiopulmonary bypass circuit in children.Methods: After written informed consent, children were randomised to receive 20 ppm nitric oxide to the gas inflow of the cardiopulmonary bypass oxygenator, or standard conduct of bypass.Results: 101 children received nitric oxide and developed low cardiac output syndrome less frequently (15 vs. 31 %, p = 0.007) than the 97 children who did not receive nitric oxide. This effect was most marked in children aged less than 6 weeks of age (20 vs. 52 %, p = 0.012) and in those aged 6 weeks to 2 years (6 vs. 24 %, p = 0.026), who also had significantly reduced ICU length of stay (43 vs. 84 h, p = 0.031). Low cardiac output syndrome was less frequent following more complex surgeries if nitric oxide was administered (17 vs. 48 %, p = 0.018). ECMO was used less often in the nitric oxide group (1 vs. 8 %, p = 0.014).Conclusions: Delivery of nitric oxide to the oxygenator gas flow during paediatric cardiopulmonary bypass reduced the incidence of low cardiac output syndrome by varying degrees, according to age group and surgery complexity.Clinical Trial Registration: ACTRN12615001376538. [ABSTRACT FROM AUTHOR]

This prospective, single-center cohort study aimed to evaluate the hemostatic response during and after Cardiopulmonary Bypass (CPB) surgery in a large cohort of children up to 6 years of age. Blood samples were drawn at eight time points: post-induction of anesthesia, pre-unfractionated heparin (UFH), post-UFH, post-initiation of bypass, pre-protamine, post-protamine, post-chest-closure, and 6 h post-chest-closure. As expected, all measures of the UFH effect increased significantly post-UFH bolus and decreased post-protamine administration. However, thrombin generation remained inhibited compared to baseline values despite the post-UFH reversal by protamine. We also demonstrate that residual UFH effect is not responsible for the ongoing inhibition of thrombin observed post-protamine administration. The significant increase in both free and total tissue factor pathway inhibitor levels during the CPB surgery might contribute to the persistent thrombin generation/endogenous thrombin potential inhibition post-protamine administration. This study makes a significant and novel contribution by investigating the physiological mechanisms behind the degree of thrombin inhibition by UFH and the residual levels of thrombin inhibition that continue despite protamine reversal and provides a new foundation for future interventional studies in the setting of paediatric CPB surgery. [ABSTRACT FROM AUTHOR]