Invited Commentary: Norwood Procedure Using Regional Cerebral Perfusion at Normothermia: Are We There Yet?

Abstract

Over the last few decades, significant advances in the field of congenital heart surgery have allowed the successful management of most forms of congenital heart disease even in the smallest patients. The two most significant challenges are the protection of the brain and the myocardium. Interventions on the aortic arch require a perturbation of the cerebral blood flow that, therefore, requires a specific protective strategy. Since the initial report by Bigelow, it was recognized that deep hypothermic circulatory arrest (DHCA) permitted a precise repair and was associated with improved surgical outcomes. This was largely due to the advantage of a “quiet and bloodless operative field” as well as organ protection from ischemia due to a significant reduction of oxygen consumption. Nevertheless, extended periods of DHCA have been associated with neurologic injury leading to adverse neurodevelopmental (ND) outcomes. The search for an optimal strategy led to the Boston Circulatory Arrest Study, which based on a subanalysis of a small subgroup of patients created the perception that low-flow hypothermic bypass was a superior strategy, when in fact the message was that each strategy had its own ND imprint. Based on this notion, when it comes to the reconstruction of the aortic arch, regional cerebral perfusion (RCP) has been widely embraced as a “superior” strategy, because it minimizes the exposure to DHCA. Nevertheless, several studies, including a large prospective randomized trial, have failed to provide such evidence.4–6 Moreover, despite the intuitive notion that antegrade or RCP is protective, Gunn and colleagues reported a 33% incidence of perioperative seizures in a cohort of patients undergoing arch reconstruction while utilizing RCP between 18 °C and 25 °C. Seizures were commonly leftsided and usually present during the period of antegrade cerebral perfusion. In addition, the reduction in left-hemispheric cerebral oxygenation reported by near-infrared spectroscopy during RCP brings into question the safety and effectiveness of this approach in its current form to ameliorate the morbidity associated with DHCA exposure. Keizman and colleagues describe their experience with patients with hypoplastic left heart syndrome comparing a strategy of arch reconstruction with antegrade cerebral perfusion at normothermia (>34 °C) versus hypothermia (<34 °C). This work is courageous and potentially promising. However, it lacks the necessary assurances that normothermic RCP is not detrimental to ND outcomes. The retrospective nature of the study and the lack of universal ND evaluation preand postintervention are serious limitations of this study. As demonstrated by the recent survey of preferences and attitudes toward perfusion techniques during neonatal arch reconstruction, there is a paucity of robust and conclusive data to inform this decision. The choice of DHCA, antegrade or RCP, or DHCA with intermittent perfusion remains largely based on personal experience, technical prowess, and surgeons’ own beliefs. I believe we should exercise extreme caution when moving away from hypothermia, which is a well-documented tool to reduce cerebral metabolic oxygen consumption, without an essential understanding of its impact on ND outcomes. In the current era, we have sophisticated tools to evaluate ND outcomes. A study with comprehensive cerebral imaging and ND evaluation would be essential to elucidate the potential advantages and safety of this normothermic strategy to support brain circulation. Until then, this remains a bridge too far.