Year : 2021 | Volume
: 8 | Issue : 1 | Page : 3--4
(Not) as cold as ice: Exploring mild hypothermia during circulatory arrest for congenital heart disease surgery
Monique M Gardner1, Venkat R Shankar2, Vijay Srinivasan3,
1 Department of Anesthesiology and Critical Care Medicine, Division of Cardiac Critical Care Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
2 Department of Anesthesiology and Critical Care Medicine, Division of Cardiac Critical Care Medicine, The Children's Hospital of Philadelphia; Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, USA
3 Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania; Department of Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
Dr. Vijay Srinivasan
Department of Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, 3401 Civic Center Boulevard, Philadelphia, PA 19104
|How to cite this article:|
Gardner MM, Shankar VR, Srinivasan V. (Not) as cold as ice: Exploring mild hypothermia during circulatory arrest for congenital heart disease surgery.J Pediatr Crit Care 2021;8:3-4
|How to cite this URL:|
Gardner MM, Shankar VR, Srinivasan V. (Not) as cold as ice: Exploring mild hypothermia during circulatory arrest for congenital heart disease surgery. J Pediatr Crit Care [serial online] 2021 [cited 2021 Sep 23 ];8:3-4
Available from: http://www.jpcc.org.in/text.asp?2021/8/1/3/306486
For neonates and infants requiring cardiopulmonary bypass (CPB) with induced circulatory arrest for repair of critical congenital heart disease, we are fortunate to work in an era that has been able to shift our approach from survive to thrive with the emphasis on improving neurodevelopmental outcomes for this vulnerable patient population. Neuroprotective strategies deployed during CPB continue to remain a major focus of the efforts to achieve these goals. While surgery itself is a nonmodifiable risk, the components of surgical technique and anesthetic management in the operating room have been investigated since the early 1990s, starting most notably with the seminal work from the Boston Circulatory Arrest Trial., The potential neurodevelopmental risks of prolonged deep hypothermic circulatory arrest (DHCA) have been well described, with a threshold for worse neurological outcomes as DHCA time exceeds 41 min. Subsequent reports have suggested that poor neurodevelopmental outcomes may be driven to a greater extent by the underlying severity of congenital heart disease, associated genetic abnormalities that predispose to neurocognitive deficits, and prolonged hospitalizations following surgery, rather than just the result of prolonged duration of DHCA. Nevertheless, the negative impact that CPB can have on the developing brain of infants remains a priority area for cardiac surgeons, cardiologists, intensivists, and anesthesiologists alike.
Selective cerebral perfusion (SCP) has emerged as an alternative strategy to provide cerebral blood flow in efforts to mitigate neurologic injury during CPB and has been integrated into some operating rooms as the standard of care, especially in arch reconstruction surgeries in newborns and infants. This strategy provides bypass-supplied targeted cerebral blood flow in efforts to reduce the suspected mechanism of brain injury of hypoperfusion and subsequent reperfusion injury that is commonly seen in DHCA. The impact on outcomes of the addition of SCP to bypass management has been variable,, and in practice, SCP can be performed in a variety of different ways with institution-specific neuromonitoring and CPB pump management. However, the optimal temperature of perfusion in SCP still remains unanswered. While many surgeons use deep hypothermia down to 18°C, others have used moderate hypothermia (29°C–31°C) with good neurocognitive outcomes.
In the current issue of Journal of Pediatric Critical Care, Bhalala et al. attempt to address this important question by examining the strategy of mild hypothermia (28.1°C–34°C) versus moderate-to-deep hypothermia (14.1°C–28°C) coupled with SCP. In this small cohort of 13 patients, the authors demonstrated that the strategy of SCP with mild hypothermia compared to SCP with moderate-to-deep hypothermia demonstrated good postsurgical outcomes, with comparable postoperative measures of end-organ dysfunction, hospital length of stay, mortality, and cerebral performance scores at the time of discharge from the hospital. While other studies have traditionally examined the addition of SCP to DCHA in reconstruction of the aorta and have not shown any strong benefit in short- and mid-term neurological outcomes,, this study is unique to examine mild hypothermia with the addition of SCP, as compared to the typical moderate-to-deep hypothermia with SCP. While there are no long-term neurological outcomes available from this study, this innovative strategy has exciting implications. Conceptually, it is an attractive idea as it may offer adequate cerebral perfusion while reducing the secondary effects of deep hypothermia and rewarming-associated injury.
The main limitation of this small study is that patients were not randomized and were evaluated retrospectively. The postoperative outcomes could be equally attributable to variations in care between different surgeons and to differences in patient-specific characteristics. A randomized prospective approach, akin to other prior similar studies on CPB strategies, would be a more ideal study design to overcome some of these biases and confounding factors in practice variation. In addition, the cohort identified in this study should also be followed by the authors for long-term neurodevelopmental outcomes, which could provide even more insight into the ultimate goal of identifying the optimal CPB strategy to ensure the best possible neurodevelopmental outcomes in children with congenital heart disease undergoing repair.
The quest for the best bypass strategy for infants will remain controversial, as dogmatic institutional preference and personal practices often impede a desire to change current practice. However, efforts to modify and optimize practices that can offer incremental neuroprotection for infants with critical congenital heart disease remain at the heart of our duty to care. As the impact of bypass-related brain (and specifically, white matter) injury in the perioperative period remains somewhat enigmatic, we are charged with considering that the quality of care we provide in the critical 1st days and weeks of life has longer reaching effects, spanning from the fetus to the first grader and beyond. With innovative approaches such as these, the path forward may not be so cold after all…
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