Cerebral NIRS—How low is low?

Abstract

Cerebral near-infrared spectroscopy (NIRS), a noninvasive means of monitoring cerebral oxygenation, is inferred to reflect the balance between tissue oxygen delivery and consumption. Although some studies have demonstrated an association between cerebral NIRS and intellectual outcome in special populations, such as those with hypoplastic left heart syndrome (J Thorac Cardiovasc Surg 2016;151:1358-66), questions remain regarding broader applicability. Although frequently used during anesthesia for congenital heart surgery, use in a broader surgical population is not established, including in adult patients (Anesth Analg 2012;115:1373-83). With this in mind, the report by Gómez-Pesquera et al in this volume of The Journal is intriguing, but raises as many questions as it answers. This was an observational study of 198 children undergoing non-cardiac surgery. A validated questionnaire was administered on post-operative day 7, and an association was found with negative behaviors (including anxiety, eating disturbances, and apathy/withdrawal) for every 1% decrease from baseline in cerebral oxygenation by NIRS. A similar association was found when comparing the degree of preoperative anxiety as measured by the modified Yale Preoperative Anxiety Scale with post-operative behaviors. General anesthesia is, of course, unavoidable at times, but these findings should prompt further inquiry into the consequences of anesthetic exposure to the developing brain. This study does not address the severity of behavioral changes nor whether there are any long-term consequences, because the only reported outcome is a survey at 7 days. And although it challenges the notion of extrapolating adult thresholds to children, it remains difficult to assess to what degree of decrement is worrisome, since, unlike systemic oxygen saturation, there are no hard and fast cutoffs for cerebral NIRS. All reports are expressed as change from baseline, with a wide biologic variability in that baseline. An additional concern is whether changing management in response to cerebral NIRS changes outcomes, as evidenced by a growing body of literature in neonates (Curr Opin Pediatr 2018;30:209-15) (Acta Paediatr 2019;108:275-81). So, although premature to advocate for specific indications or thresholds for use of cerebral NIRS during pediatric surgery, this report should encourage further investigations into the nature and consequences of anesthesia and the most effective monitoring of the developing brain. Article page 207▶ Cerebral Oxygen Saturation and Negative Postoperative Behavioral Changes in Pediatric Surgery: A Prospective Observational StudyThe Journal of PediatricsVol. 208PreviewTo evaluate if an intraoperative cerebral regional oxygen saturation (crSO2) decrease, less pronounced than 20% below baseline (the current threshold believed to be associated with cognitive dysfunction in adults), is associated with negative postoperative behavioral changes (NPOBC) in the pediatric population after noncardiac surgeries. Full-Text PDF