Near-infrared spectroscopy reveals asymmetric hemispheric blood supply during aortic arch surgery

Objectives: Bilateral and trilateral selective antegrade cerebral perfusion (SACP) aim to ensure symmetric hemispheric perfusion during aortic arch surgery, which current monitoring cannot directly assess. As a step towards real-time monitoring, we assessed the feasibility of multichannel contrast-enhanced near-infrared spectroscopy (CE-NIRS) using indocyanine green and whether hemispheric bolus timing matched expectations for each perfusion configuration. Methods: In this prospective, offline-analysed pilot study, 10 patients undergoing aortic arch surgery (9 frozen elephant trunk) received 94 boluses across 10 perfusion configurations. The interhemispheric difference in time to peak (ΔTTP) was compared with the pre-bypass baseline using a linear mixed model with Holm correction, alongside cerebral oximetry; the relationship to postoperative cerebral injury was explored post hoc. Results: 92 of 94 boluses yielded a bilateral TTP. Contrary to expectation, the left hemisphere peaked later under bilateral (+7.2 s, 95% CI 3.4-11.0; p = 0.003) and trilateral SACP (+8.7 s, 2.5-14.8; p = 0.031). With both left-sided arch vessels on body perfusion, the asymmetry reversed (-7.0 s, -11.7 to -2.3; p = 0.025). ΔTTP detected 6 of 9 configuration effects, whereas oximetry detected none after correction. The three patients with cerebral injury showed the three most pronounced reversals (exact p = 0.100) but were also those managed trilaterally. Conclusions: Multichannel CE-NIRS is feasible during aortic arch surgery, without indicator-related adverse events. Bilateral and trilateral SACP did not secure symmetric indicator delivery; the configuration-dependent asymmetry and its reversal point to two steals within the perfusion circuit that oximetry missed. Their clinical relevance requires prospective confirmation.