Prolonged Mismatch Negativity Latencies in Intensive Care Unit Patients With Active Delirium

INTRODUCTION: Delirium is a common and serious complication in critically ill patients, associated with higher mortality, prolonged intensive care unit (ICU) stays, and cognitive impairments. Furthermore, renal dysfunction is a well-recognized risk factor for delirium in the ICU. Although previous studies have explored the neurophysiologic characteristics of delirium, few have examined brain activity during active delirium episodes. To address this gap, this study aimed to use mismatch negativity (MMN)-an electrophysiologic marker of the brain's automatic ability to detect environmental changes-to deepen the understanding of the pathophysiology and phenomenology of delirium in ICU patients with renal dysfunction. METHODS: An auditory oddball paradigm, consisting of frequent standard tones and infrequent deviant tones, was presented to critically ill patients with renal dysfunction during event-related potential recordings. MMN was obtained by subtracting the event-related potential response to deviant stimuli from that of standard stimuli and was compared between patients with and without delirium. In addition, the authors examined the relationships between MMN, cognitive function, and disease severity. Finally, they assessed whether MMN could predict key clinical outcomes at ICU discharge. RESULTS: ICU patients with delirium exhibited significantly prolonged MMN latencies compared with those without delirium (P = 0.005, effect size = 0.67). Moreover, more delayed MMN latencies showed a trend toward an association with greater delirium severity. However, MMN did not predict key clinical outcomes on ICU discharge. CONCLUSIONS: Critically ill patients with renal dysfunction exhibit prolonged MMN latencies during delirium episodes compared with those without delirium, suggesting altered neural processing in this population.