Characterizing autonomic nervous system alterations in hospitalized patients with delirium: A scoping review

To characterize autonomic nervous system alterations in patients with delirium, focusing on cardiovascular, respiratory, ocular, exocrine, and gastrointestinal functions, as well as neurotransmitter levels. This review aims to synthesize current evidence and explore potential clinical implications for monitoring delirium.

A scoping review was conducted in accordance with PRISMA-ScR guidelines and the Joanna Briggs Institute framework. Searches were performed on the Web of Science, PubMed, Scopus, and EBSCOhost. Eligible studies included experimental, quasi-experimental, observational, or descriptive designs involving hospitalized adults with delirium, diagnosed using standardized tools and accompanied by documented evaluation of the autonomic nervous system.

Twenty-seven studies were included. Four domains were identified: cardiovascular activity (18 studies), which addressed heart rate variability, blood pressure variability, and blood flow. Several studies have reported changes in heart rate variability, increased blood pressure variability, and a reduction in mean arterial pressure associated with delirium. Four studies examined ocular changes, reporting reduced pupillary reflex responses in delirium. Gastrointestinal function was assessed in three studies through gut microbiota analysis, showing reduced microbial diversity and increased pathogenic taxa. Two studies examined neurotransmitter levels, reporting elevated norepinephrine in blood and urine associated with delirium.

This scoping review reveals that autonomic alterations are commonly reported in delirium across various domains, including cardiovascular, ocular, gastrointestinal, and neurochemical systems. The evidence is heterogeneous in terms of measures, timing, and study designs, which limits the integration of findings. Autonomic measures may reflect physiological vulnerability, highlighting the need for standardized and longitudinal research.