fMRI network correlates of predisposing risk factors for delirium: A cross-sectional study

Abstract

Highlights Predisposing risk is not associated with delirium-related fMRI characteristics. Older age within an elderly cohort is related to higher functional connectivity strength. This relation is in opposite direction than hypothesized. The onset of delirium may reflect new functional network impairments.

Why is delirium more frequent in the elderly?

“…According to the homeostenosis theory of the aging-related decline in reserve [ 15 ], which “matches the observation that the typical organ does not lose visible function so much as it loses measurable reserve” [ 16 ], delirium emerges when the reserve can no longer compensate for the effect of stressors. This view fits the conclusions of a meta-analysis of functional magnetic resonance imaging (fMRI) studies that the risk of delirium is related to the reduced structural connectivity of fragile networks, whereas the onset and course of clinical signs follow incidental dysfunctions of residual networks [ 17 – 19 ]. The question raised by Speciale et al [ 1 ] may therefore be fully answered by considering aging-related structural and functional changes in the brain.…”

“…Acetylcholine, dopamine, glutamine, GABA, serotonin, noradrenaline, tryptophan, phenylalanine, and histamine levels are decreased in the normal elderly [4,20], and unbalanced in delirious patients [60]. Delirium is most frequently associated with reduced acetylcholine levels, excess dopamine, noradrenaline, and/or glutamate release, or uneven amounts in serotonin, histamine, and γ-aminobutyric acid [19]. However, cholinergic deficiency [61] has so far been the most widely accepted because of the confusional state caused by anti-cholinergic drugs and the possibility of Aging could affect the neurons that regulate vascular tone (bipolar nerve cells in sub-cortical white matter and projections from the locus coeruleus, raphe, tegmentum, and nucleus basalis) [80,81], and also affect autoregulation as a result of structural alterations in arterioles and capillaries, such as the attenuation of the endothelium with loss of mitochondria, changes in connective tissue and smooth muscle fibres, the thickening of basement membranes, microglia and pericyte proliferation, the decreased expression of water channels in astrocytic feet [82,83], and β-protein overload.…”

“…Acetylcholine, dopamine, glutamine, GABA, serotonin, noradrenaline, tryptophan, phenylalanine, and histamine levels are decreased in the normal elderly [ 4 , 20 ], and unbalanced in delirious patients [ 60 ]. Delirium is most frequently associated with reduced acetylcholine levels, excess dopamine, noradrenaline, and/or glutamate release, or uneven amounts in serotonin, histamine, and γ-aminobutyric acid [ 19 ]. However, cholinergic deficiency [ 61 ] has so far been the most widely accepted because of the confusional state caused by anti-cholinergic drugs and the possibility of recovery by means of cholinergic agents.…”

Risk factors for postoperative delirium in ICU patients with severe illness based on systematic review and meta-analysis

“…The third kind of risk factor was therapeutic effect [5] mechanical ventilation, duration of mechanical ventilation [6], and sedative drug effect [7]. CAM-ICU, Pediatric Confusion Assessment Method for the ICU; ICDSC, Intensive Care Delirium Screening Checklist.…”

“…Delirium, also known as acute cerebral syndrome, refers to a clinical syndrome with a variety of causes (5). Delirium is characterized by cognitive dysfunction, lack of attention, urgent onset, obvious emotional fluctuations, and mostly occurs in the elderly (6,7). There is an obvious circadian rhythm to disturbance of consciousness, which worsens at night when there is less light.…”