Functional Magnetic Resonance of Arousal Pathways during Emergence from Sedation

Background: Sedation and general anaesthesia are at the hub of modern medicine. The practice of the administration of anaesthesia and sedation has evolved considerably and is now considered safe and reproducible. However, our understanding of the neurophysiological mechanisms governing emergence is still lacking.

Aims:

1. To characterize the dynamic, spatiotemporal brain activation sequence leading to emergence from sedation.

2. To "capture" the neural core of arousal.

Methods: Continuous dynamic fMRI acquisition of 20 healthy volunteers from the awake state to deep sedation with Propofol – target controlled infusion, and to emergence following cessation of Propofol administration.

Results: Interim data from 10 subjects, using the Locus Coeruleus, a key organizing pontine nucleus as a seed region yields a functional connectivity map with co activations of the limbic system, key elements of the default mode network (DMN) and subcortical nuclei associated with arousal. Network cohesion analyses of the limbic system and the DMN captures, for the first time, transient increase in cohesion of these networks just before the moment of emergence.

Conclusions:

1. Functional imaging of deep brain structures seems as an effective modality for the study of emergence from deep sedation.
2. Neuronal networks cohesion may contribute to emergence from sedation.