Anesthetic effects of propofol in the healthy human brain: functional imaging evidence.
Level 1 - systematic review of randomized trials
Systematic review of 18 human functional neuroimaging studies.
PubMed 25056258 · doi:10.1007/s00540-014-1889-4
What was done
A systematic review was conducted across Medline, EMBASE, CINAHL, and reference lists from 1966 to July 2013 to identify functional neuroimaging studies (positron emission tomography [PET] and functional magnetic resonance imaging [fMRI]) examining the regional central nervous system effects of propofol in humans. Eighteen studies meeting inclusion criteria were evaluated regarding imaging valuation techniques, metabolic changes, cerebral blood flow, and functional connectivity across sedation depths.
What was found
The abstract reports qualitative neuroimaging findings without numerical statistics or pooled effect sizes. In unconscious states, propofol reduced regional glucose metabolic rate (rGMR) and regional cerebral blood flow (rCBF) across all brain regions, most prominently in the thalamus. At sedative doses, rGMR decreased in occipital, temporal, and frontal lobes, while thalamic changes were minimal. On fMRI, mild sedation was associated with decreased thalamic connectivity and increased pontine connectivity. Deep sedation preserved cortical sensory reactivity with moderate impairment of specific thalamocortical networks and severe suppression of nonspecific thalamocortical networks, alongside consistent reductions in frontoparietal network connectivity.
Why it matters
This review synthesizes human neuroimaging evidence on propofol's mechanism of action, demonstrating that loss of consciousness involves widespread metabolic depression paired with targeted disruption of thalamocortical and frontoparietal networks.
Limits
The abstract reports no quantitative data, effect sizes, or confidence intervals. Total participant counts across the 18 included studies are not reported. Heterogeneity across imaging modalities (PET versus fMRI) and varying definitions of sedation depth limit direct quantitative comparisons.
Cited by
- supports Studies show that anesthesia is associated with decreased overall blood flow to the brain.