Regional cerebral blood flow and glucose metabolism during propofol anaesthesia in healthy subjects studied with positron emission tomography.
Level 3 - non-randomized controlled study
Prospective self-controlled before-and-after experimental study in humans
PubMed 22091956 · doi:10.1111/j.1399-6576.2011.02561.x
What was done
Eight healthy volunteers underwent positron emission tomography (PET) during wakefulness (baseline) and during propofol anaesthesia titrated to a target Bispectral Index of 35–40. Regional cerebral blood flow (rCBF) was measured using [15O]-water and regional cerebral glucose metabolic rate (rGMR) was measured using [18F]-fluorodeoxyglucose. Changes between states were evaluated via region-of-interest and voxel-based analyses.
What was found
At a mean propofol concentration of 4.1 ± 0.8 μg/ml, total CBF decreased by 47% and total GMR decreased by 54% compared to conscious baseline. In white matter, rCBF and rGMR dropped by 37% and 49%, respectively; in grey matter, they fell by 45% and 57%. Across all brain structures, rCBF decreased by 46–55% (P ≤ 0.01), with the largest significant decreases in the thalamus and parietal lobe. Regional GMR decreased across all brain areas to 48–66% (P ≤ 0.01), with the largest reductions in the occipital lobe, lingual gyrus, parietal lobe, temporal lobe, and thalamus. No brain region showed an increase in rCBF or rGMR.
Why it matters
This study quantitatively establishes the magnitude of concurrent cerebral blood flow and glucose metabolism reduction under steady-state propofol in humans, showing widespread depression with preferential impact on the thalamus and parietal areas.
Limits
The sample size was very small (n = 8) and limited to healthy volunteers without surgical stimulation. Only a single depth of anaesthesia (BIS 35–40) was evaluated, without examining dose-response gradations or recovery dynamics.
Cited by
- supports Studies show that anesthesia is associated with decreased overall blood flow to the brain.