Journal ArticleDOI
Effects of Surgical Levels of Propofol and Sevoflurane Anesthesia on Cerebral Blood Flow in Healthy Subjects Studied with Positron Emission Tomography
Kaike K. Kaisti,Liisa Metsähonkala,Mika Teräs,Vesa Oikonen,Sargo Aalto,Satu K. Jääskeläinen,Susanna Hinkka,Harry Scheinin +7 more
TLDR
Both anesthetic agents caused a global reduction of rCBF (propofol > sevoflurane) at the 1 MAC/EC50 level, and despite the marked global changes, SPM analysis enabled detailed localization of regions with the greatest relative decreases.Abstract:
Background The authors report a positron emission tomography (PET) study on humans with parallel exploration of the dose-dependent effects of an intravenous (propofol) and a volatile (sevoflurane) anesthetic agent on regional cerebral blood flow (rCBF) using quantitative and relative (Statistical Parametric Mapping [SPM]) analysis. Methods Using H(2)(15)O, rCBF was assessed in 16 healthy (American Society of Anesthesiologists [ASA] physical status I) volunteers awake and at three escalating drug concentrations: 1, 1.5, and 2 MAC/EC(50), or specifically, at either 2, 3, and 4% end-tidal sevoflurane (n = 8), or 6, 9, and 12 microg/ml plasma concentration of propofol (n = 8). Rocuronium was used for muscle relaxation. Results Both drugs decreased the bispectral index and blood pressure dose-dependently. Comparison between adjacent levels showed that sevoflurane initially (0 vs. 1 MAC) reduced absolute rCBF by 36-53% in all areas, then (1 vs. 1.5 MAC) increased rCBF in the frontal cortex, thalamus, and cerebellum (7-16%), and finally (1.5 vs. 2 MAC) caused a dual effect with a 23% frontal reduction and a 38% cerebellar increase. In the propofol group, flow was also initially reduced by 62-70%, with minor further effects. In the SPM analysis of the "awake to 1 MAC/EC(50)" step, both anesthetic agents reduced relative rCBF in the cuneus, precuneus, posterior limbic system, and the thalamus or midbrain; additionally, propofol reduced relative rCBF in the parietal and frontal cortices. Conclusions Both anesthetic agents caused a global reduction of rCBF (propofol > sevoflurane) at the 1 MAC/EC(50) level. The effect was maintained at higher propofol concentrations, whereas 2 MAC sevoflurane caused noticeable flow redistribution. Despite the marked global changes, SPM analysis enabled detailed localization of regions with the greatest relative decreases.read more
Citations
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Experimental and Theoretical Approaches to Conscious Processing
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Consciousness and Anesthesia
TL;DR: Anesthesia undoubtedly induces unresponsiveness and amnesia, but the extent to which it causes unconsciousness is harder to establish.
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Neural correlates of consciousness: progress and problems
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Molecular and neuronal substrates for general anaesthetics.
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Networks of the Brain
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