Low-dose Propofol–induced Amnesia Is Not due to a Failure of Encoding
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https://doi.org/10.1097/ALN.0b013e31817fd8aeMetadata
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Veselis, Robert A., Kane O. Pryor, Ruth A. Reinsel, Meghana Mehta, Hong Pan, and Ray Johnson. 2008. “Low-Dose Propofol–induced Amnesia Is Not Due to a Failure of Encoding.” Anesthesiology 109 (2) (August): 213–224. doi:10.1097/aln.0b013e31817fd8ae.Abstract
Background—Propofol may produce amnesia by affecting encoding. The hypothesis that propofolweakens encoding was tested by measuring regional cerebral blood flow during verbal encoding.
Methods—17 volunteer participants (12 M, 30.4±6.5 years old) had regional cerebral blood flow
measured using H2O15 positron emission tomography during complex and simple encoding tasks
(deep vs. shallow level of processing), to identify a region of interest in the left inferior prefrontal
cortex (LIPFC). The effect of either propofol (n=6, 0.9 mcg/ml target concentration), placebo with
a divided attention task (n=5), or thiopental at sedative doses (n=6, 3 mcg/ml) on regional cerebral
blood flow activation in the LIPFC was tested. The divided attention task was expected to decrease
activation in the LIPFC.
Results—Propofol did not impair encoding performance or reaction times, but impaired recognition
memory of deeply encoded words 4 hours later (median recognition of 35% (17–54 interquartile) of
words presented during propofol versus 65% (38–91) before drug, p<0.05). Statistical parametric
mapping analysis identified a region of interest of 6.6 cu.cm. in the LIPFC (T=7.44, p=0.014).
Regional cerebral blood flow response to deep encoding was present in this region of interest in each
group before drug (T>4.41, p<0.04). During drug infusion only the propofol group continued to have
borderline significant activation in this region (T=4.00, p=0.063).
Conclusions—If the amnesic effect of propofol were solely due to effects on encoding, then
activation in LIPFC should be minimal. As LIPFC activation was not totally eliminated by propofol,
the amnesic action of propofol must be present in other brain regions and/or affect other memory
processes.
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