Propofol Mechanism Functional Magnetic Resonance Imaging Study

Part 1 Bispectral index study and functional magnetic resonance imaging study in the anesthetic effect of propofolObjectiveUsing the bispectral index monitoring(BIS) and Blood oxygenation level-dependent functional magnetic resonance imaging(BOLD-fMRI) technology,to investigate specific brain regions related to anesthetic effect of propofol.Methods20 healthy male volunteers participated in the study,randomly allocated to 2 groups:light anesthesia group(group L)(BIS 60～80) or deep anesthesia group(group D)(BIS 40～60).Propofol was administrated by target controlled infusion system in pilot study.The target effect site concentration (ESC)of propofol in group L was defined as the average of the ESC in BIS 80 and BIS 60.The target ESC in group D was defined as the average of the ESC in BIS 60 and BIS 40.FMRI study proceeded from 1 to 2 weeks after pilot study.FMRI examinations were conducted to obtain the following sequences: structure imaging,anesthesia sequence(event-related design:15min= baseline scan 4min+infusion scan about 9min+balance scan about 2min). Recovery sequence(event-related design:15min=balance scan 4min+stop infusion scan 11min) proceeded only in group D.The monitoring data were recorded during the scanning and the OAA/S were recorded before and after each sequence.FMRI data processing is carried out with the SPM2 and Matlab 6.5 software package. Results①Activated brain region of propofol anesthesia in group L(BIS 60～80, OAA/S 3) was observed only in left inferior parietal lobule.②Activated brain regions of propofol anesthesia in group D(BIS 40～60,OAA/S 1) were observed in left insula and superior temporal gyrus and right middle temporal gyrus.③Activated brain regions of low anesthesia＞deep anesthesia were observed in bilateral insula,temporal lobe and limbic lobe and left basal nucleus and midbrain.④Activated brain region of deep anesthesia＞low anesthesia,recovery,deep anesthesia＞recovery,recovery＞deep anesthesia were all null.ConclusionActivation gradient of left inferior parietal lobule in low anesthesia varies with propofol ESC,which indicates that low anesthesia affects different brain regions in different volunteer,and common active brain regions are seldom. Activation gradient of left insula and bilateral temporal lobe in deep anesthesia vary with propofol ESC,which indicates that these regions are likely the targets of anesthetic action of propofol.No common active brain region was observed in recovery,which indicates large individual difference of active brain region during recovery. Part 2 Process dissociation procedure study and functional magnetic resonance imaging study in the amnesic effect of propofolObjectiveUsing the Process dissociation procedure(PDP) and Blood oxygenation level-dependent functional magnetic resonance imaging(BOLD-fMRI) technology,to investigate specific brain regions related to amnesic effect of propofol,and to explore processing brain regions of explicit and implicit memory.Methods20 healthy male volunteers participated in the study,randomly allocated to 2 groups:light anesthesia group(group L)(BIS 60～80) or deep anesthesia group(group D)(BIS 40～60).Propofol was administrated by target controlled infusion system in pilot study.The target effect site concentration (ESC) of propofol in group L was defined as the average of the ESC in BIS 80 and BIS 60.The target ESC in group D was defined as the average of the ESC in BIS 60 and BIS 40.FMRI study proceeded from 1 to 2 weeks after pilot study.PDP was used to estimate implicit and explicit memory for words presented during awake and anesthesia.FMRI examinations were conducted to obtain the following sequences:structure imaging,awake word sequence and anesthesia word sequence.Block design was applied as "10min45s=45s baseline+[(0.5s word stimulation+1.5s silence)×20+20s silence]".The monitoring data were recorded during the scanning and the OAA/S were recorded before and after each sequence.PDP data processing is carried out with SPSS 13.0 software package.FMRI data processing is carried out with the SPM2 and Matlab 6.5 software package.Results1.①Explicit memory during anesthesia period significantly decreased compared with awake period in group L(BIS 60～80,OAA/S 3),while implicit memory did not differ between anesthesia and awake period.②Explicit memory and implicit memory during anesthesia period both significantly decreased compared with awake period in group D(BIS 40～60,OAA/S 1). 2.①Active brain regions of word stimulation during anesthesia period in group L were observed in bilateral superior temporal gyrus.②Active brain regions of word stimulation during anesthesia period in group D were observed in right inferior parietal lobule,superior temporal gyrus,middle temporal gyrus and insula.③Active brain regions of awake word＞anesthesia word in group L were mainly observed in bilateral frontal lobe,parietal lobe and temporal lobe and left occipital lobe and basal nucleus.④Active brain regions of awake word＞anesthesia word in group D were observed in left thalamus,precentral gyrus,anterior cingulate and right basal nucleus.ConclusionAccording to PDP estimates,only explicit memory disappears during light anesthesia,but implicit memory still exists.Explicit memory and implicit memory are both disappeared during deep anesthesia.Active brain regions of awake word＞anesthesia word in group L were mainly observed in bilateral frontal lobe,temporal lobe and parietal lobe and left occipital lobe.According to PDP estimates,these regions are likely related to explicit memory processing. Active brain regions of awake word＞anesthesia word in group D were observed in left thalamus,frontal lobe and limbic lobe and right basal nucleus. According to PDP estimates,these regions are likely related to explicit and implicit memory.