Nocifensive reactions during propofol-induced loss of consciousness are not based on the development of central hyperalgesia- A functional imaging study in humans

摘要

Background: Barbiturates are widely held to have hyperalgesic properties, Using functional magnetic resonance imaging (fMRl) techniques we sought to investigate the effects of graded doses of propofol on central pain processing in the lateral and medial pain system in healthy volunteers.Methods: Touch stimuli as well as phasic and tonic mechanical pain stimuli were applied to the right hand of 18 volunteers fMRl was performed on an 1,5 T scanner using EPI-sequences, The experiments were repeated under targeted propofol plasma levels (TCI 0,1.5, 2.5 and 3,5 mug/ml), Changes of the BOLD signal in different cortical areas (primary and secondary somatosensory cortical areas S1 and S2, insular, anterior cingulate cortex and frontal areas) were investigated during propofol anaesthesia using correlation and clustering analysis,Results: Functional activation in cerebral areas belonging to the lateral pain system (S1, S2 and insular cortex) was significantly reduced with increasing propofol plasma levels, whereas activation of the medial system (anterior cingulate and prefrontal cortex) was nearly unaffected..Conclusion: Propofol seems to preferentially interfere with pain processing at the cortical level in the lateral projection system while the medial system control-Ling affective components obviously remains unchanged Therefore, the clinically