Acupuncture-induced blood oxygenation level-dependent signals in awake and anesthetized volunteers: a pilot study.

Background: There are conflicting data regarding clinical efficacy of acupuncture applied while patients are under general anesthesia. We hypothesize that these conflicting data are a result of the inhibitory effect of anesthesia on acupuncture-induced central nervous system activity that can be demonstrated using magnetic resonance imaging.

Methods: Using a crossover study design, volunteers received standardized Stomach 36 manual acupuncture in two experimental conditions: while undergoing a propofol-based general anesthetic, and while awake. Functional magnetic resonance imaging was conducted during both experimental sessions. Paired-t-test analyses were performed to examine the differences in acupuncture-induced blood oxygenation level-dependent (BOLD) signals between awake and anesthesia conditions. A secondary analysis was performed to account for the changes in regional cerebral blood flow at six regions of interest (thalamus, red nucleus, insula, periaqueductal gray, retrosplenial cingular gyri, and the inferior temporal region).

Results: Using BOLD, we found significant differences between the two experimental sessions in brain areas, including postcentral gyri, retrosplenial cingular area, left posterior insula, bilateral precuneus, thalamus, red nuclei, and substantia nigra (cluster 100, P < 0.01). A secondary analysis correcting for background cerebral blood flow found that BOLD signal differences between experimental conditions were not directly caused by changes in regional blood flow.

Discussion: Propofol-based anesthesia reduces the neurophysiological response to acupuncture stimulation as measured by acupuncture-induced BOLD signals. Further work should be conducted to determine the clinical significance of these findings.