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24/10/2005 - Anesthesia May Weaken Acupuncture's Effectiveness

News release:

A new study using functional magnetic resonance imaging (fMRI) to measure patients' pain levels, shows that anesthetics may diminish the positive effects of acupuncture when used during surgery.

Results of the study were presented here on October 22nd at the annual meeting of the American Society of Anesthesiologists (ASA) Annual Meeting.

Acupuncture is an ancient Chinese medical practice, which involves the insertion of very fine needles into the skin to stimulate specific anatomic points in the body called acupoints for therapeutic purposes by triggering the releases of neurotransmitters that constrict blood vessels and ultimately reduce pain.

Acupuncture practitioners also use heat, pressure, friction, suction, or impulses of electromagnetic energy to stimulate the points.

Despite a lack of scientific knowledge supporting acupuncture use, the technique is often used as an alternative or adjunct treatment for a variety of medical conditions.

According to lead researcher Shu-Ming Wang, MD, Director, Pediatric Preadmission Program, Associate Director, Pediatric Pain Mainagement, Department of Anesthesiology, Yale School of Medicine, New Haven, Connecticut, acupuncture has been shown to help relieve preoperative anxiety and postoperative pain, nausea and vomiting, although there is a lack of consistency in the technique's effectiveness.

Dr. Wang presented the findings of a cross-over study, which used fMRI to measure central nervous system changes in 10 patients with an average age of 28 years of age and no prior experience with acupuncture.

All subjects underwent two experimental sessions that included 12 repetitive cycles of manual acupuncture stimulation with each cycle consisting of 20 seconds on and 20 seconds off. The total stimulation process lasted 10 minutes while volunteers were awake and under propofol general anesthesia. The acupuncture intervention was performed in just below the head of the tibia, lateral to the tibia. General anesthesia was induced and maintained to keep the Bispectral Index (BIS) at 30, using 2 mg/kg of IV propofol and continuous propofol infusion 120-150 mg/kg/min.

The BIS value is obtained using a modern neurophysiologic monitoring device that to determines the patient's level of anaesthesia by continually analyzes the patient's electroencephalogram (EEG) during general anaesthesia. The BIS value ranges from 0 to 100. A BIS value of 0 equals EEG silence, 100 is the expected value in a fully awake adult.

Dr. Wang said the researchers found a significant difference between the awake and general anesthesia states in activation patterns in the central nervous system during acupuncture stimulation. They suggest that this finding may explain some of the conflicting data regarding the efficiency of acupuncture in the perioperative clinical setting.

"However, future studies are needed to determine whether these changes are caused by anesthesia agents or by a change in consciousness, and how these factors alter the effectiveness of acupuncture in the operative setting," Dr. Wang said.

Usichenko TI, et al. Evid Based Complement Alternat Med. 2005 Jun;2(2):185-189. Epub 2005 May 11.