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Department of Anesthesiology; Oklahoma University Health Sciences Center; Norman, OK OUTCOMES RESEARCH Institute; Department of Anesthesiology; University of Louisville; Louisville, KY; sessler{at}louisville.edu
In Response:
One of the points we stimulated was Liangqiu, as was spelled out in the abstract and twice in the text (1). Bagley correctly notes that this should have been identified as "St.34" rather than "Sp.34."
We used mixed-frequency (2 Hz and 10 Hz) stimulation because each frequency elicits different responses, either of which may reduce anesthetic requirement. At 2 Hz, electroacupuncture-induced analgesia is mediated by mu- and 
-receptors. Analgesia mediated by mu- and delta-receptors is reversed by naloxone and thus presumably mediated by enkephalin and endorphins, has a tendency to accumulate, and lasts at least 1 h after treatment ceases (2). In contrast, frequencies near 10 Hz induce analgesia that is mediated by the combined action of mu-, delta-, and kappa-opioid receptors (3,4). However, unlike the stimulation at lower frequencies, stimulation at frequencies exceeding 8 Hz provokes an antinociceptive response that is noncumulative and can be observed only during stimulation (5,6).
We included a needling test for three reasons: 1) to familiarize our volunteers with the procedure and thus reduce anxiety on the first study day; 2) to document a satisfactory De-qi response which is associated with acupuncture efficacy; and 3) to determine the optimal stimulation current for each point in each volunteer, defined as the maximum tolerated current that did not provoke muscle twitching, which could have unblinded the study.
Stimulation intensities thus varied slightly, though only slightly, from volunteer to volunteer and from point to point. However, the designated stimulation intensities were subsequently maintained for the duration of the study; intensity was thus identical on both stimulation study days in each volunteer. As specified in our article, the average stimulator output was 8 V at a current of 8 mA. A single volunteer was excluded from the study after developing a vaso-vagal reaction to insertion of the test needle.
A general difficulty with acupuncture studies is that they are nearly impossible to fully double blind. Much acupuncture literature is thus difficult to interpret. Tests of anesthetic requirement differ in evaluating an objective response (movement) under fully blinded conditions.
For reasons described in our article, we tested the hypothesis that acupuncture started 30 min before induction of anesthesia reduces anesthetic requirement more than acupuncture started at induction of anesthesia. The results indicated that acupuncture had no statistically significant effect on anesthetic requirement—whether started 30 min before induction or just at induction. We agree that statistical significance might have been demonstrated in a larger study. But the results of our current study is consistent with three previous studies in which various types of acupuncture were shown to reduce anesthetic requirement by only 11% (7) or 8% (8) or have no effect (9). Our overall conclusion is thus that types of acupuncture we have tested in four studies have little, if any, effect on anesthetic requirement—and certainly none that is clinically important.
References
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