Electroacupuncture parameters and [beta]-endorphin revisited.(Letter)

Acupuncture in Medicine

 

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Editor--The randomised controlled study on acupuncture (concurrent manual and electroacupuncture) for osteoarthritis (OA) of the knee in the June 2008 issue of Acupuncture in Medicine (1) is most interesting and carefully presented. However, the electroacupuncture (EA) parameters employed are unusual, and the authors' conclusions on the effects of EA on [beta]-endorphin are questionable.

Firstly, the intensity of stimulation is described as 'just above the pain threshold'. My understanding is that painful stimulation sufficient to activate high threshold C fibre afferents is not necessary to achieve analgesia using EA. Did the authors actually stimulate at just below the pain threshold, which would be more acceptable to patients, the research ethics committee which approved this study, and those who consider that A [delta] afferents only need to be activated for pain relief? It is curious that only 41% in the verum group correctly guessed their treatment allocation, only one person withdrew from the study for reasons associated with treatment (group not indicated), and fewer of those in the verum group experienced adverse effects, even though an aggravation of OA pain might be expected when local treatment is applied at high intensity (adverse effects are mentioned, but not described).

Secondly, the electrical frequency and pulse duration chosen were also unusual. Jubb et al utilised 6Hz with a pulse duration of 1 millisecond for 10 minutes each at anterior and posterior points local to the knee. The vast majority of 'low frequency' EA studies have used 2-4Hz rather than 6Hz, and with a rather shorter pulse duration (<300 microseconds). I have not in fact been able to locate reports by other research groups that have treated OA with these …

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