FAILURE TO DEMONSTRATE ANY HYPOALGESIC EFFECT OF LOW-INTENSITY LASER IRRADIATION (830NM) OF ERBS POINT UPON EXPERIMENTAL ISCHEMIC PAIN IN HUMANS

Background and Objective: This study assessed the putative analgesic e ffect of low intensity, near-infrared laser irradiation (830nm; 1.5 & 9.0J/cm(2); continuous wave). Study Design/Materials and Methods: The current study was completed under double-blind conditions using a stan dardised form of the submaximal effort tourniquet technique. Healthy n aive female volunteers (n = 48) attended on two occasions for pain ind uction in the non-dominant upper limb, the first during which baseline data were obtained and on a second occasion during which subjects wer e randomly allocated to either control, placebo, or one of two treatme nt groups. In the treatment groups, irradiation was applied to ten poi nts on the ipsilateral Erb's point immediately prior to the pain induc tion procedure at the parameters stated: For the placebo condition, sh am ''irradiation'' was delivered by applying the laser unit without ac tivating the probe. Pain was measured using computerised visual analog ue scales and McGill Pain Questionnaires to assess ''current pain inte nsity'' and ''worst pain experienced,'' respectively. Results: Whereas analysis of variance and appropriate posthoc tests showed a trend tow ard hypoalgesia at a radiant exposure of 1.5J/cm(2) no significant eff ects of laser therapy were found. Conclusions: These results do not pr ovide convincing evidence for the clinical potential of low intensity laser irradiation as a pain relieving modality, at least at the parame ters used. Further work is thus necessary to provide objective quantif iable data on the putative clinical efficacy of this modality and the relevance (if any) of irradiation parameters. (C) 1997 Wiley-Liss, Inc .