The Effect of Pre-Incisional and Post-Incisional Acupuncture on Hyperalgesia in Rat Incision Model

Postoperative pain cannot be treated adequately in all patients, even though there are new developments in analgesic agents and treatment techniques. This study investigates the effect of pre-incisional and post-incisional electro-acupuncture on mechanical hyperalgesia in rat incisional pain model.

This study was carried out with 40 healthy Sprague-Dawley male rats. The rats were divided into 5 groups: Group 1; first electro-acupuncture, then incision. Group 2; first incision, then electro-acupuncture. Group 3; first sham electro-acupuncture, then incision. Group 4; first incision, then sham electro-acupuncture. Group 5; control (incision only). Electro-acupuncture was applied to the ST36 and SP6 acupuncture points on the right hind paw. Sham electro-acupuncture was applied to the right thigh. Von Frey filaments were used to measure hyperalgesia at baseline and at 4th, 6th, 24th and 48th hours.

Shapiro Wilk test was used to determine whether the distribution of continuous variables was close to normal. Levene's test was used for homogeneity of variances. Bonferroni Correction Wilcoxon Sign test was used to determine whether the differences between follow-up times were statistically significant or not. Bonferroni Correction on Kruskal Wallis test was used to determine whether there was any difference between groups. If the Kruskal Wallis test statistics were significant, analysis was performed using Conover's multiple comparison test. p<0.05 was considered statistically significant.

This study found that electro-acupuncture decreases hyperalgesia, and there was no significant difference between pre-incisional and post-incisional application in terms of the anti-hyperalgesic effectiveness of electro-acupuncture, except for the duration of action. Pre-incisional applications are more effective than post-incisional applications. Pre-incisional sham electro-acupuncture has also been found to have anti-hyperalgesic effect.

Our findings support the studies that electro-acupuncture can be used for preemptive purposes in surgical patients. We think that researches should be continued in order to provide alternative methods for pain treatment.