Comparison of the immediate analgesic effect of perpendicular needling and transverse needling at SP6 in patients with primary dysmenorrhea: Study protocol for a randomized controlled trial.

Background: Acupuncture has been widely used to treat primary dysmenorrhea (PD) with satisfactory outcomes. Sanyinjiao (SP6) is the most commonly used acupoint for PD. Different needling techniques may influence the effect of SP6, and its underlying mechanism needs to be explored. This randomized controlled parallel trial is designed to evaluate the immediate analgesic effect and hemodynamic responses in uterine arterial blood flow of perpendicular needling and transverse needling at SP6 in patients with PD of cold-dampness stagnation pattern using color doppler ultrasonography. Methods: Forty-eight patients who meet inclusion criteria will be randomized in a ratio of 1:1 to either perpendicular needling or transverse needling groups. Every participant will receive 1 session of acupuncture treatment for 10 minutes at bilateral SP6. In the perpendicular needling group, needles will be inserted vertically 1 to 1.2 cun and will be manipulated to achieve needling sensation. In transverse needling group, the needles will be inserted transversely 1 to 1.2 cun toward the abdomen without any manipulation to avoid needling sensation. Color doppler ultrasonography will be performed before, during, and after needling. The primary outcome measure is visual analog scale for pain. The secondary outcome measures include the uterine artery blood flow changes by measuring pulsatility index, resistance index values, and ratio of systolic peak and diastolic peak, the Hamilton anxiety scale, blood pressure, and heart rate. Adverse events in both groups also will be recorded. Discussion: This trial will be the first study protocol designed to explore the influence of needling techniques on the analgesia effect of solo acupoint and its hemodynamic responses for PD. It will promote more widespread awareness of the benefits of using suitable needling techniques in acupuncture clinical setting and provide a further explanation of the underlying hemodynamic mechanism.