Autonomic Responses to Ultrasound-Guided Percutaneous Needle Electrolysis: Effect of Needle Puncture or Electrical Current?

Objective: The aim of this study was to establish if the changes in sympathetic and parasympathetic activity (analyzed through heart-rate variability [HRV]) during ultrasound (US)-guided percutaneous needle electrolysis (PNE) is due to the effect of needle puncture only or of the PNE technique per se where the puncture and galvanic current are combined. Methods: This was an experimental, case-control study that took place at the University of Seville. Subjects were 36 male footballers who were randomly allocated to three groups: a control group (CG; 12 players), for whom HRV was recorded for 10 min, both at rest and during an exhaustive US examination of the patellar tendon and adjacent structures; a first experimental group (PNE group; 12 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE in the patellar tendon; and a second experimental group (needle group; 12 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE without electrical current in the patellar tendon. The outcome measures were the diameters of the Poincaré plot (SD1, SD2), stress score, and sympathetic/parasympathetic ratio. Results: There were no differences between groups in any baseline measurements, nor were there any significant differences between CG measurements (baseline vs. intervention). The PNE group exhibited statistically significant increases in SD1 ( p = 0.01) and SD2 ( p = 0.004) and statistically significant decreases in SS and S/PS ratio ( p = 0.03), indicating increased parasympathetic and decreased sympathetic activity, respectively. The needle group exhibited statistically significant increases in SD2 ( p = 0.02) and statistically significant decreases in SS ( p = 0.02), indicating decreased sympathetic activity. Conclusions: The application of the US-guided PNE technique caused a measurable increase in parasympathetic activity (detected by HRV), which was due to the combination of needle puncture and electric current.