Pain assessment of different needle insertion angles in venipuncture: a randomized crossover clinical trial

To investigate the influence of needle insertion angle on pain during venipuncture. We enrolled 50 patients and assigned them to large-angle (30–45 degrees) or small-angle (15–30 degrees) needle insertion for venous puncture in random order. Pain was measured by Numerical Rating Scale (NRS), Verbal Rating Scale (VRS), and Wong–Baker Faces Pain Scale Revision (FPS-R) as the primary endpoint. The secondary endpoints were puncture failure and complications. All 50 enrolled patients completed the crossover trial. Wilcoxon signed-rank tests confirmed significantly lower pain scores with large-angle (30–45°) versus small-angle (15–30°) insertion across all scales (all P < 0.001). The large-angle group demonstrated median reductions of 1.0 point for NRS (95% CI: 1.0–2.0) and VRS (95% CI: 1.0–2.0), and 2.0 points for FPS-R (95% CI: 2.0–4.0). Zero pain was reported by 34–42% of patients in the large-angle group across scales, compared to none in the small-angle group. Puncture failure and complication rates did not differ between conditions. This randomized crossover clinical study demonstrated that needle insertion at a large angle could significantly reduce pain during venipuncture, irrespective of BMI. Trial Registration: This trial was retrospectively registered at Chinese Clinical Trial Registry identifier: ChiCTR2300075257, Registration Date 2023/08/01. Venipuncture is a common medical procedure often associated with patient discomfort and pain. The study was undertaken to investigate whether the angle of needle insertion during venipuncture influences pain levels, aiming to identify a less painful technique to improve patient experience. The study found that needle insertion at a larger angle (30–45 degrees) resulted in significantly lower pain scores across all measurement scales compared to a smaller angle (15–30 degrees), without increasing the risk of puncture failure or complications. Our study suggests that adopting a larger needle insertion angle during venipuncture could reduce patient pain, enhancing procedural comfort and potentially improving compliance with medical interventions requiring blood sampling or intravenous access.