Impact of the Warm Compress Method Conducted by Nurses Before Venipuncture on Blood Nitric Oxide Concentration

Adequate venous dilation is important for successful venipuncture and infusion insertion. While the warm compress method is commonly used, its mechanism remains unclear. This study investigated the impact of the warm compress method on blood nitric oxide (NO) concentration, known for its vasodilatory properties. Using a pre-and post-intervention design, participants underwent warm compress application on the non-dominant arm. The blood NO concentration, vein cross-sectional area, and skin temperature were measured pre-and post-intervention. A warm compress was applied at 39 °C to 42 °C for 5 minutes. The skin temperature was measured pre-intervention and after applying pressure with a tourniquet; a vein cross-sectional area image was acquired using ultrasonography, and 2 mL blood was drawn to measure NO. Post-intervention, skin temperature was measured, vein cross-sectional area images were obtained, and blood was similarly collected. Data were analyzed using the Wilcoxon signed-rank sum test. Among the 19 participants (7 men and 12 women; mean age: 42.6 ± 7.5 years), significant differences were observed in skin temperature (32.05 °C versus 39.40 °C), vein cross-sectional area (11.4 mm versus 14.8 mm2), and blood NO concentration (12.45 µmol/L and 11.18 µmol/L) pre- and post-intervention, possibly because the action of blood NO on vascular smooth muscle cells was promoted, leading to blood NO consumption.