Effects of locally applied water-filtered infrared a irradiation adjunctive to iloprost and carbon dioxide hand baths in patients with systemic sclerosis and severe Raynaud’s phenomenon – a randomized controlled trial

Background Almost all patients with systemic sclerosis (SSc) experience Raynaud’s phenomenon (RP) with risk of digital ulcers (DU). In severe RP, intravenous iloprost is standard, yet additive hyperthermic therapy may enhance vasodilation and microcirculation. However, whether more intensive or alternative hyperthermic modalities offer benefits beyond commonly used CO2 hand baths remains unclear.Methods In this randomized, controlled trial, all patients received a baseline therapy of iloprost plus CO2 hand baths. The intervention group (IG) received additional water-filtered infrared-A (wIRA; 2 × 30 min/day, 8 days), while the control group (CG) received baseline therapy alone. The primary endpoint was the difference in RP-associated pain (VAS 0–100 mm) after treatment. Secondary outcomes included changes in RP duration, frequency, and intensity, Health Assessment Questionnaire (HAQ), serum interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF).Results Of 46 randomized patients, 38 (IG = 19, CG = 19) completed the study. Pain decreased from 70.4 ± 27.8 to 56.7 ± 21.4 mm with wIRA and from 73.9 ± 27.5 to 65.3 ± 26.8 mm in controls. Multivariable ANCOVA showed a mean difference of −14.7, 95% CI [−28.8;−0.7], p = 0.041 in favor of wIRA. RP duration improved more in the wIRA group (day 23: β = −3.8, 95% CI [−7.4;−0.2], p = 0.041), while RP frequency, intensity, HAQ, IL-6, and VEGF showed no significant differences (all p > 0.05). No adverse events occurred.Conclusions Adjunctive wIRA during iloprost therapy was safe and yielded modest, short-term improvements in pain and RP duration. These exploratory effects warrant confirmation in larger controlled trials.