Pain Trajectories and Predictors Following Uterine Artery Embolization Using a Nitroglycerin-Lidocaine Protocol: A Prospective Study

BACKGROUND AND AIMS: Uterine artery embolization (UAE) is an effective minimally invasive treatment for symptomatic fibroids; however, post-procedural pain remains a major limitation. Intra-arterial lidocaine administration has shown inconsistent results with concerns regarding vasospasm and incomplete embolization. We addressed this by introducing a sequenced protocol utilizing prophylactic intra-arterial nitroglycerin. This study aimed to characterize post-procedural pain trajectories, identify predictors of pain severity, and evaluate the safety of the regimen. METHODS: In this prospective single-arm study, 34 women with symptomatic uterine fibroids underwent UAE between April and August 2025. To prevent vasospasm, 100 µg of intra-arterial nitroglycerin was administered into each uterine artery before embolization. Embolization was then performed to near-stasis, after which 2 mL of 1% lidocaine (20 mg per uterine artery) diluted to 4 mL was infused intra-arterially. Pain intensity was recorded using the Visual Analog Scale (VAS) at baseline and at 1, 2, 3, 6, 12, and 24 h post-procedure. Associations between fibroid characteristics and pain were analyzed using correlation analysis. RESULTS: All procedures were technically successful without complications or vasospasm. The mean patient VAS score peaked at 3 h (6.24 ± 1.67) and gradually declined thereafter. The volume of the largest fibroid correlated positively with mean pain (ρ = 0.51 [95% CI: 0.10-0.77], p = 0.02) and with pain at 1 and 2 h (both p = 0.05). No significant associations were found between pain and uterine size, parity, or adenomyosis. The low-dose intra-arterial lidocaine regimen was well tolerated and did not affect embolization outcomes. CONCLUSION: The volume of the largest uterine fibroid was associated with greater post-UAE pain. Prophylactic intra-arterial nitroglycerin administered before embolization allowed subsequent intra-arterial lidocaine administration without observed vasospasm. Larger randomized trials are needed to further evaluate and optimize this analgesic approach.