Early adjunctive local block therapy improves pain and limb swelling after Gloydius envenomation: a propensity score–adjusted retrospective cohort study in the emergency department

BACKGROUND: Snakebite envenomation remains a major neglected tropical disease worldwide and frequently results in substantial local tissue injury despite timely antivenom therapy. Effective adjunctive strategies for early local symptom control are still limited. We aimed to evaluate whether early local block therapy (LBT) is associated with improved pain and limb swelling outcomes in patients with Gloydius envenomation. METHODS: We conducted a single-center retrospective cohort study including 203 adult patients with confirmed Gloydius envenomation between 2019 and 2024. Patients were categorized according to receipt of LBT (perilesional lidocaine, dexamethasone, and α-chymotrypsin) in addition to standard care. Primary outcomes were reduction in limb swelling (change in limb circumference from admission to Day 3) and pain relief (change in VAS score within 48 h). Secondary outcome was length of hospital stay (LOS). Multivariable linear regression and propensity score-based analyses were performed to adjust for potential confounders, including baseline wound infection. RESULTS: Baseline wound infection was more frequent in the LBT group than in controls (41.3% vs. 25.2%, P = 0.015). After full adjustment, LBT remained independently associated with greater limb swelling reduction (adjusted β = 2.31 cm; 95% CI 2.08-2.54; P < 0.001) and greater pain relief (adjusted β = 2.13 points; 95% CI 1.83-2.43; P < 0.001). Findings were consistent across propensity score-matched and weighted analyses. LBT was not associated with prolonged hospitalization (adjusted β = -0.98 days; P = 0.066). CONCLUSIONS: In this real-world cohort, early adjunctive LBT was associated with clinically meaningful improvement in local symptoms without evidence of increased hospital stay. These findings support LBT as a potential adjunctive strategy for hemotoxic snakebite and warrant prospective validation in multicenter prospective studies.