Supplementary Material for: Peri-procedural Oral Hydration Patterns and Early Renal Function after Coronary Angiography and Intervention: A Prospective Real-world Cohort Study

Introduction: Guidelines recommend oral hydration to prevent contrast-associated acute kidney injury (CA-AKI) after coronary angiography or intervention, but quantitative protocols are lacking, and practice varies. Shorter hospital stays limit opportunities for post-procedure creatinine monitoring, and real-world oral hydration patterns and their early renal effects remain poorly described. This study aimed to characterize peri-procedural weight-adjusted oral hydration (OH) trajectories and to assess whether trajectory membership was associated with a change in serum creatinine within 24 hours.

Methods: This single-center prospective cohort study enrolled 192 inpatients undergoing coronary angiography or intervention between September 2024 and June 2025. We recorded weight-adjusted oral intake in four windows: pre-12 hours, post-0–6 hours, 6–12 hours, and 12–24 hours. We computed partial-overlap dynamic time warping distances and clustered trajectories using partitioning around medoids. Group comparisons used nonparametric tests. The primary outcome was percent change in serum creatinine, and dose-response was assessed with generalized additive models (GAMs) adjusted for baseline creatinine, estimated glomerular filtration rate, comorbidities, procedural indication, contrast volume, and intravenous hydration.

Results: After excluding 18 patients for missing peri-procedural oral intake or post-procedure creatinine, 174 patients were analyzed (mean age 63.3 ± 11.4 years; 71.8% male). Median weight-adjusted cumulative oral intake was 10.9, 18.6, 23.9, and 33.3 mL/kg for the pre-12 h, post-0–6 h, 0–12 h, and 0–24 h windows. Time-series clustering produced two stable groups (Low-OH n = 85, High-OH n = 89; average silhouette = 0.393; bootstrap ARI = 0.845). The largest between-group difference occurred in the 0–6 h window (median 4.12 vs 2.00 mL/kg/h, p < 0.001). No patient met CA-AKI criteria. In adjusted GAMs, the 0–6 h oral-hydration rate was not a significant smooth term (edf = 0.16, p = 0.21), and cluster membership was not associated with creatinine change. However, the High-OH cluster had substantially greater 6-hour urine output and larger positive fluid balance (p < 0.001) while serum potassium was similar between clusters.

Conclusion: Peri-procedural oral hydration was generally ample and formed two reproducible patterns. Concentrating oral intake in the first 6 hours increased early urine output and positive fluid balance but did not show a significant dose-response association with early serum creatinine change. This null result should be interpreted cautiously because the cohort was generally low-risk, follow-up was short, and the study had limited power. Future studies should validate whether early concentrated oral hydration protects renal function using earlier sensitive biomarkers and by targeting high-risk patients.