Title: A Comparison of Oral and Intravenous Sodium Bicarbonate on Urinary pH in Patients at Risk of Contrast-induced Nephropathy: A Pilot Study
Abstract: Aim: Intravenous sodium bicarbonate infusion has been shown to reduce the risk of contrast-induced nephropathy (CIN). We sought to determine whether oral sodium bicarbonate has a similar effect on urine pH to intravenous sodium bicarbonate in patients at risk of CIN. Methods: Cardiology and renal patients scheduled for a non-urgent contrast enhanced procedure and who were eligible for intravenous bicarbonate administration per Austin health guidelines to prevent CIN were invited to participate. Participants received intravenous bicarbonate (150mmole) at 3 mmol/kg/h one hour prior, then 1 mmol/kg/h during and after the procedure. Participants returned to the hospital three weeks post procedure for oral bicarbonate administration. Participants took 16× 840 mg bicarbonate capsules (160 mmol) over a seven-hour period with 1 L of water. Urine pH was measured before and after both intravenous and oral bicarbonate using a hand held pH meter. Results: Twenty-six patients were invited to participate. Only eight patients completed the study. Four males and four females with an mean age of 63 ± 10 years and a mean eGFR of 39 ± 13 mL/min/1.72 m2. Intravenous bicarbonate increased urine pH from 6.15 ± 0.75 to 6.81 ± 0.49 compared with 5.68 ± 0.41–6.55 ± 0.61 for oral bicarbonate (n = 8). The mean change in urine pH was 0.66 ± 0.38 with IV bicarbonate and 0.87 ± 0.74 for oral bicarbonate. The difference in change in urine pH between the two groups was not significant (Mann–Whitney U test, p = 0.83). Conclusion: These data suggest that oral sodium bicarbonate has a similar effect on urine pH to intravenous sodium bicarbonate when administered to patients at risk of CIN. A randomised controlled study is required to determine if oral sodium bicarbonate can reduce the risk of CIN.