Background: The effect of urinary alkalinization in cardiac surgery patients at risk of acute kidney injury (AKI) is controversial and trial findings conflicting. Accordingly, the authors performed a prospectively planned individual patient data meta-analysis of the double-blind randomized trials in this field.
Methods: The authors studied 877 patients from three double-blind, randomized controlled trials enrolled to receive either 24 h of intravenous infusion of sodium bicarbonate or sodium chloride. The primary outcome measure was a postoperative increase in serum creatinine concentration of greater than 25% or 0.5 mg/dl (> 44 μM/L) within the first five postoperative days. Secondary outcomes included the raw change in serum creatinine, greater than 50% and greater than 100% rises in serum creatinine, developing AKI (Acute Kidney Injury Network criteria), initiation of renal replacement therapy, morbidity, and mortality.
Results: Patients were similar in demographics, comorbidities, and cardiac procedures. Sodium bicarbonate increased plasma bicarbonate (P < 0.001) and urine pH (P < 0.001). There were no differences in the development of the primary outcome (Bicarbonate 45% [39-51%] vs. Saline 42% [36-48%], P = 0.29). This result remained unchanged when controlling for study and covariates (odds ratio [OR], 99% confidence interval [CI]: Bicarbonate vs. Control, 1.11 [0.77-1.60], P = 0.45). There was, however, a significant study-adjusted benefit in elective coronary artery bypass surgery patients in terms of renal replacement therapy (Bicarbonate vs. Control, OR: 0.38 [99% CI: 0.25-0.58], P < 0.0001) and the development of an Acute Kidney Injury Network grade = 3 (Bicarbonate vs. Control, OR: 0.45 [99% CI: 0.43-0.48], P < 0.0001).
Conclusions: Urinary alkalinization using sodium bicarbonate infusion is not associated with an overall lower incidence of AKI; however, it reduces severe AKI and need for renal replacement therapy in elective coronary artery bypass patients.