BACKGROUND: Acute kidney injury (AKI) is a frequent complication following cardiac surgery involving cardiopulmonary bypass (CPB). This is partly attributable to crystalloid-based priming solutions causing both hemolysis and loss of oncotic pressure with tissue edema. While colloids like albumin and starches have not shown clear benefits, pilot studies using dextran-based priming reported improved oncotic pressure, reduced hemolysis, and lower levels of a renal injury marker, suggesting potential renal protective effects.

OBJECTIVE: We hypothesized that a dextran-based priming solution can reduce the incidence of postoperative AKI in high-risk patients undergoing cardiac surgery with CPB.

METHODS: In this randomized, controlled, double-blinded, multicenter trial, adult patients with a calculated postoperative AKI risk of ≥ 50% were assigned to receive either a dextran or a crystalloid-based CPB priming solution. The primary outcome was the incidence of AKI within 96 h postoperatively. Secondary outcomes included perioperative hemolysis, net fluid balance, and the need for postoperative renal replacement therapy.

RESULTS: The trial was terminated early due to slow enrolment, with 101 of the planned 366 patients recruited. A total of 92 patients were included in the final analysis (43 in the dextran group, 49 in the control group). Postoperative AKI occurred in 81% and 53% of patients in the dextran and control groups, respectively (risk ratio 1.53, 95% confidence interval 1.15-2.06, p = 0.004). The dextran group demonstrated lower intraoperative hemolysis and a more favorable net fluid balance. Postoperative renal replacement therapy was required in 7% of the dextran group and 4% of the control group (p = 0.66). No significant differences in adverse events were observed between the groups.

CONCLUSION: In high-risk patients undergoing cardiac surgery with CPB, the use of a dextran-based priming solution was associated with a significantly increased risk of postoperative AKI.

EDITORIAL COMMENT: This randomized multicenter trial compared dextran to a crystalloid-based priming solution during cardiopulmonary bypass in participants with elevated risk of acute kidney injury. While the trial had to be terminated due to slow enrolment after about a third of planned cases were included, acute kidney injury was significantly more common in the dextran group, contrary to the primary hypothesis of the study. The study highlights the complexity and logistical challenges of conducting randomized treatment protocols for cardiopulmonary bypass, but at the same time highlights the importance of conducting such studies.

TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04293744.