There is no recommendation regarding the optimal prime solution for the cardiopulmonary bypass circuit in adult cardiac surgery. Despite the lack of scientific evidence, mannitol has frequently been added to the prime solution with intention to prevent acute kidney injury. The aim of this study was to investigate the impact of mannitol in cardiopulmonary bypass circuit prime in patients with preoperative renal dysfunction.

This prospective, randomized, double-blind study included 70 patients, who underwent coronary artery bypass grafting. One group received 1200 mL of a prime based on Ringer’s acetate (n = 35), and the other a prime consisting of 1000 mL Ringer’s acetate and 200 mL mannitol (n = 35). Primary endpoint were levels of Cystatin C, a renal function biomarker. Changes in renal-related parameters, electrolytes, osmolality and acid-base status were monitored.

The median cystatin C on day four in the mannitol group were 1.6 mg/L (IQR 1.4-2.0 mg/L) and 1,8 mg/L (IQR 1.5-2.1 mg/L) in the Ringer’s acetate group at the same time. Using mixed model analysis, no differences in cystatin C (p = 0.442), creatinine (p = 0.203), estimated glomerular filtration rate (p = 0.264) and urea (p = 0.141) could be detected between the groups. The mannitol group showed a more pronounced reduction in sodium levels after cardiopulmonary bypass circuit commencement compared to the Ringer’s acetate group p < 0.001.

In patients with preoperative renal dysfunction, the addition of mannitol in the prime solution did not show any renoprotective effect measured by cystatin C compared to a cardiopulmonary bypass circuit prime based on Ringer’s acetate.