The effect of mannitol on renal function following cardio-pulmonary bypass in patients with normal pre-operative creatinine

Mannitol is often added to the cardiopulmonary bypass pump prime to reduce the incidence of renal dysfunction, but studies so far have been inconclusive. Urinary excretion of microalbumin and retinol binding protein are more sensitive than routine biochemical tests of renal function after cardiac surgery. We performed a double-blind, randomised, controlled trial in cardiac surgical patients with pre-operative plasma creatinine < 130 μmol.l⁻¹. Twenty patients received 0.5 g.kg⁻¹ of mannitol in the pump prime, whereas 20 control patients received an equivalent volume of Hartmann's solution. Blood and urine samples were taken on the day before surgery and daily for 5 days postoperatively for measurement of plasma urea and creatinine, urinary creatinine, retinol binding protein and microalbumin. We found no differences between the mannitol and control patients for any measured variable, and conclude that mannitol has little impact on renal function in patients with normal pre-operative plasma creatinine concentrations.