24 hours preceding randomization , there were no differences in mean urine output or total output ; 24 hours post-randomization , the control group had higher mean urine output ( 4.2 2.6 ml/kg per h vs. 2.8 2.0 ml/kg per h , p = 0.02 ) but lower total output ( 6.3 2.1 ml/kg per h vs. 4.7 2.7 ml/kg per h , p = 0.01 ) .