In the 90 day observation period , 87 patients ( 22 % ) assigned to HES received renal replacement therapy vs. 65 patients ( 16 % ) assigned to Ringer 's acetate ( relative risk 1.35 , p = 0.04 ) , and 38 patients ( 10 % ) vs. 25 patients ( 6 % ) had severe bleeding ( relative risk 1.52 , p = 0.09 ) .