In the buffered crystalloid group , 102 of 1067 patients ( 9.6 % ) developed AKI within 90 days after enrollment compared with 94 of 1025 patients ( 9.2 % ) in the saline group ( absolute difference , 0.4 % [ 95 % CI , -2.1 % to 2.9 % ] ; relative risk [ RR ] , 1.04 [ 95 % CI , 0.80 to 1.36 ] ; P = .77 ) .