Off-pump ( n = @ ) vs on-pump ( n = @ ) CABG surgery reduced the risk of acute kidney injury ( @ % vs @ % , respectively ; relative risk , @ -LSB- @ % CI , @-@ @ -RSB- , P = @ ) ; however , there was no significant difference between the @ groups in the loss of kidney function at @ year ( @ % vs @ % , respectively ; relative risk , @ -LSB- @ % CI , @-@ @ -RSB- , P = @ ) .