A method for the detection of an early biomarker for assessing a change in renal status in a mammalian subject following a renal event. The method typically includes the steps of (a) providing a body fluid sample obtained from a mammalian subject; (b) analyzing the molecular weight of the proteins in the sample using proteome analysis; and (c) identifying the presence of a protein in the sample selected from the group consisting of a 6.4 kDa protein, a 28.5 kDa protein, a 33 kDa protein, a 44 kDa protein, a 67 kDa protein, and combinations thereof. The presence of one of these proteins can serve as an early biomarker for assessing a change in renal status. The levels of these proteins can be compared to predetermined levels, and thus provide a determination of the subject's renal status. The invention also includes a method of assessing the administration of aprotinin during cardio-pulmonary bypass surgery and provides for methods where the level of the 6.4 kDa biomarker in the subject's urine directs a caregiver's therapeutic decision regarding the intra-operative administration of aprotinin.