Postoperative changes in serum creatinine. When do they occur and how much is important?

The objective of this study was to evaluate the use of the serum creatinine in following postoperative renal function. In this prospective study of 278 patients (mainly hypertensives and diabetics) undergoing noncardiac surgery, the serum creatinines were followed from the first through the sixth postoperative day. Creatinine clearances were evaluated before operation and on the fourth to fifth postoperative day. During the first six days after the operation, 23% (65 of 278 patients) had an increase of serum creatinine greater than or equal to 20%. Such increases were sustained for greater than or equal to 48 hours in 12% of the patients (32 of 278), and half of these patients had not returned to their initial level of renal function by the time of discharge. Patients who sustained such a deterioration were at risk for nonoliguric renal failure if they had a subsequent insult (i.e., hypotension, reoperation, angiography, aminoglycosides). Such increases occurred early in the postoperative period--on the first or second postoperative day. As judged by the creatinine clearances, postoperative increases of greater than or equal to 20% in the serum creatinine identified most patients whose clearance fell more than 50%, although the serum creatinine did not accurately reflect changes in creatinine clearance among those patients who had undergone an amputation. It is concluded that the serum creatinine is useful in monitoring postoperative renal function. Of those patients who had postoperative increases in serum creatinine sustained for greater than or equal to 48 hours, as many as one third had evidence of impairment in renal function at the time of discharge.