Is an Acute Perioperative Increase in Creatinine Production Rate a Potential Mechanism for an Early Creatinine-Based Signal of Renal Injury After Cardiac Surgery?

Abstract

Objectives: Previous studies report a creatinine-based signal of injury within hours after cardiac surgery, which is sooner than expected based on creatinine kinetic modelling. A plausible mechanism for such an early signal has not been established, but might be explained by an acute perioperative increase in creatinine production rate (Cr_prod-rate). The authors sought to test the hypothesis that perioperative Cr_prod-rate increases from baseline in patients undergoing cardiac surgery.

Design: Prospective cohort study.

Setting: Academic medical center.

Participants: Fifty adult male patients undergoing cardiac surgery.

Interventions: None.

Measurements and main results: Based on the principle of conservation of mass, precisely timed serial measurements of patient weight, plasma and urine creatinine concentration, and urine volume were used to calculate Cr_prod-rate over 3 consecutive periods: a baseline period immediately before surgery (period 0), the 24-hour period starting from induction of anesthesia (period 1), and again from 24 to 48 hours after induction of anesthesia (period 2). The primary outcome was change in Cr_prod-rate from period 0 to period 1 (∆Cr_prod-rate0-1). Median Cr_prod-rate0 was 5.4 (interquartile range [IQR], 4.7-5.7) μmol/kg/h at baseline and increased to 6.1 (IQR, 5.6-6.5) μmol/kg/h during period 1, a median increase of 14% (95% CI, 8%-27%; p = 0.002). ∆Cr_prod-rate0-1 ranged from -58% to +129%, with an increase above baseline in 25 patients (76%) and an increase by ≥30% above baseline in 10 patients (30%).

Conclusions: Perioperative Cr_prod-rate increased from baseline in patients undergoing cardiac surgery. This may represent a mechanism for an earlier creatinine-based signal of renal injury than previously thought possible.

Keywords: Acute kidney injury; Cardiac surgery; Creatinine.