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

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). The authors sought to test the hypothesis that perioperative Cr 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 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 from period 0 to period 1 (∆Cr). Median Cr 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 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 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.