Background: The recent introduction of normothermic cardiopulmonary bypass (CPB) perfusion has raised concerns regarding the associated risk of renal dysfunction through its potential to exacerbate the systemic inflammatory response and end-organ injury. This study was designed to investigate the influence of CPB perfusion temperature on renal function.
Methods: A prospective, randomized, controlled trial of CPB perfusion temperature (28 degrees C, 32 degrees C, and 37 degrees C) was performed in 30 patients undergoing routine coronary artery bypass grafting with normal preoperative renal function. Creatinine clearance was measured before induction of anesthesia, during CPB, and during every 12-hour period thereafter for 48 hours postoperatively. Glomerular and tubular function were assessed further by measurement of urinary creatinine, albumin, total protein, and retinol binding protein levels preoperatively, during CPB, and on days 1 and 3 postoperatively.
Results: Creatinine clearance increased on CPB by 51% (28 degrees C), 185% (32 degrees C), and 112% (37 degrees C) (all p < 0.01 versus preoperative values) and returned to preoperative values by 24 hours postoperatively in all three groups. Urinary albumin/creatinine ratios rose significantly from a mean of 0.4 +/- 0.1 (standard deviation) to 10 +/- 12.5 (28 degrees C), from 0.55 +/- 0.3 to 5.2 +/- 4.9 (32 degrees C), and from 0.96 +/- 0.8 to 7.8 +/- 7.0 (37 degrees C) during CPB (all p < 0.001) but decreased gradually thereafter. Also, urinary total protein/creatinine ratios rose significantly from a mean of 0.009 +/- 0.007 to 0.034 +/- 0.02 (28 degrees C), from 0.01 +/- 0.006 to 0.026 +/- 0.01 (32 degrees C), and from 0.011 +/- 0.008 to 0.033 +/- 0.02 (37 degrees C) during CPB (all p < 0.005); however, there was a further increase by 24 hours, and ratios decreased gradually thereafter. Similarly, urinary retinol binding protein/creatinine ratios rose significantly in all three groups during CPB (all p < 0.0001) and increased further by 24 hours. There was no statistically significant difference between the renal markers in the three temperature groups in any of the observations.
Conclusion: These data suggest that cardiopulmonary bypass perfusion temperature does not influence renal function in patients undergoing coronary artery bypass grafting.