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Serum markers are not reliable measures of renal function in conjunction with cardiopulmonary bypass

Staffan Svenmarker1, Sören Häggmark, Anders Holmgren

  • 1Department of Surgical and Perioperative Science, Heart Centre, Umeå University Hospital, SE 901 85 Umeå, Sweden. staffan.svenmarker@vll.se

Interactive Cardiovascular and Thoracic Surgery
|February 8, 2011
PubMed

Insights

Cardiopulmonary bypass (CPB) during cardiac surgery causes hemodilution, significantly affecting estimated glomerular filtration rate (GFR) calculations. This can lead to an overestimation of actual kidney function in patients.

Area of Science:

  • Nephrology
  • Cardiovascular Surgery
  • Anesthesiology

Background:

  • Estimating glomerular filtration rate (GFR) is crucial for assessing kidney function.
  • Cardiopulmonary bypass (CPB) is frequently used during cardiac surgery.
  • Hemodilution is an inherent consequence of CPB, potentially altering serum marker concentrations.

Purpose of the Study:

  • To investigate the impact of hemodilution during CPB on GFR estimations.
  • To compare the effects of hemodilution on GFR calculated using cystatin C and creatinine.
  • To evaluate the influence of CPB-induced hemodilution on renal function assessment.

Main Methods:

  • Prospective study of 98 patients undergoing coronary artery bypass grafting with CPB.
  • Serum cystatin C and creatinine levels measured pre-surgery, post-CPB, and post-operative day 1.
  • GFR estimated using standard equations (MDRD, Cockcroft-Gault) based on serum markers.

Main Results:

  • Hemodilution significantly increased GFR estimates: cystatin C-based GFR by 50.5 ml/min, creatinine-based GFR by ~22 ml/min (P=0.000).
  • Similar overestimations of renal function were observed postoperatively.
  • CPB-induced hemodilution demonstrably alters serum marker concentrations used for GFR calculation.

Conclusions:

  • Hemodilution during CPB can lead to significant overestimation of GFR.
  • Relying solely on serum markers for GFR estimation post-CPB may inaccurately reflect renal function.
  • Clinical interpretation of GFR in cardiac surgery patients requires consideration of hemodilution effects.

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