Anesthesiology 2017; 126:205-13
Background: Acute kidney injury is a common complication after cardiac surgery with cardiopulmonary bypass. Theauthors evaluated the effects of normothermic cardiopulmonary bypass on renal blood flow, glomerular filtration rate, renal
oxygen consumption, and renal oxygen supply/demand relationship, i.e., renal oxygenation (primary outcome) in patients
undergoing cardiac surgery.
Methods: Eighteen patients with a normal preoperative serum creatinine undergoing cardiac surgery procedures with normothermic
cardiopulmonary bypass (2.5 l . min−1 . m−2) were included after informed consent. Systemic and renal hemodynamic
variables were measured by pulmonary artery and renal vein catheters before, during, and after cardiopulmonary bypass. Arterial
and renal vein blood samples were taken for measurements of renal oxygen delivery and consumption. Renal oxygenation
was estimated from the renal oxygen extraction. Urinary N-acetyl-β-d-glucosaminidase was measured before, during, and after
Results: Cardiopulmonary bypass induced a renal vasoconstriction and redistribution of blood flow away from the kidneys,
which in combination with hemodilution decreased renal oxygen delivery by 20%, while glomerular filtration rate
and renal oxygen consumption were unchanged. Thus, renal oxygen extraction increased by 39 to 45%, indicating a renal
oxygen supply/demand mismatch during cardiopulmonary bypass. After weaning from cardiopulmonary bypass, renal
oxygenation was further impaired due to hemodilution and an increase in renal oxygen consumption, accompanied by a
seven-fold increase in the urinary N-acetyl-β-d-glucosaminidase/creatinine ratio.
Conclusions: Cardiopulmonary bypass impairs renal oxygenation due to renal vasoconstriction and hemodilution during
and after cardiopulmonary bypass, accompanied by increased release of a tubular injury marker.