Kidney Week

Abstract: TH-PO0138

Effects of Amino Acid Loading on Recruitment of Renal Functional Reserve After Cardiopulmonary Bypass

Session Information

• AKI: Mechanisms - 1
  November 06, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Furukawa, Taku, The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia

Taku Furukawa, MD

• May, Clive N., The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia

Clive N. May, PhD

• Jufar, Alemayehu H., The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia

Alemayehu H. Jufar, PhD

• Trask-Marino, Anton Lewis, The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia

Anton Lewis Trask-Marino

• Miles, Lachlan F., The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia

Lachlan F. Miles, MBBS, PhD

• Lankadeva, Yugeesh Ryan, The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia

Yugeesh Ryan Lankadeva, PhD

Background

Cardiopulmonary bypass (CPB) may decrease the renal functional reserve (RFR). However, the temporal changes in RFR after during the recovery period after CPB remains unknown. We assessed RFR before and then weekly after CPB over four weeks following CPB in non-anesthetized sheep.

Methods

In 10 Merino ewes, amino acids were infused before CPB and weekly for four weeks post-CPB to assess RFR. At each assessment, we measured renal blood flow (RBF), renal oxygen delivery (RDO₂), creatinine clearance and medullary and cortical oxygenation. Histological assessment was performed at 4 weeks.

Results

Before CPB, amino acid infusion increased RBF from (mean ± SD) 6.60 ± 1.64 to 8.56 ± 1.80 mL/kg/min, and RDO₂ from 0.80 ± 0.28 to 1.12 ± 0.37 mL O₂/kg/min. These renal macro-circulatory responses remained consistent across all weekly assessments after CPB. Amino acid infusion also increased creatinine clearance (from 62.5 ± 15.0 to 110 ± 30.6 mL/min pre-CPB) throughout the study period. RFR remained unchanged over time (P = 0.53). However, compared with pre-CPB values, medullary (33.9 ± 9.0 pre-CPB to 15.1 ± 13.2 mmHg at 4 weeks, P = 0.0068) and cortical tissue PO₂ (46.0 ± 14.2 to 17.2 ± 6.5 mmHg, P = 0.0029) decreased over time. Furthermore, the response of the medullary (but not cortical) PO₂ to amino acid infusion changed over time (P = 0.0064). While medullary PO₂ did not change in response to amino acid infusion pre-CPB and at one week after CPB, it appeared to fall from two weeks thereafter (P = 0.039 and 0.091 at weeks 2 and 3, respectively). Despite preserved RFR, sheep exposed to CPB showed greater peritubular inflammation, interstitial fibrosis and tubular casts compared with healthy controls (P = 0.007, 0.021, 0.007, respectively).

Conclusion

In this large mammalian model of CPB, weekly amino acid administration consistently recruited RFR over four weeks, despite the presence of histological injury. However, it was associated with the development of renal medullary hypoxia after two weeks. These findings highlight the complexity of the pathophysiological response of the kidney to CPB.

Funding

• Government Support – Non-U.S.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025vm0x3fcq