Renal microvascular oxygen tension during hyperoxia and acute hemodilution assessed by phosphorescence quenching and excitation with blue and red light

Translated title of the contribution: Renal microvascular oxygen tension during hyperoxia and acute hemodilution assessed by phosphorescence quenching and excitation with blue and red light

Kyle Chin, Melina P. Cazorla-Bak, Elaine Liu, Linda Nghiem, Yanling Zhang, Julie Yu, David F. Wilson, Sergei A. Vinogradov, Richard E. Gilbert, Kim A. Connelly, Roger G. Evans, Andrew J. Baker, C. David Mazer, Gregory M.T. Hare

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Purpose: The kidney plays a central physiologic role as an oxygen sensor. Nevertheless, the direct mechanism by which this occurs is incompletely understood. We measured renal microvascular partial pressure of oxygen (PkO2) to determine the impact of clinically relevant conditions that acutely change PkO2 including hyperoxia and hemodilution. Methods: We utilized two-wavelength excitation (red and blue spectrum) of the intravascular phosphorescent oxygen sensitive probe Oxyphor PdG4 to measure renal tissue PO2 in anesthetized rats (2% isoflurane, n = 6) under two conditions of altered arterial blood oxygen content (CaO2): 1) hyperoxia (fractional inspired oxygen 21%, 30%, and 50%) and 2) acute hemodilutional anemia (baseline, 25% and 50% acute hemodilution). The mean arterial blood pressure (MAP), rectal temperature, arterial blood gases (ABGs), and chemistry (radiometer) were measured under each condition. Blue and red light enabled measurement of PkO2 in the superficial renal cortex and deeper cortical and medullary tissue, respectively. Results: PkO2 was higher in the superficial renal cortex (~ 60 mmHg, blue light) relative to the deeper renal cortex and outer medulla (~ 45 mmHg, red light). Hyperoxia resulted in a proportional increase in PkO2 values while hemodilution decreased microvascular PkO2 in a linear manner in both superficial and deeper regions of the kidney. In both cases (blue and red light), PkO2 correlated with CaO2 but not with MAP. Conclusion: The observed linear relationship between CaO2 and PkO2 shows the biological function of the kidney as a quantitative sensor of anemic hypoxia and hyperoxia. A better understanding of the impact of changes in PkO2 may inform clinical practices to improve renal oxygen delivery and prevent acute kidney injury.

Translated title of the contributionRenal microvascular oxygen tension during hyperoxia and acute hemodilution assessed by phosphorescence quenching and excitation with blue and red light
Original languageFrench
Number of pages12
JournalCanadian Journal of Anaesthesia-Journal Canadien D Anesthesie
DOIs
Publication statusAccepted/In press - 10 Nov 2020

Keywords

  • anemia
  • CaO
  • microvascular PO
  • renal oxygen sensing

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