Hypoxia during maintenance hemodialysis; the critical role of pH

Scott McGuire, Nithya Krishnan, Abdul R Malik, Alex Waddell, Sophie L Russell, Francesca Denton, Stuart Ennis, Elizabeth Horton, Djordje Jakovljevic, Gordon McGregor

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Abstract

Background
The impact and management of sub-clinical hypoxia during hemodialysis is a significant medical challenge. As key determinants of O2 availability and delivery, proposed mechanisms contributing to hypoxia include ischemia, alkalemia and pulmonary leukocyte sequestration. However, no study has comprehensively investigated and compared these interrelated mechanisms throughout a typical hemodialysis treatment week. This study aimed to comprehensively assess the physiological mechanisms that contribute to hypoxia during hemodialysis.

Methods
In 76 patients, we measured arterial blood gases and pH at four time-points during hemodialysis (start, 15 min, 60 min, end) over the course of a standard treatment week. For the mid-week hemodialysis session, we additionally measured central hemodynamics (non-invasive cardiac output monitoring) and white blood cell count.

Results
Linear regression modelling identified changes in pH, but not central hemodynamics or white blood cell count, to be predictive of changes in PaO2 throughout hemodialysis (e.g. at 60 min, β standardised coefficient pH = 0.45, model R2 = 0.25, P < 0.001). Alkalemia, hypokalemia, decreased calcium, and increased hemoglobin-O2 affinity (leftward shift in the oxyhemoglobin dissociation curve) were evident at the end of hemodialysis. pH and hemoglobin-O2 affinity at the start of hemodialysis increased incrementally over the course of a standard treatment week.

Conclusion
These data highlight the important role of pH in regulating O2 availability and delivery during hemodialysis. Findings support routine pH monitoring and personalized dialysate bicarbonate prescription to mitigate the significant risk of alkalemia and sub-clinical hypoxia.
Original languageEnglish
Pages (from-to)(In-press)
JournalClinical Kidney Journal
Volume(In-press)
Early online date24 Aug 2022
DOIs
Publication statusE-pub ahead of print - 24 Aug 2022

Bibliographical note

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

Keywords

  • bicarbonate
  • cardiac output
  • hemodialysis, hypoxia
  • PaO2
  • pH
  • mean arterial pressure
  • white blood cell count

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