We read with interest the JASN study by Kojima et al.1 concerning the acute effects of intradialytic exercise on cerebral oxygenation (rSO2) in hemodialysis patients. The authors commendably explore this critical area, highlighting a potential nonpharmacologic strategy to mitigate hemodialysis-induced cerebral hypoperfusion. Although the authors acknowledge several limitations, we wish to offer complementary perspectives on aspects that could influence the interpretation and future application of these findings.
The influence of anemia, prevalent in the study cohort (mean hemoglobin 10.1±2.2 g/dl), on rSO2 responses warrants deeper consideration. Anemia significantly affects baseline rSO2 and oxygen delivery capacity, particularly during exercise.2 Exercise in anemic individuals, especially under the physiologic stress of hemodialysis, might yield different rSO2 dynamics compared with those with better-managed anemia. It remains unclear how individual anemia levels might have modulated the approximately 1.3% rSO2 increase observed. Future work could benefit from stratifying results or adjusting for hemoglobin levels to clarify this crucial interaction.
In addition, while near-infrared spectroscopy is a valuable noninvasive tool, its application during exercise within hemodialysis presents unique challenges, potentially affecting signal interpretation beyond scalp/skin perfusion correction. Exercise-induced increases in skin blood flow, coupled with hemodialysis-related vascular and fluid shifts, might complicate near-infrared spectroscopy signal deconvolution, even with multidistance probes.3 Furthermore, translating exercise intensity based on heart rate targets derived from upright cardiopulmonary exercise testing on a nondialysis day to a supine/head-up intradialytic setting involves assumptions. Differences in posture, acute fluid status, and autonomic tone between these settings can alter cardiovascular responses, potentially affecting whether the intended physiologic exercise intensity was uniformly achieved across patients.
These considerations are offered to complement the authors' discussion and encourage further refinement in this promising research field. Understanding these nuances will be vital for optimizing intradialytic exercise prescriptions to protect brain health in hemodialysis patients effectively.
Footnotes
Y.W., X.X., and W.Y. contributed equally to this work.
See original article, “Acute Effect of Moderate-Intensity Interval Intradialytic Exercise on Cerebral Oxygenation in Hemodialysis Patients: A Randomized Crossover Trial,” in Vol. 36, Iss. 9, pages 1811–1822.
Disclosures
Disclosure forms, as provided by each author, are available with the online version of the article at http://links.lww.com/JSN/F295.
Author Contributions
Supervision: Qingyun Lv.
Writing – original draft: Yuchang Wang, Xinle Xie, Wu Yu.
Writing – review & editing: Yuchang Wang, Xinle Xie, Wu Yu.
Funding
None.
References
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