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. 2024 Jun 1;19(6):732-742.
doi: 10.2215/CJN.0000000000000435. Epub 2024 Feb 26.

Different Interdialytic Intervals and Cardiorespiratory Fitness in Patients Undergoing Hemodialysis

Eva Pella  1 , Aristi Boulmpou  2 , Afroditi Boutou  3 , Marieta P Theodorakopoulou  1 , Nasra Haddad  1 , Antonios Karpetas  4 , Panagiotis Giamalis  1 , Aikaterini Papagianni  1 , Christodoulos E Papadopoulos  2 , Vassilios Vassilikos  2 , Pantelis Sarafidis  1
Affiliations

Different Interdialytic Intervals and Cardiorespiratory Fitness in Patients Undergoing Hemodialysis

Eva Pella et al. Clin J Am Soc Nephrol. .

Abstract

Key Points:

  1. This is the first study exploring differences in cardiorespiratory fitness assessed with cardiopulmonary exercise testing between the 2-day and the 3-day interdialytic interval.

  2. The 3-day interdialytic interval was associated with further impaired cardiorespiratory fitness.

  3. This effect was predominantly driven by excess fluid accumulation during the extra interdialytic day.

Background: Long interdialytic interval in thrice-weekly hemodialysis is associated with excess cardiovascular and all-cause mortality risk. Impaired cardiorespiratory fitness is a strong predictor of mortality in hemodialysis. This study investigated differences in cardiorespiratory fitness assessed with cardiopulmonary exercise testing (CPET) between the end of the 2-day and the 3-day interdialytic interval.

Methods: A total of 28 hemodialysis patients, randomized in two different sequences of evaluation, underwent CPET and spirometry examination at the end of the 2-day and the 3-day intervals. The primary outcome was the difference in oxygen uptake at peak exercise (VO2peak [ml/kg per minute]) assessed with CPET. Volume status was assessed with interdialytic weight gain, lung ultrasound, bioimpedance spectroscopy, and inferior vena cava measurements. A total of 14 age-matched and sex-matched controls were also evaluated. Comparisons of changes in parameters of interest were performed with paired or independent t-tests or relevant nonparametric tests, as appropriate. Bivariate correlation analyses and generalized linear mixed models were used to examine associations between changes in CPET parameters and volume indices.

Results: Hemodialysis patients at the end of both 2-day and 3-day intervals presented lower values in all major CPET parameters than controls. VO2peak (ml/kg per minute) was significantly higher at the end of the 2-day than the 3-day interval (15.2±4.2 versus 13.6±2.8; P < 0.001); the results were similar for VO2peak (ml/min) (1188±257 versus 1074±224; P < 0.001) and VO2peak (% predicted) (58.9±9.2 versus 52.3±8.6; P < 0.001). Numerical but no statistically significant differences were detected in VO2 anaerobic threshold (ml/kg per minute) and VO2 anaerobic threshold (ml/min) between the two time points. Maximal work load (90.1±23.2 versus 79.3±25.1; P < 0.001), exercise duration, heart rate at peak exercise, and oxygen pulse also showed lower values at the end of the 3-day interval. Forced expiratory volume in 1-second levels were similar between the two evaluations. Generalized linear mixed model analysis, including interdialytic weight gain as random covariate, attenuated the observed differences in VO2peak (ml/kg per minute). Changes in bioimpedance spectroscopy–derived overhydration indexes were moderately correlated with changes of VO2peak (ml/kg per minute).

Conclusions: The 3-day interval was associated with further impairment of VO2 at peak exercise. This effect was predominantly driven by excess fluid accumulation during the extra interdialytic day.

Trial registration: ClinicalTrials.gov NCT05557929.

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Conflict of interest statement

A. Papagianni reports Honoraria: Baxter Hellas E.P.E., Genesis Pharma Hellas, and GlaxoSmithKline A.E.B.E. P. Sarafidis reports Consultancy: AstraZeneca, Bayer, Healthink, Innovis Pharma, Menarini, Primeview, and Recor Medical; Research Funding: AstraZeneca, Boehringer, Elpen Pharmaceuticals, and Servier; Honoraria: Astellas, AstraZeneca, Bayer, Boehringer Ingelheim, Genesis Pharma, Menarini, Peervoice, Sanofi, Springer, and Winmedica; and Advisory or Leadership Role: Council Member, European Renal Association; Editorial Board Member for American Journal of Nephrology, Hellenic Nephrology, Journal of Human Hypertension, and Nephrology Dialysis Transplantation. V. Vassilikos reports Research Funding: Bayer and Novo. All remaining authors have nothing to disclose.

Figures

None
Graphical abstract
Figure 1
Figure 1
Patient enrollment and flow chart.
Figure 2
Figure 2
CPET parameters at the end of the 2-day and the end of the 3-day interdialytic interval. (A) VO2peak (ml/kg per minute), (B) VO2peak (ml/min), (C) VO2peak (% predicted), (D) VO2 anaerobic threshold (ml/kg/min), (E) exercise time (min), and (F) maximum work load (W) are herein depicted. Data are presented as mean values±SD. CPET, cardiopulmonary exercise testing; VO2 anaerobic threshold, oxygen uptake at anaerobic threshold; VO2peak, oxygen uptake at peak exercise.
Figure 3
Figure 3
Graphical interpretation of a single patient's CPET evaluations at the end of the 2-day and the end of the 3-day interdialytic interval. Dots are representing VO2 measurements (averaged every 30 seconds) during the test. VO2 increases with increasing work load and at maximum exercise begin to plateau (blue box). VO2peak is defined as the highest VO2 achieved during the final 30-second averaging of peak exercise. Graphs constructed using data from the continuous responses during the CPET of a single study participant. VO2, oxygen uptake; VCO2, carbon dioxide consumption; VO2peak, oxygen uptake at peak exercise.
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