Cardiovascular implications of osmotic changes during hemodialysis: a potential risk factor

End-stage renal disease (ESRD) patients undergoing hemodialysis (HD) face a significantly higher risk of cardiovascular-related mortality compared to the general population. Osmotic stress, defined as the strain caused by rapid shifts in plasma solute concentration, occurs during HD and places additional burden on the cardiovascular system. Our study aimed to assess the effect of this HD-induced osmotic stress on cardiovascular parameters. A total of 46 ESRD patients treated with HD were included in the study. For each patient, plasma osmolality, blood pressure, digital electrocardiography, and subendocardial viability ratio (SEVR) were measured before and after a single HD session. Plasma osmolality decreased by 18.59 mOsm/kg (5.8%) after a single HD session (p < 0.0001), reflecting HD-related osmotic stress. A prolongation of the corrected QT (QTc) interval by 8.0 ms (p = 0.0001) and an improvement in SEVR by 14.5% (p = 0.0004) were also observed. Changes in plasma osmolality correlated with alterations in QTc interval (r = 0.434, p = 0.005), urea (r = 0.461, p = 0.002), and SEVR (r = − 0.439, p = 0.004), among others. Multiple regression analysis identified osmolality change as an independent predictor of SEVR and QTc interval changes. Interestingly, changes in urea were not significant, possibly due to urea rebound or other osmotic factors. Our study revealed that changes in plasma osmolality are reliable predictors of the QTc interval and SEVR. Interestingly, changes in urea were not significant, possibly due to the phenomenon of "urea rebound" or the influence of other osmotic factors. Hemodialysis-related osmotic changes appear to affect cardiovascular parameters, potentially predisposing patients to cardiac events.