Relation of Interdialytic Water Retention with Apparent Bicarbonate Space, HCO3−, and pH in Hemodialyzed Uremic Patients

This study determines the relationship between interdialytic water retention (IWR) and acid–base homeostasis in uremic patients under regular hemodialysis (HD). To this aim, in 33 regular bicarbonate HD sessions of 11 uremic patients (three HD sessions of 1 week for each patient), blood samples were received from arterial line immediately pre- and post-HD anaerobically in heparinized syringes and the HCO3−, pH, and pco2 were determined. Also in the studied HD sessions, the IWR was estimated and the apparent bicarbonate space percentage (ABS%) pre- and post-HD was calculated by Fernandez et al. (Eq. ). The mean ± SD values pre-HD (ABS%=54.15 ± 1.49, HCO3−=18.54 ± 2.0 mmol/L, pH=7.32 ± 0.02, pco2=35.44 ± 3.10 mmHg) and post-HD (ABS%=49.88 ± 0.6, HCO3−=26.33 ± 1.6 mmol/L, pH=7.44 ± 0.02, pco2=37.69 ± 3.00 mmHg) show metabolic acidosis pre-HD and slight alkalosis post-HD. There was a significant positive correlation between IWR and ABS% pre-HD (r = 0.650, p < .0001) and post-HD (r = 0.655, p < .0001), but a s...