[Long-term effects of acid-base equilibrium of bicarbonate dialysis]

The acid-base effects of long-term bicarbonate hemodialysis (BDH) were evaluated in five patients previously stabilized on acetate hemodialysis (AHD). Following 12 weeks on BHD, the patients were studied an additional 6 weeks on return to AHD. Hydrogen ion generation rate (calculated from urea generation rate), and pre- and post-dialysis pH, and blood gases were measured every 2 weeks. The results of the study show that, while pre-dialysis blood bicarbonate and pH did not change significantly during the stabilization period, during BHD, and following return to AHD, hydrogen ion generation rate increased substantially on the average during BHD (+6 mmol/24 h) and fell precipitously on return to AHD (-9 mmol/24 h). Pre- to post-dialysis changes in blood bicarbonate, and pH were significantly greater during BDH than during AHD. We conclude that the increase in hydrogen ion generation rate during BDH indicates that the patients increased their intake of fixed acid. Because of extreme increases observed intra-dialytically in blood bicarbonate and pH during BHD, the ability to vary bicarbonate delivery to the patient may have to be an integral part of equipment used in BDH.