Response to Acid Loading in Patients on Hemodialysis and Continuous Ambulatory Peritoneal Dialysis

Responses to a standard acid load (Ammonium Chloride 1.87 mM/ Kgm) were studied in 9 patients on hemodialysis (HD) and 16 on CAPD. There was a significant increase in H+ concentration (maximum 8.1 ± 0.6 for HD; 7.7 ± 0.8 for CAPD) and a decrease in bicarbonate levels (maximum 4.4 ± 0.4 for HD; 4.0 ± 0.3 for CAPD). PCO2 did not change significantly. CAPD patients tolerated acid loading slightly better than HD patients studied the day after regular hemodialysis treatment. The brief duration of the experiments did not allow us to study differences in recovery rate between HD and CAPD patients. Continuous Ambulatory Peritoneal Dialysis (CAPD) has emerged as an attractive alternative to hemodialysis for the management of end stage renal disease. In our institution, serum total CO2 levels are significantly higher in CAPD patients (mean 22) compared to predialysis levels in hemodialysis patients (mean 17, unpublished observations). Whether this is a function of the timing of blood sampling (i.e. predialysis vs steady state level) or represents better repletion of body buffers in CAPD patients is unknown. If higher levels do indeed represent better repletion of body buffer stores, CAPD patients should tolerate an acid challenge better than the hemodialysis patients. Responses to a standard acid loading (I) were observed to test this hypothesis.