Profiled delivery of bicarbonate during weekly cycle of hemodialysis

Background

Delivery of bicarbonate during hemodialysis (HD) is aimed at correcting metabolic acidosis in end-stage renal disease patients. We tested modified prescriptions of bicarbonate concentration in dialysis fluid (C_D,bic), aimed to achieve an optimal pre-dialytic bicarbonate plasma concentration (C_P,bic).

Methods

We used a mathematical model to prescribe individualized HD treatments consisting of 1) adjustment of C_D,bic to get the pre-dialytic C_P,bic in a prescribed range, 2) increase of bicarbonate load before the long interdialytic break, and 3) a single step of increase in C_D,bic after two hours. The outcomes were tested in 24 stable HD patients, monitored during a week of standard HD (Test Week) and a week of modified treatment (Intervention Week).

Results

The response to the model-based prescription was different whether the average C_D,bic during the Intervention Week was higher or lower than the constant value used for the Test Week. For patients with lower average C_D,bic during the Intervention Week, a significant fraction achieved the target (22 ≤ C_P,bic ≤ 24 mEq/L). In the group with higher average C_D,bic, the interventions were effective only in increasing post-dialytic C_P,bic. The simple step-increase profile was effective in linearizing the intradialytic increase in bicarbonate and decreasing the amount of time spent by patients at high plasma C_P,bic.

Conclusions

The interventions were effective mostly in patients who needed to lower their pre-dialytic CP_,bic. The resistance of the system to increasing pre-dialytic C_P,bic in other patients might be caused by modifications of breathing or in hydrogen generation that were not accounted for by our model.