P0012
SHOULD WE DEFINE A NEW STANDARD PRESCRIPTION OF BICARBONATE (HCO3-) IN HEMODIALYSIS (HD)?

One of the aims of the regular, intermittent HD therapy prescribed for patients with end-stage chronic kidney disease, is correction of metabolic acidosis by addition of HCO_3- to dialysate fluid. The KDOQI guidelines therapeutic goal is to maintain pre-dialysis HCO_3-≥22mmol/L.

The aim of the study was to evaluate an individualized HCO_3-hemodialysis prescription as a preventing factor of metabolic changes in a HD facility and define a new standard HCO_3-prescription.

36-month prospective study of patients on online high-flux hemodiafiltration. Every 3 months (13 time points) HCO_3-, Calcium (Ca²⁺), Phosphorus (P⁺), intact Parathyroid hormone (iPTH) and protein C reactive (PCR) blood levels were analyzed. HCO_3-prescription was changed using the following rules:

• HCO_3->30mmol/L: reduce 4mmol/L HCO_3-;

• HCO_3-≥25mmol/L: reduce 2mmol/L HCO_3-;

• 20mmol/L<HCO_3-<25mmol/L: no change;

• HCO_3-≤20mmol/L: increase 2mmol/L HCO_3-;

• HCO_3-<18mmol/L: increase 4mmol/L HCO_3-.

The data collected comprised demographic information, renal disease etiology, comorbidities, HD treatment information and lab results.

Categorical variables are presented as frequencies and percentages, continuous variables as means and standard deviations, or medians and interquartile ranges (IQR) for variables with skewed distributions. A p-value<0.05 was considered statistically significant. Statistical analysis was performed using SPSS version 23 for Mac OS X.

From the 50 patients that were evaluated at Time point 0, only 24 patients completed the follow-up period. Sixteen (66.7%) were males, 54.2% (n=13) diabetic and 58.3% (n=14) hypertensives and the median age was 76 years (IQR 13). At baseline (time point 0), median pH was 7.4 (IQR 0.09) and serum HCO_3-26.5 mmol/L (IQR 2.32). At time point 12, pH was 7.35 (IQR 0.12) and serum HCO_3-23.25mmol/L (IQR 1.93).

A repeated measures ANOVA determined that prescribed HCO_3- differed with statistical significance during time (F(2.787,83.308)=39.055, p=0.001), and the post Hoc tests confirmed those assumptions between time point 1 and all the others time points, as an example the mean difference between initial prescribed HCO_3-and time point 12 was 5.39mmol/L (p=0.001).

Wilcoxon Sign-Rank Tests determined that throughout the analyzed period the serum HCO_3- approached the reference serum HCO_3- (23mmol/L) that we have defined as ideal (at time point 0, median=26.5mmol/L, Z=4.144, p=0-001; at time point 12, median 23.25mmol/L, Z=1.243, p=0.214).

On the other hand, a one sample T-Test determined that the HCO_3- prescription differed more in each time point from the 32mmol/L defined as standard (at time point 12, t=-2.798, p=0.01) and approached a new suggested value of 26mmol/L. However, at time point 8, 62.5% (n=15) patients had a HCO_3-prescription of 28mmol/L, (t(23)=0.001,p=1) and at that time we had hypothesized that that a prescription of 28 mmol/L should be the new standard.

Gender, Diabetes Mellitus, Hypertension, and renal disease etiology did not influence the HCO_3- prescription neither serum HCO_3-.

HCO_3-prescription and serum HCO_3- were not influenced by comorbidities like DM and Hypertension.

Our findings suggest that the standard HCO_3- prescription of 32mmol/L should be rethought, as an individualized HCO_3- prescription could be beneficial for the patient. At this time, we suggest that a prescription of 26 mmol/L should be the new standard. However, the limitations of our findings include the small sample size, so further studies with larger samples should be attempted.