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NCT Number: NCT07688434

Pilot Trial of Oral Sodium Bicarbonate Versus Higher Dialysate Bicarbonate in Hemodialysis Patients With Metabolic Acidosis

Metabolic acidosis is frequent in chronic hemodialysis patients and is associated with adverse clinical outcomes. Two commonly used strategies to correct acidosis are oral sodium bicarbonate supplementation and increasing the bicarbonate concentration of the dialysate, but their comparative effectiveness and tolerance in routine care remain uncertain. This pilot, prospective, randomized, open-label, single-center trial will compare oral sodium bicarbonate versus higher dialysate bicarbonate in chronic hemodialysis patients with metabolic acidosis, using predialysis plasma bicarbonate concentrations, so-called "reserves alcalines" or "alkaline reserves" in local laboratory reports, as a pragmatic marker of acid-base status.

Approximately 30 acidotic patients (serum bicarbonate < 22 mmol/L) will be randomized 1:1 to receive either oral sodium bicarbonate or an increase in dialysate bicarbonate for 6 weeks. An additional non-acidotic observational group will provide descriptive reference data. The primary outcome is the change in predialysis serum bicarbonate from baseline (Day 0) to Day 42 between the two randomized arms. Secondary outcomes include the proportion of patients reaching target serum bicarbonate levels, the weekly kinetics of correction, dialysis adequacy (Kt/V and online clearance monitoring), intradialytic tolerance (blood pressure, cramps, hypotension, symptoms), sodium-related safety (natremia, interdialytic weight gain), and the effects of acidosis correction on nutritional and bone-mineral metabolism, including changes in serum albumin, calcium, phosphorus, and parathyroid hormone (PTH). Feasibility indicators such as recruitment, retention, adherence to treatment and dialysate adjustment, and data completeness will also be described to inform the design of a larger definitive trial.

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Key information

Conditions

End-stage Renal Disease (ESRD) Acid-Base Imbalance Acidosis Chronic Disease Chronic Hemodialysis Disease Attributes Female Urogenital Diseases Female Urogenital Diseases and Pregnancy Complications Kidney Diseases Kidney Failure, Chronic Male Urogenital Diseases Metabolic Acidosis Metabolic Diseases Nutritional and Metabolic Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms Renal Insufficiency Renal Insufficiency, Chronic Urogenital Diseases Urologic Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

Metabolic acidosis is a common complication in chronic hemodialysis patients and is associated with adverse nutritional, cardiovascular, and bone outcomes. In clinical practice, two main strategies are used to correct acidosis: oral sodium bicarbonate supplementation and increasing the bicarbonate concentration of the dialysate. Both approaches are recommended in guidelines, but their comparative effectiveness and tolerance in routine hemodialysis care, particularly in resource-limited settings, remain uncertain.

This pilot, prospective, randomized, open-label, single-center study will compare these two strategies in adult chronic hemodialysis patients with metabolic acidosis, defined by low predialysis serum (or plasma) bicarbonate concentrations, so-called "reserves alcalines" or "alkaline reserves" in local laboratory reports. Approximately 30 acidotic patients (serum bicarbonate < 22 mmol/L) will be enrolled and randomized in a 1:1 ratio to either oral sodium bicarbonate supplementation (Arm A) or an increase in dialysate bicarbonate concentration (Arm B) for 6 weeks. In addition, a non-acidotic observational control group of hemodialysis patients with stable, adequate serum bicarbonate levels will be followed descriptively to provide reference data on acid-base status, dialysis adequacy, and tolerance.

Randomization among acidotic patients will be performed after matching them in pairs according to the severity of metabolic acidosis (baseline predialysis serum bicarbonate / "reserves alcalines") and age. Patients will be ordered from the lowest to the highest serum bicarbonate value, then matched two-by-two on similar bicarbonate level and age. Within each pair, allocation to oral sodium bicarbonate (Arm A) or increased dialysate bicarbonate (Arm B) will be determined by a computer-generated random number in a spreadsheet, corresponding to a block randomization with block size 2 after matching on acidosis severity. The non-acidotic control group will not be randomized and will receive usual care.

The primary outcome is the change in predialysis serum bicarbonate from baseline (Day 0) to Day 42, comparing the two randomized arms. Secondary outcomes include the proportion of patients achieving target serum bicarbonate at Day 42, the weekly kinetics of bicarbonate correction over 6 weeks, changes in serum potassium, and dialysis adequacy assessed by Kt/V and online clearance monitoring. Intradialytic and interdialytic tolerance will be evaluated through blood pressure, interdialytic weight gain, cramps, hypotension, thirst, digestive symptoms, and any treatment discontinuation or dose reduction related to intolerance. Sodium-related safety will be assessed by predialysis natremia and interdialytic weight gain, given the potential impact of both oral sodium bicarbonate and higher dialysate bicarbonate on sodium load.

As a pilot trial, this study also includes predefined feasibility objectives. Feasibility outcomes will describe recruitment and retention rates, adherence to oral treatment and to the dialysate bicarbonate adjustment algorithm, and data completeness for key clinical and laboratory variables. These feasibility indicators will be used to judge the practicality of the protocol and to inform the design and assumptions of a larger, definitive randomized controlled trial.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥ 18 years.
  • Chronic hemodialysis for at least 3 months.
  • Stable hemodialysis prescription: 3 times a week, high-flux dialyzers, no major change in dialysis prescription in the previous weeks.
  • Predialysis low "alkaline reserves" (serum bicarbonate concentration) according to the operational threshold used in the unit (e.g., "alkaline reserves" < 22 mmol/L), consistent with KDIGO 2017 definition of metabolic acidosis.
  • Ability to give written informed consent.

For the observational group:

  • Age ≥ 18 years.
  • Chronic hemodialysis for at least 3 months.
  • Hemodialysis 3 times a week, high-flux dialyzers.
  • Predialysis "alkaline reserves" considered stable and within the locally defined normal range (≥ 22mmol/L).
  • Ability to give written informed consent.

Exclusion criteria

  • Recent hemodynamic instability (e.g., repeated intradialytic hypotension or unstable blood pressure in the previous weeks).
  • Recent hospitalization for an acute condition.
  • Acute infection or major intercurrent acute event at the time of screening.
  • Major change in dialysis prescription in the 2 weeks prior to inclusion (e.g., change in dialysis schedule, duration, or dialysate composition outside the study protocol).
  • Severe digestive disorders limiting oral intake (e.g., persistent vomiting, severe malabsorption, or any condition preventing safe oral Bicardis administration).
  • Known hypernatremia or high risk of uncontrolled sodium and fluid overload (as judged by the investigator).
  • Severe uncontrolled hypercalcemia or hypocalcemia.
  • Any condition that, in the investigator's judgment, would preclude safe participation or interfere with study procedures (e.g., very limited life expectancy, inability to attend scheduled visits).
  • Refusal to participate or inability to provide written informed consent.

Treatment and study plan

oral sodium bicarbonate

Dietary Supplement

Oral sodium bicarbonate given as Bicardis 500 mg capsules, used as a dietary supplement in Tunisia, administered according to a standardized algorithm based on predialysis serum bicarbonate concentrations, so-called "reserves alcalines" in local laboratory reports. At baseline, an initial dose is prescribed according to the severity of metabolic acidosis: 1 capsule/day if 20-21.9, 2 capsules/day if 18-19.9, 3 capsules/day if 16-17.9, 4 capsules/day if <16 mmol/L. At each weekly visit, the same dose is maintained if reserves alcalines remain below the target range and the weekly increase is ≤ 3 mmol/L; the dose is reduced to the previous lower level if the weekly increase is > 3 mmol/L or if predialysis bicarbonate enters the predefined target range (22-24 mmol/L); oral bicarbonate is reduced or stopped if predialysis bicarbonate exceeds the upper limit of the target range (> 24 mmol/L) to avoid alkalosis, and the dose is increased if reserves alcalines do not improve or decrease.

Other names: Bicardis

Increased Dialysate Bicarbonate

Other

Adjustment of the dialysate bicarbonate concentration will be performed according to a standardized titration strategy based on predialysis serum bicarbonate concentrations ("reserves alcalines" in local laboratory reports). At baseline, an initial increase in dialysate bicarbonate is prescribed according to the severity of metabolic acidosis: +1 mmol/L if serum bicarbonate is 20-21.9 mmol/L, +2 mmol/L if 18-19.9 mmol/L, +3 mmol/L if 16-17.9 mmol/L, and a larger or individualized increase if < 16 mmol/L.

At each weekly visit, dialysate bicarbonate is then adjusted as follows: it is maintained if reserves alcalines remain below the target range and the weekly increase is ≤ 3 mmol/L; it is reduced to the previous lower level if the weekly increase is > 3 mmol/L or if predialysis bicarbonate enters the predefined target range (22-24 mmol/L); and it is reduced or returned to the standard level if predialysis bicarbonate exceeds the upper limit of the target range (> 24 mmol/L).

Primary outcomes

  1. Change in Predialysis Serum Bicarbonate ("Reserves Alcalines") Between Day 0 and Day 42

    Time frame: From baseline (Day 0) to Day 42

    Predialysis serum (or plasma) bicarbonate concentrations, so-called "reserves alcalines" or "alkaline reserves" in local laboratory reports, will be measured at baseline (Day 0) and after 6 weeks (Day 42) in chronic hemodialysis patients with metabolic acidosis. The primary outcome is the change in predialysis serum bicarbonate between Day 0 and Day 42 (Δ serum bicarbonate), comparing the oral sodium bicarbonate arm and the higher dialysate bicarbonate arm. Serum bicarbonate will be expressed in mmol/L, and metabolic acidosis at inclusion is defined as predialysis serum bicarbonate < 22 mmol/L.

Secondary outcomes

  1. Proportion of Patients Achieving Target Serum Bicarbonate at Day 42

    Time frame: Day 42

    Proportion of randomized acidotic hemodialysis patients in each active arm (oral sodium bicarbonate vs higher dialysate bicarbonate) who achieve a predialysis serum (or plasma) bicarbonate level within the predefined target range at Day 42. Serum bicarbonate corresponds to "reserves alcalines" or "alkaline reserves" in local laboratory reports and will be expressed in mmol/L. Proportion will be expressed as a percentage of each active arm (%).

  2. Weekly Kinetics of Predialysis Serum Bicarbonate

    Time frame: Day 0, Day 7, Day 14, Day 21, Day 28, Day 35, Day 42.

    Trajectory of predialysis serum (or plasma) bicarbonate ("reserves alcalines" / "alkaline reserves") over the 6-week study period, measured at baseline (Day 0) and weekly at Days 7, 14, 21, 28, 35 and 42, comparing the oral sodium bicarbonate and higher dialysate bicarbonate arms. Results will be expressed as absolute values (mmol/L) and changes from baseline at each time point.

  3. Intradialytic hypotension episodes

    Time frame: From baseline (Day 0) to Day 42

    Number of intradialytic hypotension episodes per patient over 6 weeks in each treatment arm. Intradialytic hypotension is defined as:

    Systolic blood pressure (SBP) < 90 mmHg or a decrease in SBP ≥ 20 mmHg compared with the pre-dialysis value, accompanied by at least one intolerance symptom (such as cramps, nausea, dizziness, or other intradialytic complaints).

  4. Dialysis Adequacy

    Time frame: From baseline (Day 0) to Day 42

    Dialysis adequacy assessed by single-pool Kt/V and online clearance monitoring (OCM), measured weekly or according to local routine, in the oral sodium bicarbonate and higher dialysate bicarbonate arms. The outcome will describe the stability of Kt/V and OCM over the 6-week period and compare any changes between arms.

  5. Predialysis Serum Sodium

    Time frame: From baseline (Day 0) to Day 42

    Predialysis serum sodium concentration (natremia), expressed in mmol/L, measured at baseline and weekly up to Day 42, to evaluate sodium-related safety in each arm. The outcome will compare changes in natremia over time between oral sodium bicarbonate and higher dialysate bicarbonate.

  6. Dialysis symptom burden

    Time frame: Baseline (day 0), day 21, and day 42 (end of treatment).

    Dialysis symptom burden will be assessed using the Dialysis Symptom Index (DSI), which records the presence and severity of common symptoms in hemodialysis patients (e.g., cramps, headaches, thirst, nausea, and fatigue). The DSI will be administered at baseline (day 0), day 21, and day 42 in each treatment arm.

    The reported outcome will be the change in total DSI score over time (baseline to day 21 and baseline to day 42), with higher scores indicating greater symptom burden.

  7. Change in serum Calcium

    Time frame: From baseline (Day 0) and Day 42

    Serum total calcium concentration will be measured at baseline (Day 0) and at Day 42 in each treatment arm and in the non-acidotic control group. The outcome will describe the change in serum calcium between Day 0 and Day 42 in chronic hemodialysis patients with metabolic acidosis treated with oral sodium bicarbonate or higher dialysate bicarbonate, and in non-acidotic hemodialysis patients, in order to explore the effect of metabolic acidosis correction on calcium homeostasis and phosphocalcic balance. Serum calcium will be expressed in mmol/L.

  8. Change in serum Phosphorus

    Time frame: From baseline (Day 0) and Day 42

    Serum phosphorus concentration will be measured at baseline (Day 0) and at Day 42 in each treatment arm and in the non-acidotic control group. The outcome will describe the change in serum phosphorus between Day 0 and Day 42 in chronic hemodialysis patients with metabolic acidosis treated with oral sodium bicarbonate or higher dialysate bicarbonate, and in non-acidotic hemodialysis patients, in order to evaluate the impact of metabolic acidosis correction on serum phosphate levels and phosphocalcic balance. Serum phosphorus will be expressed in mmol/L.

  9. Change in Serum Parathormone (PTH)

    Time frame: From baseline (Day 0) and Day 42

    Parathormone (PTH) will be measured at baseline (Day 0) and at Day 42 in each treatment arm and in the non-acidotic control group, using an immuno-enzymatic assay according to local laboratory methods. The outcome will describe the change in PTH between Day 0 and Day 42 in chronic hemodialysis patients with metabolic acidosis treated with oral sodium bicarbonate or higher dialysate bicarbonate, and in non-acidotic hemodialysis patients, in order to explore the effect of metabolic acidosis correction on parathyroid function and renal osteodystrophy risk. Serum PTH will be expressed in pg/mL.

  10. Change in serum albumin

    Time frame: Baseline and week 6 (end of intervention)

    Change in serum albumin concentration (g/L) from baseline to the end of the 4-week intervention, comparing the oral Bicardis group, the increased dialysate bicarbonate group, and the control group. This outcome is used as a surrogate marker of global protein-nutritional status potentially influenced by correction of metabolic acidosis.

  11. Change in interdialytic weight gain

    Time frame: Baseline (week 1) and the end of the intervention (week 6)

    Change in mean weekly interdialytic weight gain (kg and % of dry weight) between baseline (week 1) and the end of the intervention (week 6) in each randomized arm, to assess the impact of oral sodium bicarbonate versus higher dialysate bicarbonate on sodium and fluid balance.

Other outcomes

  1. Feasibility of the Pilot Trial

    Time frame: From study start (screening and inclusion) to Day 42

    Feasibility of the study procedures will be assessed descriptively to inform the design of a future definitive randomized trial. Feasibility outcomes include: (1) recruitment rate, defined as the proportion of eligible chronic hemodialysis patients with metabolic acidosis who consent and are enrolled; (2) retention rate, defined as the proportion of randomized participants who complete the Day 42 visit with primary outcome assessment; (3) adherence to oral sodium bicarbonate in the experimental arm, defined as the proportion of prescribed doses actually taken over 6 weeks; (4) adherence to the dialysate bicarbonate adjustment algorithm in the active comparator arm, defined as the proportion of dialysis sessions performed with a dialysate bicarbonate level consistent with the predefined weekly serum bicarbonate ("reserves alcalines"); and (5) data completeness, defined as the proportion of expected measurements available for key variables.

Study contacts

Contact information is provided by the study sponsor or research team.

Azza KHEDHIRI, MD

CONTACT

[email protected]

+21623146019

Lobna Ben Mahmoud, MD, PhD, Professor

CONTACT

[email protected]

+21696365092

Sponsors and collaborators

Lead sponsor

University of Sfax

Other

Registry information

Official study title

Comparative Pilot Trial of Oral Sodium Bicarbonate Versus Increased Dialysate Bicarbonate in Chronic Hemodialysis Patients With Metabolic Acidosis

Acronym: Bicarbonate-HD

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Jul 7, 2026
Registry last updated
Jul 21, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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