From the Guidelines
The typical range of bicarbonate concentrations in dialysate baths is 30-40 mEq/L, with most standard formulations containing 35 mEq/L. This concentration is carefully selected to correct metabolic acidosis in patients with end-stage renal disease while avoiding complications from excessive alkalinization. During hemodialysis, bicarbonate from the dialysate diffuses into the patient's blood to replace the buffer deficit caused by impaired kidney function. Nephrologists may adjust this concentration based on individual patient needs, prescribing lower concentrations (30-32 mEq/L) for patients prone to post-dialysis alkalosis or higher concentrations (38-40 mEq/L) for those with severe acidosis. The bicarbonate concentration works alongside other electrolytes in the dialysate, particularly sodium, potassium, calcium, and magnesium, to maintain overall electrolyte balance during treatment. Regular monitoring of pre-dialysis and post-dialysis bicarbonate levels helps guide appropriate adjustments to the dialysate prescription, as recommended by guidelines such as those from the National Kidney Foundation 1.
Some key points to consider when determining the appropriate bicarbonate concentration in dialysate include:
- The patient's individual needs and medical history
- The presence of conditions such as metabolic acidosis or alkalosis
- The need to maintain electrolyte balance during treatment
- The potential for complications such as post-dialysis alkalosis or severe acidosis
- The importance of regular monitoring and adjustment of the dialysate prescription, as supported by studies on the management of acid-base balance in patients undergoing dialysis 1.
It is also important to note that the choice of dialysate calcium concentration can impact the management of bone metabolism and disease in patients with chronic kidney disease, and that individualization of dialysate calcium concentration may be necessary to meet specific patient needs 1. However, the primary focus when determining the bicarbonate concentration in dialysate should be on correcting metabolic acidosis and maintaining electrolyte balance, rather than on managing bone metabolism or other secondary considerations.
From the Research
Dialysate Bicarbonate Concentrations
- The range of bicarbonate concentrations typically available in dialysate baths can vary, but studies suggest that a common range is between 32-35 mEq/L 2.
- One study found that 75% of patients were on dialysate bicarbonate of 32-34 mEq/L after individualized adjustment of the dialysate bicarbonate concentration according to pre- and post-dialysis total carbon dioxide (TCO2) values 3.
- Reducing dialysate bicarbonate concentration from 35 to 32 mEq/L has been shown to safely decrease pre- and post-dialysis TCO2, avoiding acidosis overcorrection and improving secondary hyperparathyroidism control 2.
- The optimal serum bicarbonate target or dialysate bicarbonate concentration is not clearly defined, but target values for predialysis serum bicarbonate concentrations have been established primarily based on observational studies and expert opinion, with a suggested level of at least 22 mmol/l 4, 5, 6.
- Personalization of dialysate bicarbonate concentration is recommended to reach a midweek pre-dialysis serum bicarbonate concentration of 22 mmol/l 6.