From the Guidelines
To reduce metabolic acidosis during Continuous Renal Replacement Therapy (CRRT), increase the bicarbonate concentration in the dialysate or replacement fluid to 35-40 mEq/L from the standard 32 mEq/L, as recommended by recent guidelines 1. This approach is supported by the fact that bicarbonate has become the preferred buffer for CRRT due to its ability to effectively correct metabolic acidosis without the risks associated with lactate, especially in patients with lactic acidosis or liver failure 1. The adjustment can be made by either adding sodium bicarbonate to the dialysate solution or by selecting commercially available solutions with higher bicarbonate content. For severe acidosis (pH < 7.2 or bicarbonate < 15 mEq/L), consider initially using a dialysate with 40 mEq/L of bicarbonate, then titrating down as the acidosis improves, as part of a strategy to closely monitor and manage the patient's acid-base balance 1. Monitoring arterial blood gases every 4-6 hours is crucial to assess the response to these adjustments and to make further changes as necessary. Additionally, ensuring adequate CRRT flow rates (typically 25-35 mL/kg/hr) is important to optimize the clearance of acid metabolites and support the recovery of kidney function 1. If acidosis persists despite these measures, it is essential to evaluate for ongoing acid production from conditions like lactic acidosis, ketoacidosis, or tissue hypoperfusion that may require additional interventions beyond dialysate adjustments. The choice of bicarbonate as the buffer is further supported by its widespread availability and the increased evidence of its benefits over lactate-based solutions for CRRT, making it a practical and effective choice for reducing metabolic acidosis in this context 1.
From the Research
Adjusting Dialysate to Reduce Acidosis on CRRT
To adjust dialysate and reduce metabolic acidosis on Continuous Renal Replacement Therapy (CRRT), several strategies can be employed:
- Adjusting the composition of the dialysate and replacement fluids to manage electrolyte and acid-base imbalances, as standard solutions may not be suitable for all patients 2.
- Using bicarbonate-based fluids, which can help control acidosis better than lactate-based fluids, especially in patients with severe tissue acidosis, liver failure, or high-volume exchanges 3.
- Avoiding the use of dextrose-free dialysate solutions, which can lead to increased caloric loss, net glucose deficit, and shifting of the metabolic pathway towards gluconeogenesis and ketogenesis, resulting in metabolic acidosis 4.
- Administering dextrose-containing fluids or tube feeds to patients developing CRRT-associated ketoacidosis, which can help resolve ketonemia and acidosis 4.
- Considering the use of citrate anticoagulation, which can provide an adequate supply of anionic base to control metabolic acidosis, but may require careful monitoring to avoid hypercitratemia 3.
Key Considerations
When adjusting dialysate to reduce acidosis on CRRT, it is essential to:
- Monitor patients closely for signs of metabolic acidosis, such as hyperlactatemia or hypercitratemia, and adjust the dialysate composition accordingly 3.
- Be aware of the potential risks of using unbalanced electrolyte preparations, which can induce hyperchloremic acidosis and worsen kidney-related outcomes 5.
- Consider the use of bicarbonate-based fluids, which can improve kidney-related endpoints in critically ill patients, but may also have potential side effects 5.