How to manage acidosis in patients undergoing Continuous Renal Replacement Therapy (CRRT)?

From the Guidelines

To decrease acidosis in patients undergoing Continuous Renal Replacement Therapy (CRRT), using bicarbonate-based solutions with concentrations of 25-35 mEq/L is recommended, as suggested by the most recent and highest quality study 1.

Managing Acidosis in CRRT

The primary management strategy involves adjusting the dialysate or replacement fluid composition.

• For severe metabolic acidosis (pH <7.2 or bicarbonate <15 mEq/L), consider increasing the bicarbonate concentration in the dialysate to 35-40 mEq/L or administering supplemental intravenous sodium bicarbonate (1-2 mEq/kg over 1-2 hours) 1.
• Increase CRRT effluent dose to 25-35 mL/kg/hr to enhance clearance of acid-producing substances, as recommended by the KDIGO clinical practice guideline for acute kidney injury 1.

Monitoring and Adjusting Therapy

• Monitor acid-base status every 4-6 hours initially, then every 8-12 hours once stabilized, adjusting therapy accordingly.
• Simultaneously, identify and treat underlying causes of acidosis such as sepsis, tissue hypoperfusion, or toxin ingestion.

Nutrition and Protein Intake

• Ensure adequate nutrition with appropriate protein intake (1.2-1.5 g/kg/day) while avoiding excessive protein that can increase acid load. This comprehensive approach addresses both the immediate correction of acid-base disturbances and the underlying pathophysiology, improving outcomes in critically ill patients requiring CRRT, as supported by the study 1.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Tromethamine Injection is administered by slow intravenous infusion, by addition to pump-oxygenator ACD blood or other priming fluid or by injection into the ventricular cavity during cardiac arrest In general, dosage should be limited to an amount sufficient to increase blood pH to normal limits (7.35 to 7. 45) and to correct acid-base derangements. The intravenous dosage of Tromethamine Injection may be estimated from the buffer base deficit of the extracellular fluid in mEq/liter determined by means of the Siggaard-Andersen nomogram.

To decrease acidosis on CRRT, tromethamine can be administered by slow intravenous infusion. The dosage should be limited to an amount sufficient to increase blood pH to normal limits (7.35 to 7.45) and to correct acid-base derangements. The intravenous dosage can be estimated from the buffer base deficit of the extracellular fluid in mEq/liter determined by means of the Siggaard-Andersen nomogram 2.

DOSAGE AND ADMINISTRATION Sodium Bicarbonate Injection, USP is administered by the intravenous route. In less urgent forms of metabolic acidosis, Sodium Bicarbonate Injection, USP may be added to other intravenous fluids The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight - depending upon the severity of the acidosis as judged by the lowering of total CO2 content, blood pH and clinical condition of the patient

Alternatively, sodium bicarbonate can be administered by the intravenous route to decrease acidosis on CRRT. The amount of bicarbonate to be given over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight, depending on the severity of the acidosis 3.

• Key considerations:
  • Monitor blood gases, plasma osmolarity, arterial blood lactate, hemodynamics, and cardiac rhythm during therapy.
  • Avoid full correction of low total CO2 content during the first 24 hours of therapy to prevent unrecognized alkalosis.
  • Adjust dosage based on clinical response and laboratory results.

From the Research

Managing Acidosis in CRRT

To manage acidosis in patients undergoing Continuous Renal Replacement Therapy (CRRT), several strategies can be employed:

• Adjusting fluid composition and regulating CRRT dose to mitigate and correct acid-base disturbances 4
• Using separate intravenous infusions to correct electrolyte imbalances 4
• Understanding the principles of acid-base and electrolyte management using CRRT, including the removal of excess fluid and solutes retained as a consequence of acute kidney injury 5
• Selecting the appropriate CRRT modality, such as continuous venovenous hemofiltration, continuous venovenous hemodialysis, or continuous venovenous hemodiafiltration, based on the patient's specific needs 6

Alkalinizing Agents

The use of alkalinizing agents, such as sodium bicarbonate or THAM, can also be considered:

• Sodium bicarbonate is considered the standard alkali therapy in metabolic acidosis, but it can have side effects such as decreasing serum potassium levels and increasing serum sodium levels 7
• THAM is an alternative alkalizing agent that can be used in patients with mild metabolic acidosis, particularly those with hypernatremia or mixed acidosis with high PaCO2 levels 7

CRRT Prescription and Troubleshooting

When prescribing and troubleshooting CRRT, it is essential to consider the patient's individual needs and the logistics available at the institution:

• Initial prescription and CRRT dosing should be tailored to the patient's specific requirements, including severe hyponatremia management and concomitant extracorporeal membrane oxygenation support 8
• Adjustments to CRRT delivery, such as dialysis catheter placement and use of regional citrate anticoagulation, should be made based on the patient's clinical status and the institution's available resources 8