From the Guidelines
Extracorporeal treatment for metabolic acidosis is recommended for severe cases with high anion gap metabolic acidosis, especially when associated with renal failure or when the glycolate concentration is > 12 mmol/L or anion gap > 27 mmol/L, as evidenced by the EXTRIP workgroup recommendations 1. The main extracorporeal modalities include hemodialysis, continuous renal replacement therapy (CRRT), and peritoneal dialysis.
- For acute severe metabolic acidosis, intermittent hemodialysis is the preferred initial approach due to its rapid correction capability.
- A typical hemodialysis prescription would include a 3-4 hour session using a bicarbonate-based dialysate with concentration of 35-40 mEq/L.
- For hemodynamically unstable patients, CRRT is preferred, typically as continuous venovenous hemodiafiltration (CVVHDF) with a bicarbonate-based replacement fluid at 25-35 mL/kg/hr. The underlying cause of acidosis must be addressed simultaneously, as extracorporeal therapy treats the acid-base disturbance but not necessarily the primary condition.
- These treatments work by removing acid anions (such as lactate, ketones, or toxins) and providing bicarbonate, effectively increasing serum bicarbonate and normalizing pH. Careful monitoring of electrolytes, especially potassium, calcium, and phosphate, is essential during treatment as rapid correction can lead to electrolyte imbalances and potential complications like hypocalcemia or hypokalemia, as supported by the EXTRIP workgroup recommendations for extracorporeal treatment in ethylene glycol poisoning 1. In addition, the dosage of antidotes (fomepizole or ethanol) needs to be adjusted during extracorporeal treatment, highlighting the importance of careful management and monitoring in these cases 1.
From the Research
Extracorporeal Treatment for Metabolic Acidosis
- Metabolic acidosis is a common laboratory finding in clinical practice, and rapid pH correction is often necessary 2.
- Extracorporeal treatments such as hemodialysis and continuous renal replacement therapy (CRRT) can be used to correct metabolic acidosis, especially in patients with severe acidosis and renal failure 2, 3.
- The use of bicarbonate replacement therapy is also recommended in some cases, particularly in patients with high anion gap metabolic acidosis and concurrent metformin use 2.
- However, the effectiveness of bicarbonate infusions in correcting acidosis is still a topic of debate, and some studies suggest that it may not be beneficial in all cases 3, 4.
- The management of metabolic acidosis should focus on correcting the underlying causative disturbances, rather than just treating the symptoms 3, 5.
Types of Metabolic Acidosis
- Metabolic acidosis can be categorized into different types, including hyperchloremic and high-anion-gap acidosis 5.
- The diagnosis of metabolic acidosis should involve identifying the primary causative etiology, which can often be determined from the patient's history and physical exam 5.
- In some cases, further diagnostic studies may be necessary to determine the underlying cause of the metabolic acidosis 5.
Treatment Options
- Hemodialysis and CRRT are effective treatments for metabolic acidosis, particularly in patients with severe acidosis and renal failure 2, 3.
- Bicarbonate replacement therapy may also be used in some cases, although its effectiveness is still a topic of debate 2, 3, 4.
- The treatment of metabolic acidosis should be individualized based on the patient's underlying condition and the severity of the acidosis 3, 4.