From the Guidelines
A patient with acute renal failure and a severely low bicarbonate (HCO3) level of 7 mEq/L should start dialysis immediately with a bicarbonate-based dialysate, as recommended by the most recent guidelines 1. The standard dialysate bicarbonate concentration should be adjusted to 30-35 mEq/L rather than the typical 35-40 mEq/L to avoid too rapid correction of the metabolic acidosis.
Key Considerations
- The initial dialysis session should be shorter (2-3 hours instead of 4 hours) with lower blood flow rates (200-250 mL/min) and a smaller surface area dialyzer to prevent dialysis disequilibrium syndrome.
- Continuous renal replacement therapy (CRRT) may be preferable in hemodynamically unstable patients, as suggested by the KDIGO conference 1.
- During dialysis, frequent monitoring of electrolytes, especially potassium, calcium, and phosphorus, is essential as these can shift rapidly during treatment, according to the ESPEN practical guideline on clinical nutrition in hospitalized patients with acute or chronic kidney disease 1.
- The severe metabolic acidosis (indicated by the low HCO3 of 7) is life-threatening and requires urgent correction, but must be done gradually to prevent complications like cerebral edema, hypocalcemia, or hypokalemia that can occur with too rapid pH normalization.
Additional Recommendations
- Dialysis solutions containing potassium, phosphate, and magnesium should be used to prevent electrolyte disorders during KRT, as recommended by the ESPEN practical guideline 1.
- The adoption of phosphate-containing KRT solutions has been reported as a safe and effective strategy to prevent CKRT-related hypophosphatemia, limiting the need for exogenous supplementations.
- The use of regional citrate anticoagulation for continuous RRT in patients who do not have a contraindication remains supported by existing data, as stated in the KDIGO conference 1.
From the Research
Implications of Starting Dialysis with Low Bicarbonate Level and Hypercapnia
- A patient with acute renal failure starting dialysis with a bicarbonate (HCO3) level of 7 mEq/L and hypercapnia may experience significant electrolyte and acid-base disturbances 2.
- The initiation of dialysis can efficiently treat these complications, but the choice of dialysis modality is crucial to tailor the therapy according to the clinical scenario 2.
- Metabolic acidosis, which is characterized by low bicarbonate levels, can be treated with bicarbonate therapy, but its effectiveness is limited in patients with severe metabolic acidosis (pH < 7.1 and bicarbonate < 6 mEq/L) 3.
- However, bicarbonate therapy may yield improvement in survival for patients with accompanying acute kidney injury 3.
- The use of continuous renal replacement therapy (CRRT) with appropriate bicarbonate levels can help regulate and predict the systemic bicarbonate level, providing a valuable tool for systemic blood pH control 4.
- It is essential to monitor the dialysate pH and adjust the bicarbonate levels accordingly to avoid iatrogenically induced metabolic acidosis or alkalosis 5, 6.
- Oral bicarbonate supplementation can result in a more balanced acid-base status, avoiding post-dialysis alkalemia, and may be a suitable option for maintaining acid-base status during the interdialytic period 6.