Manual Dilution of Continuous Renal Replacement Therapy Fluids in Anuric Patients with Severe Hyponatremia: A Case Report and Systematic Review.

Introduction: When a patient with severe hyponatremia requires renal replacement therapy, a too rapid correction of sodium levels may occur. Manual dilution of the fluids during continuous renal replacement therapy (CRRT) is a method that can lead to a controlled correction of sodium. We present a case and add a systematic review to determine the feasibility of this method.

Case presentation: A female was admitted to the intensive care unit with acute kidney failure due to anti-glomerular basement membrane antibody glomerulonephritis, anuria, and an initial sodium level of 100 mmol/L. She received CRRT with manually diluted fluids for 6 days, in which sodium levels increased from 108 mmol/L to 130 mmol/L. A search in Medline, Web of Science, and Google Scholar was added for the systematic review. The search yielded 49 cases, including the current report, of which 47 were anuric or oliguric, in which the fluids were diluted to a median of 8 mmol/L (interquartile range 5-11) (range 0-17) above the serum sodium, the median CRRT dose was 27 mL/kg/h (22-30) (13-77.5). This led to an increase in serum sodium of 0.2 mmol/L/h (0.1-0.3) (0-0.7).

Conclusion: CRRT with manually diluted fluids in patients with severe hyponatremia and anuria can lead to a controlled increase serum sodium, while allowing sufficient RRT dose and fluid removal. Still, errors in dilution may occur and we recommend 4 hourly monitoring of serum sodium levels to timely detect an inadvertent increase in sodium.