Continuous renal replacement therapy in the treatment of severe hyperkalemia: An in vitro study

Introduction: Continuous renal replacement therapy is not presently recommended in the treatment of life-threatening hyperkalemia. There are no specific recommendations in hemodialysis to treat hyperkalemia. We hypothesized an in vitro model may provide valuable information on the usefulness of continuous renal replacement therapy to treat severe hyperkalemia. Methods: A potassium-free solute was used instead of diluted blood for continuous renal replacement therapy with a simulated blood flowrate set at 200 mL/min. The mode of elimination included continuous filtration, continuous dialysis, and continuous diafiltration using a flowrate of 4000 mL/min for continuous filtration and continuous dialysis modes, and a ratio of 2500/1500 in the continuous diafiltration mode. Results: The mean initial potassium in the central compartment was 10.1 +/- 0.4 mmol/L. The clearances in the continuous diafiltration, continuous filtration, and continuous dialysis were 3.4 +/- 0.5, 3.6 +/- 0.1, and 3.7 +/- 0.1 L/h, respectively, not significantly different. Continuous dialysis resulted in the lowest workload for staff. Increasing the continuous dialysis flowrates from 2000 to 8000 mL/h increased clearance from 2.3 +/- 0.3 to 6.2 +/- 0.8 L/h. The delays in decreasing the potassium concentration to 5.5 mmol/L dropped from 120 to 45 min, respectively. Potassium eliminated in the first hour increased from 18 to 38 mmol that compared favorably with hemodialysis. Decrease in simulated blood flowrate from 200 to 50 mL/min moderately but significantly decreased the clearance from 3.7 to 3.0 L/h. Conclusion: Hyperkalemia is efficiently treated by continuous renal replacement therapy using the dialysis mode. Caution is needed to prevent the onset of severe hypokalemia within 40 min after initiation of the session.