From the Guidelines
To set up CVVHDF for a 70kg patient with hyperkalemia, I recommend using a standard CVVHDF prescription with adjustments to target potassium removal, prioritizing a blood flow rate of 150-200 mL/min, dialysate flow rate of 25-35 mL/kg/hr, and replacement fluid rate of 10-15 mL/kg/hr, as this approach effectively removes potassium through diffusion and convection, addressing hyperkalemia while providing renal replacement therapy 1.
Key Considerations
- Blood flow rate: 150-200 mL/min
- Dialysate flow rate: 25-35 mL/kg/hr (1750-2450 mL/hr) for a 70kg patient
- Replacement fluid rate: 10-15 mL/kg/hr (700-1050 mL/hr) for a 70kg patient
- Use a potassium-free or low-potassium dialysate and replacement fluid (typically 0-2 mEq/L K+)
- Set ultrafiltration rate based on fluid removal goals, typically 50-200 mL/hr depending on volume status
Anticoagulation and Monitoring
- For anticoagulation, use regional citrate (starting at 3-4 mmol/L) or systemic heparin (initial bolus 15-25 units/kg followed by 5-10 units/kg/hr) to prevent circuit clotting
- Monitor serum potassium every 2-4 hours initially, then every 4-6 hours once stabilized
- Adjust calcium replacement as needed with citrate anticoagulation, considering the treatment of severe hyperkalemia aims at protecting the heart from the effects of hyperkalemia by antagonizing the effect of potassium on excitable cell membranes, forcing potassium into cells to remove it promptly from the circulation, and removing potassium from the body 1
Additional Considerations
- The higher dialysate flow rate enhances potassium clearance through increased concentration gradient, while the replacement fluid maintains appropriate fluid balance and electrolyte composition
- CVVHDF is a form of renal replacement therapy that uses an external pump and a venovenous circuit, with solute removal through both diffusion and convection, making it an effective treatment for hyperkalemia in patients with renal failure 1
From the Research
Setting up CVVHDF for a 70kg Patient with Hyperkalemia
To set up Continuous Veno-Venous Hemodiafiltration (CVVHDF) for a 70kg patient with hyperkalemia, several factors need to be considered, including the patient's weight, potassium levels, and the need for efficient removal of waste products and excess fluids.
- Replacement Fluid Rate: The replacement fluid rate can be calculated based on the patient's weight. A study by 2 used a mean replacement fluid rate of 31 mL/kg/h, which can be considered for this patient.
- Potassium Removal: CVVHDF can be effective in removing potassium from the blood. A study by 3 used CVVHDF with citrate anticoagulation to treat a patient with hypercalcemia and thrombocytopenia, and it may be considered for potassium removal as well.
- Dialysate Flow Rate: The dialysate flow rate can be adjusted based on the patient's blood flow rate and the desired level of solute removal. A study by 4 used a mean dialysate flow rate of 3925 +/- 2398 ml/min/1.73 m(2) in children with inborn errors of metabolism.
- Anticoagulation: Citrate anticoagulation can be used to prevent clotting in the CVVHDF circuit. A study by 2 used trisodium citrate as an anticoagulant, and it may be considered for this patient.
- Monitoring: Close monitoring of the patient's electrolyte levels, fluid status, and hemodynamic parameters is essential during CVVHDF. A study by 5 monitored patients' vasodepressor dependency index and found a significant reduction in the high-flow group.
Key Considerations
- The patient's potassium level is 7, which is higher than normal. CVVHDF can be effective in removing potassium from the blood, but the dialysate potassium concentration should be adjusted accordingly.
- The patient's weight is 70kg, which can be used to calculate the replacement fluid rate and dialysate flow rate.
- The choice of anticoagulant, such as citrate, should be considered to prevent clotting in the CVVHDF circuit.
- Close monitoring of the patient's electrolyte levels, fluid status, and hemodynamic parameters is essential during CVVHDF.