What are the recommendations for using citrate-based dialysate in a critically ill adult patient with impaired renal function?

Citrate-Based Dialysate in Critically Ill Patients with Acute Kidney Injury

For continuous renal replacement therapy (CRRT) in critically ill patients without contraindications, regional citrate anticoagulation should be preferred over heparin-based anticoagulation, as it provides superior filter patency with minimal bleeding risk. 1

Primary Recommendation for Anticoagulation Strategy

KDIGO guidelines suggest using regional citrate anticoagulation rather than heparin in CRRT patients who lack contraindications for citrate (Grade 2B recommendation). 1 This represents the highest-level guidance available, though the KDOQI commentary notes that citrate is not FDA-approved as an anticoagulant for CRRT in the United States, and commercially available citrate solutions are hypertonic blood banking products that increase metabolic complication risks. 1

Key Decision Point: Patient Selection

The choice of anticoagulation must be determined by:

• Patient bleeding risk and coagulation status 1
• Presence of citrate contraindications 1
• Local institutional expertise and nursing comfort 1
• Availability of appropriate citrate solutions and monitoring protocols 1

Contraindications and Cautions

Relative (Not Absolute) Contraindications

Severely impaired liver function and shock with muscle hypoperfusion are listed as major contraindications by KDIGO, but the Canadian Society of Nephrology clarifies these should be considered relative rather than absolute contraindications. 1

• In liver failure: Citrate accumulation can be tracked by monitoring systemic ionized calcium levels and the total calcium-to-ionized calcium ratio 1
• In septic shock: Multiple randomized controlled trials have demonstrated safety of regional citrate anticoagulation even in severe septic shock 1
• CRRT is primarily used during hemodynamic instability in North America, making shock an impractical absolute contraindication 1

Essential Protocol Requirements

Mandatory Components Before Implementation

A strict protocol with adequate staff education must be in place before introducing regional citrate anticoagulation to avoid prescription errors leading to metabolic complications. 1, 2

The protocol must detail:

• Infusion rates of citrate and calcium 1, 2
• Composition of dialysate and replacement fluid 1, 2
• Intensity of metabolic monitoring including acid-base status, serum sodium, and total/ionized calcium levels 1, 2

Monitoring Requirements

Critical Parameters to Track

Frequent measurements of post-filter and serum-ionized calcium should be performed to appropriately titrate citrate and calcium replacement doses. 2

Essential monitoring includes:

• Post-filter ionized calcium (target 0.23-0.38 mmol/L) 3, 4
• Systemic ionized calcium (maintain 1.06 mmol/L) 3, 4
• Total calcium-to-ionized calcium ratio (surrogate marker for citrate accumulation) 1, 2
• Serum sodium levels (prevent hypernatremia) 2, 4
• Acid-base balance (particularly in high-risk patients) 2, 3

Dialysate Composition for Optimal Outcomes

Electrolyte Management Strategy

Dialysate should contain potassium (4 mEq/L), phosphate, and magnesium (≥0.70 mmol/L) to prevent severe electrolyte depletion, with bicarbonate concentration (26-34 mmol/L) adjusted to correct metabolic acidosis initially and prevent metabolic alkalosis after 72 hours. 5

Critical electrolyte considerations:

• Magnesium levels must be maintained ≥0.70 mmol/L, as magnesium-citrate complexes are lost in effluent during regional citrate anticoagulation 2, 5
• Hypomagnesemia causes refractory hyperkalemia that cannot be corrected without magnesium repletion 6, 5
• Phosphate-containing dialysate prevents severe hypophosphatemia (target >0.81 mmol/L) that develops within 24-72 hours 5
• Electrolyte repletion through dialysate composition is safer and more effective than intravenous supplementation 2, 5

Calcium-Containing vs. Calcium-Free Dialysate

For continuous venovenous hemodialysis (CVVHD), calcium-containing dialysate (1.81 mmol/L) avoids mandatory systemic calcium supplementation while maintaining safety. 4 Research demonstrates excellent control with prefilter serum ionized calcium of 1.06 mmol/L and postfilter of 0.23 mmol/L using this approach. 4

For prolonged intermittent hemodialysis, calcium-free citrate-containing dialysate with calcium reinjection according to ionic dialysance provides efficient heparin-free anticoagulation without requiring systemic ionized calcium monitoring. 7

Clinical Outcomes and Filter Patency

Expected Performance Metrics

Research demonstrates:

• Median filter run time of 61.5 hours with only 5% requiring change due to clotting 3
• Mean filter life of 26-38 hours depending on protocol 4, 8
• Filter survival at 48 hours of 38.2% 8
• Circuit clotting occurs in approximately 24% of filters 8

Common Pitfalls and How to Avoid Them

Metabolic Complications

Persistent metabolic alkalosis occurs in approximately 13% of patients but can be rapidly corrected by modifying dialysate flow or blood flow rate. 3, 8

Citrate accumulation (indicated by total calcium >3 mmol/L or high calcium substitution needs) occurs in approximately 5% of patients. 3

Hypernatremia, metabolic alkalosis, and hypocalcemia can be controlled without clinical consequences using a strict protocol. 1

Prevention Strategies

• Use dialysate with variable bicarbonate concentrations (13-34 mmol/l) to control acid-base status and prevent hypernatremia 4
• Adjust dialysate sodium concentrations between 121-140 mmol/L as needed 4
• Monitor for mild hypocalcemia (ionized calcium <3.6 mg/dL) which occurs in 23% of patients, though severe hypocalcemia (<2.8 mg/dL) is rare 8

U.S.-Specific Considerations

Because citrate is not FDA-approved for CRRT anticoagulation and commercially available solutions are hypertonic blood banking products, citrate cannot be universally recommended over heparin in the United States until standardized protocols are created and appropriate citrate solutions are developed and approved. 1 However, where institutional protocols exist with appropriate solutions and monitoring, citrate remains the preferred option based on efficacy and safety data. 1