Citrate anticoagulation for CRRT: don't always trust the postfilter iCa results!

Area of Science:

• Nephrology
• Critical Care Medicine
• Clinical Chemistry

Background:

• Citrate anticoagulation is preferred for continuous renal replacement therapy (CRRT) due to its safety and efficacy compared to heparin.
• Citrate functions by reducing ionized calcium (iCa) levels, necessitating careful monitoring of systemic and postfilter iCa concentrations.
• Target postfilter iCa levels are typically 0.20–0.35 mmol/l to optimize anticoagulation during CRRT.

Purpose of the Study:

• To evaluate the reliability of different blood gas analyzers in measuring postfilter ionized calcium (iCa) concentrations during citrate-based CRRT.
• To highlight the challenges and potential inaccuracies in monitoring low iCa levels in the postfilter range.

Main Methods:

• A comparative study analyzing systemic and postfilter iCa measurements from six different devices in patients undergoing citrate-based CRRT.
• Assessment of the performance of instruments in the low iCa concentration range relevant to postfilter monitoring.

Main Results:

• Significant unreliability was observed in postfilter iCa measurements, with instruments unable to be validated in the low iCa range.
• The maximum mean difference between two instruments reached 0.33 mmol/l, indicating substantial variability.
• Potential for falsely high or low postfilter iCa readings, impacting anticoagulation management.

Conclusions:

• Current blood gas analyzers exhibit inaccuracies in measuring low postfilter iCa concentrations, requiring improvement.
• Clinicians must exercise caution with postfilter iCa results and consider increasing citrate flow if filter clotting persists despite readings within the target range, while monitoring for citrate accumulation.