Comparison of pre-filter and post-filter ionised calcium monitoring in continuous veno-venous hemodiafiltration (CVVHD-F) with citrate anti-coagulation

Regional citrate anti-coagulation dose titration: impact on dose of continuous renal replacement therapy

BACKGROUND

Regional citrate anti-coagulation (RCA) is the recommended anti-coagulation for continuous renal replacement therapy (CRRT). Citrated replacement fluids provide convenience but may compromise effluent delivery when adjusted to maintain circuit ionised calcium levels (circuit-iCa). This study aims to evaluate the effect of RCA titration on the delivered CRRT effluent dose.

METHODS

This prospective observational study evaluated patients on RCA-CRRT in continuous veno-venous hemodiafiltration mode. Citrated replacement fluid was titrated to target circuit-iCa 0.26-0.40 mmol/L. Patients were then stratified into 'reduced-dose' who required citrate down-titration and 'stable-dose' who did not.

RESULTS

Data from 200 RCA-CRRT sessions were collected. The reduced-dose RCA group (n = 114) had higher median initial citrate dose (3.00 vs 2.50; P < 0.001) but lower time-averaged dose (2.49 vs 2.60; P < 0.001). In addition, median prescribed effluent dose was 33.3 mL/kg/h (28.6-39.2) but median delivered effluent dose was significantly lower at 29.9 mL/kg/h (25.4-36.9; P < 0.001). Mortality was higher in the reduced-dose RCA group (39.5% vs 25.6%; P = 0.022) and in patients with delivered-to-prescribed effluent dose ratio of < 0.9 vs ≥ 0.9 (51.3% vs 29.2%; P = 0.014).

CONCLUSION

RCA titration can significantly impact delivered CRRT effluent dose. Measures should be taken to address the CRRT dose deficit and prevent poor outcomes due to inadequate dialysis.

The possibility of using effluent ionized calcium to assess regional citrate anticoagulation in continuous renal replacement therapy

AIM

This study aimed to investigate whether effluent ionized calcium was an appropriate indicator to assess anticoagulant effect in continuous renal replacement therapy with regional citrate anticoagulation instead of post-filter ionized calcium.

METHODS

In total, 48 paired samples of effluent fluid and post-filter blood were obtained from critically ill patients who required continuous renal replacement therapy. All samples were taken for ionized calcium measurements and were assessed by point-of-care analyzer. Correlations and agreements between two methods were performed by Pearson linear analysis and Bland-Altman analysis accordingly.

RESULTS

The mean post-filter ionized calcium was 0.42 ± 0.12 mmol/L, and mean ionized calcium level of effluent fluid was 0.39 ± 0.11 mmol/L. The ionized calcium level of effluent fluid was significantly correlated with post-filter ionized calcium in all continuous renal replacement therapy patients. Bland-Altman analysis showed that the mean difference of ionized calcium between two sampling sites in all continuous renal replacement therapy patients was -0.02 mmol/L with 95% confidence interval ranging from -0.09 to 0.04 mmol/L. The significant correlations and agreements were also demonstrated in continuous veno-venous hemofiltration, continuous veno-venous hemodialysis, and continuous veno-venous hemodiafiltration modalities separately.

CONCLUSION

The effluent ionized calcium could be a considerable substitute for post-filter ionized calcium to monitor the validity of regional citrate anticoagulation in continuous renal replacement therapy with less blood loss.

Regional Citrate Anticoagulation for Continuous Renal Replacement Therapy - A Safe and Effective Low-Dose Protocol

AIMS

Regional citrate anticoagulation (RCA) is the preferred mode of anticoagulation for continuous renal replacement therapy (CRRT). Conventional RCA-CRRT citrate dose ranges from 3 to 5 mmol/L of blood. This study explored the effectiveness of an RCA protocol with lower citrate dose and its impact on citrate-related complications.

METHODS

This prospective observational study compared two RCA-CRRT protocols in the intensive care unit. RCA Protocol 1 used an initial citrate dose of 3.0 mmol/L while Protocol 2 started with 2.5 mmol/L. The citrate dose was titrated by sliding scale to target circuit-iCa 0.26-0.40 mmol/L. Calcium was re-infused post-dialyzer and titrated by protocol to target systemic-iCa 1.01-1.20 mmol/L.

RESULTS

Two hundred RCA-CRRT sessions were performed (81 Protocol 1; 119 Protocol 2). The median age was 65.4 years and median APACHE-II score was 23. Citrate dose for Protocol 1 was significantly higher than Protocol 2 in the first 12 h. The circuit clotting rate was similar in both arms (Protocol 1: 9.9%; Protocol 2: 9.2%; P = 0.881). With Protocol 2, circuit-iCa levels were 2.42 times more likely to be on target (P = 0.003) while the odds of hypocalcaemia was 4.67 times higher with Protocol 1 (P < 0.001). There was a wider anion gap was noted with Protocol 1, which suggests a propensity for citrate accumulation with higher citrate exposure.

CONCLUSION

The RCA protocol with a lower initial citrate dose of 2.5 mmol/L blood had less citrate-related complications with no loss of efficacy. A more precise RCA prescription at the start of treatment avoids unnecessary citrate exposure and improves safety.

Comparison of pre-filter and post-filter ionised calcium monitoring in continuous veno-venous hemodiafiltration (CVVHD-F) with citrate anti-coagulation

Background

It is widespread practice during citrate anticoagulated renal replacement therapy to monitor circuit ionised calcium (iCa²⁺) to evaluate the effectiveness of anticoagulation. Whether the optimal site to sample the blood path is before or after the haemofilter is a common question.

Methods

Using a prospectively collected observational dataset from intensive care patients receiving pre-dilution continuous veno-venous haemodiafiltration (CVVHD-F) with integrated citrate anticoagulation we compared paired samples of pre and post filter iCa²⁺ where the target range was 0.3–0.5 mmol.L^-1 as well as concurrently collected arterial iCa²⁺. Two nested mixed methods linear models were fitted to the data describing post vs pre filter iCa²⁺, and the relationship of pre, post and arterial samples.

Setting

An 11 bed general intensive care unit.

Participants

450 grouped samples from 152 time periods in seven patients on CRRT with citrate anticoagulation.

Results

The relationship of post to pre-filter iCa²⁺ was not 1:1 with post = 0.082 + 0.751 x pre-filter iCa²⁺ (95% CI intercept: 0.015–0.152, slope 0.558–0.942). Variation was greatest between patients rather than between circuits within the same patient or citrate dose. Compared to arterial iCa²⁺ there was no significant difference between pre and post-filter sampling sites (F-value 0.047, p = 0.827)

Conclusion

These results demonstrate that there is minimal difference between pre and post filter samples for iCa²⁺ monitoring of circuit anticoagulation in citrate patients relative to the arterial iCa²⁺ in CVVHD-F however compared to pre-filter sampling, post filter sampling has a flatter response and greater variation.