Anticoagulation assessment methods in plasma exchange with regional citrate anticoagulation: evaluation of post-filter and filtered plasma ionized calcium.

AIM

To assess the possibility of using filtered plasma instead of postfilter ionized calcium (iCa) for the assessment of anticoagulation in plasma exchange (PE) with citrate anticoagulation.

METHODS

140 PE treatments were performed using either 4% or 15% citrate at a comparable dose. Paired samples of postfilter blood and filtered plasma were taken for iCa measurements with a point-of-care analyzer. Anticoagulation was also assessed with a bedside clotting time and visual assessment of the circuit after procedures.

RESULTS

In 490 paired samples, mean postfilter iCa was 0.39 ± 0.14 mmol/L, and filtered plasma iCa was 0.33 ± 0.11 mmol/L. Mean bedside clotting time was 18 ± 7 minutes. Neither the postfilter (r = 0.03, p = 0.73) nor the filtered plasma iCa (r = 0.09, p = 0.25) correlated significantly with bedside clotting time. Bland-Altman analysis showed a modest agreement between filtered plasma and postfilter iCa values (mean difference -0.07 mmol/L, upper and lower 95% limits of agreement 0.10 and -0.23 mmol/L). Median visual assessment score was excellent at all three checkpoints.

CONCLUSIONS: A modest agreement between filtered plasma and postfilter iCa values could be acceptable if only a confirmation of anticoagulant effect is required. Measuring filtered plasma instead of postfilter iCa would reduce blood loss with sampling, which could be important in some settings.
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