Key result
Replacing ABL800 membranes at 4 weeks prevents a >40% drift in ionized calcium measurements.
Why the study?
Measurements of ionized calcium below 0.3 mmol/L are required for postfilter control during extracorporeal circulation with citrate anticoagulation, but the stability of these measurements over time was uncertain.
For ABL800 instruments, replacing the Ca2+ membrane after four weeks instead of the usual 12 weeks prevents clinically significant overestimation of ionized calcium at concentrations <0.3 mmol/L.
May risk >40% overestimation of postfilter Ca2+ on ABL800; leaves open optimal QC intervals for citrate anticoagulation.
Background Measurements of ionized calcium (Ca 2+ ) at concentrations less than 0.3 mmol/L are required for postfilter control in patients who receive extracorporeal circulation with sodium citrate anticoagulation. This study evaluates the stability of the Ca 2+ measurements at such concentrations. Methods The stability of the Ca 2+ measurements was tested by measuring daily the external standard Qualicheck concentration 3 s7950, Radiometer (0.22–0.25 mmol/L) by blood gas instruments ABL800 and ABL90, Radiometer. Two different Ca 2+ membrane lots were tested for the usual membrane lifetime of 12 weeks at ABL800 instruments. For the ABL90 instrument, the sensor cassette (with Ca 2+ membrane and electrode) was replaced after four weeks as required. Results We observed over 40% Ca 2+ increase within the usual 12 weeks lifetime of the Ca 2+ membrane at the ABL800 instruments. Measurements of Ca 2+ at concentrations less than 0.3 mmol/L were within acceptable limits for both ABL800 and ABL90 instruments when Ca 2+ membrane and sensor cassette were replaced after four weeks. Conclusions For ABL800 instruments, it is necessary to use an extra quality control (<0.3 mmol/L) in addition to the usual quality controls to monitor Ca 2+ measurements below 0.3 mmol/L. The acceptable stability of the Ca 2+ measurements can be achieved by the Ca 2+ membrane and sensor cassette replacement after four weeks. If the usual 12 weeks of Ca 2+ membrane lifetime is maintained, it may result in a clinically significant overestimation of Ca 2+ by ABL800 instruments.
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Averina et al. (2016) studied Extracorporeal circulation with sodium citrate anticoagulation. Ca2+ membrane and sensor cassette replacement after four weeks vs. Usual 12 weeks lifetime was evaluated on Stability of ionized calcium measurements at concentrations less than 0.3 mmol/L. Over 40% Ca2+ increase was observed within the usual 12-week membrane lifetime at ABL800 instruments, whereas replacement after 4 weeks maintained measurements within acceptable limits.
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