Feldkamp Thorsten, Weiler Norbert, Marx Michael, Luppa Peter B, Junker Ralf
Clin Lab. 2016 Oct 1;62(10):2025-2031. doi: 10.7754/Clin.Lab.2016.160331.
During the course of acute kidney injury (AKI) patients may require renal replacement therapy (RRT). The preferred therapeutic measure for such patients is continuous RRT (CRRT). Anticoagulation is required to prevent clotting of the extracorporeal circuit. The actual KDIGO guidelines recommend citrate as the first line anticoagulant.
Citrate dose infused into the extracorporeal circuit should achieve an extracorporeal calcium concentration of 0.2 - 0.3 mmol/L. Here, we evaluated two blood gas analysers for their ability of covering the calcium concentration range needed for CRRT (Radiometer ABL 835; Instrumentation Laboratory GEM 4000). Measurements of iCa from 0.2 to 3.0 mmol/L were performed in aqueous 0.9% NaCl solutions with and without human serum albumin (HAS) and also in patient samples.
Using the GEM analyser, differences of measured results to target values were low throughout the whole concentration range. Using the ABL system, the difference increased with lower target values and exceeded up to 60% at 0.2 mmol/L. The results were reproduced in patient samples.
Measuring Ca2+ concentrations could result in an overdosing or underdosing of citrate when using an analytical method which is different to the instrument used initially to achieve the recommended concentrations. If measurement of the new method results in lower Ca2+ concentration and, therefore, reduced anticoagulation by citrate infusion this could lead to more clotting events. Overestimation of the calcium concentration by the new method in the extracorporeal circuit would result in an increased citrate dose delivered to the patient, leading to in vivo hypocalcemia and a pronouncement of citrate induced acid base derangements. Therefore, to monitor Ca2+ concentrations in CRRT during citrate anticoagulation, specific target values for each individual instrument must be established.
在急性肾损伤（AKI）病程中，患者可能需要肾脏替代治疗（RRT）。此类患者的首选治疗措施是持续肾脏替代治疗（CRRT）。需要进行抗凝以防止体外循环凝血。KDIGO现行指南推荐枸橼酸盐作为一线抗凝剂。
输注到体外循环中的枸橼酸盐剂量应使体外钙浓度达到0.2 - 0.3 mmol/L。在此，我们评估了两款血气分析仪覆盖CRRT所需钙浓度范围的能力（雷度ABL 835；美国仪迈GEM 4000）。在含和不含人血清白蛋白（HAS）的0.9%氯化钠水溶液以及患者样本中进行了0.2至3.0 mmol/L的离子钙（iCa）测量。
使用GEM分析仪时，在整个浓度范围内测量结果与目标值的差异较小。使用ABL系统时，差异随着目标值降低而增大，在0.2 mmol/L时差异高达60%。患者样本中也重现了这些结果。
当使用与最初用于达到推荐浓度的仪器不同的分析方法时，测量钙浓度可能导致枸橼酸盐过量或不足。如果新方法的测量结果导致钙浓度降低，从而通过输注枸橼酸盐减少抗凝，这可能导致更多凝血事件。新方法高估体外循环中的钙浓度会导致输送给患者的枸橼酸盐剂量增加，导致体内低钙血症并加剧枸橼酸盐诱导的酸碱紊乱。因此，在枸橼酸盐抗凝期间监测CRRT中的钙浓度时，必须为每个仪器建立特定的目标值。
