Aziz Fahad, Sam Ramin, Lew Susie Q, Massie Larry, Misra Madhukar, Roumelioti Maria-Eleni, Argyropoulos Christos P, Ing Todd S, Tzamaloukas Antonios H
Department of Medicine, Division of Nephrology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA.
Department of Medicine, Zuckerberg San Francisco General Hospital, School of Medicine, University of California in San Francisco, San Francisco, CA 94110, USA.
J Clin Med. 2023 Jun 15;12(12):4076. doi: 10.3390/jcm12124076.
Pseudohyponatremia remains a problem for clinical laboratories. In this study, we analyzed the mechanisms, diagnosis, clinical consequences, and conditions associated with pseudohyponatremia, and future developments for its elimination. The two methods involved assess the serum sodium concentration ([Na]) using sodium ion-specific electrodes: (a) a direct ion-specific electrode (ISE), and (b) an indirect ISE. A direct ISE does not require dilution of a sample prior to its measurement, whereas an indirect ISE needs pre-measurement sample dilution. [Na] measurements using an indirect ISE are influenced by abnormal concentrations of serum proteins or lipids. Pseudohyponatremia occurs when the [Na] is measured with an indirect ISE and the serum solid content concentrations are elevated, resulting in reciprocal depressions in serum water and [Na] values. Pseudonormonatremia or pseudohypernatremia are encountered in hypoproteinemic patients who have a decreased plasma solids content. Three mechanisms are responsible for pseudohyponatremia: (a) a reduction in the [Na] due to lower serum water and sodium concentrations, the electrolyte exclusion effect; (b) an increase in the measured sample's water concentration post-dilution to a greater extent when compared to normal serum, lowering the [Na] in this sample; (c) when serum hyperviscosity reduces serum delivery to the device that apportions serum and diluent. Patients with pseudohyponatremia and a normal [Na] do not develop water movement across cell membranes and clinical manifestations of hypotonic hyponatremia. Pseudohyponatremia does not require treatment to address the [Na], making any inadvertent correction treatment potentially detrimental.
假性低钠血症仍是临床实验室面临的一个问题。在本研究中，我们分析了假性低钠血症的机制、诊断、临床后果、相关情况以及消除该问题的未来发展方向。所涉及的两种方法是使用钠离子特异性电极评估血清钠浓度（[Na]）：（a）直接离子特异性电极（ISE），和（b）间接ISE。直接ISE在测量前不需要对样品进行稀释，而间接ISE需要在测量前对样品进行稀释。使用间接ISE进行的[Na]测量会受到血清蛋白质或脂质异常浓度的影响。当使用间接ISE测量[Na]且血清固体成分浓度升高时，就会发生假性低钠血症，导致血清水和[Na]值出现相应降低。在血浆固体成分降低的低蛋白血症患者中会出现假性正常钠血症或假性高钠血症。假性低钠血症由三种机制引起：（a）由于血清水和钠浓度降低导致[Na]降低，即电解质排斥效应；（b）与正常血清相比，稀释后测量样品的水浓度增加幅度更大，从而降低了该样品中的[Na]；（c）当血清高粘度降低血清输送到分配血清和稀释剂的设备时。假性低钠血症且[Na]正常的患者不会出现跨细胞膜的水移动和低渗性低钠血症的临床表现。假性低钠血症不需要针对[Na]进行治疗，任何无意的纠正治疗都可能有害。
