Cherney D Z, Zevallos G, Oreopoulos D, Halperin M L
Perit Dial Int. 2001 Jan-Feb;21(1):7-13.
The basis for hyponatremia is a negative balance for sodium (Na+) plus potassium (K+) and/or a positive balance for water. In patients with normal renal function, vasopressin is needed to prevent the excretion of electrolyte-free water. Vasopressin is not important when there is little residual renal function. If hyponatremia is accompanied by a quantitatively appropriate gain in weight, this implies that a gain of electrolyte-free water was the basis for hyponatremia. In the absence of this weight gain, a loss of salts is to be suspected. If the extracellular fluid (ECF) volume is obviously low, hyponatremia is due to a deficit of NaCl, unless there is a deficit of K+. With a KCl deficit and a contracted ECF volume, there should also be a large shift of Na+ into cells, so metabolic alkalosis would not be an expected finding. In contrast, those patients with no change in weight who have a normal or expanded ECF volume are subdivided into those with a gain of solutes restricted to the ECF compartment (glucose, mannitol), or those with a deficit of solutes of intracellular fluid origin, which implies that a catabolic state (malnutrition) may be present.
低钠血症的基础是钠（Na⁺）加钾（K⁺）的负平衡和/或水的正平衡。在肾功能正常的患者中，需要抗利尿激素来防止无电解质水的排泄。当残余肾功能很少时，抗利尿激素并不重要。如果低钠血症伴有体重适度增加，这意味着无电解质水的增加是低钠血症的基础。如果没有这种体重增加，则应怀疑有盐分丢失。如果细胞外液（ECF）容量明显降低，低钠血症是由于NaCl缺乏所致，除非存在K⁺缺乏。伴有KCl缺乏和ECF容量减少时，也应有大量Na⁺移入细胞内，因此代谢性碱中毒不是预期的表现。相反，体重无变化且ECF容量正常或增加的患者可分为两类：一类是溶质仅在ECF间隙增加（葡萄糖、甘露醇），另一类是细胞内液来源的溶质缺乏，这意味着可能存在分解代谢状态（营养不良）。
