Mallié J P, Ait-Djaffer Z, Laroche F, Mario J, Perrier J C, Voltz C, Halperin M L
Laboratoire d'Exploration Fonctionnelle Rénale, CHU Nancy, France.
Clin Nephrol. 1998 May;49(5):287-92.
There is an inverse relationship between changes in the concentration of sodium in plasma (PNa) and intracellular fluid (ICF) volume. Intakes and losses of sodium (Na), potassium (K) and water can be divided into two volumes: isotonic and electrolyte-free water (EFW). Calculations of these volumes assess a tonicity balance, a tonicity imbalance results in a change of PNa: when EFW is added to body fluids, PNa decreases. Moreover, the concept of EFW permits a good understanding of the renal contribution to the defence of body tonicity.
To illustrate that the measurement of a tonicity balance provides the best estimate of changes in PNa in an ICU setting.
Twenty-two patients were admitted to the Post-Operative Intensive Care Unit. We investigated how well changes in EFW balance correlated with PNa variations and what is the best formula to calculate EFW in this setting.
PNa changes depend on EFW balance; there is no significant relationship with other classical factors such as urinary osmolality or Na-free water.
The utility of a tonicity balance is demonstrated. A formula is derived facilitating at the bedside the prediction of changes in PNa following fluid therapy: PNa2 = [(PNa1.TBW) + balance (Na + K)]/[TBW + balance H2O]. PNa changes can be understood and/or modified exclusively by a careful measurement of intakes and losses of Na, K and water.
血浆钠浓度（PNa）的变化与细胞内液（ICF）体积之间存在反比关系。钠（Na）、钾（K）和水的摄入与丢失可分为两个量：等渗和无电解质水（EFW）。这些量的计算评估了张力平衡，张力失衡会导致PNa的变化：当向体液中添加EFW时，PNa会降低。此外，EFW的概念有助于很好地理解肾脏对维持机体张力的作用。
说明在重症监护病房（ICU）环境中，测量张力平衡能最好地估计PNa的变化。
22例患者入住术后重症监护病房。我们研究了EFW平衡的变化与PNa变化的相关性如何，以及在这种情况下计算EFW的最佳公式是什么。
PNa的变化取决于EFW平衡；与尿渗透压或无钠水等其他经典因素无显著关系。
证明了张力平衡的实用性。推导了一个公式，便于在床边预测液体治疗后PNa的变化：PNa2 = [(PNa1.TBW) + 平衡量(Na + K)]/[TBW + 平衡量H2O]。通过仔细测量Na、K和水的摄入量和丢失量，可以单独理解和/或改变PNa的变化。
