Bodonyi-Kovacs Gabor, Lecker Stewart H
Renal Unit, Beth Israel Deaconess Medical Center, Harvard Medical School, DA 517, 330 Brookline Avenue, Boston, MA 02215, USA.
Clin Exp Nephrol. 2008 Feb;12(1):74-8. doi: 10.1007/s10157-007-0021-6. Epub 2008 Jan 9.
Hypernatremia usually results from the loss of water from the body in excess of loss of electrolytes. Although urinary loss of free water is usually thought of when the urine is dilute, it can also occur when the urine is relatively concentrated, for example after administration of osmotic diuretics. We present a case of hypernatremia in the setting of resolving acute renal failure. Quantitative analysis of urinary losses and the concept of electrolyte-free water clearance help to explain the development and persistence of hypernatremia in this case. Urine in such cases is typically rich in urea (an irrelevant osmole from the perspective of plasma sodium) with low concentrations of sodium and potassium (osmoles that determine plasma sodium concentration). So from the perspective of plasma sodium-determining osmoles (sodium and potassium) this hyperosmolar urine is actually "dilute", resulting in loss of free water and a rise in the plasma sodium concentration. This case illustrates the utility of the electrolyte-free water concept in understanding the development of hypernatremia in resolving acute renal failure. We discuss the evolution of these concepts and how they can be applied to typical clinical situations.
高钠血症通常是由于机体水分丢失超过电解质丢失所致。虽然当尿液稀释时通常会想到自由水经尿液丢失的情况，但在尿液相对浓缩时也可能发生，例如在使用渗透性利尿剂后。我们报告一例在急性肾衰竭缓解期出现高钠血症的病例。对尿液丢失进行定量分析以及无电解质水清除率的概念有助于解释该病例中高钠血症的发生和持续情况。此类病例的尿液通常富含尿素（从血浆钠的角度来看是无关的渗透溶质），而钠和钾的浓度较低（决定血浆钠浓度的渗透溶质）。因此，从决定血浆钠的渗透溶质（钠和钾）的角度来看，这种高渗尿液实际上是“稀释的”，导致自由水丢失，血浆钠浓度升高。该病例说明了无电解质水概念在理解急性肾衰竭缓解期高钠血症发生过程中的作用。我们讨论了这些概念的演变以及它们如何应用于典型的临床情况。
