Pozzoni Pietro, DI Filippo Salvatore, Pontoriero Giuseppe, Locatelli Francesco
Department of Nephrology and Dialysis, A. Manzoni Hospital, University of Milano-Bicocca, Lecco, Italy.
Hemodial Int. 2007 Apr;11(2):169-77. doi: 10.1111/j.1542-4758.2007.00165.x.
The attainment of a neutral sodium balance represents a major objective in hemodialysis patients. It requires that at the end of each dialysis session, total body water volume (V(f)) and total plasma water sodium concentration (Na(pwf)) are constant. Whereas to achieve a constant V(f) it is sufficient that ultrafiltration equals the interdialytic increase in body weight, it is impossible to predict the value of Na(pwf) and calculate the dialysate sodium concentration needed to obtain it without making use of kinetic mathematical models. The effectiveness of both sodium and conductivity kinetic models in predicting Na(pwf) has already been validated in previous clinical studies. However, applying the sodium kinetic model appears to be poorly feasible in the everyday clinical practice, due to the need for blood samples at the start of each dialysis session for the determination of predialysis plasma water sodium concentration. The conductivity kinetic model appears to be more easily applicable, because no blood samples or laboratory tests are needed to determine plasma water conductivity (C(pw)) and ionic dialysance (ID), used in place of plasma water sodium concentration and sodium dialysance, respectively. We applied the 2 models in 69 chronic hemodialysis patients using the Diascan Module for the automatic determination of C(pw) and ID, and using the latter as an estimate of sodium dialysance in the sodium kinetic model. The conductivity kinetic model was shown to be more accurate and precise in predicting Na(pwf) as compared with the sodium kinetic model. Both accuracy and imprecision of the 2 models were not significantly affected by the method used to estimate total body water volume. These findings confirm the conductivity kinetic model as being an effective and easily applicable instrument for the achievement of a neutral sodium balance in chronic hemodialysis patients.
实现钠平衡是血液透析患者的一个主要目标。这要求在每次透析结束时，总体液量（V(f)）和血浆总水量钠浓度（Na(pwf)）保持恒定。虽然要实现恒定的V(f)，超滤量等于透析间期体重增加量就足够了，但如果不使用动力学数学模型，就无法预测Na(pwf)的值并计算获得该值所需的透析液钠浓度。钠动力学模型和电导率动力学模型在预测Na(pwf)方面的有效性已在先前的临床研究中得到验证。然而，在日常临床实践中应用钠动力学模型似乎可行性较差，因为每次透析开始时都需要采集血样来测定透析前血浆总水量钠浓度。电导率动力学模型似乎更易于应用，因为测定血浆总水量电导率（C(pw)）和离子透析率（ID）时不需要采集血样或进行实验室检测，分别用它们来代替血浆总水量钠浓度和钠透析率。我们使用Diascan模块对69例慢性血液透析患者应用这两种模型，自动测定C(pw)和ID，并在钠动力学模型中使用后者作为钠透析率的估计值。结果表明，与钠动力学模型相比，电导率动力学模型在预测Na(pwf)方面更准确、更精确。两种模型的准确性和不精确性均未受到估计总体液量方法的显著影响。这些发现证实，电导率动力学模型是实现慢性血液透析患者钠平衡的一种有效且易于应用的工具。
