A method for evaluating hemodialysis adequacy based on sodium balance

Abstract

The application discloses a hemodialysis sufficiency evaluation method based on sodium balance, and relates to the technical field of hemodialysis, and the method comprises the following steps: obtaining the body weight, dry body weight and serum sodium concentration of a patient before dialysis; calculating a target sodium removal amount Na_target=DeltaW* [Na]s / 0.93, and establishing a quantitative equivalent relationship between the body weight increase and sodium accumulation; obtaining or calculating an actual sodium removal amount (including two ways of convection and diffusion); calculating a sodium removal ratio R_Na=Na_actual / Na_target; and evaluating the dialysis sufficiency according to the R_Na. The application firstly changes the dialysis sufficiency evaluation from 'urea removal' to'sodium and water removal', and directly aims at the main pathological burden of kidney failure patients, i.e. sodium and water retention. The sodium removal ratio R_Na is more directly related to the volume state and cardiovascular prognosis of the patient than the traditional Kt / V index. The method only needs the body weight and serum sodium before and after dialysis to be calculated, and can be integrated into the existing dialysis information system.

Description

Technical Field

[0001] This invention relates to the field of hemodialysis technology, and in particular to a method for assessing the adequacy of hemodialysis based on sodium-water balance. Background Technology

[0002] In 1985, Gotch and Sargent established a urea kinetic model based on the National Cooperative Dialysis Study (NCDS) in the United States and proposed Kt / V as an indicator of dialysis adequacy. For more than 40 years since then, Kt / V has become the most widely used adequacy assessment standard in the global dialysis field and has been recommended by clinical guidelines in various countries as a core reference indicator for dialysis prescription.

[0003] However, Kt / V only reflects the clearance efficiency of small molecule urea (molecular weight 60 Da), while urea itself has extremely low toxicity. The most significant pathological burden in patients with renal failure is volume overload, hypertension, and cardiovascular events caused by sodium and water retention. Extensive clinical evidence shows that even when Kt / V is within the target range (≥1.2), patients commonly experience hypertension and cardiovascular complications, suggesting that Kt / V does not effectively reflect the effectiveness of dialysis in clearing sodium and water load.

[0004] In his 2018 paper (Hemodial Int. 2018;22(4):413-437), Twardowski clearly pointed out that "sodium is a neglected uremic toxin" and called for a shift in dialysis focus from urea clearance to sodium clearance. However, this paper only put forward a conceptual viewpoint and did not provide quantitative assessment methods and calculation models for sodium clearance.

[0005] Patients with kidney failure lose the kidneys' ability to excrete sodium and water. Sodium and water ingested between dialysis sessions accumulate in the body, leading to volume overload. The core task of each dialysis session should be to remove the sodium and water accumulated between dialysis sessions, allowing the patient to return to a dry weight. The body's sodium content and water volume are closely coupled through serum sodium concentration (approximately 140 mmol / L): excess sodium is inevitably accompanied by a proportional amount of water retention, and vice versa. Therefore, "water excretion" and "sodium excretion" are physiologically equivalent.

[0006] Sodium removal during dialysis involves two pathways: convective removal (sodium carried away by ultrafiltration) and diffusion removal (sodium transport driven by concentration gradient). Existing literature uses the diffusion equilibrium concentration formula C_eq = σ × [Na]d (σ being the Donnan factor ≈ 0.97) to calculate diffusion removal, which suffers from overcorrection. This formula predicts a diffusion gradient of 150.5 - 0.97 × 140 = 14.7 mmol / L under isosodium dialysis conditions ([Na]s = 140, [Na]d = 140), significantly overestimating diffusion-induced sodium excretion. Another previously proposed formula, C_eq = [Na]d / 0.93, goes to the other extreme: predicting a zero gradient under isosodium conditions, completely ignoring the Gibbs-Donnan effect. This invention recognizes that the correct diffusion equilibrium concentration should be C_eq = [Na]d / σ (σ = 0.97 being the Gibbs-Donnan factor). The physical basis is that plasma proteins carry a net negative charge, which, through the Gibbs-Donnan effect, reduces the effective diffuse sodium concentration on the blood side to σ×[Na]s / 0.93; while the dialysate is a 100% aqueous solution, containing no protein, and its sodium concentration does not require correction. Under isosodium conditions, the diffusion gradient is 0.97×150.5 - 140 = 6.0 mmol / L, which is neither zero nor 14.7, but accurately reflects the true physical gradient of the Gibbs-Donnan effect.

[0007] More generally, the driving force of diffuse sodium transport involves two independent physical effects: (1) plasma aqueous phase correction: plasma consists of an aqueous phase (approximately 93%) and a protein / lipid phase (approximately 7%). Sodium is only soluble in the aqueous phase, so the plasma sodium concentration Ce = [Na]s / 0.93; (2) Gibbs-Donnan effect: plasma proteins carry a net negative charge, reducing the concentration of sodium ions that can freely diffuse across the membrane to σ×Ce (σ=0.97), i.e., the effective diffuse sodium concentration on the blood side is σ×[Na]s / 0.93. The dialysate is a pure aqueous solution, containing no protein, so there is no need for aqueous phase correction or Gibbs-Donnan effect, and its sodium concentration [Na]d directly participates in the gradient calculation. Therefore, the diffusion driving force = σ×[Na]s / 0.93 - [Na]d, which is equivalent to C_eq = [Na]d / σ in the ODE model.

[0008] It should be noted that the correction formula C_eq = [Na]d / σ (σ=0.97) of this invention reveals an important physical fact: under isosodium conditions ([Na]d = [Na]s = 140), the diffusion gradient is not zero, but approximately 6.0 mmol / L, which is the true physical result of the Gibbs-Donnan effect. The condition for the diffusion gradient to reach zero is [Na]d = σ×[Na]s / 0.93 ≈ 146 mmol / L. When [Na]d is below or above this equilibrium point, the direction and magnitude of diffusion transport can be accurately predicted. Summary of the Invention

[0009] The technical problem to be solved by this invention is to provide a method for assessing the adequacy of hemodialysis with sodium-water balance as the core, overcome the fundamental defects of the existing dialysis adequacy assessment system with urea clearance rate (Kt / V) as the core indicator, establish a quantitative equivalence relationship of "water removal ≡ sodium removal", and provide an intuitive and operable dialysis prescription assessment tool for clinical use.

[0010] Therefore, this invention proposes a method for assessing the adequacy of hemodialysis based on sodium-water balance, comprising the following steps: Step S1: Obtain the patient's predialysis parameters. Obtain the patient's predialysis weight W_pre (kg), dry weight W_dry (kg), and predialysis serum sodium concentration [Na]s (mmol / L). Dry weight is the ideal weight for the patient when there is no edema and blood pressure is normal, and is determined by the clinician based on the patient's condition.

[0011] Step S2: Calculate the target sodium removal amount Na_target. The calculation formula is: Na_target = (W_pre - W_dry) × [Na]s / 0.93 Where: (W_pre - W_dry) represents the weight gain ΔW during the interdialysis period, in kg, approximately equal to liters; [Na]s / 0.93 converts serum sodium concentration to plasma water-sodium concentration, since plasma contains approximately 93% water and 7% protein / lipid, sodium is only soluble in the aqueous phase—0.93 is the volume fraction of the aqueous phase in plasma, a physical constant determined by plasma composition rather than an empirical coefficient. The physical meaning of Na_target is: the total amount of sodium contained in the water accumulated during the interdialysis period.

[0012] Step S3: Obtain or calculate the actual sodium clearance, Na_actual. The actual sodium clearance includes the sum of convective sodium clearance and diffuse sodium clearance. Convective sodium clearance, Na_conv = V_UF × [Na]s / 0.93, where V_UF is the total actual ultrafiltration volume (L). Diffuse sodium clearance is calculated using a two-chamber sodium kinetic model or estimated using the pre- and post-dialysis mass balance method: Na_actual = V_pre × C_pre - V_post × C_post, where V_pre and V_post are the total water volume before and after dialysis, and C_pre and C_post are the plasma sodium and water concentrations before and after dialysis.

[0013] Step S4: Calculate the sodium clearance ratio R_Na and assess dialysis adequacy. R_Na = Na_actual / Na_target. The criteria are: R_Na ≥ 1.0 indicates adequate dialysis (sodium clearance meets or exceeds the target); 0.8 ≤ R_Na < 1.0 indicates borderline adequate dialysis (requires attention); R_Na < 0.8 indicates inadequate dialysis (prescription adjustment required).

[0014] Step S5 (Optional): Equivalent water displacement conversion. Convert sodium clearance to equivalent water displacement for easier clinical understanding: V_equiv = Na_actual / 140. This value indicates how many liters of water are needed to clear sodium at a concentration of 140 mmol / L in body fluids.

[0015] The beneficial effects of this invention compared to the prior art are: (1) For the first time, the assessment of dialysis adequacy was shifted from "urea clearance" to "sodium and water clearance", directly targeting the most important pathological burden of patients with renal failure - sodium and water retention.

[0016] (2) A quantitative equivalence relationship of "water removal ≡ sodium removal" was established (Na_target = ΔW × [Na]pw), unifying the seemingly independent "ultrafiltration amount" and "sodium removal amount" into two expressions of the same physical quantity.

[0017] (3) A corrected diffusion equilibrium concentration formula, C_eq = [Na]d / σ (σ=0.97), was proposed, which correctly distinguishes two independent physical effects: 0.93 (volume fraction of plasma aqueous phase) is used to convert serum sodium into plasma water-sodium concentration, and cannot be omitted in the calculation of Na_target and Na_conv; σ=0.97 (Gibbs-Donnan factor) reflects the constraint of plasma protein negative charge on diffusing sodium ions, and cannot be omitted in the diffusion equilibrium calculation. This formula corrects the diffusion gradient under isosodium conditions from 14.7 mmol / L (traditional Donnan formula) to 6.0 mmol / L, accurately reflecting the true physical gradient of the Gibbs-Donnan effect.

[0018] (4) Sodium clearance ratio R_Na is a dimensionless index that directly reflects the degree of sodium and water load clearance during each dialysis session. It is more directly related to the patient's volume status and cardiovascular prognosis than Kt / V.

[0019] (5) Equivalent drainage volume V_equiv provides clinicians with an intuitive assessment tool: for example, "equivalent drainage volume of this dialysis is 2.1L" is easier to understand and guide prescription adjustments than "Kt / V=1.4".

[0020] (6) This method can be integrated with existing dialysis information systems, and only requires body weight and serum sodium before and after dialysis to calculate, without the need for additional equipment.

[0021] (7) The sodium clearance ratio R_Na is not a "pure sodium diffusion indicator," but rather a "result of multiple mechanisms superimposed in the dialysis system." It is simultaneously affected by: dialysate sodium setting, ultrafiltration volume, plasma protein (Donnan), convection ratio, dialysis time, and body fluid distribution. Therefore, it is a "comprehensive effect indicator," not a "mechanism-pure indicator." In a dialysis setting, the sodium clearance ratio reflects the dynamic changes in sodium load during actual treatment, which is more in line with the understanding of clinical medical staff in their actual work. Attached Figure Description

[0022] The present invention will be further described in detail below with reference to the accompanying drawings, which are simulation experimental results based on common clinical dialysis parameters. The basic experimental parameters are: patient weight 65kg, dry weight-related volume balance, dialysate sodium concentration range 134-145mmol / L, dialysis time 3-8 hours, and ultrafiltration volume 0-4L.

[0023] Figure 1 shows the effect of different dialysate sodium concentrations on serum sodium, sodium clearance, convection / diffusion ratio, and ECF volume (dialysis time 4 h, ultrafiltration volume 2 L, 65 kg, C_eq = [Na]d / σ (σ = 0.97)). Figure 1(A) shows the change in serum sodium concentration over time during dialysis, with the horizontal axis representing Time (min) and the vertical axis representing serum sodium concentration (mmol / L). The curve is labeled [Na] d = 134, 136, 138, 140, 142, 145. Figure 1(B) shows the change in total sodium clearance over time, with the horizontal axis representing Time (min) and the vertical axis representing total sodium clearance (mmol), labeled Target301mmol. The curve is the same as the dialysate sodium concentration mentioned above. Figure 1(C) shows the ratio of convective sodium clearance to diffuse sodium clearance, with the horizontal axis representing [Na] d (mmol / L) and the vertical axis representing sodium clearance (mmol), labeled Convective and Diffusive, respectively. Figure 1(D) shows the change in extracellular fluid (ECF) volume over time, with the horizontal axis representing Time (min) and the vertical axis representing ECF volume (L), labeled Dry weight. ECF (extracellular fluid volume per dry body weight), the curve is the same as the dialysate sodium concentration mentioned above; this figure reflects that dialysate sodium concentration is a key factor affecting sodium clearance and patient body fluid volume.

[0024] Figure 2 shows the effect of different dialysis times on sodium removal and ultrafiltration rate safety (dialysis solution sodium concentration 138 mmol / L, ultrafiltration volume 2 L). Figure 2(A) shows the change in serum sodium concentration with dialysis time, with Time (min) on the horizontal axis and serum sodium concentration (mmol / L) on the vertical axis. The curves are labeled 180 min, 240 min, 300 min, 360 min, and 480 min. Figure 2(B) shows the change in sodium removal with dialysis time, with Time (min) on the horizontal axis and serum sodium concentration (mmol / L) on the vertical axis. The curves are labeled 180 min, 240 min, 300 min, 360 min, and 480 min. Figure 2(C) shows the relationship between sodium removal and ultrafiltration rate (UFR), with dialysis time (min) on the horizontal axis and sodium removal (mmol) on the left and ultrafiltration rate (UFR) (ml / h / kg) on ​​the right on the vertical axis. The Na removal and UFR curves are labeled respectively. This figure reflects that extending the dialysis time can improve the sodium removal effect, and the ultrafiltration rate needs to be controlled within a safe range to ensure treatment safety.

[0025] Figure 3 shows the sodium removal contour plot (dialysis time 4h, 65kg); Figure 3(A) shows the total sodium clearance contour lines with ultrafiltration volume (UF volume) on the horizontal axis and dialysate sodium concentration on the vertical axis. The horizontal axis represents UF volume (L), and the vertical axis represents [Na] d (mmol / L). The contour lines are labeled 80, 160, 240, 400, 480, 560, and 640 (mmol). Figure 3(B) shows the serum sodium concentration contour lines after dialysis. The horizontal axis represents UF volume (L), and the vertical axis represents [Na] d (mmol / L). The contour lines are labeled 135.2, 136.0, 136.8, 138.4, 139.2, 140.0, and 140.8 (mmol / L). These figures allow for a direct view of the sodium clearance effect under different combinations of ultrafiltration volume and dialysate sodium concentration, providing a reference for initial prescription adjustments.

[0026] Figure 4 is a schematic diagram of the safe and effective prescription range (dialysis time 4h, 65kg, weight gain 2kg between dialysis sessions). The graph uses ultrafiltration volume as the horizontal axis and dialysate sodium concentration as the vertical axis, superimposed with three constraints: target sodium clearance (301 mmol), safe range of serum sodium, and ultrafiltration rate limit (2.6 L @ 10 ml / h / kg). The intersection of these constraints represents the safe and effective range of the dialysis prescription. Clinicians can directly adjust the ultrafiltration volume and dialysate sodium concentration within this range to achieve safe and effective sodium and water clearance.

[0027] Figure labeling: [Na] d - dialysate sodium concentration, UF - ultrafiltration volume, UFR - ultrafiltration rate, ECF - extracellular fluid, ΔW - weight gain during interdialysis. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, specific embodiments of the invention will be described in detail below with reference to the accompanying drawings. These embodiments are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0029] Example 1: Assessment of dialysis adequacy in standard patients Patient's basic parameters: predialysis weight W_pre = 67 kg, dry weight W_dry = 65 kg, predialysis serum sodium [Na]s = 140 mmol / L, dialysis time 4 hours, dialysate sodium concentration [Na]d = 138 mmol / L.

[0030] Step S1: Obtain the parameters. ΔW = W_pre - W_dry = 67 - 65 = 2.0 kg.

[0031] Step S2: Calculate the target sodium removal amount.

[0032] Na_target = 2.0 × 140 / 0.93 = 2.0 × 150.5 = 301 mmol Physical meaning: The 2.0 kg weight gain in the patient between dialysis intervals contains 301 mmol of sodium.

[0033] Step S3: Calculate the actual sodium removal amount.

[0034] Assuming the actual ultrafiltration rate V_UF = 2.0 L, then the convective sodium removal rate is: Na_conv = 2.0 × 140 / 0.93 = 301 mmol The amount of diffuse sodium cleared was calculated using a two-chamber sodium kinetic model. When [Na]d = 138 mmol / L, the effective diffuse sodium concentration in the blood was σ×[Na]s / 0.93 = 0.97×150.5 = 146.0 mmol / L, and the diffusion gradient was 146.0 -138 = 8.0 mmol / L, indicating a positive diffusion gradient. The model calculated the amount of diffuse sodium cleared to be approximately 25 mmol.

[0035] Na_actual = 301 + 25 = 326 mmol Step S4: Assess dialysis adequacy.

[0036] R_Na = 326 / 301 = 1.08 R_Na > 1.0 indicates adequate dialysis.

[0037] Step S5: Equivalent drainage volume.

[0038] V_equiv = 326 / 140 = 2.33 L Clinical interpretation: The equivalent drainage volume of this dialysis was 2.33 L, which exceeded the weight gain of 2.0 L, indicating that not only was the sodium-water accumulated between dialysis sessions removed, but also some sodium was removed in addition.

[0039] Example 2: Effect of dialysate sodium concentration on sodium removal like Figure 1 As shown, for the same patient (65 kg, ΔW = 2 kg, [Na]s = 140 mmol / L, dialysis for 4 hours), the sodium concentration of the dialysate was set to 134, 136, 138, 140, 142, and 145 mmol / L, and the changes of each parameter were simulated and calculated using a two-chamber sodium kinetic model.

[0040] Simulation results show that: (1) the lower the sodium concentration in the dialysate, the more sodium is excreted through diffusion, and the greater the total sodium clearance; (2) when [Na]d = 140 mmol / L (isosodium dialysis), there is still a diffusion gradient of about 6.0 mmol / L (Gibbs-Donnan effect), resulting in a small amount of sodium excretion through diffusion; (3) when [Na]d > 146 mmol / L (exceeding σ×[Na]s / 0.93), the diffusion direction reverses, sodium is infused from the dialysate into the patient's body, and the total sodium clearance decreases. This verifies the correctness of the formula C_eq = [Na]d / σ (σ=0.97) in this invention.

[0041] Example 3: The effect of dialysis time on sodium clearance and safety like Figure 2 As shown, with a fixed ultrafiltration volume of 2.0 L and a dialysate sodium concentration of 138 mmol / L, dialysis times of 3, 4, 5, 6, and 8 hours were set. The results showed that extending the dialysis time reduced the ultrafiltration rate (improving safety) while increasing the diffusion sodium removal time and thus increasing the total sodium clearance. When the dialysis time was extended from 3 hours to 5 hours, the ultrafiltration rate decreased from 11.1 ml / h / kg to 6.7 ml / h / kg (below the safety threshold of 10 ml / h / kg), while sodium clearance increased by approximately 15%.

[0042] Example 4: Determination of the safe and effective prescription range like Figure 3 and Figure 4 As shown, in the two-dimensional parameter space (ultrafiltration volume × dialysate sodium concentration), three constraints are superimposed: (1) sodium clearance reaches the target value Na_target; (2) ultrafiltration rate does not exceed 10 ml / h / kg; (3) serum sodium after dialysis is in the range of 136-143 mmol / L. The region enclosed by the three constraints is the "safe and effective prescription interval", and any combination of (V_UF, [Na]d) within this interval can achieve adequate and safe dialysis.

[0043] Example 5: Evaluation System Implementation The present invention also provides a hemodialysis adequacy assessment system based on sodium-water balance, comprising: The data acquisition module is used to acquire the patient's predialysis weight W_pre, dry weight W_dry, predialysis serum sodium concentration [Na]s, and parameters such as ultrafiltration volume, dialysate flow rate and sodium concentration during dialysis. The target sodium removal calculation module is used to calculate the target sodium removal amount based on Na_target = (W_pre - W_dry) × [Na]s / 0.93; The actual sodium removal calculation module is used to calculate the sum of convective sodium removal and diffuse sodium removal during dialysis, Na_actual, based on a two-chamber sodium kinetic model. The adequacy assessment module is used to calculate the sodium clearance ratio R_Na = Na_actual / Na_target and determine the adequacy of sodium clearance during dialysis. The display module is used to display the real-time value and trend curve of R_Na, as well as the equivalent displacement V_equiv = Na_actual / [Na]s.

[0044] The modules are connected via a data bus and can be integrated into the dialysis machine control system or operated as an independent add-on module.

[0045] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for assessing the adequacy of hemodialysis based on sodium-water balance, using sodium clearance instead of urea clearance rate Kt / V as the core assessment indicator for dialysis adequacy, characterized in that, Includes the following steps: Step S1: Obtain the patient's predialysis weight W_pre, dry weight W_dry, and predialysis serum sodium concentration [Na]s; Step S2: Based on the quantitative relationship that "water removal is equivalent to sodium removal", calculate the target sodium removal amount: Na_target = ΔW × [Na]pw = (W_pre - W_dry) × [Na]s / 0.93 Where ΔW represents the weight gain during interdialysis, [Na]pw = [Na]s / 0.93 represents the plasma water-sodium concentration, and 0.93 represents the plasma aqueous phase volume fraction—plasma is 93% water and 7% protein and lipids, and sodium ions are distributed only in the aqueous phase of plasma rather than in the total plasma volume. This coefficient is a physical constant determined by the plasma composition rather than an empirical fitting parameter; the target sodium clearance is equal to the total amount of sodium accumulated in the body due to sodium and water intake during interdialysis. This formula establishes a quantitative equivalence relationship between weight gain (water accumulation) and sodium accumulation. Step S3: Calculate the actual sodium removal amount Na_actual during dialysis, where the actual sodium removal amount is the sum of the convective sodium removal amount and the diffuse sodium removal amount; Step S4: Use the sodium clearance ratio R_Na as an indicator of dialysis adequacy. R_Na = Na_actual / Na_target A value of R_Na ≥ 1.0 indicates adequate dialysis, meaning that the sodium accumulated between dialysis sessions has been completely removed; 0.8 ≤ R_Na < 1.0 indicates adequate borderline dialysis; and R_Na < 0.8 indicates inadequate dialysis.

2. The method as described in claim 1, characterized in that, The quantitative relationship of "water removal is equivalent to sodium removal" in step S2 is based on the following physiological principle: the sodium content and water volume in patients with renal failure are closely coupled through serum sodium concentration, and excess sodium is necessarily accompanied by a proportional water retention; therefore, removing water accumulated during the interdialysis period (i.e., ultrafiltration to dry weight) is physiologically equivalent to removing the corresponding sodium, and the target sodium removal amount Na_target is the total amount of sodium that needs to be removed to restore the patient's weight from the predialysis weight to dry weight.

3. The method as described in claim 1, characterized in that, The calculation of the amount of dispersed sodium removed in step S3 uses the corrected dispersion equilibrium concentration formula: C_eq = [Na]d / σ (σ=0.97 is the Gibbs-Donnan factor) Where [Na]d is the setpoint for the sodium concentration of the dialysate, and σ=0.97 is the Gibbs-Donnan factor. This correction is based on the following physical fact: plasma proteins carry a net negative charge, which reduces the concentration of freely diffusing sodium ions in plasma water to σ×Ce (Ce=[Na]s / 0.93 is the plasma water sodium concentration) through the Gibbs-Donnan effect, i.e., the effective diffuse sodium concentration on the blood side is σ×[Na]s / 0.

93. The dialysate is a 100% aqueous solution, free of protein, and requires no correction; its sodium concentration [Na]d directly participates in the diffusion gradient calculation. Therefore, the diffusion driving force is σ×[Na]s / 0.93 - [Na]d. Under isosodium conditions ([Na]d=140, [Na]s=140), the diffusion gradient is 0.97×150.5 - 140 = 6.0 mmol / L, reflecting the true Gibbs-Donnan effect. This formula replaces the over-corrected C_eq = in the prior art. The formula σ×[Na]d (σ≈0.97) (which predicts a gradient of 14.7 mmol / L under isosodium conditions, severely overestimating diffuse sodium excretion) also replaces the erroneous formula C_eq = [Na]d / 0.93 (which predicts a gradient of zero under isosodium conditions and ignores the Gibbs-Donnan effect). The condition for the diffuse gradient to return to zero is [Na]d = σ×[Na]s / 0.93 ≈ 146 mmol / L, not [Na]d = [Na]s.

4. The method as described in claim 1, characterized in that, The formula for calculating the amount of sodium scavenged by convection is as follows: Na_conv = V_UF × [Na]s / 0.93 V_UF represents the actual total ultrafiltration volume during the dialysis process.

5. The method as described in claim 3, characterized in that, The amount of diffuse sodium clearance was calculated using a two-chamber sodium kinetic model, which divides the patient's body fluid into an extracellular fluid chamber and an intracellular fluid chamber, wherein cell membrane aquaporins transport only water and do not carry sodium ions, i.e., water transmembrane transport does not produce solvent-drafted sodium transport.

6. The method as described in claim 1, characterized in that, The actual sodium removal amount can also be calculated using the pre- and post-dialysis mass balance method: Na_actual = V_pre × C_pre - V_post × C_post Where V_pre and V_post represent the total water volume before and after dialysis, and C_pre and C_post represent the plasma water and sodium concentrations before and after dialysis.

7. The method as described in claim 1, characterized in that, It also includes step S5: converting the actual sodium removal amount into equivalent water displacement. V_equiv = Na_actual / [Na]s The equivalent water displacement directly represents the sodium removal effect of this dialysis session as equivalent to how many liters of body fluid are discharged. It is used to replace Kt / V to provide clinicians with a directly understandable assessment of dialysis effectiveness.

8. The method as described in claim 1, characterized in that, When R_Na < 1.0, the method further includes a step of guiding prescription adjustment based on sodium removal deficit (Na_target - Na_actual), including one or more of the following adjustment strategies: reducing dialysate sodium concentration to increase diffuse sodium removal, increasing ultrafiltration volume to increase convective sodium removal, and extending dialysis time to increase total sodium removal time.

9. The method as described in claim 1, characterized in that, The sodium clearance ratio R_Na was also used to predict postdialysis blood pressure control, interdialysis weight gain trends, and cardiovascular event risk, serving as a quantitative indicator for prognostic assessment of dialysis patients.

10. The method as described in claim 1, characterized in that, The method is applicable to hemodialysis (HD), hemodiafiltration (HDF), and online-HDF.

11. A hemodialysis adequacy assessment system based on sodium-water balance, using sodium clearance instead of urea clearance rate Kt / V as the core assessment indicator for dialysis adequacy, characterized in that... include: The data acquisition module is used to acquire the patient's predialysis weight, dry weight, and serum sodium concentration; The target sodium removal calculation module calculates the target sodium removal amount based on the quantitative relationship that "drainage is equivalent to sodium removal" and according to the formula Na_target = (W_pre - W_dry) × [Na]s / 0.

93. The actual sodium removal calculation module is used to calculate the sum of convective sodium removal and diffuse sodium removal during dialysis. The adequacy assessment module calculates the sodium clearance ratio R_Na = Na_actual / Na_target, and outputs the dialysis adequacy assessment results based on the value of R_Na. The display module is used to display the target sodium clearance, actual sodium clearance, sodium clearance ratio R_Na, and equivalent water displacement V_equiv to clinicians in real time.

12. The system as claimed in claim 11, characterized in that, The system is integrated into the dialysis information system or dialysis machine, automatically obtains ultrafiltration volume and dialysate sodium concentration parameters from the dialysis machine, obtains patient weight and serum sodium data from the electronic medical record, updates sodium clearance progress in real time during dialysis, and automatically generates a sodium balance assessment report at the end of dialysis.

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