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The following is a summary of “Acid–base implications of the Gibbs-Donnan effect during continuous veno-venous hemofiltration,” published in the March 2025 issue of Journal of Nephrology by Zadek et al. 

Researchers conducted a retrospective study to analyze the Gibbs-Donnan effect across the filter during continuous veno-venous hemofiltration (CVVH) and its acid-base implications using the physical-chemical approach.  

They used the PrismaMax machine (Baxter),2 in-vitro CVVH experiments, with and without albumin, quantified the Gibbs-Donnan effect. Electrolytes, glucose, and osmolarity changes were measured across the filter and in the ultrafiltrate. Strong ion difference and sieving coefficients of key solutes were calculated. Similar measurements were taken in oligo-anuric individuals with critical illness undergoing CVVH.  

The results showed that in-vitro experiments without albumin had a sieving coefficient of 1 for both positive and negative ions. With albumin, the sieving coefficient varied with concentration (r = −0.94, P < 0.001 for sodium; r = 0.88, P < 0.001 for chloride), leading to a linear increase in post-filter strong ion difference (β = 1.1, r = 0.77, P = 0.003). In 22 individuals, albumin concentration rose across the filter (2.2 ± 0.5 g/dL vs 3.1 ± 0.7 g/dL), causing sodium retention (138 ± 6 vs. 141 ± 6 mmol/L, P < 0.001) and chloride excretion (100 ± 5 vs 97 ± 5 mmol/L, P < 0.001), increasing post-filter strong ion difference (46 ± 4 vs 40 ± 4 mmol/L, P < 0.001).  

Investigators concluded that albumin linearly altered ion sieving, increased plasma water strong ion difference, and was systemically alkalized during filtration. 

Source: link.springer.com/article/10.1007/s40620-025-02238-0#Abs1