Acid base status during treatment of chronic uremia with diafiltration

Treatment of chronic uremia by hemodiafiltration requires replacement of the filtrate. Using Ringer's solution alone, there is a depression of pH because of bicarbonate loss. To bring the acid base status back to normal, sodium lactate in increasing concentrations (283 mg% = 32 mM/1, 361 mg% = 40 mM/1; 462 mg% = 51 mM/1; 508 mg% = 57 mM/1) was added to the replacement fluid. The optimal concentration is 450 mg% (=50 mM/1) sodium lactate, provided the following conditions are fulfilled: (a) substitution after the filter; (b) mixing ratio of blood and substitution fluid 1:2. Using 12-15 liters of substitution fluid during a 5 hr treatment, the added lactate amounts to 60 g (=0.54 M). With continuous addition of lactate, the serum concentration of lactate is 3.5 times normal and the concentration of serum pyruvate 4 times normal. An excess lactate concentration, according to Huckabee [1,2], was thus not observed. The sieving coefficients were the following: sodium, potassium, urea, lactate, pyruvate, and phosphate 1; chloride greater then 1; calcium and protein less than 1. Serum osmolality fell, on the average, 9 mOsmol/1 during diafiltration.