Plasma middle molecules in asymptomatic and "sick" uremic patients

By using high speed gel filtration combined with ion exchange gradient elution chromatography, the concentrations of plasma (p) middle molecules (MM) were determined in 126 samples from 90 non-dialyzed azotemic patients and in 210 pre-dialysis samples from 53 regular hemodialysis and 24 intermittent peritoneal dialysis patients. Samples were taken, when the patients were free from major uremic symptoms (controls) and when they presented symptoms or signs of complication, i.e., intercurrent infection, edema, vomiting, pericarditis--in hemodialysis patients also malnutrition. Compared with the symptom-free controls, the patients with infection and malnutrition revealed higher p-MM fraction 7c. In patients with edema 7a and 7b were elevated. Vomiting was not associated with accumulation of MM. In non-dialyzed patients with symptoms, p-urea was higher than in the controls. No such difference was found in dialyzed patients. The p-creatinine concentrations did not differ between the groups studied. The results of this survey imply that uremic "sickness" is more often associated with high p-MM concentrations than with high urea or creatinine, whether the accumulation of MM is cause-effect related to uremic symptomatology or an epiphenomenon remains as an open question.