vitamin-b-12 and Anuria

Previous theoretic and clinical studies have shown that continuous flow peritoneal dialysis (CFPD) provides a high dose of small-solute removal; however, the dose of middle-molecule removal with CFPD therapy has not been evaluated. We used a variable-volume, two-compartment model to calculate theoretical steady-state solute kinetic profiles during CFPD, continuous ambulatory peritoneal dialysis (CAPD), and hemodialysis using a high-flux dialyzer (HFHD), for an anuric 70-kg patient and two measures of dose: equivalent renal clearance (EKR) and standard Kt/V (stdKt/V). Dose measures during each therapy were calculated for five solutes: urea, creatinine, vitamin B12, inulin, and beta 2-microglobulin. Fluid (1 L daily) was assumed to accumulate in and to be removed from the extracellular space, and non renal clearance was assumed to be zero for all solutes except beta 2-microglobulin. Calculated doses for CFPD were higher than for CAPD or HFHD when assessed by either EKR or stdKt/V. Dose enhancements for CFPD were highest for small solutes, but were still considerable for middle molecules. We conclude that CFPD achieves higher doses than CAPD or HFHD for both small-solute and middle-molecule removal.

Topics: Anuria; beta 2-Microglobulin; Computer Simulation; Creatinine; Dialysis Solutions; Humans; Inulin; Kidney; Models, Theoretical; Molecular Weight; Peritoneal Dialysis; Peritoneal Dialysis, Continuous Ambulatory; Renal Dialysis; Urea; Vitamin B 12

1. An increase in apparent renal clearances is frequently observed on restoring urine flow after a period of anuria or on increasing it after oliguria. An analysis of such 'peaks' in clearance has been made in experiments on anaesthetized dogs, using two preparations of labelled vitamin B12 and urine collections of 1-2 min. [57Co]B12 was infused throughout the experiments, while [58Co]B12 was given as a single injection during periods of anuria or oliguria induced by noradrenaline infusion, haemorrhage or aortic obstruction. 2. The apparent high clearance in the first minute or two of restored or increased flow is an artifact explained by inclusion in the peak of material filtered earlier, but not excreted. By means of the integrated plasma concentration ratio of the two B12 isotopes during the period of low or absent flow, the excess B12 in the peak may be reapportioned between the period before the 58Co was injected and the period after it. 3. The findings indicate that filtration may temporarily continue during anuria, but this is concealed as a result of failure of onward flow of filtrate. In oliguria a similar concealment of filtration may result from the cessation of onward flow in some nephrons.

Topics: Animals; Anuria; Artifacts; Cobalt Radioisotopes; Dogs; Glomerular Filtration Rate; Hemorrhage; Kidney; Norepinephrine; Oliguria; Renal Artery; Sympathomimetics; Vitamin B 12