UREA KINETICS AND WHEN TO COMMENCE DIALYSIS

Blood urea and serum creatinine levels are important factors in deciding when to start dialysis. Recently, in the assessment of dialysis adequacy, emphasis has shifted from reliance on these parameters to use of kinetic methods. We therefore applied urea kinetic modelling (UKM) to 63 consecutive chronic renal failure (CRF) patients at the time dialysis commenced and compared the results to those obtained after 6 months of dialysis treatment. Mean normalised urea clearance (daily KT/V) at the commencement of dialysis (KTi/V) was 0.15 +/- 0.05, a level indicative of underdialysis in regularly dialysed patients. After 6 months, mean daily KT/V was 0.35 +/- 0.12 in patients subsequently established on CAPD, and 0.49 +/- 0.08 in those subsequently haemodialysed (both p < 0.001 compared to mean KTi/V). Serum creatinine levels on commencing dialysis were similar to those after 6 months treatment by either mode. Mean age (p < 0.01) and co-morbidity index (p < 0.05) were higher, and mean KTiN lower (p < 0.05) in the 6 patients who died during a mean follow-up period of 10 +/- 4.5 months than in survivors. Hospitalisation rates during follow-up (excluding admissions for access surgery and training) correlated with age (r = 0.332, p < 0.01), co-morbidity index (r = 0.351, p < 0.01) and KTiN (r = -0.302, p < 0.05). Blood urea and serum creatinine levels on commencing dialysis were the same in those who died and in survivors and did not correlate with hospitalisation rates. Diabetics started dialysis with a similar mean KTi/V to non-diabetics but with a Lower mean serum creatinine (p < 0.005). UKM may help to define the optimum time to start dialysis, especially in diabetics, and in many patients may result in earlier treatment.