Effect of residual renal function on minimum dialysis requirements.

In two groups of haemodialysis patients, the effect of residual renal function (RRF) on motor nerve conduction velocity (MNCV) was prospectively studied. Patients belonging to Group I had stable GFR of greater than 1 ml/min while Group II patients had gradually declining GFR. As a result, the dialysis index for middle molecules, DI(MM), remained above 1.0 in Group I despite dialysis schedules as short as 6 hr/wk. DI(MM) in Group II fell gradually below 1.0 as renal function deteriorated on equally short dialysis schedules. None of the five patients in Group I developed neuropathy during 1.2-4.1 years of reduced dialysis. However, all four patients belonging to Group II developed significant (p less than .01) slowing of MNCV when their GFR declined below 0.5 ml/min. Neuropathy in this group was arrested or reversed by increasing DI(MM). It is, therefore, proposed that residual renal function is a major determinant of dialysis requirements.