Unanswered questions pertaining to dialysis adequacy in 1992

Adequacy and survival in long-term hemodialysis are discussed by attempting to answer three questions. Firstly, are hemodialysis times too short today? The answer is that the shortening, while still permitting adequate urea removal, does not permit adequate fluid removal unless high dialysate sodium is used. The consequence is hypertension which may affect mortality insidiously and take over five years to manifest. The extensive use of hypotensive drugs may conceal the danger of hypertension due to short dialysis times. Secondly, is adequacy of dialysis judged by Kt/V valid today? The answer is no. The basis for the prescription of adequate dialysis by the use of Kt/V assumes that urea is an adequate surrogate for uremic toxicity. There is no proof for this assumption. Furthermore, protein catabolism determined by urea kinetics is not valid. At best it is an approximation and has never been adequately validated by correctly performed nitrogen balance studies. The need for close clinical supervision to ensure adequate dialysis therapy is stressed. Thirdly, does reuse contribute to inadequate dialysis? The answer is yes. The unpredictable variability in dialyzer function with reuse is stressed in a certain percentage of patients and the lack of adequate quality control tests of the reused dialyzer are emphasized. The total failure to guarantee sterility has resulted in deaths directly attributable to reuse. Thus, today quality control assurances for function and sterility are inadequate. Prospective studies are necessary to ascertain whether mortality is affected by reuse of dialyzers. Meanwhile, a moratorium on reuse is suggested.