Single Needle Dialysis

Abstract

This review traces the development of single needle dialysis (SND)from its inception in 1972 to determine its potential role in modern dialysis practice. The use of one needle rather than two is an attractive alternative but has never become popular. Several possible reasons for this are considered. Haemodialysis can be carried out using a single needle with a double lumen. Single needle ‘tidal flow’ systems have, however, provided the most realistic option to date and are of much more topical interest. For ease of discussion such SND systems are first subdivided into two major types depending on the number of blood pumps employed. Because there are several clearly defined ‘problem areas’ regarding the adoption of SND these are first considered from a theoretical standpoint. In particular, the problems of mean blood flow and recirculation are examined in relation to single and double pump tidal flow systems. Theoretical predictions of how each type is likely to perform in practice are made. Brief reference is then made to several ‘in vitro’ studies which have lent support to these predictions. The clinical experiences of the past 10 years with SND systems which have been introduced, stayed on the market or disappeared, are discussed in some detail. Finally, conclusions are drawn regarding the potential place of SND. Indeed, the question is posed as to whether or not it is justified to continue using twin needles for routine haemodialysis. Several minor questions remain unanswered but the major question relates to the safety of the SND systems now being introduced.