Searching for the stone of wisdom

Evert J. Dorhout Mees

Vorden The Netherlands Email: m.dorhoutmees{at}tref.nl

Sir,

It is good that renewed attention of the dialysis world is being drawn to the control of extracellular volume as a vital part of adequate dialysis. The idea is gaining ground that ‘if we only knew our patients’ dry weight, we could treat them better’. Bioimpedance is the most logical approach to this problem and the authors of ‘Can technology solve the clinical problems of dry weight?’ [1] are to be congratulated on their thoughtful review.

However, without denying the usefulness of this technique, it may be erroneous to conclude ‘Now that we can estimate dry weight, the problem of volume control is solved’, for two reasons. First, as the authors remark in their discussion, ‘currently used short dialysis sessions may cause hypotension long before dry weight is reached’. In other words, they make it impossible to reach the desired goal. But when it can be reached, time-end careful ‘probing for dry weight’ [2] is still required before a steady state is established.

The second consideration is that even if dry weight is reached during each session, interdialytic weight gain of 2–3 kg three times a week means that average volume excess will remain at least 1 l [3], high enough to sustain hypertension. Indeed, it is not surprising that normal blood pressure is often not reached unless better salt restriction is implemented. In addition, the effect of such unphysiological ‘harmonica’ changes of the extra- and intravascular compartments on the cardiovascular system has never been investigated.

In conclusion, expecting that technology will solve this clinical problem resembles the search for the stone of wisdom during the middle ages. Technology will be very helpful, but is not essential. Clinical judgement, however, is and the dialysis team will always have to spend time (a scarce commodity) to counsel and convince the patient.

Conflict of interest statement. None declared.

References

  1. Hoenich NA, Levin NW. Can technology solve the clinical problem of dry weight? Nephrol Dial Transplant 2003; 18: 647–650[Free Full Text]
  2. Carra B, Bergstrom J, Scribner B. Blood pressure control in dialysis patients: importance of the lag phenomenon. Am J Kidney Dis 1998; 32: 720–724[ISI][Medline]
  3. Dorhout Mees EJ. Cardiovascular Aspects of Dialysis Treatment. Kluwer, Dordrecht, 2000




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