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The Janus-faced aspect of 'dry weight'.

BACKGROUND
The goal of haemodialysis treatment in end-stage renal disease (ESRD) patients is to correct the complications of the uraemic condition. Among the main complications are fluid overload and subsequent hypertension that are corrected by achievement of 'dry weight'. We report in this study the evolution of post-dialysis body-weight and blood pressure in patients who began their HD treatment in our unit.


METHODS
We studied the monthly evolution of post-dialysis body-weight (expressed as a percentage of pre-dialysis body-weight at the first HD treatment) and predialysis mean arterial pressure (MAP) over 24 months in 61 patients (21 females, mean age 59.8 years; 20% diabetic), treated with cellulosic membranes for 8 h, 3 times a week.


RESULTS
The post-dialysis body-weight decreased between the onset of HD and month 2 (M2) (-4.40+/-0.52%). Then it went up, reaching -1.56+/-0.96% at M6, +0.3+/-1.27% at M12, +1.27+/-1.38% at M18 and +1.64+/-1.33% at M24. The post-dialysis body-weight increased by 6% between M2 and M24. The mean arterial pressure (MAP) decreased from 111.3+/-2.5 mmHg at M0 to 94.4+/-1.7 at M6, and then remained stable after M6. Between M2 and M6 the post-dialysis body-weight increased, whereas the predialysis MAP continued to decline. The incidence of hypotension episodes was maximal during the first 4 months of HD treatment.


CONCLUSIONS
After the second month of dialysis treatment, the simultaneous increase of post-dialysis body-weight and decrease of pre-dialysis MAP are related to the effects of two processes, i.e. increased weight as the result of anabolism induced by the HD treatment on the one hand and normalization of blood pressure by fluid removal on the other. Continuous clinical assessment of the patient is necessary to provide adequate prescription of post-dialysis body-weight. During the first months of HD treatment, the nephrologist, like Janus, is a double-faced gatekeeper: he must be willing to decrease post-dialysis weight to achieve 'dry weight' and to normalize blood pressure, but he must also be prepared to increase it to compensate for anabolism and to avoid episodes of hypotension.