Fluid state and blood pressure control in patients treated with long and short haemodialysis

Background. Patients treated at the haemodialysis (HD) centre in Tassin, Fr ance have been reported to have superior survival and blood pressure (BP) c ontrol. This control has been ascribed to maintenance of an adequate fluid state, antihypertensive drugs being required in <5% of the patients, althou gh it could not be excluded that a high dose of HD regarding removal of ura emic toxins might also have been of value. Methods. The aim of the study was to assess the fluid state and BP in normo tensive patients on long HD (8 h) in Tassin (group TN) using bioimpedance t o measure extracellular volume (ECV), ultrasound for determining the inferi or vena cava diameter (IVCD), and 'on-line' monitoring of the change in blo od volume (BV), and to compare them with normotensive (group SN) and hypert ensive (group SH) patients on short HD (3-5 h) at centres in Sweden. ECV wa s normalized (ECVn) by arbitrarily setting the median ECV (in % of body wei ght) in SN patients at 100% for each gender, recalculating the individual v alues and combining the results for male and female patients in each group. Results. The dose of HD (Kt/V urea) was higher for TN patients than for Swe dish patients who had a similar Kt/V, whether hypertensive or not. SH patie nts had significantly higher ECVn and IVCD than TN and SN patients. TN and SN patients did not differ significantly regarding ECVn and IVCD before and after HD. However, in a subgroup of eight TN patients, ECVn was below the range of that in SH and SN patients, due to obesity with a high body mass i ndex. Another subgroup of 14 TN patients had a higher ECVn than most of the SN patients and also higher than the median ECVn in the SH group, without any difference in body mass index, but they were nevertheless normotensive. The fall in BV was greater in SN than in TN patients, presumably due to a higher ultrafiltration rate in SN patients. However, SH patients had a smal ler change in BV than SN patients, presumably because their state of overhy dration facilitated refilling of BV from the interstitial fluid. Conclusions. Normotension can be achieved independently of the duration and dose (Kt/V urea) of KD, if the control of post-dialysis ECV is adequate. H owever, this is more difficult to achieve with short than with more prolong ed HD during which the ultrafiltration rate is lower, BV changes are smalle r and intradialysis symptoms less frequent. The results in the subgroup of patients with high ECVn at Tassin suggest that normotension may also be ach ieved in patients with fluid overload provided that the dialysis time is lo ng enough to ensure more efficient removal of one or more vasoactive factor s that cause or contribute to hypertension.