Reproducibility of the response to short-term low salt intake in essential hypertension.
BACKGROUND
The reproducibility of the arterial pressure response to change in salt intake in essential hypertensives has been little investigated.


OBJECTIVE
To study the reproducibility of the response to salt in 14 untreated patients with mild essential hypertension.


METHODS
After a run-in phase (1 month), each patient ingested, in random order and with cross-over, 1 week of high salt intake (170 mmol/day) and 1 week of low salt intake (40 mmol/day). The identical experimental protocol was then repeated after an average interval of 3.4 months. Arterial pressure was measured (clinic arterial pressure and 24 h ambulatory monitoring) on the seventh day of each diet period. The reproducibility of the arterial pressure response was assessed in terms the intraclass correlation coefficient and the K statistics.


RESULTS
There was a good compliance with the dietary prescription because the urinary Na excretion was on average very close to the prescribed intake both during the first and during the second salt intake period. Both clinic and 24 h arterial pressure fell significantly (P < 0.01) and to the same extent in the low-salt phases of the study. Clinic arterial pressure was consistently higher than 24 h ambulatory arterial pressure but the average changes induced by salt depletion were similar. The variability of 24 h ambulatory arterial pressure at constant salt intake was lower than that of clinic arterial pressure. However, the arterial pressure response to salt showed the same variability with the two methods. The reproducibility of the dichotomous classification of patients into salt-sensitive and -resistant was low both in terms of 24 h ambulatory and in terms of clinic blood pressure.


CONCLUSIONS
Although on rechallenging the average arterial pressure response to salt remains unchanged in essential hypertensives, the individual responses are variable and the reproducibility of the dichotomous classification is unsatisfactory. The problem of dichotomizing patients into salt-sensitive and -resistant ones is only in very little part resolved by more precise arterial pressure estimates.
Zoccali
C
C
Divisione di Nefrologia e Centro di Fistologia Clinica CNR, Reggio Cal, Italy.
Mallamaci
F
F
Cuzzola
F
F
Leonardis
D
D
D000328:Adult; D001794:Blood Pressure; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000178:diet therapy*; D008297:Male; D008875:Middle Aged; D012083:Renin / Q000097:blood; D015203:Reproducibility of Results; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
D017673:Sodium Chloride, Dietary; D012083:Renin