Sodium Excretion and Blood Pressure in Essential Hypertensive Patients during the Early Phase of Hospital Admission

Abstract

1.In 91 essential hypertensive patients cumulative sodium balance was studied during the first week after they were taken into hospital. Sodium intake was fixed at 55 mmol/day. 2.After the first week, when sodium equilibrium was achieved, haemodynamic and endocrinological studies were carried out (cardiac output, renal plasma flow, plasma volume, measurements of plasma concentrations of total and active renin, aldosterone and noradrenaline). 3. On the basis of cumulative sodium balance a discrimination could be made between three groups. Group I (23 patients) accumulated sodium (52 mmol) before attaining equilibrium; group I1 (35 patients) were in balance from the beginning; group I11 (33 patients) exhibited a negative balance and lost on the average 125 mmol before equilibrium was attained. 4. On admission blood pressure and other characteristics were similar in the three groups. The decrease in blood pressure over the first 24 h period was equal. After that, the group characterized by a negative cumulative sodium balance (111) continued to exhibit a fall in blood pressure whereas groups I and II did not. 5.After sodium equilibrium had been attained, the haemodynamic profiles were somewhat different between groups. Group I (with a positive balance) showed greater systemic and renal vascular resistances than the other groups. 6.It is concluded that sodium loss contributes to the decrease in blood pressure on the second day EA Rotterdam, The Netherlands. of hospital admission and after. The blood pressure reduction during the first day is due to an independent mechanism, e.g. a decrease in sympathetic nervous tone. 7.It is also apparent that the attainment of sodium equilibrium during clinical investigations constitutes no guarantee that subjects are physiologically comparable; the preceding sodium balance has to be taken into account.

Race Affects the Decline in Blood Pressure With Hospitalization

“…As previously shown, [13][14][15][16] the findings also indicated that the patient's preadmission BP was the single strongest determinant of hospital BP (ie, the greatest drop in BP following hospitalization occurred in those with the highest preadmission BP, those subjects with hypertension). Prior to the development of antihypertensive medications, hospitalization was one of the few treatments available for hypertension.…”

“…BP typically returned to prehospital admission levels within a few days following discharge. [13][14][15][16] This phenomenon appears to be related to diverse factors associated with hospitalization itself, including changes in sodium intake, habituation to the medical environment, and isolation from the stress and worries of the patient's regular environment. 13,14,16,17 Despite the literature on racial differences in BP, few if any studies have examined whether ethnicity influences this effect of hospitalization on BP.…”

“…3,4,6 -8,10 -12 It is well established that hospitalization is associated with a reduction in BP in both hypertensive and normotensive individuals. 13,14 Indeed, hospitalization was one of the only treatments available for hypertension prior to the development of antihypertensive medications. Unfortunately, the ''cure'' was temporary.…”

Influence of hospitalization and placebo therapy on blood pressure and sympathetic function in essential hypertension.

“…Lake et al 1 " suggest that the stress of venipuncture may significantly elevate plasma noradrenaline, although this experience has not been confirmed by others. 18 A recent study 20 demonstrated that a fall in BP during the early phase of hospitalization may be related to excessive salt excretion. Ninety-one patients with essential hypertension were hospitalized and classified on the basis of their sodium balance.…”

“…Alternatively, it is possible that the sympatholytic effect of placebo tablets is similar to that of anxiolytics such as benzodiazepines, which may reduce stress-induced peaks of sympathetic activity without altering basal sympathetic tone. 20 -" Both BP and plasma norepinephrine were measured under basal conditions at discrete time points, and thus the sympatholytic potency of placebo might not be evident. Urinary catecholamines, however, represent an index of sympathetic activity that is integrated across the time of the collection period, thus incorporating the peaks of stress, and would be a more sensitive measure of the postulated placebo effect.…”