The Effect of Acute Salt Loads on the Urinary Sodium Output of Normotensive and Hypertensive Patients before and after Surgery

Abstract

Under the stress of acute hypertonic salt loading, hypertensives excrete sodium at a much greater rate than normotensives. Immediately following splanchnicectomy, sodium excretion is markedly reduced in the hypertensive, but after several months it returns toward preoperative levels. There appears to be a rough correlation between maximum rate of sodium excretion and mean blood pressure. Normotensives by contrast exhibit insignificant differences pre-and postoperatively.E VIDENCE from various sources indicates that the metabolism of sodium in patients with essential hypertension is probably different from that of normotensive patients. Perera and Blood' found that sodium restriction in normotensive control subjects was followed by a significant weight loss and increased urinary volume output, but these effects were not evident in hypertensive patients subjected to the same degree of sodium restriction. The sodium values in the urine, however, decreased to the same extent in both the normotensive and the hypertensive subjects. It is well known that hypertensives tolerate sodium restriction without difficulty and occasionally will exhibit a lowering of blood pressure. This is in marked contrast to the normotensive subject, who tolerates very poorly rigid sodium restriction. in many instances that hypertensive patients postoperatively are unable to tolerate the strict regime of 200 mg. of sodium daily. The postsplanchnicectomy hypertensive patient thus appears to be more sensitive to sodium restriction than the unoperated one. We have numerous cases in which neither splanchnicec--tomy nor low-sodium diet alone was satisfactory in lowering blood pressure, but the combination of splanchnicectomy and moderate sodium restriction effected the desired result. Furthermore, there is some recent experimental evidence'-' which suggests that the sympathetic nerves may actually affect the handling of sodium by the kidney. On this background, therefore, we have studied the urinary output of sodium in normotensive and hypertensive patients subjected to acute sodium loads.SUBJECTS AND METHODS Acute salt loading tests were performed on eight hypertensive and five normotensive patients. Six of the hypertensives and four of the normotensives were tested before and immediately after surgery (one to two weeks). Three of the hypertensive patients were retested several months later. The hypertensives had bilateral splanchnicectomy performed, in which sympathetic ganglia D-8 to L-1 inclusive and the splanchnic nerves were removed. The normotensives had operations of comparable magnitude. All patients had normal renal and cardiac function. Salt and water intake was unrestricted in the days prior to the study except for the eight hours immediately prior to testing when the patients were thirsting and fasting. All tests were Circulation, VoMume X, December, 1954 by guest on May 12, 2018 http://circ.ahajournals.org/ Downloaded from

Renal Excretion of Sodium in Arterial Hypertension

“…The studies were performed on the following subjects: 16 with essential hypertension of varying severity, 4 with labile hypertension, 4 with secondary hypertension, and 11 with normal blood pressure. In the presentation of the data, the subjects with essential hypertension have been grouped in order of increasing blood pressure as follows: group I 130-160/90-110, group II 160-224/110-130, group III 236-240/134-140.…”

Sodium Chloride Excretion Following Salt Loading in Hypertensive Subjects

“…However, since some reduction in blood pressure also occurred, it is not possible from these studies to evaluate the precise role of the nervous system alone in causing an augmented sodium chloride excretion in hypertension. 7 Among possible humoral influences, the secretion of the adrenal cortex, the adrenal medulla, and the pituitary, as well as renin, deserve consideration. Hypertensive patients are said to excrete excess aldosterone in the urine.…”

The Response to the Administration of an Isotonic Sodium Chloride-Lactate Solution in Patients With Essential Hypertension

“…(Submitted for publication December 21, 1959; accepted January 8, 1960) Many studies indicate that patients with essential hypertension have a greater natriuretic response to rapidly administered sodium chloride solutions than have normotensive individuals (1)(2)(3)(4)(5)(6)(7). However, in most instances other factors known to influence the rate of sodium excretion in the normal subject such as diet, posture, and time of day have not been rigidly controlled (8,9).…”