Background. Hypertension is a frequent complication of chronic renal failure, but its causes are not fully understood. There is indirect evidence that increased activity of the sympathetic nervous system might contribute to hypertension in patients with end-stage renal disease, but sympathetic-nerve discharge has not been measured directly in patients or animals with chronic renal failure. Methods. We recorded the rate of postganglionic sympathetic-nerve discharge to the blood vessels in skeletal muscle by means of microelectrodes inserted into the peroneal nerve in 18 patients with native kidneys who were undergoing long-term treatment with hemodialysis (of whom 14 had hypertension), 5 patients receiving hemodialysis who had undergone bilateral nephrectomy (of whom 1 had hypertension), and 11 normal subjects. Results. The mean (±SE) rate of sympathetic-nerve discharge was 2.5 times higher in the patients receiving hemodialysis who had not undergone nephrectomy than in the normal subjects (58±3 v...

https://www.nejm.org/doi/pdf/10.1056/NEJM199212313272704

Sympathetic overactivity in patients with chronic renal failure.

A variety of different techniques have been used for the assessment of the blood pressure response to changes in salt and water balance in humans. These have generally been found to be reproducible and to yield congruent results. This review surveys the characteristics of subjects identified as salt sensitive and salt resistant by different investigators from demographic and physiological perspectives.

Salt Sensitivity of Blood Pressure in Humans

This document has been developed as an expert consensus document by the American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA), in collaboration with the American Academy of Neurology (AAN), the American College of Physicians (ACP), the American Geriatrics Society (AGS), the American Society of Hypertension (ASH), the American Society of Nephrology (ASN), the American Society for Preventive Cardiology (ASPC), the Association of Black Cardiologists (ABC), and the European Society of Hypertension (ESH). Expert consensus documents are intended to inform practitioners, payers, and other interested parties of the opinion of ACCF and document cosponsors concerning evolving areas of clinical practice and/or technologies that are widely available or new to the practice community. Topics chosen for coverage by expert consensus documents are so designed because the evidence base, the experience with technology, and/or clinical practice are not considered sufficiently well developed to be evaluated by the formal ACCF/AHA practice guidelines process. Often the topic is the subject of considerable ongoing investigation. Thus, the reader should view the expert consensus document as the best attempt of the ACCF and document cosponsors to inform and guide clinical practice in areas where rigorous evidence may not yet be available or evidence to date is not widely applied to clinical practice. When feasible, expert consensus documents include indications or contraindications. Typically, formal recommendations are not provided in expert consensus documents as these documents do not formally grade the quality of evidence, and the provision of “Recommendations” is felt to be more appropriately within the purview of the ACCF/AHA practice guidelines. However, recommendations from ACCF/AHA practice guidelines and ACCF appropriate use criteria are presented where pertinent to the discussion. The writing committee is in agreement with these recommendations. Finally, some topics covered by expert consensus documents will be addressed subsequently by the ACCF/AHA …

ACCF/AHA Expert Consensus Document ACCF/AHA 2011 Expert Consensus Document on Hypertension in the Elderly A Report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents

Reports of elevated plasma catecholamine levels and augmented responses to autonomic blockade suggest increased sympathetic tone in borderline hypertension. It is not known if this reflects greater sympathetic neural outflow. We directly recorded muscle sympathetic nerve activity (microneurography) in 15 normotensive and 12 borderline hypertensive age-matched men to determine whether borderline hypertensive individuals have elevated sympathetic nerve activity. Supine heart rate, blood pressure, plasma norepinephrine, and efferent muscle sympathetic nerve activity (peroneal nerve) were measured after 6 days of both low and high dietary sodium intake (10 and 400 meq sodium/24 hr). Sympathetic nerve activity was elevated significantly in borderline hypertensive individuals on both low (37 +/- 1 in borderline hypertensive individuals vs. 29 +/- 1 bursts/min in normotensive individuals; p less than 0.01) and high (25 + 1 in borderline hypertensive individuals vs. 16 +/- 1 bursts/min in normotensive individuals; p less than 0.01) sodium diets. The borderline hypertensive group had higher systolic (p less than 0.01) and diastolic (p less than 0.05) blood pressures independent of sodium intake. Across both groups, high sodium intake reduced muscle sympathetic nerve activity (p less than 0.001), plasma norepinephrine (p less than 0.001), diastolic blood pressure (p less than 0.02), heart rate (p less than 0.002), and increased weight (p less than 0.005). A significant (p less than 0.05) group-by-diet interaction was observed for plasma norepinephrine levels. Specifically, compared with the normotensive group, plasma norepinephrine levels in the borderline hypertensive group tended to be higher on low sodium diet (p = 0.08) and lower on high sodium diet (p = 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated sympathetic nerve activity in borderline hypertensive humans. Evidence from direct intraneural recordings.

To clarify the role of sodium intake in the regulation of blood pressure in obese subjects, we measured blood pressure in 60 obese and 18 nonobese adolescents after successive two-week periods of a high-salt diet (>250 mmol of sodium per day) and a low-salt diet (<30 mmol per day). When they were changed from a high-salt to a low-salt diet, the obese group had a significantly larger mean change (±SE) in mean arterial pressure (-12±1 mm Hg) than did the nonobese group (+1±2 mm Hg; P<0.001). The variables that best predicted the degree of sodium sensitivity were the fasting plasma insulin level, the plasma aldosterone level while the low-salt diet was being given, the plasma norepinephrine level while the high-salt diet was being given, and the percentage of body weight made up by fat. Fifty-one of the obese adolescents were also studied before and after a 20-week weight-loss program. After the weight-loss program, the 36 subjects who lost more than 1 kg of body weight had a reduced sensitivity of ...

The Effect of Weight Loss on the Sensitivity of Blood Pressure to Sodium in Obese Adolescents

Abnormal relationship between sodium intake and sympathetic nervous system activity in salt-sensitive patients with essential hypertension.

https://www.kidney-international.org/article/S0085-2538(15)32544-8/pdf

Mechanisms of autonomic nervous system dysfunction in uremia

The effect of the state of sodium balance on the activity of the sympathetic nervous system has been evaluated previously by measuring urinary catecholamine excretion. Since urinary catecholamine may be affected by factors such as renal function or renal production of catecholamines, blood catecholamines may provide a better index of the activity of the sympathetic nervous system. The present study was undertaken to evaluate the effect of varying sodium intake on blood catecholamines. Thirteen normal subjects were studied for a period of 3 weeks in a metabolic ward. They received during the first, second, and third week 10, 100, and 200 meq sodium/day, respectively. On the seventh day of each week, when the patients had achieved sodium balance, urinary sodium excretion as well as blood levels of PRA, norepinephrine (NE), epinephrine (Ep), and dopamine (D) were measured in the supine position, at 5, 10, 15, and 20 min of upright posture, and at the end of 40 min of ambulation. The results show that: 1) blo...

Mark S. Romoff

Papers

Abnormal relationship between sodium intake and sympathetic nervous system activity in salt-sensitive patients with essential hypertension.

Mechanisms of autonomic nervous system dysfunction in uremia

Effect of Sodium Intake on Plasma Catecholamines in Normal Subjects

Mechanisms of Autonomic Nervous System Dysfunction in Uremia

Role of sympathetic nerve inhibition and body sodium-volume state in the antihypertensive action of clonidine in essential hypertension