Sympathetic Function Tests Research Articles

Diabetic gastroparesis is associated with an abnormality in sympathetic innervation

Objective To investigate the hypothesis that diabetic gastroparesis might be associated with sympathetic, as well as parasympathetic, autonomic nervous system abnormailites. Patients We evaluated 12 consecutive patients with diabetes mellitus who presented with symptoms of gastroparesis. Methods The autonomic function tests included two measurments of sympathetic adrenergic function [reflex vasoconstriction to cold stress and the postural adjustment ratio (PAR)], and measurement of sympathetic cholinergic function (resting skin temperature) and vagal cholinergic function [EKG R-R interval (RRI)]. Gastric emptying was also measured and analysed by a power exponential model to estimate the solid gastric emptying slope. Patients were separated into delayed and nondelayed solid gastric emptying subgroups, the latter including two patients with rapid gastric emptying. Results All autonmic function measures were significantly lower in the diabetes mellitus group than in normal controls (P <0.001); diabetic patients as a group had slower solid gastric emptying slopes than nondiabetic controls (P ≤0.01). There was no significant correlation between measures of vagal cholinergic function by RRI, the sympathetic cholinergic function by PAR, or sympathetic cholinergic function by skin temperature and solid gastric emptying, but a statistically significant correlation was found between the sympathetic adrenergic measure of vasoconstriction to cold stress and the slope of solid gastric emptying (r = 0.79, P 7ge; 0.01). Diagnostic values for the autonomic function tests when compared to solid gastric emptying revealed sensitivites of 50% for the RRI, 88% for vasoconstriction, 63% for PAR and 71% for skin temperature. Conclusion We recommend that autonomic function measurements in patients with diabetes mellitus and upper gut symptoms should incude tests of sympathetic function as well as traditional tests of vagal cholinergic function.

The effects of rilmenidine on tests of autonomic function in humans.

The effects of rilmenidine, a new centrally acting antihypertensive agent, on a number of tests of autonomic function were investigated in six healthy male volunteers. Baroreflex function (delta RR interval [in milliseconds] with each millimeter of mercury change in systolic blood pressure) was determined in response to changes in pressure after injections of phenylephrine and nitroglycerin. Reflex cardiovascular responses to handgrip and standing, as well as during deep breathing and the Valsalva maneuver, were also investigated. Rilmenidine produced a dose-dependent decrease in blood pressure that was not accompanied by an increase in heart rate. Under conditions of low basal sympathetic activity, rilmenidine enhanced parasympathetic tone during the early reflex heart rate changes that occur immediately after standing and during deep breathing, as well as baroreflex heart rate responses to phenylephrine. During a test of sympathetic function, standing blood pressure, and heart rate after 3 minutes, rilmenidine reduced sympathetic tone.

Invited review: autonomic dysfunction in peripheral nerve disease.

The autonomic nervous system is affected in most peripheral neuropathies, but only in a small number of conditions, such as diabetes, amyloidosis, Guillain-Barré syndrome, porphyria, and familiar dysautonomia, is autonomic dysfunction of clinical importance. The pathological changes in the peripheral autonomic nervous system are similar to those in the peripheral somatic nerves. Autonomic disturbances are most likely to occur when there is acute demyelination or damage to small myelinated and unmyelinated fibers. Autonomic investigations should include tests of both sympathetic and parasympathetic function. Treatment consists of management of the underlying cause of peripheral neuropathy, physical and pharmacological measures.

Age-related normal tolerance intervals for retinal vascular response to systemic autonomic nerve stimulation

This study establishes the age-adjusted tolerance intervals for retinal vascular responses to sustained handgrip contraction (a test of sympathetic nerve function). Forty adult subjects (mean age: 39.7 +/- 14.1 years, range: 20 to 72 years; 19 males) were included in the final analysis. Mean percentage calibre change in response to sustained handgrip contraction in this population was -5.61% with a significant correlation between subject age and percentage retinal vessel calibre change (p less than 0.001). Mean retinal arteriolar calibre change in response to systemic autonomic stimulation varied significantly with age: between -8.48% at age 20 years and -2.06% at age 70 years with a mean of -5.95% at the mean age of 39.7 years. The standard deviation is 3.04% and the 95% confidence intervals were set between +/-6.17%. This autoregulatory reflex appears to be inversely related to age.

Autonomic function in Friedreich's ataxia.

Autonomic function studies were performed on 15 patients with Friedreich's ataxia, and the results compared with those of 76 healthy subjects. There was an increase in resting supine heart rate, attributed to cardiac abnormalities. Other tests of sympathetic and parasympathetic function were normal. The normal autonomic function studies are consistent with the pathological findings of degeneration predominantly of large diameter myelinated fibres with sparing of small myelinated and unmyelinated fibres.

Peripheral autonomic surface potential: A quantitative technique for recording sympathetic conduction in man

Using EMG equipment with time locked recording and standard averaging facilities we were able to record a previously poorly defined skin potential. The potential, termed by us the peripheral autonomic surface potential (PASP), was recorded from the palmar surface of the hand and the plantar surface of the foot in 30 normal subjects. The PASP usually consisted of a biphasic potential with an initial negative and a later positive peak. It was elicited by randomly timed electrical stimuli over the median nerve at the wrist. The mean palmar PASP latency was 1.52 ± 0.13 s and the mean plantar PASP latency was 2.07 ± 0.16 s. The mean palmar and plantar PASP amplitudes were 479 ± 105 μV and 101 ± 40 μV, respectively. A mean sympathetic conduction velocity was calculated to be 1.28 ± 0.18 m/s. In 5 normal subjects a similar technique was used to record a PASP from the volar surface of the left middle finger. Iontophoresis of atropine into the skin under the recording site abolished the PASP in all subjects. Palmar and plantar PASPs were recorded in 10 diabetic patients. The amplitudes (palmar 179 ± 158 μV, plantar 17 ± 16 μV) were significantly reduced compared to normals ( P < 0.001). Five patients with unilateral lumbar or cervical sympathectomy were studied. The PASP was absent or markedly reduced on the side of the sympathectomy in all patients. The study indicates that the PASP may prove a useful quantitative test of sympathetic function.

Two patients with abnormalities of regional sympathetic nervous tone.

The traditional biochemical tests of sympathetic nervous system function used in clinical diagnosis (urine and plasma catecholamine measurements) are indices of "overall" sympathetic nervous activity, and incapable of detecting localised changes in sympathetic tone confined to individual organs. Recently developed radiotracer methods, which enable the pattern of sympathetic nervous dysfunction in disease states to be delineated, were used to detect abnormalities in regional sympathetic nervous system activity in two patients presenting problems in management. In one, the abnormality of sympathetic function was iatrogenic, a post-sympathectomy denervation of the lower regions of the body, associated with incapacitating postural hypotension. In the other, unexplained persistent sinus tachycardia proved to be due to an increase in sympathetic nervous tone restricted to the innervation of the heart. Knowledge of the underlying sympathetic nervous pathophysiology in these patients influenced the choice of drugs subsequently used in their treatment.

Is blood pressure variability related to activity of the sympathetic system?

1. In 70 patients with untreated essential hypertension, blood pressure variability was correlated to plasma catecholamines and to the response of blood pressure and peripheral flow to cold pressure and handgrip tests. 2. Supine blood pressure was recorded every 5 min, during 3 h. Variability was defined as the standard deviation of the mean of the readings in that period. 3. Blood pressure variability is positively and significantly correlated to the level of pressure and to age. 4. No significant correlation could be found with plasma catecholamines and sympathetic function tests. 5. It is concluded that blood pressure variability is related to the level of pressure but not to activity of the sympathetic nerves.

Skin Wrinkling on Immersion of Hands

Skin wrinkling of the fingers following immersion in warm water depends on intact sympathetic innervation. It is abolished by lesions affecting both central and peripheral sympathetic pathways. It affords a simple and reliable clinical test of sympathetic function.

Idiopathic orthostatic hypotension from failure of noradrenaline release in a patient with vasomotor innervation.

A 26 year old man is described with life-long orthostatic hypotension unrelated to autonomic nerve degeneration and apparently due to failure of peripheral noradrenaline realese. Tests of parasympathetic and sympathetic cholinergic nerve function were normal, but sympathetic adrenergic activity was defective. Thus blood pressure regulation was abnoraml. There was no pressor response to tyramine, an indirect sympathomimetic drug, but a marked pressor response to the directly acting sympathomimetic drugs phenylephrine and noradrenaline. On standing there was a progressive fall rather than a rise in circulating noradrenaline concentrations, although adrenaline levels rose normally. The pupils showed diminished responses to ephedrine and cocaine, and a normal response to phenylephrine. Fluorescence microscopy of blood bessels showed that they were innervated with adrenergic nerves. His orthostatic hypotenstion responded well to oral phenylephrine (50 mg five times daily) but not to other forms of therapy. It is suggested that this patient's symptoms were due to failure of noradrenaline release even though sympathetic adrenergic nerves were present. We therfore wish to draw attention to a further cause of orthostatic hypotension, failure of peripheral noradrenaline release without autonomic neuropathy.

Human sweating response to electrophoresed acetylcholine: a test of postganglionic sympathetic function.

Human sweating response to electrophoresed acetylcholine: a test of postganglionic sympathetic function.