Sympathetic Function Tests Research Articles

Autonomic dysfunction in dementia

Background: There are no studies of autonomic function comparing Alzheimer’s disease (AD), vascular dementia (VAD), dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD). Aims: To assess cardiovascular autonomic...

Has the phoenix risen?

Has the phoenix risen?

Water-immersion wrinkling is due to vasoconstriction.

The underlying mechanism of the water-immersion skin wrinkling test, which is used as a test of sympathetic nerve function, remains elusive. We investigated changes of blood circulation in the hand occurring with water-immersion wrinkling by measuring the velocity of ulnar and digital artery blood flow, and of digit skin blood flow, in healthy subjects before and during wrinkling. Wrinkling was accompanied by significant reduction in blood flow velocity in all vessels, with a maximum in digital vessels. Our data show that water-immersion wrinkling is a function of digit pulp vasoconstriction. This test of sympathetic function can now be quantified using parameters of blood flow velocity, enabling its more widespread and accurate use.

N -methyl 11 C]meta-Hydroxyephedrine positron emission tomography in Parkinson's disease and multiple system atrophy

Orthostatic hypotension (OH) can be present in idiopathic Parkinson's disease (IPD) as well as in atypical parkinsonian syndromes such as multiple system atrophy (MSA). According to clinical tests of sympathetic nerve function and histopathological data, OH is caused by primarily postganglionic sympathetic dysfunction in IPD and by predominantly central and preganglionic degeneration in MSA. It has been proposed that this concept of a different underlying pathogenesis for OH should be applied in the differential diagnosis of parkinsonian disorders, in the form of measurements of sympathetic myocardial innervation. In this pilot study, myocardial imaging with [ N-methyl (11)C]meta-hydroxyephedrine ((11)C-HED) and positron emission tomography (PET) was used as a quantitative tool to evaluate the feasibility of such an approach. Seven patients were included in the study. Two had MSA and OH, three had probable IPD and OH (duration of disease, >3 years), one had probable IPD without OH (disease duration, 3 years) and one had possible IPD without OH (disease duration, 2 years). Ratios of maximal (11)C-HED uptake in the myocardium to that in the liver at 5 and 40 min post injection (p.i.) and - based on kinetic modelling - tracer influx rates K(1) were calculated. Compared with MSA patients ( n=2), IPD patients with OH ( n=3) showed definitely lower uptake ratios at both 5 min p.i. (0.39-0.57 vs 0.78-0.79) and 40 min p.i. (0.21-0.60 vs 0.89-1.06), as well as lower K(1) values (0.198-0.359 vs 0.384-0.450 min(-1)). The patient with probable IPD without OH showed intermediate values (uptake ratio at 5 min: 0.65; uptake ratio at 40 min: 0.87; K(1)=0.363). In the patient with possible IPD, values (uptake ratio at 5 min: 0.96; uptake ratio at 40 min: 1.04; K(1)=0.400) did not differ from those observed in MSA. These results support the hypothesis that measurement of myocardial innervation may contribute to the differential diagnosis of parkinsonian disorders and suggest a need for quantitative pathophysiological imaging, particularly at early stages of disease.

Clinical and physiologic evaluation of stellate ganglion blockade for complex regional pain syndrome type I. (Ludwig-Maximilians-University, Munich, Germany) Clin J Pain. 2001;17:94-100.

Stellate ganglion blockade with local anesthetics was carried out via an anterior paratracheal approach in 33 patients suffering from complex regional pain syndrome type I. Twenty-three (70%) of the 33 patients developed an increased in temperature difference between the treated hand and the contralateral hand of more than 1.5°C after the procedure, which is a clinical sign of sympathicolysis. In 48% of these patients, the sympathetic function test showed an undisturbed sympathetic nervous function. In 10 patients, no significant increase in temperature difference was observed. Only 7 patients with pain relief revealed both clinical sympathicolysis and extinguished sympathetic nerve function and qualified for sympathetically maintained pain. Conclude that clinical investigation is not reliable in the assessment of stellate ganglion blockade. Proof of sympathetically maintained pain based on pain relief after stellate ganglion blockade is not conclusive.

Assessment of sympathetic blocks

Sympathetic nervous system blockade provides both diagnostic and therapeutic potentials in certain chronic pain states. Sympathetically maintained pain associated with complex regional pain syndrome and chronic intractable abdominal or pelvic pain are perfect examples for such conditions. Because pain relief is a subjective phenomenon, it is important to establish an objective way of assessing the success of the sympathetic blockade. This report will discuss various tests of sympathetic function that could be used in clinical practice. Special emphasis in this report will be on changes in cutaneous temperature, blood flow, provocative sweat tests, and electrical skin conduction as indicators of sympathetic function. Copyright © 2001 by W.B. Saunders Company

Clinical and physiologic evaluation of stellate ganglion blockade for complex regional pain syndrome type I.

The efficacy of peripheral sympathetic interruption after stellate ganglion blockade was assessed by a sympathetic function test. Results were compared with clinical signs such as temperature changes, pain reduction, and the development of Horner syndrome to evaluate the correlation with clinical investigations. Stellate ganglion blockade with local anesthetics was carried out via an anterior paratracheal approach in 33 patients suffering from complex regional pain syndrome type I. Patients were examined before and after the procedure. For assessment of sympathetic nervous function, the vasoconstrictor response to sympathetic stimuli was assessed using laser Doppler flowmetry. Clinical parameters like surface temperature changes (thermography), pain relief (visual analogue scale), and Horner syndrome were monitored. Twenty-three (70%) of 33 patients developed an increase in temperature difference between the treated hand and the contralateral hand of more than 1.5 degreesC after the procedure, which is a clinical sign of sympathicolysis. In 48% (n = 11) of these patients, the sympathetic function test showed an undisturbed sympathetic nervous function. In 10 patients, no significant increase in temperature difference was observed. Although these patients presented with a normal sympathetic vasoconstrictor response, 4 felt pain relief of more than 50%, suggesting a placebo effect. Only 7 patients with pain relief revealed both clinical sympathicolysis and extinguished sympathetic nervous function and qualified for sympathetically maintained pain. Clinical investigation is not reliable in the assessment of stellate ganglion blockade. Proof of sympathetically maintained pain based on pain relief after stellate ganglion blockade is not conclusive.

Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes.

Patients with diabetic neuropathy typically have decreased sweating in the feet but excessive sweating in the upper body. Previous studies of sudomotor function in diabetes have included patients with longstanding disease. The present study was designed to test for the early presence of sudomotor dysfunction and to characterize its relation to glycemic control and other aspects of peripheral nerve function. A total of 37 patients (10 males, 27 females) enrolled in a longitudinal study, in which autonomic function was evaluated annually for 3 years. Patients enrolled 2-22 months after the diagnosis of type 1 diabetes. Forty-one age- and sex-matched healthy control subjects were also studied. Sweat production in response to acetylcholine stimulation was dramatically increased in the forearm at the time of the first evaluation (1.67 +/- 0.24 micro/cm2 in the diabetic patients vs. 1.04 +/- 0.14 microl/cm2 in the control subjects, P < 0.05). Likewise, the ratio of sweating in the forearm to sweating below the waist was higher in the diabetic patients (0.553 +/- 0.07 microl/cm2) than in the control subjects (0.385 +/- 0.04 microl/cm2, P < 0.05). Forearm sweat was negatively associated with the renin-toprorenin ratio and vanillylmandelic acid (VMA) excretion (P < 0.025), tests of sympathetic nerve function. The ratio of sweating in the forearm to sweating in the foot was likewise increased in diabetic patients with poor glycemic control. We interpret this redistribution of sudomotor responses to be indicative of sympathetic nerve injury and conclude 1) that the sympathetic nervous system is especially vulnerable to the adverse effects of chronic hyperglycemia and 2) that sympathetic dysfunction can be detected very early in type 1 diabetes.

Skin wrinkling for the assessment of sympathetic function in the limbs.

Wrinkling of the skin of the palm and sole is considered to be dependent on the presence of intact sympathetic nervous activity. Loss of sympathetic integrity could be simply and usefully assessed by the absence of wrinkling. To test this hypothesis, the skin wrinkle test was compared with the starch-iodine sweat test and sympathetic skin response (SSR) in patients with abnormal sympathetic function. The three tests were carried out in 34 patients (68 limbs) undergoing temporary or permanent disruption of the sympathetic chain to upper or lower limbs. Included in this group were six diabetics undergoing chemical or surgical sympathectomy, lumbar epidural infusions following vascular surgery, and patients for whom sympathectomy was being considered. Sensitivity and specificity analysis and predictive values of the wrinkling response and the starch-iodine test were related to the SSR as the standard. The wrinkle test showed a sensitivity of 97% and specificity of 95%, and bore good correlation to the SSR. The starch-iodine test showed sensitivity of 55% and specificity of 93%. A hypothesis for the mechanism of wrinkling based on the observations of the present study is proposed. The wrinkle test is a reliable test of sympathetic function, is inexpensive and is easy to perform at the bedside. The sweat gland myo-epithelial cells and absence of sebum could play an important role in the wrinkling response. It can be used to select patients who will benefit from sympathectomy, and can adequately evaluate sympathetic blockade.

Assessing cardiovascular autonomic neuropathy in diabetes mellitus: How many tests to use?

The aim was to evaluate the relative importance of an established battery of five function tests used in the assessment of cardiovascular autonomic neuropathy (CAN) in diabetes employing spectral analysis of heart rate variability (HRV) as the reference test. In a population-based sample of 178 diabetic persons and 194 non-diabetic controls, five function tests ( E/ I ratio, Valsalva, 30:15 ratio, Orthostatic-BP, and sustained Handgrip) and power spectral analysis of a 24-h Holter recording were carried out. The high-frequency power during nighttime (LnHF NIGHT) was taken to express the parasympathetic function and the daytime low-frequency power (LnLF DAY) to express the sympathetic function. The readings were log transformation when appropriate, age-corrected, and standardized to units of standard deviation. Combinations of the three mainly parasympathetic tests and the two mainly sympathetic tests were computed by averaging the standardized readings. A high value of the mean sum of squares in LnHF NIGHT or LnLF DAY — explained in regression analysis — was assumed to represent the better test or combination of tests. The three parasympathetic function tests each correlated significantly to LnHF NIGHT. The E/ I ratio had a correlation to LnHF NIGHT similar to the combination of the three parasympathetic tests and the combination of all five function tests, whereas Valsalva and 30:15 ratio had a significantly poorer association. Sustained Handgrip-correlated significantly poorer to LnLF DAY compared to Orthostatic BP and the combination of the two sympathetic tests explained a significantly smaller part of the variation in LnLF DAY and LnHF NIGHT than did the combination of all five tests. This study indicates that: (1) no information is gained by adding the sympathetic function tests to the parasympathetic tests, (2) the most informative test is the E/ I ratio, (3) and knowledge about the degree of CAN as defined by reduced HRV is not significantly increased when the four other function tests assessed are added to the E/ I ratio.

Cardiovascular autonomic dysfunction in multiple sclerosis: correlation with orthostatic intolerance.

Autonomic dysfunction is frequently observed in patients with multiple sclerosis (MS), but clinical studies disagree on the frequency and type of abnormalities in autonomic function tests. Orthostatic dizziness (OD) has been reported in up to 49% of patients, but the pathophysiological mechanisms are poorly understood. This study investigated cardiovascular reflex tests and their association with OD in patients with MS in order to examine the hypothesis that the sympathetic nervous system is specifically involved in these patients. Forty patients with clinically active relapsing-remitting (n = 27) and secondary progressive MS (n = 13), aged 35.0+/-8.5 years, were studied by parasympathetic (heart rate responses to the Valsalva maneuver, deep breathing, and active change in posture) and sympathetic function tests (blood pressure responses to active change in posture and sustained handgrip), and by spectral analysis of heart rate variability during rest and during standing. Results were compared to those obtained in 24 healthy volunteers, aged 29.4+/-7.2 years. A standardized questionnaire was used to evaluate symptoms of orthostatic intolerance. Abnormal responses on at least one cardiovascular reflex test were observed in 40% of MS patients, compared to 17% of the control group, with a statistically significant involvement of the sympathetic vasomotor system. Orthostatic intolerance was reported in 50% of patients (controls: 14%, P<0.006). Subgroup comparison of patients with and without OD suggests that orthostatic intolerance results from impaired sympathetic vasoconstriction. These results provide further evidence that the sympathetic nervous system is involved in patients with MS.

Autonomic Dysfunction in Migraineurs

To evaluate autonomic function and sympathovagal balance in migraineurs and healthy controls. The pathophysiology of migraine is still largely unknown. An imbalance of the autonomic nervous system could explain many of the clinical manifestations of the disorder. We undertook autonomic function tests in 17 women suffering from migraine (8 with aura) (average age 36 +/- 7 years) and 16 healthy women (average age 34 +/- 7 years). Autonomic nervous system studies consisted of tests of sympathetic function (the quantitative sudomotor axon reflex test, beat-to-beat blood pressure responses to the Valsalva maneuver, sustained handgrip, cold pressor test, and head-up tilt and tests of parasympathetic function (heart rate responses to deep breathing and the Valsalva maneuver). The data from the tilt test were further evaluated by time-frequency analysis (Wigner distribution). Subjects with migraine with aura had a smaller increase of mean blood pressure during phase IV of the Valsalva maneuver (P<0.05) and a lower blood pressure increment during the handgrip test (P=0.08); their time-frequency distribution showed reduced power at the nonrespiratory frequencies in the R-R interval at both minutes 1 (P<0.03) and 5 (P<0.04) of head-up tilt. Sympathovagal balance (a ratio of spectral power of nonrespiratory frequency variations in blood pressure to that at respiratory frequency variations in the R-R interval) was significantly increased in migraineurs, both with and without aura, by 10 minutes of head-up tilt. Subjects with migraine with aura had resting supine sympathetic hypofunction and intact parasympathetic function. With head-up tilt, sympathovagal balance is increased. The dynamic alterations in autonomic nervous system function may contribute to the development of aura in patients with migraine.

Relation with preoperative fructosamine and autonomic nerve function and blood pressure during anesthesia in diabetics: a retrospective study.

Many diabetics may have a high risk involving the cardiovascular system. In an attempt to predict the intraoperative risks of diabetics during anesthesia, we evaluated retrospectively the relationship among the biochemical assay or autonomic nerve function obtained as parts of the preoperative examination, and the blood pressure changes relating to the stimulation of intubation and extubation for anesthesia. In 40 diabetic surgical patients examined the biochemical assay (HbA1c, fructosamine level and blood glucose level) beforehand, the autonomic nerve function was quantified preoperatively by analysis of ECG R-R variability recorded in supine and subsequent standing position using an HRV analyzer, and some parameters of autonomic nerve function especially responsive sympathetic nerve activities were obtained. We assessed the correlation with systolic blood pressure changes in these cases at intubation for general anesthesia comparing to similar conditioned 40 non-diabetics. A diabetics with low vagal activity became larger systolic blood pressure afterdrop at tracheal intubation for anesthesia (r=0.513, p<0.001). Otherwise the blood pressure afterdrop at extubation became larger in a non-diabetics with high sympathetic activity (r=0.502, p<0.001). The preoperative fructosamine concentration in diabetics correlated positively with the responsive sympathetic nerve irritability index; "mRR(sup)-RRmin(std)" (r=0.432, p<0.05) and the responsive sympathetic nerve excitability index; "mRR(sup-std)" (r=0.448, p<0.05). However HbA1c had no correlation with these parameters of autonomic nerve function and blood pressure rise at tracheal intubation. Because of above correlation with blood pressure rise at intubation for anesthesia induction, the preoperative fructosamine examination and the responsive sympathetic nerve function test must be useful preoperative examination for detection of the unexpected heart events of diabetic patients during operation.

Sympathetic function test of vasoconstrictor changes in foot arteries in diabetic patients.

We studied the relationship between vasoconstrictor changes in foot arteries (pedal, metatarsal, and digital arteries) and autonomic neuropathy in diabetic patients to estimate the degrees of sympathetic dysfunction. Sixty-two patients and nineteen age-matched control subjects were studied. The resistance index (RI) and pulsatility index (PI) were measured as vascular hemodynamic parameters using Doppler sonography, and the increases in these hemodynamic parameters (%RI and %PI) from rest to a deep breath were measured as indexes of the degrees of sympathetic vasoconstrictor function. Cardiovascular autonomic function tests (AFTs) were performed and the score was compared to %RI and %PI values obtained. Of the 62 diabetic patients, 51 had various degrees of autonomic neuropathy. Both %RI and %PI in the diabetic patients were significantly less than those in the control subjects for all foot arteries tested (all P < 0.001). There were strongly inverse correlations between the %RI and %PI of foot arteries and the AFT score (r = -0.556 to -0.846, P < 0.0001). The %RI of the digital artery was the most strongly correlated with AFT score (r = -0.846, P < 0.0001) among foot arteries tested. The abnormality of sympathetic vasoconstriction was detectable in the majority of the diabetic patients with the early phase of autonomic neuropathy (%RI: 89.5%; %PI: 94.5%). We conclude that the %RI of the digital artery is a useful and reliable sympathetic function test of early phase in diabetic patients.

Towards a diagnostic test of abdominal sympathetic dysfunction

Extrinsic denervation of the gastrointestinal tract is associated with motility disorders; there is no simple, noninvasive, accurate method to evaluate abdominal sympathetic innervation. Thus, circulating catecholamines and cardiovascular reflexes do not accurately reflect abdominal sympathetic function (GE 1994; 106:1124-8). Our aim was to evaluate the role of superior mesenteric artery (SMA) blood flow in the pathophysiology of orthostatic hypotension (OH) in patients with generalized autonomic failure as a means to develop a test of abdominal sympathetic adrenergic function. Methods: 12 patients (5M, 7F; mean age, 60 years) with symptomatic neurogenic OH (6 multiple system atrophy, 3 pure autonomic failure, 3 diabetic neuropathy) and 12 healthy controls (5M, 7F; mean age, 43 years) underwent SMA flow measurements during cold pressor test, head-up tilt, and tilt plus meal ingestion. SMA flow was measured by a color Doppler ultrasonography scanner with a 3.75 MHz phased array sector transducer. Autonomic failure was independently assessed using standard tests of function of the sympathetic adrenergic, cardiovagal and postganglionic sympathetic sudomotor function. Results: SMA flow volume and time-averaged velocity were similar in patients and controls at rest in the supine position; however, responses to cold pressor test and uptight tilt were attenuated (p < 0.05) in patients compared to controls. Head-up tilt after the meal evoked a profound fall of mean blood pressure (84 12mmHg in controls, 54 ± 13 in patients; p < 0.05) and SMA flow in the patients.

NEW ASSESSMENT FOR PERIPHERAL FACIAL PALSY BY SYMPATHETIC SKIN RESPONSE(SSR)

S292 Introduction The cause of facial palsy is mainly considered due to the peripheral circulartory disturbance. Satellate ganglion block(SGB) is as one of the treatments for the facial palsy. Susceptible effect of SGB is to increase the blood flow and to improve peripheral circulation around the facial nerve. On the other hand, there still lacks the basic data whether facial palsy is correlated with sympathetic dysfunction. The reason why is that there was no simple way to evaluate sympathetic function. Skin sympathetic response(SSR) is newly non-invasive electrophysiological technique for assessing sympathetic functions [1]). The aim of this study is to investigate the relationship between facial palsy and sympathetic dysfunction and to evaluate the prognosis of the patient due to SSR. Method The study was carried out in 40 peripheral facial palsy patients (25 men and 15 women ranging in age from 24 to 70 years, with a mean age of 48 years). Sympathetic function test was performed by means of skin sympathetoic response(SSR). Pairs of surface electrodes were placed on the bilateral palms and dorsum of the hands. SSR was evoked by magnetic single stimulation of median nerve at wrist. (intensity 400 V, magnetic field 0.2 tesla). Neuropack 4 (Nihonkohden co. ltd.)was used for this study(analysis time 10s, high cut 1 kHz, low cut 1 Hz). Each responses was recorded on a photographic paper. Differences of amplitude and latency between intact side and palsy side were investigated. The significant differences of sympathetic function between left and right side(amplitude) were more than 30%. We have classified the patient who was treated by SGB for 20 times into two groups, GI and GII. GI was that facial palsy score is more than 20 points (full score is 40) and GII is that the score was less than 20. Both SSR and facial palsy score were estimated at every 10 times of SGB treatment. All subjects gave their informed consent for this study. Result The period of treatment in GI was 1.3 +/- 0.7 month and GII was but 8.3 +/- 4.4 month, respectively(mean +/- SD, p<0.05). The facial palsy score at first treatment in GI was 8.0 +/- 4.4 points and 5.0 +/- 3.3 in GII. Four week after treatment, the facial palsy score in GI improved to 36.1 +/- 3.9, although the score of GII was still significantly less compare to that of GI(12.5 +/- 4.5, p<0.05). Differences of SSR amplitude between left and right side were seen in both GI and GII in the early periods. Differences disappeared according to increase of facial palsy score in GI. However GII showed the significant differences between left and right side and showed less recovery of facial palsy scores. Discussion From our results, it was indicated that disturbance of sympathetic function might correlate with the prognosis of facial palsy. SSR is considered as one of the valuable method to assess the sympathetic function and could be one of the parameters for anticipating the prognosis of facial palsy.

AAEM minimonograph #48: autonomic nervous system testing.

The autonomic nervous system maintains internal homeostasis by regulating cardiovascular, thermoregulatory, gastrointestinal, genitourinary, exocrine, and pupillary function. Testing and quantifying autonomic nervous system function is an important but difficult area of clinical neurophysiology. Tests of parasympathetic cardiovagal regulation include heart rate analysis during standing (the 30:15 ratio), heart rate variation with deep breathing, and the Valsalva ratio. Tests of sympathetic adrenergic vascular regulation include blood pressure analysis while standing, the Valsalva maneuver, sustained handgrip, mental stress, and cold water immersion. Tests of sympathetic cholinergic sudomotor function include the sympathetic skin response, quantitative sudomotor axon reflex test, sweat box testing, and quantification of sweat imprints. Pupil function is tested pharmacologically and with pupiilographic techniques. Tests of gastrointestinal and genitourinary function do not satisfactorily isolate autonomic regulation from their other functions. The available tests have various sensitivities and ease of administration. They are typically administered in a battery of multiple tests, which improves sensitivity and reliability, and allows probing of various autonomic functions.

Autonomic dysfunction in patients with non-alcoholic chronic liver disease

Aims: To assess the presence of autonomic neuropathy in patients with non-alcoholic chronic liver disease and its relationships with the severity of liver damage. Methods: Thirty non-alcoholic patients with chronic liver disease and 26 healthy control subjects were studied. The silicone imprint technique was used to quantify the number of functioning sweat glands in order to assess peripheral sympathetic dysfunction. Heart rate variations in response to deep breathing at 6 per minute (ΔR6), to a Valsalva maneuver, and with orthostatism (RR max/RR min) were determined to assess parasympathetic vagal function. Results: Mean values for autonomic tests were significantly lower in the group of patients with non-alcoholic chronic liver disease than in the control subjects. The number of activated sweat glands in the foot was abnormal in 19 (63%) patients. Among vagal tests, Valsalva ratio was abnormal in 14 (46%) and ΔR6 in 11 (36%) patients with liver disease. Vagal neuropathy (two or more abnormal heart rate tests) was definite in nine patients (30%). Conclusions: A high prevalence of abnormalities in both sympathetic and parasympathetic function tests, with a poor relationship with liver function parameters has been found in patients with non-alcoholic chronic liver disease.

No change in automatic function tests during uncomplicated haemodialysis.

Uraemic autonomic dysfunction is reckoned to participate in dialysis hypotension, but a clear relationship has not been established. However, autonomic function is usually tested at rest, and possibly autonomic dysfunction arises or worsens during dialysis. We therefore performed easily repeatable tests of efferent sympathetic function, that is static exercise test and parasympathetic function, that is heart rate variability during Valsalva manoeuvre and deep breathing, at successive stages of a standard haemodialysis session; before dialysis, 20 min after dialysis without ultrafiltration, after 3 h of dialysis combined with ultrafiltration, and 20 min after dialysis. Studies were performed in 22 patients on chronic haemodialysis on a cuprophane dialyser. The mean ultrafiltration volume was 2.2 +/- 0.61. We found that blood pressure elevation upon static exercise, and heart rate variability during Valsalva or deep breathing test remained unaltered at the various stages of dialysis. On past performance the patients were divided into hypotension prone (n = 6) or resistant (n = 16). Hypotension prone patients showed a greater blood pressure drop during dialysis, but also showed an appropriately enhanced heart rate acceleration. The occurrence of autonomic dysfunction was not elevated in this group, nor did such dysfunction develop along dialysis. Predialysis parasympathetic function tests were abnormal in 10 patients. These patients also showed an augmented intradialytic blood pressure decrease, but no enhanced acceleration in heart rate. Their parasympathetic dysfunction did not worsen during dialysis. Based upon the predialysis exercise test, low responding patients (blood pressure increase 5 +/- 2 mmHg, n = 11) were distinguished. These subjects were not characterized by a greater blood pressure decrease or different heart rate acceleration. Generally, the responses upon exercise, whether low or high, remained unaltered during dialysis. we conclude that haemodialysis has no systematic effect on autonomic function. Hypotension-prone patients are not distinguished by a disturbed predialytic or intradialytic autonomic blood pressure control.

Comparative Effects of Rilmenidine and Atenolol on Tests of Autonomic Function and Mental and Dynamic Exercise in Patients with Essential Hypertension

The aim of the present study was to compare the effects of rilmenidine (1-2 mg/day) and atenolol (50-100 mg/day) on tests of mental arithmetic, bicycle exercise, and autonomic function. Twelve male patients with mild-to-moderate hypertension (blood pressure, 160/95 +/- 15/7 mm Hg; age range, 32 to 60 years) completed a randomized, double-blind, crossover study. Both drugs were well tolerated and, after 4 weeks of monotherapy, were associated with significant reductions in supine and erect BP. Hemodynamic responses to mental arithmetic were similar for both drugs, and neither agent affected mental performance as judged by psychomotor testing. The increase in heart rate during bicycle exercise was significantly greater with rilmenidine (50 vs. 41 beats/min, p = 0.04), and during the postexercise recovery phase, areas under the curve for diastolic blood pressure and heart rate were smaller after atenolol than after rilmenidine: 46,450 versus 51,400 mm Hg.s (p = 0.02) and 49,445 versus 63,597 beats/min.s (p = 0.001), respectively. In conclusion, rilmenidine and atenolol exert comparable antihypertensive effects both at rest and during mental and dynamic exercise. Although atenolol blunted the heart rate responses to dynamic exercise and the Valsalva maneuver, rilmenidine showed no interference with physiological hemodynamic responses of blood pressure and heart rate during tests of sympathetic and parasympathetic function.