Effect of cadralazine on brachial artery hemodynamics and forearm venous tone in essential hypertension

Forearm venous tone and brachial artery hemodynamics, including determinations of the arterial diameter and compliance by the use of pulsed Doppler systems, were measured in 16 patients with sustained essential hypertension before and after acute oral cadralazine dosing. Systolic and diastolic blood pressures significantly decreased, whereas heart rate increased. Brachial artery diameter and vascular resistance decreased, respectively, from 0.501 +/- 0.015 to 0.485 +/- 0.015 cm (P less than 0.001) and from 124.8 +/- 13.8 to 99.3 +/- 11.9 mm Hg/ml . sec (P less than 0.01). Blood flow velocity increased (P less than 0.05) but volumic flow, pulse wave velocity, and brachial artery compliance did not change. Forearm venous tone increased but the increase was inversely related to the degree of arteriolar vasodilatation. Our results indicate that, with cadralazine, forearm vascular resistance decreased while forearm blood flow was unchanged, the dilatation of small arteries contrasted with a significant reduction in the diameter of the large brachial artery, and the decrease in blood pressure was associated with a lack of increase in arterial compliance and changes in venous tone. This suggests an overriding influence of the activation of the autonomic nervous system on the action of cadralazine on large arteries and veins.     

分娩性臂丛神经损伤后患肢主要动脉的彩色多普勒超声观察

目的 探讨彩声多普勒超声观察分娩性臂丛神经损伤后患肢主要动脉的管径和血流速度变化,为临床观测患儿上肢发育状况提供一定的参考价值.方法 对31例分娩性臂丛神经损伤患儿进行彩色多普勒超声检查,测量腋动脉、肱动脉管径及血流峰值速度,并行患、健侧对比.结果 患侧腋动脉和肱动脉管径较健侧细,腋动脉平均管径患侧为(0.22±0.0...     

Reduced sympathetic skin response in the isolated spinal cord of subjects with spinal cord injury

OBJECTIVE: To compare the excitability of the sympathetic skin response (SSR) between subjects with spinal cord injury (SCI) and healthy controls with intact supraspinal connection. DESIGN: Cross-sectional survey. SETTING: Referral center. PARTICIPANTS: A total of 37 men with traumatic neurologically complete SCI (26 with tetraplegia, 11 with paraplegia) and history of autonomic dysreflexia were included. Twenty age-matched healthy male controls were recruited as the control group. Subjects with SCI were at the mean age +/- standard deviation of 36.5+/-11.0 years (range, 20.1-61.3 y) and the mean injury duration was 11.3+/-9.3 years (range, 1.0-38.1 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The SSR tests were grouped into 3 test sets according the stimulation and recording sites: (1) right supraorbital nerve stimulation with left hand recording (SH set); (2) right supraorbital nerve stimulation and left foot recording (SF set); and (3) right posterior tibial nerve stimulation and left foot recording (TF set). RESULTS: In patients with tetraplegia (n=26), none showed positive SSR in the SH or the SF set, and only 5 (19.2%) showed a positive SSR in the TF set. In subjects with paraplegia (n=11), the positive response rates of SSR were 72.7% for the SH set, 0% for the SF set, and 9.1% for the TF set. Electric stimulation at high intensity (100 mA for 1 ms) was required to elicit SSR for the TF set in the patients with SCI. The SSR amplitudes in the SH and TF sets were smaller in subjects with SCI than those in controls (SH set, P=.004; TF set, P<.001). The SSR latency in the SH set was longer in patients with SCI (P=.04), whereas the SSR latency in the TF set tended to be shorter in subjects with SCI (P=.09). CONCLUSIONS: The excitability of SSR was reduced in an isolated spinal cord. This suggests that excitability of sympathetic sudomotor response in subjects with an isolated spinal cord is lower than in healthy controls.     

Pectoral nerve conduction studies: technique in healthy subjects and evaluation of brachial plexopathy

OBJECTIVE: To define the optimal nerve conduction study (NCS) technique of the pectoral nerves and evaluate its clinical utility. DESIGN: Prospective electrophysiologic study with healthy controls. SETTING: Electrophysiologic laboratory in a large general hospital. PARTICIPANTS: Thirty healthy controls and 10 patients with cervical root or brachial plexus pathologies. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Correlation of pectoral NCS with electromyography and magnetic resonance imaging. RESULTS: For pectoral NCS, the mean values +/- standard deviation of onset latency, amplitude, and interside amplitude ratio (ratio of smaller over larger amplitude) were 2.01+/-0.22 ms, 11.75+/-2.21 mV, and .95+/-.04 mV, respectively. Subject age correlated significantly with both onset latency (r=.46, P<.001) and amplitude (r=-.34, P<.008). All 5 patients with brachial plexopathy had amplitude ratios below the normal limit of controls (.87). However, this was not seen for all 5 patients with cervical spondylotic radiculopathy. CONCLUSIONS: The pectoral NCS technique is feasible in healthy subjects. It is useful when differentiating brachial plexopathy from cervical root lesions.     

Endothelial function in young subjects with vaso-vagal syncope.

BACKGROUND: The aim of this study was to determine whether endothelial function and inappropriate peripheral vasomotion have a significant role in the pathogenesis of neurally mediated syncope. METHODS: In 16 patients (mean age 28.2+/-5.8 years) with previous vaso-vagal syncope and in matched healthy subjects, endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent response to glyceryl trinitrate (GTN), 25 mug, were measured in the brachial artery from high-resolution ultrasonography. Heart rate variability (HRV) analysis at rest and during tilt test was compared between two groups. RESULTS: In the subjects with positive tilt test, all HRV parameters were significant higher respect to subjects with negative tilt test (P<0.001). The patients with positive tilt test, showed persistent, marked variability of heart rate (HR), due to increased vagal activity with withdrawal sympathetic tone and consequently reduction of blood pressure (BP) (-30.4+/-4.2 mmHg, P<0.001) accompanied by a decrease in HR (-24.3+/-4.5 beats/min, P<0.001) compared to negative tilt test subjects. These findings prove the real presence of vagal hypertone in patients with syncope. In our study, HR reached values lower than 40 beats/min. FMD in patients with neurally mediated syncope were significantly greater than those in controls (respectively, 9.2+/-2.8% vs. 4.6+/-1.4%, P<0.01) whereas no differences were shown in the response to GTN (18.4+/-4.4% vs. 16.1+/-4.2%, n.s.). CONCLUSIONS: The augmented endothelial function and the abnormal vasodilation of peripheral arteries in association with bradycardia play an important role in the development of vaso-vagal syncope in young subjects.     

Cardiac vagal response to water ingestion in normal human subjects

In healthy young subjects there is direct evidence for sympathetic vasoconstrictor activation after drinking water, but this is not accompanied by an increase in arterial blood pressure. A marked pressor response to water ingestion has, however, been observed in elderly subjects and in patients with autonomic failure. We examined the effect of water ingestion on haemodynamic variables and heart rate variability (HRV) markers of cardiac vagal control in ten healthy young subjects and four cardiac transplant recipients with confirmed persistent cardiac vagal denervation. In a random order crossover protocol, changes in heart rate, blood pressure and measures of high frequency (HF) HRV were compared over time following the ingestion of 500 ml and 20 ml (control) of tap water. In healthy subjects, after drinking 500 ml of water the heart rate fell from 67.6+/-2.0 (mean+/-S.E.M.) to 60.7+/-2.4 beats/min (P<0.01), and the bradycardic response peaked between 20 and 25 min. There were no significant changes in arterial blood pressure. Over the same time course, water ingestion caused increases in measurements of HF HRV: root-mean-square of successive RR interval differences (RMSSD) increased by 13+/-2.7 ms after 500 ml versus 2+/-3.1 ms after 20 ml (P<0.05); HF power increased by 686+/-400 versus -63+/-322 (P<0.01). In transplant recipients water ingestion was followed by a pressor response (range 13 to 29 mmHg). These results provide evidence that water ingestion in normal subjects is followed by an increase in cardiac vagal control that may counteract the pressor effects of sympathetic activation. We suggest that in the elderly, in transplant recipients and in autonomic failure, loss of this buffering mechanism explains the pressor response to drinking water.     

Hyperoxia-induced arterial compliance decrease in healthy man

INTRODUCTION: Oxygen therapy is commonly used in emergency department and intensive care units without careful evaluation of its effects, especially on the haemodynamics and artery characteristics. MATERIALS AND METHODS: A prospective laboratory study evaluated brachial circulatory effects of normobaric hyperoxia using ultrasonography-Doppler. The study was set in a hospital research laboratory. The subjects were thirteen healthy volunteers. Investigations were performed under normal air ventilation and after 20 min of hyperoxic mixture ventilation using a high concentration mask. Two dimensional images and brachial blood flow velocities were recorded using ultrasonography and pulsed Doppler to study changes in cross sectional area, blood flow, resistance index, and cross-sectional compliance coefficient. RESULTS: During hyperoxic exposure, mean PaO2 was 372 +/- 21 mmHg. A significant decrease of heart rate was observed. Arterial pressures (systolic and diastolic arterial pressures) were not modified. A decrease of cross sectional areas at end diastole and end systole was observed. Pulsed Doppler study showed a decrease of brachial artery blood flow and an increase of the resistance index. Furthermore, a decrease of the cross-sectional compliance coefficient was observed during hyperoxic exposure in all subjects. CONCLUSION: This study using two-dimensional ultrasonography and pulsed Doppler could demonstrate an increase in brachial arterial tone and a decrease in brachial blood flow under normobaric hyperoxia.     

Water ingestion increases sympathetic vasoconstrictor discharge in normal human subjects

A marked pressor response to water drinking has been observed in patients with autonomic failure and in the elderly, and has been attributed to sympathetic vasoconstrictor activation, despite the absence of such a pressor response in healthy subjects with intact sympathetic mechanisms. We investigated whether water drinking in normal subjects affected peripheral sympathetic neural discharge and its effect on vascular resistance. In nine normal human subjects, we examined the effect of water ingestion on muscle sympathetic neural activity from the peroneal nerve, as multi-unit bursts (muscle sympathetic nerve activity; MSNA) and as single-unit impulses (s-MSNA) with vasoconstrictor function, and on calf vascular resistance for 120 min. In each subject, water ingestion caused increases in s-MSNA and MSNA which peaked at 30 min after ingestion; they increased respectively (mean+/-S.E.M.) from 42+/-4 to 58+/-5 impulses/100 beats (P<0.01) and from 36+/-4 to 51+/-5 bursts/100 beats (P<0.001). There were corresponding increases in calf vascular resistance and in plasma noradrenaline levels. A significant correlation occurred between all of these data. In conclusion, measurement of MSNA has provided direct evidence that water drinking in normal human subjects increases sympathetic nerve traffic, leading to peripheral vasoconstriction. This sympathetic activation was not accompanied by significant changes in arterial blood pressure.     

Evaluation of Autonomic Influences on QT Dispersion Using the Head-Up Tilt Test in Healthy Subjects

Our objective was to examine the autonomic influence on QT interval dispersion using the head-up tilt test in healthy subjects. RR and QT intervals, heart rate variability, and plasma norepinephrine concentration were measured in the supine position and tilting to 70 degrees for 20 minutes using a footboard support in 15 healthy male volunteers (mean age +/- SD: 28.0 +/- 4.5 years). The rate-corrected QT interval (QTc) was calculated using Bazett's formula, and QT and QTc dispersions were defined as the maximum minus minimum values for the QT and QTc, respectively, from the 12-lead ECG. Spectral analysis of the heart rate variability generated values for the low- and high-frequency powers (LF and HF) and their ratio (LF/HF). Compared with values obtained in the supine position, tilting significantly increased QT (P < 0.05) and QTc dispersion (P < 0.01), the LF/HF ratio (P < 0.0001), and plasma norepinephrine concentration (P < 0.0001), and significantly decreased HF (P < 0.0001). QTc dispersion was positively correlated with the LF/HF ratio and plasma norepinephrine concentration, and negatively correlated with HF. These results suggest that head-up tilt testing increases QT dispersion by increasing sympathetic tone and/or decreasing vagal tone in healthy subjects.     

Saphenous nerve conduction in healthy subjects

Saphenous nerve conduction was studied in 40 healthy subjects utilizing a slight modification of the method described by Wainapel et al. The mean values obtained were as follows: distal sensory latency, 2.9 +/- 0.3 msec for 10 cm distance; conduction velocity, 46.6 +/- 3.5 m/sec; and amplitude of sensory nerve action potential, 10.7 +/- 4.3 microV. The technique should be useful in the electrodiagnostic differentiation between lumbar root (L3, L4) lesions and postganglionic lesions such as lumbar plexus and femoral nerve lesions and entrapment neuropathy of the saphenous nerve.     

L-arginine-induced vasodilation of the renal vasculature is preserved in uremic type 1 diabetic patients after kidney and pancreas but not after kidney-alone transplantation

OBJECTIVE: In uremic type 1 diabetic patients, kidney and pancreas transplantation (KP) and kidney-alone transplantation (KD) provide full restoration of normal renal function; however, only KP, i.e., curing diabetes, is expected to prevent endothelial damages. Our aim was to study L-arginine-induced vasodilation of the renal vasculature in uremic type 1 diabetic patients after KP or KD using magnetic resonance (MR). RESEARCH DESIGN AND METHODS: MR quantitative flow measurements were performed in 15 KP patients (mean age 39.0 +/- 1.7 years, 10 men and 5 women), in 11 KD patients (mean age 47.3 +/- 1.9 years, 7 men and 4 women), and in 8 nondiabetic kidney transplant patients (mean age 44.0 +/- 4.8 years, 7 men and 1 woman), who were used as control subjects, to measure renal blood flow and velocity and renal vascular resistance before and immediately after infusion of L-arginine. RESULTS: Renal blood flow and velocity were not different at baseline in KP, KD, and control subjects. In contrast, during L-arginine administration renal blood flow increased significantly in KP subjects (basal 8.4 +/- 0.6 vs. post 9.6 +/- 0.8 ml/s, Delta 14.3 +/- 4.4%, P < 0.05) and in control subjects (basal 9.3 +/- 0.8 vs. post 9.1 +/- 0.8 ml/s, Delta 17.3 +/- 6.2%, P < 0.01), while it remained unchanged in KD subjects (basal 10.0 +/- 0.8 vs. post 11.6 +/- 0.9 ml/s, Delta -1.36 +/- 6.9%, NS). Parallel results have been achieved for renal blood velocity (KP subjects: 20.1 +/- 4.9%, P < 0.01; control subjects: 23.0 +/- 7.99%, P < 0.01; and KD subjects: -0.3 +/- 6.5%; NS). A reduction in renal vascular resistance in response to L-arginine was evident in KP and control subjects but not in KD patients. CONCLUSIONS: L-Arginine vasodilatory response was successfully assessed with MR quantitative flow measurements. KP patients and control subjects, but not those with KD, showed a preserved L-arginine-induced vasodilation of the renal vasculature.     

Significance of primary T wave aberrations in the electrocardiogram of asymptomatic young men, III. Systolic time intervals and autonomic tone

Fifteen healthy male subjects, aged 18-19 years, with primary T wave aberrations consisting mainly of notches in the T wave without concomitant ST depression (group T) were compared to twenty-six controls of the same age with normal electrocardiograms. The T wave aberrations were eliminated by beta-adrenergic blockade in thirteen subjects in group T. Physical exercise decreased all the T wave aberrations. Group T was on average shorter and had signs of higher sympathetic tone, as shown by a higher heart rate and systolic blood pressure, than the controls and the parasympathetic tone was lower, as indicated by a higher heart rate during beta-adrenergic blockade. No significant differences in physical work capacity and heart volumes were found. Measurement of systolic time intervals suggested increased sympathetic influence on the heart and no signs of cardiac impairment. Thus the majority of subjects with aberrant T waves had changes in the autonomic tone and no signs of functional impairment of the heart.     

Lack of cutaneous hyperemia in response to insulin-induced hypoglycemia in IDDM

Cutaneous blood flow was measured with the laser Doppler technique and by recording cutaneous O2 tension on the forearm and forehead in nine young adult patients with insulin-dependent diabetes mellitus (IDDM) and nine sex- and age-matched healthy control subjects after induction of hypoglycemia. In the healthy subjects, cutaneous blood flow measured with the laser Doppler technique was increased by 120 +/- 26% in the forehead (P less than 0.01) and 196 +/- 50% in the forearm (P less than 0.01) at the glucose nadir (blood glucose 1.8 +/- 0.2 mM) compared with basal blood flow. In contrast, in diabetic patients, cutaneous blood flow was unchanged. The corresponding changes, at the glucose nadir, with cutaneous O2 tension recordings were 286 +/- 131% (P less than 0.05) in control subjects and -22 +/- 15% (NS) in diabetic patients. An impairment of sympathetic nervous function, not detectable by simple cardiovascular tests, could be responsible for the lack of cutaneous hyperemia and sweating and could contribute to unawareness of hypoglycemia in diabetic patients.     

Coronary vasomotor and blood flow responses to isoflavone-intact soya protein in subjects with coronary heart disease or risk factors for coronary heart disease

Results in animals suggest favourable coronary vasomotor actions of isoflavones; however, the effects of isoflavones on the human coronary circulation have not been determined. In the present study, we therefore investigated the effects of short-term isoflavone-intact soya protein ingestion on basal coronary arterial tone and stimulated vasoreactivity and blood flow in patients with CHD (coronary heart disease) or risk factors for CHD. Seventy-one subjects were randomized, double-blind, to isoflavone-intact soya protein [active; n=33, aged 58+/-8 years (mean+/-S.D.)] or isoflavone-free placebo (n=38, aged 61+/-8 years) for 5 days prior to coronary angiography. In 25 of these subjects, stimulated coronary blood flow was calculated from flow velocity, measured using intracoronary Doppler and coronary luminal diameter before and after intracoronary adenosine, ACh (acetylcholine) and ISDN (isosorbide dinitrate) infusions. Basal and stimulated coronary artery luminal diameters were measured using quantitative coronary angiography. Serum concentrations of the isoflavones genistein, daidzein and equol were increased by active treatment (P<0.001, P<0.001 and P=0.03 respectively). Basal mean luminal diameter was not significantly different between groups (active compared with placebo: 2.9+/-0.7 compared with 2.73+/-0.44 mm, P=0.31). There was no difference in luminal diameter, flow velocity and volume flow responses to adenosine, ACh or ISDN between groups. Active supplement had no effect on basal coronary artery tone or stimulated coronary vasoreactivity or blood flow compared with placebo. Our results suggest that short-term consumption of isoflavone-intact soya protein is neither harmful nor beneficial to the coronary circulation of humans with CHD or risk factors for CHD. These results are consistent with recent cautions placed on the purported health benefits of plant sterols.     

Cardiovascular responses and postexercise hypotension after arm cycling exercise in subjects with spinal cord injury

OBJECTIVE: To examine postexercise hypotension and contributing factors in subjects with spinal cord injury (SCI). DESIGN: Prospective clinical research study. SETTING: Rehabilitation center. PARTICIPANTS: Subjects with chronic cervical-level (n=19) and thoracic-level (n=8) SCI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Subjects underwent graded arm-cycling with electrocardiogram and oxygen uptake monitoring to exhaustion. Heart rates and blood pressures were measured before and after exercising. Injury to motor and sensory pathways was determined by American Spinal Injury Association grade, and to autonomic pathways by sympathetic skin responses (SSRs) (n=16). RESULTS: Resting blood pressures and heart rates were lower in cervical than thoracic SCI (mean arterial pressure [MAP]: cervical, 76.6+/-2 mmHg; thoracic, 93.5+/-3 mmHg; P<.001). Following exercise, heart rate responses were greater in thoracic than cervical SCI; MAP increased in thoracic SCI (8.4+/-5 mmHg) and markedly decreased in cervical SCI (-9.3+/-2 mmHg) (P<.001). No subject had significant electrocardiographic abnormalities at rest or during exercise. There were correlations between SSR and heart rate and blood pressure responses to exercise; the correlation between the SSR and blood pressure response was due to an interaction between the heart rate and blood pressure responses. CONCLUSIONS: Abnormal cardiovascular responses to exercise and transient postexercise hypotension were common in cervical, but not thoracic SCI. This may be partly related to loss of descending sympathetic nervous control of the heart and vasculature following high SCI.     

Analysis of Heart Rate Variability Five Minutes Before the Onset of Paroxysmal Atrial Fibrillation

BACKGROUND: Various experimental and clinical observations suggest changes in sympathetic and vagal neural regulatory mechanisms play a critical role in altering cardiac electrical properties and favor the occurrence of arrhythmic events. There is limited information about the influences of the autonomic tone on the development of episodes of paroxysmal atrial fibrillation in patients with no evidence of organic heart disease. The aim of this study was to investigate changes in sympatho-vagal balance 5 minutes before the onset of atrial fibrillation. METHODS: We evaluated 28 patients with no history of heart disease who were not undergoing pharmacological treatment and who had at least one episode of paroxysmal atrial fibrillation recorded during an 24-hour ECG Holter monitoring. We analyzed values of frequency domain heart rate variability parameters 5 minutes before the onset of atrial fibrillation (prefa period) compared to an equivalent period at least 1 hour after from atrial fibrillation (random period). RESULTS: Thirty-six episodes of atrial fibrillation were recorded and our results showed we had two types of episodes. Eighteen were classified as Type A, in which we had an increase of low frequency (LF) (79.15 +/- 10.76 in comparison with 62.64 +/- 19.55) (P = 0.004) and a decrease of high frequency (HF) (20.82 +/- 10.74 in comparison with 37.64 +/- 20.20) (P = 0.004) consistent with an increase of sympathetic tone; and 18 were classified as Type B in which there was a decrease of LF (62.82 +/- 15.38 in comparison with 85.97 +/- 8.48) (P < 0.001), and an increase of HF (36.79 +/- 14.72 compared with 14.01 +/- 8.48) (P < 0.001), consistent with an increase of parasympathetic tone. CONCLUSION: We observed abrupt changes in sympathovagal balance in the last 5 minutes preceding an episode of atrial fibrillation. This can be related to a double behavior in the neurogenic drive: in Type A episodes there is an increase of the LF spectrum, LF:HF ratio, and a decrease of the HF spectrum consistent with an increase of neurogenic sympathetic drive; in Type B episodes there is a reduction of the LF spectrum, LF/HF ratio, and an increase of HF spectrum consistent with an enhancement of the neurogenic parasympathetic drive. In some patients, we found that the two mechanisms operate during different hours of the day and that sometimes there is an increase of sympathetic tone, and in the same instances an increase of parasympathetic tone. Heart-rate variability measures fluctuation in autonomic inputs to the heart rather than the mean level of autonomic impulse; autonomic imbalance is probably more important than the vagal or sympathetic drive alone.     

The short-term effects of myofascial trigger point massage therapy on cardiac autonomic tone in healthy subjects

AIM OF THE STUDY: To investigate the effects of myofascial trigger-point massage therapy to the head, neck and shoulder areas on cardiac autonomic tone.Background. No studies have reported on the effect of back massage on autonomic tone as measured by heart rate variability. This is especially relevant to the nursing profession, as massage is increasingly available as a therapy complementary to conventional nursing practice. DESIGN/METHODS: An experimental study in which subjects were initially placed in age- and sex-matched groups and then randomized to treatment or control by alternate allocation. The study involved 30 healthy subjects (16 female and 14 male, aged 32.47 +/- 1.55 years, mean +/- standard error). A 5-minute cardiac interbeat interval recording, systolic and diastolic blood pressure and subjective self-evaluations of muscle tension and emotional state were taken before and after intervention. Autonomic function was measured using time and frequency domain analysis of heart rate variability. RESULTS: Following myofascial trigger-point massage therapy there was a significant decrease in heart rate (P < 0.01), systolic blood pressure (P=0.02) and diastolic blood pressure (P < 0.01). Analysis of heart rate variability revealed a significant increase in parasympathetic activity (P < 0.01) following myofascial trigger-point massage therapy. Additionally both muscle tension and emotional state, showed significant improvement (P < 0.01). CONCLUSIONS: In normal healthy subjects myofascial trigger-point massage therapy to the head, neck and shoulder areas is effective in increasing cardiac parasympathetic activity and improving measures of relaxation.     

Dynamic cerebral autoregulatory capacity is affected early in Type 2 diabetes

Type 2 diabetes is associated with an increased risk of endothelial dysfunction and microvascular complications with impaired autoregulation of tissue perfusion. Both microvascular disease and cardiovascular autonomic neuropathy may affect cerebral autoregulation. In the present study, we tested the hypothesis that, in the absence of cardiovascular autonomic neuropathy, cerebral autoregulation is impaired in subjects with DM+ (Type 2 diabetes with microvascular complications) but intact in subjects with DM- (Type 2 diabetes without microvascular complications). Dynamic cerebral autoregulation and the steady-state cerebrovascular response to postural change were studied in subjects with DM+ and DM-, in the absence of cardiovascular autonomic neuropathy, and in CTRL (healthy control) subjects. The relationship between spontaneous changes in MCA V(mean) (middle cerebral artery mean blood velocity) and MAP (mean arterial pressure) was evaluated using frequency domain analysis. In the low-frequency region (0.07-0.15 Hz), the phase lead of the MAP-to-MCA V(mean) transfer function was 52+/-10 degrees in CTRL subjects, reduced in subjects with DM- (40+/-6 degrees ; P<0.01 compared with CTRL subjects) and impaired in subjects with DM+ (30+/-5 degrees ; P<0.01 compared with subjects with DM-), indicating less dampening of blood pressure oscillations by affected dynamic cerebral autoregulation. The steady-state response of MCA V(mean) to postural change was comparable for all groups (-12+/-6% in CTRL subjects, -15+/-6% in subjects with DM- and -15+/-7% in subjects with DM+). HbA(1c) (glycated haemoglobin) and the duration of diabetes, but not blood pressure, were determinants of transfer function phase. In conclusion, dysfunction of dynamic cerebral autoregulation in subjects with Type 2 diabetes appears to be an early manifestation of microvascular disease prior to the clinical expression of diabetic nephropathy, retinopathy or cardiovascular autonomic neuropathy.     

Haemodynamics of the pressor effect of oral water in human sympathetic denervation due to autonomic failure

Oral water ingestion increases blood pressure in normal elderly subjects and in patients suffering from autonomic failure, but the time course of the haemodynamic changes is not known. We therefore studied 14 subjects with documented sympathetic denervation due to pure autonomic failure, with continuous haemodynamic recordings obtained before and after ingestion of 500 ml of distilled water at room temperature. The time course of changes in values of systolic and diastolic beat-by-beat finger blood pressure, heart rate, stroke volume, cardiac output, ejection fraction and total peripheral resistance were analysed. Systolic blood pressure rose from 115+/-8 mmHg (mean+/-S.E.M.) to 133+/-8 mmHg (P<0.001), and diastolic blood pressure from 64+/-4 to 73+/-4 mmHg (P<0.001), with the pressor response beginning a few minutes after water ingestion, plateauing between 10 and 35 min (peak at 14 min), and returning to baseline at 50 min. Heart rate fell from 71+/-2.5 to 67+/-2 beats/min (P<0.001), and total peripheral resistance increased from 1.31+/-0.19 to 1.61+/-0.24 m-units (P<0.001). There were no significant changes in ejection fraction, stroke volume or cardiac output. This study confirmed a pressor response to oral water in subjects with sympathetic denervation. The temporal profile of the response did not favour reflexly mediated sympathetic activation. As subjects with autonomic failure are prone to salt and water depletion, and since blood pressure is exquisitely sensitive to such changes, it may be that the observed response is due to repletion or restoration of intravascular and extravascular fluid volume.     

交感神经皮肤反应诊断多发性硬化自主神经病变

目的探讨交感神经皮肤反应(SSR)及3项诱发电位对多发性硬化(MS)的诊断价值.方法对43例临床确诊和临床可能的MS患者进行SSR及3项诱发电位检测,并与正常对照组比较分析.结果MS患者SSR异常率为79%,比异常的诱发电位更为常见.潜伏期与对照组比较有显著差异P＜0.01,有自主神经症状的12例,而SSR异常34例.结论SSR能客观有效地评估自主神经功能状态,发现MS自主神经的亚临床病变.SSR与3项诱发电位联合应用,有助于MS的早期诊断,对评价MS中枢神经及自主神经系统损害,具有更高的敏感性.