Reduced Skin Blood Flow Research Articles

Changes in Skin Blood Flow and Skin Sympathetic Nerve Activity in Response to Manual Acupuncture Stimulation in Humans

To determine the effects of manual acupuncture stimulation (MAS) on skin sympathetic nerve activity (SSNA), SSNA and skin blood flow (SBF) were measured during a resting period and during MAS. Twelve healthy male subjects were divided into an acupuncture group (n = 7) and a control group (n = 5). SSNA was recorded from the left median nerve at the elbow using microneurography, while SBF was recorded using laser Doppler flowmeter. In the acupuncture group, MAS was delivered to LI 4 point in the right thenar muscle. The acupuncture needle was retained for 2 minutes before being removed. SSNA and SBF recordings were performed for a total of 12 minutes, from 5 minutes prior to MAS until the end of the trial. In the control group, the 2-minute period of acupuncture was replaced by 2 minutes of rest. During the first minute of MAS, we observed an increase in SSNA accompanied by a reduction in SBF. In the acupuncture group, these parameters returned to baseline values in the second minute of MAS. Parameters in the control group were unchanged throughout the experimental procedure. A significant negative correlation was observed between changes in SSNA and SBF during the first minute of MAS. In addition, a negative correlation was demonstrated between the basal value of SSNA and the change in SSNA in response to MAS. These results suggest that MAS elicited a transient increase in SSNA and that this increase is dependent on the baseline of SSNA.

Mechanisms of Raynaud’s disease

Raynaud's phenomenon is due to transient cessation of blood flow to the digits of the hands or feet. An attack of Raynaud's phenomenon is classically manifested as triphasic color changes. The white phase is due to excessive vasoconstriction and cessation of regional blood flow. This phase is followed by a cyanotic phase, as the residual blood in the finger desaturates. The red phase is due to hyperemia as the attack subsides and blood flow is restored. An attack is frequently associated with pain and/or paresthesia due to sensory nerve ischemia. Variants of Raynaud's phenomenon include acrocyanosis and primary livedo reticularis, each of which is associated with reduced skin blood flow, exacerbated by cold or emotional upset. Raynaud's phenomenon in the absence of other disorders is primary Raynaud's phenomenon, or Raynaud's disease. The mechanisms of Raynaud's disease include increased activation of the sympathetic nerves, in response to cold or emotion; an impaired habituation of the cardiovascular response to stress may contribute. In addition, there appears to be a local fault, which is likely multifactorial. This local fault is due to an alteration in vascular function rather than vascular structure. The alteration in vascular function may be related to increased sensitivity to cold of the adrenergic receptors on the digital artery vascular smooth muscle. In some cases, locally released or systemically circulating vasoconstrictors may participate, including endothelin, 5-hydroxytryptamine and thromboxane. A deficiency or increased degradation of nitric oxide, possibly due to increased oxidative stress, may be involved in some cases. These recent pathophysiological insights may lead to new therapeutic options.

Evaluation of the Antioxidant Capacity and Preventive Effects of a Topical Emulsion and Its Vehicle Control on the Skin Response to UV Exposure

Supplying topical exogenous antioxidants to the skin may prevent or minimize free radical-induced damaging. This study determines antioxidative capacity of a topical skin care emulsion (an oil-in-water vitamin E-containing formulation) versus its vehicle on human skin that was exposed to ultraviolet radiation (UVR) by utilizing a photochemiluminescence device and biophysical methods. Ten healthy Caucasians (3 male and 7 female; mean age 47 ± 10 years) were enrolled. In a randomized and double-blind manner, a pH-balanced vitamin E emulsion or its vehicle control was applied onto predesignated forearm prior to UVR exposure. Thirty minutes after application, these test sites were exposed to a UV light to induce the minimal erythema dose. One untreated site served as a blank control. Visual scoring and instrumental measurements were recorded at baseline and at 24 h and 48 h thereafter. At day 3, after completing instrumental measurements, each test site was stripped three times in a consecutive manner with a proprietary adhesive tape disc. These tapes were quantified for antioxidant capacity using a photochemiluminescence device.Vitamin E emulsion and vehicle control significantly (p < 0.05) suppressed visual scores when compared with blank control at day 2 and day 3 after UV exposure. However, vitamin E emulsion showed significantly (p < 0.05) lower visual scores when compared with vehicle control at day 2 and day 3 after UV exposure.Also,vitamin E emulsion and its vehicle control significantly (p < 0.05) diminished skin color measurement (a*) values when compared with blank control at day 2 and day 3 after UV exposure. At day 2 after UV exposure, only vitamin E emulsion significantly (p < 0.05) reduced skin blood flow volume when compared with blank control. Vitamin E emulsion and its vehicle control showed significant (p < 0.05) reduction of blood flow volume when compared with blank control at day 3 after UV exposure. Vitamin E emulsion and its vehicle control proved effective in preventing induction of erythema and reducing inflammatory damage caused by UV exposure. The effect of vitamin E emulsion exceeded that of an ‘active control’.

No effect of 85 mT permanent magnets on laser-Doppler measured blood flow response to inspiratory gasps

Although no effects of permanent magnets on resting skin blood flow (SBF) in humans have yet been demonstrated, the possibility that magnet related effects might modify dynamic SBF changes has not been previously studied. We hypothesized that magnets may alter local neurovascular mechanisms to cause changes in normal SBF vasoactive responses. To test this, we studied the effects of a magnet on SBF reductions induced by sympathetic reflexes associated with deep inspirations. SBF was continuously monitored by a dual channel laser-Doppler flowmeter with probes on the middle finger dorsum of both hands of 24 healthy subjects. In the first of two successive intervals, each of the fingers rested on sham ceramic magnets (control interval). Subsequently, one finger rested on an active magnet and the other finger on a sham (experimental interval). Skin temperatures were also measured. The magnet was a 37 mm diameter x 14 mm thick ceramic magnet with a surface field strength of 85 mT measured in the geometrical center of the magnet. Field strength at the finger dorsum, 13 mm above magnet, was 31.5 mT. During each interval, three deep breaths were used to elicit SBF reductions. Responses were calculated as the percent reduction in SBF from its prior 20 s average. Breaths in each interval were spaced 3 min apart to permit full recovery between responses. The experimental interval started after an active magnet was in place for 20 min. Results showed no significant difference in either vasoconstrictive responses or skin temperature due to the magnet. We conclude that magnets of the type, strength and duration used, have no significant effect on vasoconstrictive processes associated with this sympathetic reflex in this group of healthy subjects.

Skin Blood Flow in Diabetic Dermopathy

Diabetic dermopathy has been termed the most common cutaneous finding in diabetes, occurring in as many as 40% of diabetic patients older than 50 years. Using laser Doppler technology, we tested the hypothesis that dermopathy lesions represented areas of cutaneous ischemia. A survey of cutaneous blood flow in diabetic patients with dermopathy and comparison of values with those in nondiabetic patients. Outpatient clinic specializing in diabetes. A consecutive sample of 61 diabetic patients (52 men and 9 women; mean +/- SEM age, 58 +/- 2 years) with dermopathy had blood flow measurements performed at the sites of dermopathy and at contiguous uninvolved sites. Flow values were also determined at several reference sites and compared with those in 41 nondiabetic control subjects (30 men and 11 women; mean age, 53 +/- 3 years). Heat-stimulated blood flow values at the knee, ankle, and toe were about 50% lower for the dermopathy patients than for the nondiabetic controls. Yet, despite their reduced skin blood flow reserve, the dermopathy lesions did not show relative ischemia. At the basal temperature of 35 degrees C, flow was 1.1 +/- 0.1 mL /min per 100 g of tissue in apparently normal skin vs 2.2 +/- 0.2 at dermopathy sites; at 44 degrees C, flow at the normal sites was 7.9 +/- 0.3 mL /min per 100 g of tissue vs 12.9 +/- 0.6 at dermopathy sites (P<.01 for both comparisons). Although patients with diabetic dermopathy exhibited reduced skin blood flow compared with nondiabetic volunteers, flow levels were considerably higher at the dermopathy sites than at contiguous uninvolved skin sites. These results refute the hypothesis that diabetic dermopathy represents local ischemia. However, it is still possible that the scarring represented by dermopathy lesions is related to decreased skin perfusion due to diabetes.

Orthostatic challenge does not alter skin sympathetic nerve activity in heat-stressed humans

Perturbations that load or unload baroreceptors do not alter skin sympathetic nerve activity (SSNA) in normothermic individuals. However, in pronounced heat-stressed individuals, when a significant component of the SSNA signal is sudomotor and possibly vasodilator in origin, the effects of baroreceptor unloading via an orthostatic stress on SSNA remain unclear. The purpose of the present study was to test the hypothesis that low and moderate levels of orthostatic stress via lower body negative pressure (LBNP) alter SSNA in pronounced heat-stressed individuals. In both normothermic and heat-stressed conditions, progressive LBNP at −3, −6, −9, −12, −15, −18, −21 and −40 mm Hg were applied to 11 subjects for 2 min per stage. Whole-body heating increased sublingual temperature by 0.7±0.1 °C, heart rate by 28±2.1 bpm, SSNA by 259±76 %, forearm skin blood flow by 631±142% and forearm sweat rate to 0.68±0.14 mg/cm 2/min (all p<0.005), but did not change mean arterial blood pressure (MAP) ( p>0.05). LBNP did not change total SSNA in normothermic or heat-stressed conditions (both p>0.05), although skin blood flow and sweat rate decreased during moderate levels of LBNP while heat stressed. These data suggest that in pronounced heat-stressed individuals, when a significant component of the SSNA signal contains sudomotor and possibly cutaneous active vasodilator activities, low and moderate levels of baroreceptor unloading via LBNP do not alter total SSNA. This observation, coupled with reductions in skin blood flow and sweating during moderate levels of LBNP, suggests that integrated SSNA should not be used as an indicator of baroreflex modulation of the cutaneous vasculature or sweat rate in heat-stressed subjects.

Skin sympathetic outflow in Buerger’s disease

To clarify if sympathetic outflow is altered in Buerger’s disease (thromboangitis obliterans, TAO), we measured skin sympathetic nerve activity (SSNA) in TAO patients, and observed the sweating and vasoconstrictive responses during resting and with activating maneuvers. Multiunit postganglionic sympathetic activity was recorded in a skin fascicle of the tibial nerve innervating the skin of the sole (glabrous skin) and peroneal nerve innervating the skin of the dorsum pedis (hairy skin) from five TAO patients and five healthy subjects simultaneously with skin blood flow and sweat expulsion. TAO patients showed significantly less vasoconstrictor SSNA than healthy subjects (17.0±1.9 vs. 31.5±5.8 bursts/min, P<0.001). Moreover, we found no relationship between vasoconstrictor SSNA and skin blood flow in some patients, while they were well correlated in healthy subjects. There was no evidence for increased sympathetic activity in TAO patients, and no hypersensitive relationship was found between SSNA and skin blood flow. These observations suggested that these TAO patients exhibiting no relationship between skin blood flow reduction and vasoconstrictor activity might not respond to sympathectomy, which is generally expected to result in an increase in skin blood flow. The absence of increased sympathetic nerve activity provides further indirect evidence of a local vascular abnormality in TAO.

Skin sympathetic neuroeffector response is attenuated dose-dependently by systemic prostaglandin E1 injection in humans

To clarify the effects of prostaglandin E1 (PGE1) on the vasoconstrictive responses, we compared the correlation between the amplitude of integrated skin sympathetic nerve activity (SSNA) and per cent reduction in skin blood flow (SBF) before and after the infusion of lipo PGE1 and placebo (bolus one-shot infusion, single blind study), and constant rate infusion of PGE1 (10 and 50 ng kg−1 min−1 by infusion pump, dose-dependency study) in ten healthy men. SSNA was recorded microneurographically from the median nerve simultaneously with SBF by laser Doppler flowmetry at the index fingertip. The measurement was conducted 30 min after injection of lipo PGE1 or placebo, and during the drip infusion of 10 and 50 ng kg−1 min−1 of PGE1 with maneuvers to enhance SSNA. The resting and activated skin blood flow were not significantly different between 10 ng lipo PGE1 and placebo administration, and between baseline and 10, 50 ng kg−1 min−1 of PGE1 injection. The vascular response, defined as the slope of regression line between logarithm of amplitude of integrated SSNA bursts and the reduction in SBF, was significantly suppressed by injection of lipo PGE1 as compared with that by placebo. It was also decreased dose-dependently by the constant rate infusion of PGE1 (10 and 50 ng kg−1 min−1). We concluded that the intravenous injection of PGE1 attenuates vasoconstrictive responses to SSNA, and analysis of the relations between SSNA and vasoconstrictive response, i.e. the neuroeffector response, is suggested to be an important tool to assess the drug effect.

Microcirculatory Responses To Electrical Spinal Cord Stimulation In Painful Diabetic Neuropathy And Other Painful Conditions

Electrical spinal cord stimulation (ESCS) has been used to provide pain relief in a number of conditions, including painful diabetic neuropathy (PDN). ESCS has also been shown to increase microvascular blood flow in peripheral vascular disease. If nerve hypoxia contributes to pain in PDN, ESCS may relieve this by increasing nerve blood flow. We have therefore investigated skin and sural nerve microvascular responses to ESCS. We studied subjects implanted with ESCS for pain relief, 4 had PDN and 7 were controls with other painful conditions. Blood flow, before and during stimulation, was assessed using Laser Doppler flowmetry. Only one (PDN) subject showed a statistically significant increase in skin blood flow during stimulation. The three remaining PDN subjects showed significant reductions in skin blood flow, as did 3/7 of controls. Sural nerve blood flow was measured on a separate occasion. During stimulation nerve blood flow increased in 1 (control) subject, decreased in 1 (PDN) subject and did not change in the other 5 tested (3 PDN and 2 control). In summary, ESCS did not produce any consistent increase in skin or nerve microvascular blood flow. ESCS reduces pain in a variety of different conditions, however this does not appear to be mediated by changes in blood flow. Until a thorough understanding of the pathogenic mechanisms causing PDN is achieved, therapy will be limited to providing symptomatic relief.

Fluid and electrolyte supplementation for exercise heat stress

During exercise in the heat, sweat output often exceeds water intake, resulting in a body water deficit (hypohydration) and electrolyte losses. Because daily water losses can be substantial, persons need to emphasize drinking during exercise as well as at meals. For persons consuming a normal diet, electrolyte supplementation is not warranted except perhaps during the first few days of heat exposure. Aerobic exercise is likely to be adversely affected by heat stress and hypohydration; the warmer the climate the greater the potential for performance decrements. Hypohydration increases heat storage and reduces a person's ability to tolerate heat strain. The increased heat storage is mediated by a lower sweating rate (evaporative heat loss) and reduced skin blood flow (dry heat loss) for a given core temperature. Heat-acclimated persons need to pay particular attention to fluid replacement because heat acclimation increases sweat losses, and hypohydration negates the thermoregulatory advantages conferred by acclimation. It has been suggested that hyperhydration (increased total body water) may reduce physiologic strain during exercise heat stress, but data supporting that notion are not robust. Research is recommended for 3 populations with fluid and electrolyte balance problems: older adults, cystic fibrosis patients, and persons with spinal cord injuries.

A comparison of skin blood flow and skin conductance response in the measurement of autonomic arousal

Aim: A pilot study to compare skin blood flow (SBF) as measured by laser Doppler flowmetry (LDF) with measures of skin conductance.Method: Changes in SBF and skin conductance in response to a variety of stimuli were investigated in twelve healthy volunteers. The stimuli included three manoeuvres – breath holding, Valsalva and head turning – and a series of auditory and shock stimuli. Evidence of correlation between the two measures as well as evidence of habituation were investigated.Results: A simultaneous reduction in SBF and increase in skin conductance followed each manoeuvre and stimulus. A significant correlation between the two responses was found (p < .001). Habituation of skin conductance to shock stimuli was demonstrated and found to be statistically significant. Habituation of skin conductance through the course of the protocols (comparing the first auditory stimulus to the last shock stimulus) was demonstrated and found to be statistically significant. Habituation of SBF was not evident in ter...

Measurement of cutaneous vasomotor responses by laser Doppler flowmetry

Background: The cutaneous vasomotor response may be a biological marker of anxiety. Vasoconstriction of skin blood vessels in anxious subjects has been previously demonstrated by plethysmography. Building on recent studies which have used laser Doppler flowmetry to measure changes in skin and regional blood flow in animals, this study investigates laser Doppler flowmetry measures of skin blood flow in response to a series of alerting stimuli presented to normal human subjects.Method: Cutaneous vasomotor responses to both auditory stimuli and a series of cold tests were measured by laser Doppler flowmetry in ten healthy subjects. Latency and magnitude of responses were measured and compared to pulse rate changes. Trough latencies as well as recovery times were also measured. Evidence of habituation or sensitisation of responses to stimuli was investigated.Results: A reduction in skin blood flow followed each stimulus. The skin blood flow response to stimuli was clearly discernible from background activity....

Impaired skin vasomotor reflexes in patients with erythromelalgia

Erythromelalgia (EM) is a chronic disorder characterized by intermittent burning pain, warmth and erythema of the extremities. Increasing the local temperature and dependency of the affected limb(s) precipitates the symptoms, whereas direct cooling and elevation of the limb(s) can provide partial relief. Our previous findings showed that patients with EM have enhanced cutaneous vascular tone at rest and during stimulation, which may be due to an increase in sympathetic neural activity. To test this, we measured skin vasoconstrictor responses to contralateral arm cold challenge (CC) and inspiratory gasp (IG) using laser Doppler flowmetry at the toe pulp and fingertip. These areas were chosen because of their dense sympathetic innervation. An index of the vasoconstrictor response (between 0 and 1) was calculated from the change in skin perfusion from baseline following CC and IG. In control subjects, vasoconstrictor responses to CC at the toe and fingertip were both 0. 70+/-0.02 (mean+/-S.E.M.), which were significantly greater (P<0. 001) than corresponding values in patients with EM (0.37+/-0.04 and 0.45+/-0.04 respectively). Similarly, vasoconstrictor responses to IG were significantly greater (P<0.001) at the toe and fingertip in control subjects (0.70+/-0.03 and 0.70+/-0.02 respectively) compared with values in EM patients (0.27+/-0.03 and 0.45+/-0.15 respectively). These data show that, in contrast with control subjects, patients with EM have diminished sympathetic vasoconstrictor responses to both CC and IG. Denervation supersensitivity may play a part by increasing vasoconstrictor responses to circulating catecholamines, leading to a reduction in skin blood flow. Therefore an interplay between neural and vasoactive agents may be involved in the pathophysiology of EM.

Impaired skin vasomotor reflexes in patients with erythromelalgia

Erythromelalgia (EM) is a chronic disorder characterized by intermittent burning pain, warmth and erythema of the extremities. Increasing the local temperature and dependency of the affected limb(s) precipitates the symptoms, whereas direct cooling and elevation of the limb(s) can provide partial relief. Our previous findings showed that patients with EM have enhanced cutaneous vascular tone at rest and during stimulation, which may be due to an increase in sympathetic neural activity. To test this, we measured skin vasoconstrictor responses to contralateral arm cold challenge (CC) and inspiratory gasp (IG) using laser Doppler flowmetry at the toe pulp and fingertip. These areas were chosen because of their dense sympathetic innervation. An index of the vasoconstrictor response (between 0 and 1) was calculated from the change in skin perfusion from baseline following CC and IG. In control subjects, vasoconstrictor responses to CC at the toe and fingertip were both 0.70±0.02 (mean±S.E.M.), which were significantly greater (P &lt; 0.001) than corresponding values in patients with EM (0.37±0.04 and 0.45±0.04 respectively). Similarly, vasoconstrictor responses to IG were significantly greater (P &lt; 0.001) at the toe and fingertip in control subjects (0.70±0.03 and 0.70±0.02 respectively) compared with values in EM patients (0.27±0.03 and 0.45±0.15 respectively). These data show that, in contrast with control subjects, patients with EM have diminished sympathetic vasoconstrictor responses to both CC and IG. Denervation supersensitivity may play a part by increasing vasoconstrictor responses to circulating catecholamines, leading to a reduction in skin blood flow. Therefore an interplay between neural and vasoactive agents may be involved in the pathophysiology of EM.

Skin blood flow responses during sleep by laser Doppler flowmetry.

Skin surface blood flow at the fingertips was measured in a 21-year-old woman during sleep using laser Doppler flowmetry. Skin blood flow responses (SBFR) are transient reductions in skin blood flow of about 25s in duration. In our subject, SBFR showed a delay time of 8-9s from the onset of skin potential responses (SPR) and appeared more consistently than SPR. The frequency of SBFR decreased during non-rapid eye movement sleep, especially when the sleep stage became deep. These findings indicate the validity of SBFR as a discrete index of autonomic function during sleep.

Hydration effects on temperature regulation.

During exercise in the heat, sweat output often exceeds water intake which results in a body water deficit (hypohydration) and electrolyte losses. Daily water losses can be substantial and persons need to emphasize drinking during exercise as well as at mealtime. Aerobic exercise tasks are likely to be adversely affected by heat stress and hypohydration; and the warmer the climate the greater the potential for performance decrements. Hypohydration increases heat storage and reduces one's ability to tolerate heat strain. The increased heat storage is mediated by reduced sweating rate (evaporative heat loss) and reduced skin blood flow (dry heat loss) for a given core temperature. Hyperhydration (increased total body water) has been suggested to reduce physiologic strain during exercise heat stress, however, data supporting that notion are not robust.

Skin vasomotor reflex induced by laryngoscopy: comparison of the McCoy and Macintosh blades

We studied 22 female patients (ASA I or II) to investigate if laryngoscopy and intubation induced the skin vasomotor reflex (SVmR), and to compare the effects of the McCoy and Macintosh blades on the SVmR. Anaesthesia was induced with fentanyl, midazolam, vecuronium and nitrous oxide. In 11 patients, the vocal cords were seen for 3 s with the McCoy blade. Two minutes later, laryngoscopy was performed with the Macintosh blade and the trachea was intubated. In the other 11 patients, the first and second laryngoscopies, respectively, were performed with the Macintosh and McCoy blades. Laryngoscopy alone and intubation with laryngoscopy significantly reduced skin blood flow in the ring finger of all patients (P < 0.01), indicating that both procedures provoked the SVmR. The magnitude of the SVmR and haemodynamic changes did not differ significantly between the two groups.

Does change in skin perfusion provide a good index to monitor the sympathetic response to a noxious stimulus in preterm newborns?

Skin perfusion was measured using laser Doppler fluximetry (LDF) in 16 preterm babies undergoing a standardised heel prick procedure. Although there was a significant reduction in skin blood flow following the heel prick, this was variable and dependent on basal skin blood flow. This, together with loss of data due to movement artefact, makes this technique unreliable in quantifying the sympathetic response to a noxious stimulus in preterm infants.

Persistence of effects of nitric oxide synthase inhibitors: Comparisons on blood flow and plasma exudation in guinea pig skin

Plasma protein extravasation has been measured in guinea pig skin using 125 I -albumin and blood flow using 133 X enon ( 133 X e) clearance. The nitric oxide (NO) synthase inhibitors N G-nitro- l-arginine methyl ester ( l-NAME), N G-monomethyl- l-arginine (l -NMMA) and N G-nitro- l-arginine ( l-NOArg) and the α-adrenoceptor agonist, phenylephrine, inhibited bradykinin induced plasma protein extravasation when co-injected with the peptide. The inhibitory effects of l-NAME and l-NOArg lasted for up to 8 and 4 h, respectively, whereas phenylephrine and l-NMMA had no persistent inhibitory effects. When co-injected with 133 X e, l-NAME, l-NMMA, l-NOArg and phenylephrine, but not d-NAME, produced significant reductions in skin blood flow. When injected prior to 133 X e, l-NAME and l-NOArg, but not phenylephrine or l-NMMA, significantly reduced flow. The effect of l-NAME on flow was not significant at 8 h. Thus, although the inhibitory effects of the NO synthase inhibitors on mediator induced plasma protein extravasation show correlations with their effects on blood flow, the persistent effect of l-NAME on exudation appears to extend beyond its effect on flow.

Cutaneous norepinephrine application in complex regional pain syndrome

Patients with complex regional pain syndrome (CRPS) ( n=20) were examined in order to evaluate cutaneous reactions to norepinephrine (NE) on both the affected and the unaffected limb in comparison to healthy controls. Sixteen female and four male patients suffering from very acute and therefore untreated CRPS with a mean duration of 5.5 weeks were included in this study. Two groups of healthy volunteers served as control groups: the first group ( n =18) according to the same study protocol as CRPS patients, and the second group ( n =10) after warming up one limb. Norepinephrine was iontophoresized (0.2 mA, 120 s) and vasoconstriction was recorded by laser-doppler flowmetry. Pain sensations were simultaneously rated on a visual analogue scale (VAS). Five patients underwent a second trial with higher intracutaneous NE concentrations in order to study possible dose-dependent effects of NE on pain sensation. After acclimatization, skin temperature was recorded by infra-red thermography. The NE-induced reduction of skin blood flow was significantly higher in the affected limb in the patient group (33.0 vs 11.2%, p<0.005). None of the patients reported pain or hyperalgesia. The skin temperature of CRPS patients was significantly higher in the affected limb (34.7 vs 32.5°C, p<0.001). The first control group did not show any difference between left and right sides concerning NE-induced vasoconstriction or skin temperature. The second control group had an increased unilateral skin temperature after warming up (35.0 vs 34.3°C, p<0.006) and demonstrated a significantly increased vasoconstriction on the warmer side (52.0 vs 20.2%, p<0.03) corresponding to findings in patients with acute CRPS. The present study proves that there are signs of decreased sympathetic activity in the affected limb in very acute CRPS. However, no indication was found for increased sensitivity of vascular α-receptors in the very acute stages of CRPS, and there was also no indication for a significant direct contribution of the sympathetic nervous system to pain in very acute CRPS.