Reduced Skin Blood Flow Research Articles

Abstract 11874: Sympathetic Control of Reflex Cutaneous Vasoconstriction in Human Hypertension

Introduction: Cardiovascular-related morbidity and mortality during environmental cold exposures increase disproportionally in hypertensive (HTN) adults. Although alterations in central control of sympathetic outflow and peripheral regulation of vascular function are evident in hypertension and contribute to increased cardiovascular risk, no studies have examined sympathetic control of reflex cutaneous vasoconstriction during cold stress in humans with hypertension. We hypothesized that 1) whole-body cold stress would elicit exaggerated increases in skin sympathetic nervous system activity (SSNA) and greater reductions in skin blood flow in HTN [n=10; 56±3 yrs; resting blood pressure (BP) 145±7/84±3 mmHg] compared to normotensive adults (NTN; n=12, 55±3 yrs; resting BP 126±4/79±3 mmHg) and 2) cutaneous adrenergic sensitivity would be increased in HTN adults. Methods: In Protocol 1, reflex vasoconstriction was induced by gradual whole-body cooling (to a mean skin temperature of 30.5°C) using a water-perfused suit. SSNA (peroneal microneurography) and red cell flux (laser Doppler flowmetry; dorsum of foot) were measured continuously. SSNA was expressed as a percent change from baseline. In Protocol 2, an intradermal microdialysis fiber was placed in the skin of the lateral calf to measure red cell flux in response to graded intradermal infusions of norepinephrine (NE; 10 -12 to 10 -2 M). In each study, cutaneous vascular conductance (CVC=flux/mean arterial pressure) was expressed as a change from baseline. Results: During cooling, HTN exhibited greater increases in SSNA compared to NTN adults (Δ = 194±26% HTN vs. 51±12% NTN; P<0.01) but cutaneous vasoconstriction was not different between groups (ΔCVC base = -0.03±0.003 ητν vs. -0.02±0.01 flux units mmHg -1 NTN; P=0.97). The slope of the relation between ΔSSNA and ΔCVC base during cold stress was blunted in HTN adults (P<0.01). There was no group difference in cutaneous adrenergic responsiveness to exogenous NE (dose-response logEC 50 ; -7.2±0.2 HTN vs. -7.5±0.4 NTN; P=0.75). Conclusion: Although cutaneous microvascular adrenergic responsiveness to NE is preserved, the sensitivity of the sympathetic reflex response to whole-body cold stress is diminished in human hypertension.

Diabetes and temperature

Diabetes and temperature

Effect of Physiological Changes in the Skin on Systemic Absorption of Tacrolimus Following Topical Application in Rats.

Tacrolimus (TL) ointment is a topical treatment for atopic dermatitis, a disease that exhibits various skin conditions. The effect of skin pathologies on the systemic absorption of TL and related side effects remains unknown. This study aimed to investigate factors affecting the cutaneous absorption of TL. We prepared various skin models in hairless rats by tape stripping, injection of prophlogistic material solution (PMS), and continuous subcutaneous adrenaline (Adr) infusion. In vivo absorption studies were conducted, with measurements of transepidermal water loss (TEWL) and skin blood flow as physiological parameters. Very little TL absorption was observed through intact skin. Greater TL absorption was noted in skins with high TEWL values and fully stripped skin with PMS injections. In contrast, Adr infusion, which reduced skin blood flow, resulted in decreased TL absorption through fully stripped skin. Combined use of TL and Adr on skin with PMS injections resulted in suppression of TL absorption. Our results revealed that TL absorption following topical application is affected by alterations in the skin barrier, blood flow, and vascular permeability. We propose an administration plan for TL in a flowchart as a means of preventing systemic side effects.

The effects of ice vest pre-cooling on skin blood flow at rest and during exercise in the heat

Ice vest pre-cooling has been show to lower rectal tem- perature during intermittent exercise in hot conditions but only after 40 min of exercise [1]. The authors sug- gested that the ice vest may have initiated a strong local cutaneous vasoconstrictor response reducing skin blood flow [2] and thus the cooling potential, until increases in body temperature and skin blood flow occurred later in exercise. Therefore, the purpose of this study was to determine whether ice vest pre-cooling reduces skin blood flow during intermittent exercise in the heat com- pared to a no cooling control.

Sympathetic control of reflex cutaneous vasoconstriction in human aging.

This Synthesis highlights a series of recent studies that has systematically interrogated age-related deficits in cold-induced skin vasoconstriction. In response to cold stress, a reflex increase in sympathetic nervous system activity mediates reductions in skin blood flow. Reflex vasoconstriction during cold exposure is markedly impaired in aged skin, contributing to the relative inability of healthy older adults to maintain core temperature during mild cold stress in the absence of appropriate behavioral thermoregulation. This compromised reflex cutaneous vasoconstriction in healthy aging can occur as a result of functional deficits at multiple points along the efferent sympathetic reflex axis, including blunted sympathetic outflow directed to the skin vasculature, reduced presynaptic neurotransmitter synthesis and/or release, and altered end-organ responsiveness at several loci, in addition to potential alterations in afferent thermoreceptor function. Arguments have been made that the relative inability of aged skin to appropriately constrict is due to the aging cutaneous arterioles themselves, whereas other data point to the neural circuitry controlling those vessels. The argument presented herein provides strong evidence for impaired efferent sympathetic control of the peripheral cutaneous vasculature during whole body cold exposure as the primary mechanism responsible for attenuated vasoconstriction.

Effects of Topical Menthol on Skin Blood Flow and Active Sweat Gland Density during Hyperthermia

Topical application of menthol evokes cold sensation and cutaneous vasoconstriction without actual reduction in tissue temperature via the stimulation of a specific cold receptor family known as TRPM8. While being widely used to reduce joint pain, muscle inflammation, and soft tissue injuries in athletes and individuals with musculoskeletal disease, topical menthol may adversely affect body’s heat loss mechanisms. PURPOSE: To investigate if topical application of menthol reduces skin blood flow (SkBF) and active sweat gland density (ASGD) to the extent to which body heat loss is significantly reduced during recovery from exercise-induced hyperthermia. METHODS: Ten healthy male subjects (22±1 yrs) underwent two trials of cycle exercise at 50% VO2max in the heat (45°C, 50%) until their rectal temperatures (Tre) elevate 1.5°C above the baseline. Following the cessation of exercise, either 10g of 3.1% menthol gel (MEN) or placebo Lanolin cream (PBO) was applied on the limbs except hands and feet after which subjects recovered on a chair for 30min in thermoneutral condition (23°C, 50%). SkBF and ASGD were measured using a laser Doppler flowmetery and an iodine-impregnated cotton paper on ventral forearm and anterior thigh. Thermal measurements included Tre, 4-sites mean skin temperature (Tsk), and thermal sensation (TS: −4 very cold ~ 4 very hot). RESULTS: Cold TS in MEN was significantly greater than in PBO (F=29.22, P<.01) while reduction in SkBF and ASGD in MEN did not show significant difference compared to PBO. These slight alterations in vasomotor/sudomotor responses to topical menthol did not significantly impair Tre or Tsk recovery from hyperthermia.Table: No title available.CONCLUSION: Topical application of menthol does not adversely affect body heat loss during recovery from exercise-induced hyperthermia while significantly inducing cold TS.

Impaired increases in skin sympathetic nerve activity contribute to age-related decrements in reflex cutaneous vasoconstriction.

The reduction in skin blood flow during whole-body cooling is impaired in healthy older adults. However, the relative contributions of altered skin sympathetic nerve activity (SSNA), transduction of this efferent neural outflow to the cutaneous vasculature, and peripheral vascular responsiveness to adrenergic stimuli to the impaired reflex vasoconstrictor response to whole-body cooling in human ageing remain unclear. We report that the SSNA response to whole-body cooling is blunted in healthy older adults, and this attenuated sympathetic response is related to a marked impairment in reflex cutaneous vasoconstriction. Further, the reflex SSNA response to a non-thermoregulatory stimulus was preserved in older adults during cooling. We additionally show that cutaneous vascular responsiveness to adrenergic stimuli is not reduced in older adults. These results further our understanding of the physiological mechanisms underlying impaired thermal-cardiovascular integration in healthy ageing. Reflex cutaneous vasoconstriction is impaired in older adults; however, the relative roles of altered skin sympathetic nerve activity (SSNA) and end-organ peripheral vascular responsiveness are unclear. We hypothesized that in older adults whole-body cooling would elicit a blunted SSNA response and cutaneous adrenergic responsiveness would be reduced. Twelve young adults (Y; 24±1years) and 12 older adults (O; 57±2 years) participated in two protocols. In Protocol1, SSNA (peroneal microneurography) and red cell flux in the affected dermatome (laser Doppler flowmetry; dorsum of foot) were measured during whole-body cooling (mean skin temperature (Tsk ) 30.5°C; water-perfused suit). Mental stress was performed at mean Tsk 34.0°C (thermoneutral) and at 30.5°C. In Protocol2, an intradermal microdialysis fibre was placed in the skin of the lateral calf for graded infusions of noradrenaline (norepinephrine) (NA; 10(-12) to 10(-2) m). Cutaneous vascular conductance (CVC=flux/mean arterial pressure) was expressed as a change from baseline (ΔCVCbase ). Vasoconstriction was attenuated in O. SSNA increased significantly during cooling in Y (+184±37%; P<0.05) but not O (+51±12%; P>0.05). Mental stress at Tsk 30.5°C further increased SSNA in both groups. There was no age-related difference in adrenergic responsiveness to exogenous NA (logEC50 :-6.41±0.24 inY, -6.37±0.25in O; P>0.05). While the SSNA response to whole-body cooling is impaired with ageing, SSNA can be further increased by a non-thermoregulatory stimulus. Cutaneous adrenergic sensitivity is not reduced in O. These findings suggest that alterations in afferent signalling or central processing likely contribute to blunted SSNA responses to cooling and subsequent impairments in reflex cutaneous vasoconstriction in ageing.

The effect of exercise training on skin blood flow: a systematic review and meta‐analysis

Background Microvascular disease results in reduced skin blood flow (SkBF) and an increased risk of poor healing, ulceration and amputation, particularly in the lower extremity. Regular exercise is known to produce significant cardiovascular benefits and improved functional outcomes in people with chronic disease. However, it is unknown if these benefits also translate into improvements in SkBF. The purpose of this study was to evaluate the efficacy of exercise training on altering SkBF in adults by systematic review and meta-analysis.

PO-0342 Can Photoplethysmography Be Used To Automate Capillary Refill Time? Preliminary Results From Healthy Children

Background Capillary refill time (CRT) is widely used in paediatrics to assess cardiovascular status, especially during the early phase of shock when skin perfusion is reduced, but is prone to marked variability (Pickard 2011). CRT is used in early warning scores aimed at identifying and quantifying severity of illness and effectiveness of resuscitation efforts (APLS 2011). CRT is one of the most sensitive predictors of dehydration and bacterial infection in children, and it correlates with markers of end organ perfusion (Tibby 1999, Craig 2010). Automating CRT using photoplethysmography (PPG) with a pressure application system may improve its accuracy and reliability. Aim Establish if a green light PPG and a pressure application system could detect an increase in CRT after skin cooling. Methods Healthy children (aged 5–18 years) underwent selective arm cooling as a model of reduced skin blood flow through the microcirculation (Roustit and Cracowski 2013). An automated green light PPG CRT device was attached to their forearm and their arm was then placed into a refrigeration device at 4°C for 20 min. Using 7 min rolling averages, the trough (early phase) and peak (late phase) CRT values were compared. Ethical approval was given. Results Participants (n = 16) demonstrated a significant increase in CRT (as assessed by green PPG) in 15 of the 16 cases (P Conclusions It is feasible to measure changes in the microcirculation of children using an automated device that mimics CRT testing. Further work in clinical settings is needed to establish if this has clinical utility.

Differences in conductive foot cooling: a comparison between males and females.

This study investigated possible sex-related and intra-menstrual differences in local vascular and skin temperature responses when conductive cooling was applied to the soles of the feet. Twelve females and twelve males exposed the soles of their feet to a cooling plate (which cooled from 35 to 15 °C) on two occasions 12-15 days apart. For females, sessions took place during their inactive and active contraceptive pill phases. Tip of Great toe temperature and Great toe skin blood flow were recorded throughout. Females' feet cooled to a greater extent than males' (P = 0.001). Sensitivity of toe skin blood flow to changes in skin temperature (1 or 2 °C) was not different between males and females. Dimensions of males' feet were larger than females' (P < 0.05) and correlations between foot dimensions and toe skin cooling were found (r = 0.728, P < 0.001). Analysis of the residual variance showed that foot volume, contact area and skin blood flow correlated with the rate of toe skin cooling (r = 0.812, r (2) = 0.659, P < 0.001). No intra-menstrual differences were found. The feet of females cooled at a faster rate than those of males in response to the same conductive cooling stimulus to the soles of the feet. However, similar reductions in skin blood flow were found for the same change in toe skin temperature. Therefore, sex related differences may be due to the differing dimensions of the feet, but further research including males and females matched for foot dimensions are required to confirm this mechanism.

Forehead versus forearm skin vascular responses at presyncope in humans.

Facial pallor is commonly observed at presyncope in humans, suggestive of reductions in facial skin blood flow (SkBF). Yet, cutaneous vasoconstriction is usually minimal at presyncope when measured at the forearm. We tested the hypothesis that reductions in forehead SkBF at presyncope are greater than in the forearm. Forehead and forearm SkBF (laser-Doppler) and blood pressure (Finometer or radial artery catheterization) were measured during lower body negative pressure (LBNP) to presyncope in 11 normothermic and 13 heat-stressed subjects (intestinal temperature increased ∼1.4°C). LBNP reduced mean arterial pressure from 91 ± 5 to 57 ± 7 mmHg during normothermia (P ≤ 0.001) and from 82 ± 5 to 57 ± 7 mmHg during heat stress (P ≤ 0.001). During normothermia, LBNP decreased forehead SkBF 55 ± 14% compared with 24 ± 11% at the forearm (P = 0.002), while during heat stress LBNP decreased forehead SkBF 39 ± 11% compared with 28 ± 8% in the forearm (P = 0.007). In both conditions, most (≥68%) of the decreases in SkBF were due to decreases in blood pressure. However, a greater contribution of actively mediated reductions in SkBF was observed at the forehead, relative to the forearm during normothermia (32 ± 13% vs. 11 ± 11%, P = 0.031) and heat stress (30 ± 13% vs. 10 ± 13%, P = 0.004). These data suggest that facial pallor at presyncope is due to a combination of passive decreases in forehead SkBF secondary to reductions in blood pressure and to active decreases in SkBF, the latter of which are relatively greater than in the forearm.

Adenosine receptor inhibition attenuates the suppression of postexercise cutaneous blood flow

The time-dependent contributions of active vasodilation (e.g. nitric oxide) and noradrenergic vasoconstriction to the postexercise suppression of cutaneous perfusion despite persistent hyperthermia remain unknown. Moreover, adenosine receptors have been shown to mediate the decrease in cutaneous perfusion following passive heating. We examined the time-dependent modulation of nitric oxide synthase, noradrenergic vasoconstriction and adenosine receptors on postexercise cutaneous perfusion. Eight males performed 15 min of high-intensity (85% VO2 max) cycling followed by 60 min of recovery in temperate ambient conditions (25°C). Four microdialysis probes were inserted into the forearm skin and continuously infused with: (1) lactated Ringer solution (Control); (2) 10 mm N(G)-nitro-l-arginine methyl ester (l-NAME; nitric oxide synthase inhibitor); (3) 10 mm bretylium tosylate (BT; inhibitor of noradrenergic vasoconstriction); or (4) 4 mm theophylline (THEO; adenosine receptor inhibitor). Cutaneous vascular conductance (CVC) was expressed as a percentage of maximum and was calculated as perfusion units (laser Doppler) divided by mean arterial pressure. End-exercise CVC was similar in Control, THEO and BT (P > 0.1), but CVC with l-NAME (39 ± 4%) was lower than Control (59 ± 4%, P < 0.01). At 20 min of recovery, Control CVC (22 ± 3%) returned to baseline levels (19 ± 2%, P = 0.11). Relative to Control, CVC was reduced by l-NAME for the first 10 min of recovery whereas CVC was increased with BT for the first 30 min of recovery (P < 0.03). In contrast, CVC with THEO was elevated throughout the 60 min recovery period (P ≤ 0.01) compared to Control. We show that adenosine receptors appear to have a major role in postexercise cutaneous perfusion whereas nitric oxide synthase and noradrenergic vasoconstriction are involved only earlier during recovery.

A Decrease in Spatially Resolved Near-Infrared Spectroscopy-Determined Frontal Lobe Tissue Oxygenation by Phenylephrine Reflects Reduced Skin Blood Flow

Spatially resolved near-infrared spectroscopy-determined frontal lobe tissue oxygenation (ScO2) is reduced with administration of phenylephrine, while cerebral blood flow may remain unaffected. We hypothesized that extracranial vasoconstriction explains the effect of phenylephrine on ScO2. We measured ScO2 and internal and external carotid as well as vertebral artery blood flow in 7 volunteers (25 [SD 4] years) by duplex ultrasonography during IV infusion of phenylephrine, together with middle cerebral artery mean blood velocity, forehead skin blood flow, and mean arterial blood pressure. During phenylephrine infusion, mean arterial blood pressure increased, while ScO2 decreased by -19% ± 3% (mean ± SE; P = 0.0005). External carotid artery (-27.5% ± 3.0%) and skin blood flow (-25.4% ± 7.8%) decreased in response to phenylephrine administration, and there was a relationship between ScO2 and forehead skin blood flow (Pearson r = 0.55, P = 0.042, 95% confidence interval [CI], = 0.025-0.84; Spearman r = 0.81, P < 0.001, 95% CI, 0.49-0.94) and external carotid artery conductance (Pearson r = 0.62, P = 0.019, 95% CI, 0.13 to 0.86; Spearman r = 0.64, P = 0.012, 95% CI, 0.17-0.88). These findings suggest that a phenylephrine-induced decrease in ScO2, as determined by INVOS-4100 near-infrared spectroscopy, reflects vasoconstriction in the extracranial vasculature rather than a decrease in cerebral oxygenation.

Short-term sensory and cutaneous vascular responses to therapeutic ultrasound in the forearms of healthy volunteers.

BackgroundTherapeutic ultrasound (US) is used for a variety of clinical pathologies and is thought to accelerate tissue repair and help with pain reduction via its thermal and nonthermal effects. The evidence on physiological effects of US on both sensory and vascular functions in humans is incomplete. Hence, the purpose of this study was to determine the short-term impact of two doses of US (3 MHz, 1:4, 0.25 W/cm2, 5 min; 1 MHz, continuous, 0.8 W/cm2, 3 min), on sensory and vascular responses in the healthy forearms.MethodsTwenty healthy subjects were recruited (mean age, 29.6 ± 8.8 years) for the study. Superficial blood flow (SBF) in the distal forearms was determined using the tissue viability imaging system. Sensory perception thresholds (SPT) were determined from ring finger (C7, C8) to assess A-beta (at 2,000 Hz) and C fiber function (at 5 Hz), using a Neurometer CPT/C device. Subject’s two hands were randomly allocated to group order (AB/BA). Scores were obtained before and immediately after the application of US and control. Differences in these were analyzed using repeated measures.ResultsBoth 3 MHz pulsed US and 1 MHz continuous US showed small to moderate (effect size = 0.12 to 0.68), statistically significant reductions in SBF (3 MHz, mean change = 2.8 AU and 1 MHz, mean change = 3.9 AU, p < 0.05 respectively), skin temperature (2.5°C and 1.1°C, p < 0.05), and SPT at 5 Hz (1.3 and 1 mA, p < 0.05) across time. SPT at 2,000 Hz remained unaltered by all three conditions (p > 0.05). Age and gender also had no effect on all outcome measures (p > 0.05).ConclusionThis study demonstrated minor reductions in skin blood flow, skin temperatures, and C fiber perception thresholds immediately after 3 MHz, and 1 MHz US. The responses observed may have been due to a thermo-cooling effect of the gel or due to the direct effect of US on C fibers of median and ulnar nerves. US had a negligible effect on A-beta fibres. This would suggest that future studies looking at physiological effects of US should move towards investigating larger dosages and study the effects in patient populations.

Involvement of nitric oxide production in the impairment of skin blood flow response to local cooling in diabetic db/db mice

An enhanced vasoconstrictor activity of cutaneous vessels participates in the reduction of skin blood flow induced by cooling. The present study investigated changes in the local response to cooling in hyperglycemic conditions. Male diabetic db/db and control C57BL/6J mice, anaesthetized with pentobarbitone, were treated with tetrodotoxin for eliminating the sympathetic nerve tone and artificially ventilated. The plantar skin blood flow (PSBF) was measured by laser Doppler flowmetry. Cooling the air temperature around the foot reduced PSBF in a temperature-dependent manner in control and db/db mice. The PSBF reduction was significantly smaller in db/db mice than in control mice. Phentolamine, a non-selective α-antagonist, bunazosin, a selective α1-antagonist, MK-912, a selective α2C-antagonist, and Y-27632, a Rho-kinase inhibitor, significantly inhibited the PSBF reduction induced by cooling to 15°C in both mice and the inhibitory effects were comparable between these mice. The cooling-induced PSBF reduction was also significantly inhibited by Nω-nitro-l-arginine, an inhibitor of nitric oxide synthase, in control mice; however, the inhibitory effect of Nω-nitro-l-arginine was not observed in db/db mice. The reduction of PSBF induced by the intraarterial administration of adrenaline was comparable between control and db/db mice both before and after the treatment with Nω-nitro-l-arginine. It is thus likely that the reduction of skin blood flow induced by local cooling might be partly mediated by a decrease in endothelium-derived nitric oxide production, and that an impairment of the nitric oxide production might be related to reduced vasoconstrictor response to cooling in db/db mice.

Evidence that chronic inhibition of the mammalian Target of Rapamycin (mTOR) reduces skin blood flow in humans

Chronic mTOR inhibition causes vascular dysfunction in rodents. We hypothesized that a similar effect would be observed in humans. 6 middle‐aged persons participated. mTOR was antagonized by topical application of 8% rapamycin (RAPA) ointment to skin. RAPA was applied twice daily for 7 days to an 8×8 cm area of skin on the abdomen while a second site was similarly treated with ointment vehicle only. We examined the effect of these treatments on skin blood flow (SkBF) as monitored by laser‐Doppler flowmetry (LDF). Local skin temperature (Tloc) was controlled with combined LDF/local heating probe holders. Tloc was maintained initially at 34°C and then was raised to 43°C to cause maximal local vasodilation (maxLDF).ResultsAt Tloc=34°C, SkBF was 72±4.3% maxLDF at RAPA treated sites and was 80±4.9% maxLDF at sites that received vehicle only (p&lt;0.03 between sites). maxLDF (in mV) when Tloc was 43°C did not differ between RAPA and vehicle treated sites (p&gt;;0.05). We conclude that chronic RAPA treatment reduces SkBF levels at normothermic skin temperatures in middle‐aged persons without an effect on maximal vasodilation. (supported by NIH Grant AG041365)

1131 Cardiovascular and Hormonal Responses to Hypoxic Stress in the Preterm Piglet

Background and AimsImmature control of the cardiovascular system may be a contributing factor to poor cardiovascular function and associated increases in mortality and morbidity in preterm infants. This study aimed...

The involvement of nitric oxide synthase in the die‐away phenomenon during prolonged local skin heating

Previous studies have described the die‐away phenomenon as a gradual, albeit progressive, reduction in skin blood flow following &gt;60 min of local skin heating. We investigated the involvement of nitric oxide synthase (NOS) in this die‐away phenomenon. Participant forearms were instrumented with microdialysis fibers, local skin heaters, and laser‐Doppler probes. Skin sites were treated with either a saline solution (control) or the NOS inhibitor, Nω‐nitro‐L‐arginine methyl ester hydrochloride (L‐NAME). Skin sites were heated from 33 to 41 °C at a rate of 0.5 °C · 10 s−1and held stable for 90 min. Baseline, initial peak, plateau, and die‐away phases were compared between sites. Both skin sites exhibited the characteristic biphasic response to local heating while also demonstrating a decrease in skin blood flow following an established plateau. L‐NAME treated sites were different across all measures (P&lt;0.05). Importantly, the magnitude of the die‐away was reduced under conditions of L‐NAME treatment compared to control (P&lt;0.05). These data suggest that NOS is involved in the die‐away phenomenon. Supported by The University of Alabama.

Water ingestion reduces skin blood flow through sympathetic vasoconstriction

Water ingestion induces a pressor effect in patients with efferent baroreflex impairment and a mild pressor effect in elderly healthy subjects. However, water raised the total peripheral vascular resistance (TPR) without a prominent change in blood pressure in young healthy subjects. We try to investigate whether water elicits a cardiovascular response via regulating regional skin blood flow (SkBF) in young healthy subjects. In a randomized, controlled, crossover fashion, 15 healthy male subjects (19-27years old) ingested either 500 (water session) or 50ml of water (control). The heart rate, blood pressure, cardiac index, and TPR were measured using a Task Force Monitor. A laser Doppler velocimeter was used to determine the change in the SkBF at the left thenar eminence. Plasma catecholamines and their metabolites were also measured. At 25min after ingestion of 500ml water, the cardiac index and SkBF significantly decreased compared to control. In contrast, the TPR significantly increased after ingestion of 500ml water. Plasma dihydroxyphenylalanine significantly increased at 25min after water. Water ingestion decreases the cardiac index to compensate for the increase in the TPR, leading to no net change in blood pressure in young healthy subjects. This study suggests that water decreases the SkBF, a mechanism that might account partly for the nature of osmopressor response to water in young healthy subjects.

Skin blood flow abnormalities in diabetic dermopathy

Diabetic dermopathy is the most common specific cutaneous finding in diabetes. Using laser Doppler technology, we tested the hypothesis that diabetic dermopathy arises from abnormal local skin blood flow. We measured cutaneous blood flow in patients with type 1 diabetes without dermopathy and compared values with those in a control group of patients with type 1 diabetes without diabetic dermopathy and in a nondiabetic group. We measured at 3 separate sites on the pretibial area on the legs of each participant, at dermopathy lesions, and at a number of standard sites on the upper and lower extremities. We studied 25 patients with diabetes and diabetic dermopathy, average age 51± 2 years, mean duration of diabetes 28± 3 years. In all, 58 patients with type 1 diabetes without diabetic dermopathy served as control patients, average age 41± 2 years, mean duration of diabetes 23± 2 years. There were 67nondiabetic control subjects, average age 47± 3 years. The patients with diabetic dermopathy showed a marked reduction in skin blood flow at 35°C at normal-appearing skin areas on the pretibial surface of the legs (1.1± 0.1 mL/min/100 g) compared with 1.7± 0.1 mL/min/100 g (P= .01) in the type 1 diabetic control group and 2.1± 0.3 mL/min/100 g (P< .01) in the nondiabetic group. The dermopathy lesions themselves showed markedly higher blood flow: 2.5± 0.3 mL/min/100 g. Our diabetic dermopathy patients were somewhat older than the control type 1 diabetes subjects, but were of comparable age to the nondiabetic subjects. These results suggest that patients susceptible to diabetic dermopathy have a functional abnormality in blood flow leading to this scarring process.