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Blood Flow Responses (blood + flow_response)
Kinds of Blood Flow Responses Selected AbstractsDoes aerobic fitness influence microvascular function in healthy adults at risk of developing Type 2 diabetes?DIABETIC MEDICINE, Issue 4 2005A. R. Middlebrooke Abstract Aim To investigate whether aerobic fitness is associated with skin microvascular function in healthy adults with an increased risk of developing Type 2 diabetes. Methods Twenty-seven healthy normal glucose-tolerant humans with either a previous diagnosis of gestational diabetes or having two parents with Type 2 diabetes and 27 healthy adults who had no history of diabetes were recruited. Maximal oxygen uptake was assessed using an incremental exercise test to exhaustion. Skin microvascular function was assessed using laser Doppler techniques as the maximum skin hyperaemic response to a thermal stimulus (maximum hyperaemia) and the forearm skin blood flow response to the iontophoretic application of acetylcholine (ACh) and sodium nitroprusside. Results Maximal oxygen uptake was not significantly different in the ,at-risk' group compared with healthy controls. Maximum hyperaemia was reduced in those ,at risk' (1.29 ± 0.30 vs. 1.46 ± 0.33 V, P = 0.047); however, the peak response to acetylcholine or sodium nitroprusside did not differ in the two groups. A significant positive correlation was demonstrated between maximal oxygen uptake and maximum hyperaemia (r = 0.52, P = 0.006 l/min and r = 0.60, P = 0.001 ml/kg/min) and peak ACh response (r = 0.40, P = 0.04 l/min and r = 0.47, P = 0.013 ml/kg/min) in the ,at-risk' group when expressed in absolute (l/min) or body mass-related (ml/kg/min) terms. No significant correlations were found in the control group. Conclusions In this ,at-risk' group with skin microvascular dysfunction maximal oxygen uptake was not reduced compared with healthy controls. However, in the ,at-risk' group alone, individuals with higher levels of aerobic fitness also had better microvascular and endothelial responsiveness. [source] Cardiac autonomic dysinnervation and myocardial blood flow in long-term Type 1 diabetic patientsDIABETIC MEDICINE, Issue 5 2003N. Hattori Abstract Aims The aim of the study was to assess scintigraphically the relationship between myocardial blood flow response and sympathetic dysinnervation in long-term Type 1 diabetic patients. Effects of the iron chelator deferoxamine on myocardial blood flow were studied and they were investigated according to the presence of cardiac sympathetic dysfunction. Methods Myocardial blood flow (MBF) was assessed with N-13 ammonia positron emission tomography in 13 long-term Type 1 diabetic patients and 13 control subjects at rest and in response to sympathetic stimulation (cold pressor test (CPT)). In diabetic patients, the study was repeated after preinfusion with deferoxamine. Furthermore, 123I metaiodobenzylguanidine (MIBG) scintigraphy was applied to assess regional cardiac sympathetic dysinnervation (uptake score 1 = normal, homogeneous uptake , 6 = no uptake). Results In diabetic patients, MBF increased in response to CPT from 78 ± 18 ml/100 g/min to 84 ± 26 ml/100 g (8%, P < 0.001). Control subjects demonstrated an increase from 63 ± 17 ml/100 g to 84 ± 26 ml/100 g (33%, P < 0.001), respectively. Resting MBF was higher in diabetic patients than in control subjects (P < 0.001). In diabetic patients, increase in MBF in response to CPT was significant in regions with a MIBG uptake score of , 3. Regions with a MIBG uptake score of > 3 did not exhibit a significant increase in MBF in response to CPT. After administration of deferoxamine, the increase in MBF in response to CPT was 23% and the magnitude of increase was related to the MIBG uptake score (r = 0.40, P < 0.0001). Conclusions Myocardial blood flow response to sympathetic stimulation is significantly impaired in long-term Type 1 diabetes. After preinfusion with deferoxamine the impairment is partially reversed and a relationship between myocardial blood flow and the extent of cardiac sympathetic dysfunction is observed. Diabet. Med. 20, 375,381 (2003) [source] Circulation in normal and inflamed dental pulpENDODONTIC TOPICS, Issue 1 2007ELLEN BERGGREEN In the pulp, arteries branch into a capillary network before they leave the pulp as venules through the apical foramina. The tissue has low compliance, as it is enclosed in dentin, and has a relatively high blood flow and blood volume. The interstitial fluid pressure (IFP) and colloid osmotic pressure are relatively high whereas the net driving blood pressure is low. The high pulsatile IFP is probably the major force for propelling lymph in the dental pulp. Vasodilation in neighboring tissue as well as arteriovenous (AV) shunts in the pulp itself can contribute to a fall in total and coronal pulpal blood flow, respectively. The pulp blood flow is under nervous, humoral, and local control. Inflammatory vascular responses, vasodilation, and increased vessel permeability induce an increase in IFP that can be followed by a temporarily impaired blood flow response. Lipopolysaccharides (LPS) from bacteria may cause endothelial activation in the pulp, leading to vasoconstriction and reduced vascular perfusion. Lymphatic vessels are identified with specific lymphatic markers in the pulp but so far, little is known about their function. Because of the special circulatory conditions in the pulp, there are several clinical implications that need to be considered in dental treatment. Received 13 February 2009; accepted 28 August 2009. [source] Monochloramine impairs mucosal blood flow response and healing of gastric lesions in rats: Relation to capsaicin-sensitive sensory neuronsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 3 2001Koji Takeuchi Abstract Aims: We examined the effects of monochloramine (NH2Cl) on the gastric mucosal blood flow (GMBF) response and the healing of ethanol-induced gastric lesions in rats. Methods: Rats fasted for 18 h were given the 99% ethanol p.o. for induction of gastric lesions, and were fed normally from 1 h later onwards. Monochloramine, at non-ulcerogenic doses (5~20 mmol/L), was given p.o. twice daily for 7 days, starting 2 h after ethanol treatment. Results: Gastric lesions caused by ethanol healed almost completely within 7 days with re-epithelialization. The repeated administration of NH2Cl significantly delayed the healing of ethanol-induced gastric lesions in a dose-dependent manner. The damaged mucosa showed a marked rise in H+ permeability, resulting in luminal acid loss, but this process was accompanied by an increase of mucosal blood flow. Monochloramine did not affect the increased mucosal H+ permeability observed in the stomach after damage by ethanol, but significantly inhibited the mucosal hyperemic response associated with luminal acid loss. Prior exposure of the mucosa to NH2Cl (20 mmol/L) did not affect the gastric hyperemic response caused by mucosal application of misoprostol (a prostaglandin E1 derivative) or NOR-3 (a nitric oxide donor), but totally attenuated the increase of GMBF in response to intragastric capsaicin. Impaired healing and GMBF responses were also observed in rats following chemical ablation of capsaicin-sensitive sensory neurons. Conclusions: These results suggest that NH2Cl impaired the healing of acute gastric mucosal lesions at low concentrations, and this action may be attributable, at least partly, to the impairment of gastric hyperemic response caused by the dysfunction of capsaicin-sensitive sensory neurons. [source] Acetylcholine-Induced Vasodilation and Reactive Hyperemia Are Not Affected by Acute Cyclo-Oxygenase Inhibition in Human SkinMICROCIRCULATION, Issue 4 2004Anne Dalle-Ave Objective: To examine whether prostaglandins are involved in endothelium-dependent vasodilatory responses of the skin microcirculation. Methods: Twenty-three young male volunteers were studied on 2 different days 1,3 weeks apart. On each experimental day the forearm skin blood flow response to iontophoretically applied acetylcholine (Ach, an endothelium-dependent vasodilator) was determined with laser Doppler imaging following the intravenous administration of either the cyclo-oxygenase inhibitor lysine acetylsalicylate (L-AS), 900 mg, or the oral intake of indomethacin, 75 mg. Acetylcholine was iontophoresed both in presence and in absence of surface anesthesia. In some subjects, the effects of L-AS on skin reactive hyperemia were also assessed. Results: Acute cyclo-oxygenase inhibition with either drug influenced neither the skin blood flow response to 4 different doses of Ach (0.28, 1.4, 7, and 14 mC/cm2) nor reactive hyperemia. The peak vasodilatory response to Ach was significantly increased by skin anesthesia, regardless of whether the subjects received the cyclo-oxygenase inhibitor or not. For example, the mean response (± SD) to the largest dose of Ach (tested in 6 subjects, expressed in perfusion units) were as follows: in absence of anesthesia: L-AS 339 ± 105, placebo 344 ± 68; with anesthesia: L-AS 453 ± 76, placebo 452 ± 65 (p < .01 for effect of anesthesia). Conclusions: These data give no support for a contribution of prostaglandins to acetylcholine-induced vasodilation or to reactive hyperemia in the skin microcirculation. In this vascular bed, local anesthesia seems to amplify acetylcholine-induced vasodilation via a prostaglandin-independent mechanism. [source] 3251: From elementary concept in animal models to new frontiers in humans: neurovascular coupling in the ocular circulationACTA OPHTHALMOLOGICA, Issue 2010C RIVA Purpose The retina and optic nerve, both optically accessible components of the central nervous system, are ideally suited for the investigation of the intrinsic physiological process by which blood ,ow, metabolism and neural activity are tightly coupled (Roy and Sherrington. 1890). Methods Using various techniques in the cat and human eye, the changes in blood flow in the retina and optic nerve in response to increased neural activity by flicker stimulation have been determined. The effect of varying the stimulus parameters, such as flicker modulation depth, frequency, luminance and red-green color ratio, on the blood flow response was investigated. Putative mediators of the activity-induced flow changes and the relationship between activity, blood flow and metabolic changes were assessed. Results Visual stimulation with flicker increases rapidly and markedly both retinal and optic nerve blood ,ows (functional hyperemia). Moreover, the data reveal unequivocally the presence, under specific conditions of flicker, of a neurovascular/neurometabolic coupling in these tissues, partly mediated by local potassium ions and nitric oxide production. Furthermore, the activity-induced hyperemia is altered during a number of physiological and pharmacological interventions and in some pathologic conditions. Conclusion Flicker stimulation of the retina offers a new and powerful means to modulate blood flow and investigate the neurovascular coupling in the neural eye tissues. Exploration of this activity-induced hyperemia and the mechanism(s) underlying the neurovascular coupling will lead to an increased understanding of the pathophysiology of various ocular diseases. [source] Effect of fat digestion on superior mesenteric artery blood flow in humansCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 1 2007T. Symersky Summary Background and aim:, Intraluminal nutrients stimulate superior mesenteric artery (SMA) blood flow. Of the macronutrients, especially fat affects the magnitude of the SMA blood flow response to a meal. Little is known however on the influence of fat hydrolysis on SMA flow. Methods:, We compared in eight healthy volunteers the SMA flow response (Doppler ultrasonography) to continuous intraduodenal fat perfusion (LCT, 240 kCal h,1) during conditions with normal hydrolysis (placebo, control), increased hydrolysis (pancreatic enzyme supplementation; 50 kU lipase) and impaired hydrolysis (orlistat 240 mg). Results:, Intraduodenal LCT significantly (P<0·01) increased SMA flow in all experiments over basal. The SMA flow response to fat during pancreatic enzyme supplementation (1·49 ± 0·1 l min,1) was significantly (P<0·05) higher compared with placebo (1·11 ± 0·16 l min,1). Lipase inhibition with orlistat did not significantly affect fat stimulated SMA flow compared with placebo: 0·89 ± 0·08 l min,1 versus 1·11 ± 0·16 l min,1. Conclusions:, Administration of pancreatic enzymes significantly increases fat stimulated SMA flow. Fat digest products in the intestinal lumen contribute to the regulation of SMA blood flow. [source] Regional cerebral blood flow responses to hyperventilation during sevoflurane anaesthesia studied with PETACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2010L. SCHLÜNZEN Background: Arterial carbon dioxide tension (PaCO2) is an important factor controlling cerebral blood flow (CBF) in neurosurgical patients. It is still unclear whether the hypocapnia-induced decrease in CBF is a general effect on the brain or rather linked to specific brain regions. We evaluated the effects of hyperventilation on regional cerebral blood flow (rCBF) in healthy volunteers during sevoflurane anaesthesia measured with positron emission tomography (PET). Methods: Eight human volunteers were anaesthetized with sevoflurane 1 MAC, while exposed to hyperventilation. During 1 MAC sevoflurane at normocapnia and 1 MAC sevoflurane at hypocapnia, one H215O scan was performed. Statistical parametric maps and conventional regions of interest analysis were used for estimating rCBF differences. Results: Cardiovascular parameters were maintained constant over time. During hyperventilation, the mean PaCO2 was decreased from 5.5 ± 0.7 to 3.8 ± 0.9 kPa. Total CBF decreased during the hypocapnic state by 44%. PET revealed wide variations in CBF between regions. The greatest values of vascular responses during hypocapnia were observed in the thalamus, medial occipitotemporal gyrus, cerebellum, precuneus, putamen and insula regions. The lowest values were observed in the superior parietal lobe, middle and inferior frontal gyrus, middle and inferior temporal gyrus and precentral gyrus. No increases in rCBF were observed. Conclusions: This study reports highly localized and specific changes in rCBF during hyperventilation in sevoflurane anaesthesia, with the most pronounced decreases in the sub cortical grey matter. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve during hypocapnia. [source] Comparison of gingival blood flow during healing of simplified papilla preservation and modified Widman flap surgery: a clinical trial using laser Doppler flowmetryJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 10 2007M. Retzepi Abstract Aim: This prospective randomized-controlled clinical trial compared the gingival blood flow responses following simplified papilla preservation (test) versus modified Widman flap (control). Materials and Methods: Twenty contra-lateral upper sites with pocket depth 5 mm after initial treatment in 10 chronic periodontitis patients were randomly assigned to either test or control treatment, using a split-mouth design. Laser Doppler flowmetry recordings were performed pre-operatively, following anaesthesia, immediately post-operatively and on days 1, 2, 3, 4, 7, 15, 30 and 60, at nine selected sites per flap. Results: Significant ischaemia was observed at all sites following anaesthesia and immediately post-operatively. At the mucosal flap basis, a peak hyperaemic response was observed on day 1, which tended to resolve by day 4 at the test sites, but persisted until day 7 at the control sites. The buccal and palatal papillae blood perfusion presented the maximum increase on day 7 in both groups and returned to baseline by day 15. Both surgical modalities yielded significant pocket depth reduction, recession increase and clinical attachment gain. Conclusions: Periodontal access flaps represent an ischaemia,reperfusion flap model. The simplified papilla preservation flap may be associated with faster recovery of the gingival blood flow post-operatively compared with the modified Widman flap. [source] The acute effects of smokeless tobacco (snuff) on gingival blood flow in manJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2001Antonios Mavropoulos Snuff-induced blood flow responses in the gingiva were evaluated in 22 healthy casual consumers of tobacco. Laser Doppler flowmetry (LDF) was used to measure blood flow simultaneously and continuously on two gingival sites (buccal aspect of the papillae between the upper lateral incisors and canines). In addition, measurements of skin blood flow in the forehead and palmar side of the left thumb were performed. Arterial blood pressure (BP) and heart rate (HR) were also recorded. Unilateral application of commercial snuff (500 mg, 1%) caused a marked and rapid increase in gingival blood flow (GBF) on the exposed side (p<0.001). Blood flow increased also in the contralateral gingiva and forehead skin (p<0.05). Skin blood flow in the thumb showed an insignificant decrease. BP and HR increased. Vascular conductance increased significantly in the snuff-exposed gingiva but not in the contralateral gingiva or the forehead. Vascular conductance was largely unaffected in the thumb. It is concluded that acute application of snuff, besides giving rise to typical changes in BP and HR, increases GBF in and around the exposed area, probably through activation of sensory nerves and the subsequent release of vasodilatory peptides from their peripheral endings. Blood flow in unexposed gingival and forehead skin may increase probably due to humoral or nervously mediated mechanisms. However, a passive pressure-induced hyperaemia in the unexposed gingiva and forehead skin can not be excluded. [source] Comparison of red and green laser doppler imaging of blood flowLASERS IN SURGERY AND MEDICINE, Issue 3 2004Andrea K. Murray PhD Abstract Background and Objectives Laser Doppler imaging (LDI) of perfusion has been performed with a novel green wavelength (532 nm) for comparison with a HeNe laser (633 nm), the aim being validation of the green laser wavelength as a research tool. Study Design/Materials and Methods The effect of wavelength and power on images was investigated and perfusion response following both finger occlusion and local heating of the dorsum were examined as reproducible stimuli for clinical studies. Results The most striking difference between red and green LDI is the absence of veins on green LDI, which are seen with red LDI. Differences have been quantified using vein LDI profiles. Differences were found between blood flow responses imaged by red and green LDI (3 and 5 mW, respectively) for occlusion and heat stimuli. Results are discussed in the context of light penetration. Conclusions Red and green wavelengths appear to image different components of the microcirculation. Lasers Surg. Med. 35:191,200, 2004. © 2004 Wiley-Liss, Inc. [source] Uterine blood flow responses to ICI 182 780 in ovariectomized oestradiol-17,-treated, intact follicular and pregnant sheepTHE JOURNAL OF PHYSIOLOGY, Issue 1 2005Ronald R. Magness Oestrogen dramatically increases uterine blood flow (UBF) in ovariectomized (Ovx) ewes. Both the follicular phase and pregnancy are normal physiological states with elevated levels of circulating oestrogen. ICI 182 780 is a pure steroidal oestrogen receptor (ER) antagonist that blocks oestrogenic actions in oestrogen-responsive tissue. We hypothesized that an ER-mediated mechanism is responsible for in vivo rises in UBF in physiological states of high oestrogen. The purpose of the study was to examine the effect of an ER antagonist on exogenous and endogenous oestradiol-17, (E2,)-mediated elevations in UBF. Sheep were surgically instrumented with bilateral uterine artery blood flow transducers, and uterine and femoral artery catheters. Ovx animals (n= 8) were infused with vehicle (35% ethanol) or ICI 182 780 (0.1,3.0 ,g min,1) into one uterine artery for 10 min before and 50 min after E2, was given (1 ,g kg,1i.v. bolus) and UBF was recorded for an additional hour. Intact, cycling sheep were synchronized to the follicular phase using progesterone, prostaglandin F2,(PGF2,) and pregnant mare serum gonadotrophin (PMSG). When peri-ovulatory rises in UBF reached near peak levels, ICI 182 780 (1 or 2 ,g (ml uterine blood flow),1) was infused unilaterally (n= 4 sheep). Ewes in the last stages of pregnancy (late pregnant ewes) were also given ICI 182 780 (0.23,2.0 ,g (ml uterine blood flow),1; 60 min infusion) into one uterine artery (n= 8 sheep). In Ovx sheep, local infusion of ICI 182 780 did not alter systemic cardiovascular parameters, such as mean arterial blood pressure or heart rate; however, it maximally decreased ipsilateral, but not contralateral, UBF vasodilatory responses to exogenous E2, by ,55,60% (P < 0.01). In two models of elevated endogenous E2,, local ICI 182 780 infusion inhibited the elevated UBF seen in follicular phase and late pregnant ewes in a time-dependent manner by ,60% and 37%, respectively; ipsilateral , contralateral effects (P < 0.01). In late pregnant sheep ICI 182 780 also mildly and acutely (for 5,30 min) elevated mean arterial pressure and heart rate (P < 0.05). We conclude that exogenous E2,-induced increases in UBF in the Ovx animal and endogenous E2,-mediated elevations of UBF during the follicular phase and late pregnancy are partially mediated by ER-dependent mechanisms. [source] Mechanisms influencing the vasoactive effects of lidocaine in human skin,ANAESTHESIA, Issue 2 2007D. J. Newton Summary The vasodilator properties of lidocaine are believed to be due mainly to the inhibition of action potentials via sodium channel blocking in vasoconstrictor sympathetic nerves. However, mechanisms involving the vascular endothelium may also play a role, and in this study we investigated the potential influences of nitric oxide release, the cyclo-oxygenase pathway and the ,-adrenoceptors of vascular smooth muscle. Laser Doppler imaging was used to measure microvascular blood flow responses to intradermal injection of lidocaine 2%, with or without the addition of preservatives, in eight healthy, male volunteers. Co-injection of the nitric-oxide,synthase inhibitor N,-nitro- l -arginine methyl ester caused a 60% reduction in the response after about 20 min, and this reduction was enhanced with the lidocaine solution containing the preservatives methylhydroxybenzoate and propylhydroxybenzoate. No reduction in response was seen after blocking the cyclo-oxygenase or ,-adrenoceptor pathways. Nitric oxide release contributes to the vasoactivity of lidocaine in human skin. [source] Improved endothelial function after endothelin receptor blockade in patients with systemic sclerosisARTHRITIS & RHEUMATISM, Issue 6 2009Carmine Cardillo Objective Impaired endothelium-dependent vasodilator function may contribute to vascular damage in patients with systemic sclerosis (SSc). This study was undertaken to investigate whether increased activity of the endothelin 1 (ET-1) system plays a role in the occurrence of endothelial dysfunction in patients with SSc. Methods In 12 patients with SSc (6 with diffuse cutaneous SSc [dcSSc] and 6 with limited cutaneous SSc [lcSSc]), forearm blood flow responses to graded doses of acetylcholine (ACh) and sodium nitroprusside (SNP) given intraarterially were assessed by plethysmography, during infusion of saline and following selective blockade of ETA receptors with BQ-123 (10 nmoles/minute). Results During saline infusion, the vasodilator response to ACh was blunted in patients with SSc as compared with that in healthy controls (P < 0.001), whereas the response to SNP was not different between groups (P = 0.27). The vasodilator effect of ETA receptor antagonism was higher in patients than in controls (P < 0.001), indicating enhanced ET-1,mediated vasoconstriction in SSc. In patients, ETA receptor blockade resulted in a potentiation of the vasodilator response to ACh (P < 0.001 versus saline), but did not affect the response to SNP (P = 0.31). Notably, both the vasodilator effect of ETA receptor antagonism and the improvement in the responsiveness to ACh following BQ-123 infusion were higher in patients with dcSSc than in those with lcSSc (P < 0.01). Conclusion ET-1,dependent vasoconstrictor tone is increased predominantly in the subgroup of SSc patients with dcSSc, in whom acute blockade of ETA receptors was able to improve impaired endothelium-dependent vasodilator function. Our results suggest novel vasculoprotective effects of ETA receptor antagonism and support further exploration of strategies that target the ET-1 pathway in SSc. [source] PRETREATMENT WITH INTRAVENOUS ASCORBIC ACID PRESERVES ENDOTHELIAL FUNCTION DURING ACUTE HYPERGLYCAEMIA (R1)CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2005Brian A Mullan SUMMARY 1.,Acute hyperglycaemia may impair endothelial function. Ascorbic acid (AA), administered intra-arterially, has been reported to improve endothelium-dependent vasodilatation during a forearm hyperglycaemic clamp. Using a randomized, double-blind, placebo-controlled, cross-over study, we investigated the potential for intravenous ascorbic acid to modify the endothelial response to acute systemic hyperglycaemia in humans. 2.,Nine healthy male volunteers were recruited from the hospital staff. Endothelial function was determined by measuring the forearm blood flow responses to intrabrachial infusions of endothelium-dependent (ED) and endothelium-independent (EID) vasodilators. The endothelial function index (EFI) was derived from the ratio of ED and EID vasodilatation. Haemodynamic and endothelial function measurements were performed at baseline and then repeated 2 h after a systemic hyperglycaemic clamp (14 mmol/L). The subjects, studied on two separate occasions, were randomized to placebo or 2 g intravenous ascorbic acid prior to the initiation of hyperglycaemia. 3.,After systemic hyperglycaemia with placebo pretreatment, the EFI fell from 1.08 ± 0.21 to 0.74 ± 0.13 (difference (95% confidence interval): 0.34 (0.20, 0.47); P < 0.001). When subjects were pretreated with ascorbic acid, the EFI was not affected by hyperglycaemia (1.11 ± 0.21 to 1.12 ± 0.17; P = 0.938). This difference between placebo and ascorbic acid was significant (P < 0.001). Plasma ascorbate concentrations decreased during hyperglycaemia and correlated directly with the reduction in the EFI (r = 0.798; P < 0.001). 4.,Pretreatment with an intravenous bolus of ascorbic acid can prevent endothelial dysfunction during acute systemic hyperglycaemia. Therefore, ascorbic acid may have potential therapeutic use in clinical situations where acute hyperglycaemia may be a complication. [source] Heel skin hyperaemia: direct compression versus vascular occlusionCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2003Harvey N. Mayrovitz Summary Vulnerability of the heel to ulceration in bed-bound persons is related to direct pressure-induced blood flow decreases. Periodic pressure reduction is a clinical strategy to help prevent ulcers by allowing flow-repayment hyperaemia that has a magnitude and duration thought to be related to the duration of the prior interval of ischaemia. However, there are reasons to question whether effects of flow stoppages caused by direct tissue loading are similar to those because of ischaemia without superimposed direct pressure. This question was investigated by comparing posterior heel skin blood flow responses via laser-Doppler perfusion monitoring of 27 supine-lying subjects in whom blood flow was reduced by 5-min of direct heel loading on a support surface and by 5-min of ankle-cuff compression. Results showed that blood flow reductions were the same for both methods but the hyperaemia was significantly greater when flow reduction was produced by direct heel loading. This was true for ratio of peak hyperaemic flow to baseline (8·20 ± 1·32 s versus 4·68 ± 0·80 s, P,0·001), hyperaemic to baseline 3-min flow-time area ratios (4·70 ± 0·65 s versus 1·95 ± 0·29 s, P,0·001) and for total hyperaemia durations (352 ± 39 s versus 181 ± 14 s, P<0·001). These findings raise new questions regarding the precise physiological effects of heel and tissue loading in general, the factors that contribute to the hyperaemic response and their clinical impact and interpretation. Possible sources of the observed greater post-loading hyperaemia responses are discussed. [source] | |||||||||||||||||||