SEARCH · PubMed Health

Results for “Microcirculation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources

PubMed1994

Noncontact, two-dimensional measurement of retinal microcirculation using laser speckle phenomenon.

PURPOSE: To report a new apparatus for noncontact, two-dimensional measurement of retinal microcirculation using the laser speckle phenomenon and to demonstrate that this apparatus can document known or expected changes in retinal blood flow. METHODS: The rabbit fundus was illuminated by an argon (blue) laser spot (0.62 x 0.62 mm), and its image speckle was detected with an image sensor. The difference between the average of the speckle intensity (Imean) and the speckle intensity for successive scannings was calculated, and the ratio of Imean to this difference was defined as normalized blur (NB), a quantitative index of blood velocity in the retinal microcirculation. The results were displayed on a color monitor showing the two-dimensional variation of the NB level in the measurement area. Using this apparatus in the rabbit, the NB in the retinal field free of visible surface vessels was determined and compared with the retinal blood flow rate measured using the microsphere technique in the same eye simultaneously. In addition, the effect of the ocular perfusion pressure (OPP) on NB was studied. In the above experiments, a stepwise reduction in OPP was introduced by elevating the intraocular pressure manometrically. RESULTS: The relative decrease in the average NB (NBav) over the field measured, with the reduction in OPP, showed significant correlation with the relative change in the blood flow rate determined using the microsphere technique (r = 0.59, P < 0.001). Although NBav in the retina was little affected by OPP change when OPP was greater than 50 mm Hg, NB decreased along with OPP at levels less than 50 mm Hg. CONCLUSIONS: The NBav showed significant correlation with the retinal blood flow rate determined with microsphere technique. Retinal microcirculation under various conditions can be studied two dimensionally and noninvasively in the living eye with the present apparatus.

Animals↗

PubMed1994

Mental stress induces different reactions in nutritional and thermoregulatory human skin microcirculation: a study in borderline hypertensives and normotensives.

It has recently been shown that the reactivity of total (= thermoregulatory) and nutritional (= capillary) skin microcirculation differs in hypertension and normotension (NT) with a reduced stress response in hypertension. The present study investigated skin microcirculation in 40 patients with borderline hypertension (BHT) and 38 NT controls. Capillary blood flow (CBV, dynamic capillaroscopy) and subpapillary thermoregulatory flow (Laser Doppler fluxmetry, LDF) was measured at rest, after arterial occlusion and during and after a mental stress test. Resting CBV (0.48 vs. 0.50 mm/s) and LDF (3.19 vs. 3.06 AU) were equal in the two groups and no difference was found in postocclusive hyperaemia response. Reactivity to mental stress was similar in both groups with a significant increase in LDF (45% and 39%) and a significant decrease in CBV (35% and 30%). In nonsmokers the BHT group tended to increase less in LDF (50% vs. 72%) and decrease slightly more in CBV (35% vs. 28%) than the NT group. No such difference was seen in smokers. Mental stress induces opposite reactions in total and nutritional skin microcirculation both in borderline hypertensives and normotensives. There were no significant differences in reactivity between the two groups, possibly due to the alleviated responses seen in smokers in both groups.

Adult↗

PubMed1994

The effects of halothane and isoflurane on cerebrocortical microcirculation and autoregulation as assessed by laser-Doppler flowmetry.

The effects of volatile anesthetics on red blood cell flow in the cerebral microcirculation have not been compared. We used laser-Doppler flowmetry, which measures red blood cell flow in the microcirculation to compare the effects of differing concentrations of isoflurane and halothane on cerebrocortical microcirculation. Sprague-Dawley rats were anesthetized with pentobarbital (65 mg/kg intraperitoneally). The animals were tracheotomized, paralyzed, and artificially ventilated. In the first protocol laser-Doppler flow (LDF) was recorded at 0.5, 1, 1.5, and 2 minimum alveolar anesthetic concentration (MAC) halothane or isoflurane, with blood pressure controlled by intravenous phenylephrine infusion (0.5-5 micrograms.kg-1.min-1). In the second protocol the effects of 0.5 and 1.5 MAC halothane and isoflurane on LDF changes in response to changes in mean arterial blood pressure (MABP) were compared. MABP was increased by phenylephrine infusion and decreased by hemorrhage. LDF increased with each 0.5 MAC increase in halothane and isoflurane concentration (P < 0.05). LDF was greater at 1.5 and 2 MAC isoflurane than at equi-MAC halothane (P < 0.01). Autoregulation of LDF was present but attenuated at MABP of 60-140 mm Hg at low halothane and isoflurane concentrations. LDF was increased at 1.5 MAC vs 0.5 MAC for both drugs (P < 0.01). The autoregulation coefficients (percent LDF change/mm Hg MABP change) were 0.41 +/- 0.10, 0.42 +/- 0.07, 0.27 +/- 0.04, and 0.20 +/- 0.05 at 0.5 MAC halothane, 0.5 MAC isoflurane, 1.5 MAC halothane, and 1.5 MAC isoflurane, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

[The effect of hyperbaric oxygenation on the microcirculation, oxygen budget and acid-base equilibrium in patients with diabetic angiopathy of the lower extremities].

These effects were studied in 52 patients with degrees III-IV diabetic angiopathies of the lower limbs. Microcirculation parameters were found changed in this patient population, this leading to disorders of the oxygen budget and development of metabolic acidosis. Development of destructive changes in the limb evidences failure of the compensatory adaptive mechanisms of microcirculation. Addition of hyperbaric oxygenation to multiple-modality treatment of patients with diabetic angiopathies was conducive to improvement of the blood rheology, of tissue saturation with oxygen, and to essential reduction of metabolic acidosis. The detected microcirculation disorders necessitate addition to the therapeutic complex of the drugs improving the biophysical characteristics of the blood.

Acid-Base Equilibrium↗

PubMed1994

[Adaptation of peripheral microcirculation in the course of pregnancy].

The present prospective study investigates the changes of the peripheral microcirculation during pregnancy and puerperium, especially in preeclampsia. Using videocapillary microscopy we investigated 30 pregnant women at 4 different times. We studied red cell velocity as well as reactivity to artificial ischaemia of capillary blood vessels. An increase of red cell velocity during the course of pregnancy of approximately 30% and a reduction near normal values within 12 weeks after delivery was demonstrated. There is an obvious decrease of vascular reactivity to ischaemia as a consequence of increasing physiological vasodilatation in pregnancy. 24 pregnant pregnant women with normal peripheral microcirculation at the beginning of pregnancy had an uneventful pregnancy but 3 out of 6 pregnant women with an obviously impaired microcirculation developed pregnancy induced hypertension. These 3 were smokers.

Adult↗

PubMed1994

Techniques used to evaluate the cutaneous microcirculation: application of photoplethysmography to the assessment of a phlebotropic agent in the treatment of leg ulcers.

Over recent years, a number of functional investigations have been developed that allow a better evaluation of the physiology of the cutaneous microcirculation than that provided by the morphologic method. These investigations are also useful in pharmacologic studies. Following a review of the anatomy and physiology of the cutaneous microcirculation, the author presents the principal techniques of investigation and the results obtained with Daflon 500 mg* on the cutaneous microcirculation evaluated by photoplethysmography of the skin in patients with venous insufficiency and leg ulcers.

Blood Pressure↗

PubMed1993

The influence of hemorrhage on liver microcirculation of the cirrhotic rat.

Bleeding from esophageal varices is highly lethal in cirrhotics, the main cause of death being liver failure. Because adequate hepatic perfusion is a prerequest for the maintenance of liver function, the present study was designed to evaluate the influence of hemorrhagic shock on liver microcirculation in rats with portal hypertension due to cirrhosis of the liver induced by CCl4. In 16 cirrhotic rats and an equal number of controls, hepatic microcirculation was continuously assessed--by means of laser-Doppler flowmetry, through a self-adhesive probe attached to the liver surface, before and during a 15 min period of arterial hypotension (40 mmHg) induced by blood withdrawal. Our findings revealed that immediately following hemorrhage there is a statistically significant reduction of microcirculation in cirrhotics versus controls. The results of this study assist in the better understanding of the hemodynamic conditions which prevail in the cirrhotic liver during the first minutes of hemorrhage.

Acute Disease↗

PubMed1993

[Hemorheologic effects of ginkgo biloba extract EGb 761. Dose-dependent effect of EGb 761 on microcirculation and viscoelasticity of blood].

METHOD: In a randomized open clinical trial involving 42 patients with pathological visco-elasticity values, the effect of a single intravenous injection of 50, 100, 150 or 200 mg of the Ginkgo biloba extract EGb 761, commercially available as Tebonin p.i. on the microcirculation of the skin (Doppler flowmetry) and the visco-elasticity of whole blood was investigated. RESULTS: A dose-dependent significant increase in the microcirculation was found. In the case of visco-elasticity, this dose-dependence was less marked. The present study thus confirms the positive effect of EGb 761 on the microcirculation and whole-blood visco-elasticity in patients with pathological visco-elasticity values, already found in earlier studies, and shows it to be dependent on the dose employed.

Aged↗

PubMed1993

[Changes in microcirculation in the facial nerve with electrical stimulation and chemical blockade of cervical sympathetic trunks].

The cervical sympathetic trunks send peripheral branches to the external carotid artery system which in turn provides feeding vessels to the facial nerves. In this study, the changes in the tonus of these trunks and the associated changes in the microcirculation of the facial nerves were studied by electrical stimulation and by chemical blockade of the cervical sympathetic trunks in mongrel dogs. With electrical stimulation, marked increases in arterial blood pressure and the heart rate were observed although the common carotid arterial blood flow and tissue blood flow in facial nerves decreased markedly. This suggests that microcirculation in the facial nerve is definitely impaired by electrical stimulation of the cervical sympathetic trunks and that hypertonicity of the sympathetic nervous system is closely involved in the onset of facial palsy. When chemical blockade was applied to the same trunks, the arterial blood pressure and heart rate showed no significant changes. However, there were marked increases of the blood flow in common carotid artery and facial nerve tissue. This finding of improved microcirculation in the facial nerve after chemical blockade suggests that stellate ganglion block may be a very effective treatment for Bell's palsy.

Animals↗

PubMed1996

Melatonin prevents ischemia reperfusion injury in hamster cheek pouch microcirculation.

OBJECTIVE: We used the hamster cheek pouch microcirculation to investigate the effects of melatonin (ME) on ischemia reperfusion (I-R) injury by in vivo microscopy. ME is a hormone produced by the pineal gland and is the most powerful and effective hydroxyl radical scavenger detected to date in vitro. The second aim was to determine the scavenger effect of ME in cheek pouch microcirculation when topically applying an oxygen-derived free radical generating system. METHODS: Ischemia was induced by clamping the cheek pouch for 30 min followed by 30 min of reperfusion. We quantified the increase in permeability, the perfused capillary length and leukocyte adhesion by computerized methods. Microcirculation was also exposed to a hypoxanthine-xanthine oxidase (H-X) system. RESULTS: In control hamsters I-R was associated with increased permeability, increased number of leukocytes sticking to venules, and decreased perfused capillary length. Treatment with ME completely inhibited microvascular edema formation and reduced the number of leukocytes sticking to venules after reperfusion. Moreover, ME prevented the marked decrease in perfused capillary length, preserving microvascular perfusion. ME topically applied reduced significantly the permeability increase due to H-X exposure. CONCLUSIONS: The beneficial effect of ME may be related to its antioxidant properties. These protect the endothelial barrier integrity as well as preserve microvascular blood perfusion by dysfunctions after I-R.

Animals↗

PubMed1996

[Laser Doppler flowmetry--a new promising technique for assessment of the microcirculation].

The laser Doppler flowmetry is a new technique for evaluating microcirculation. It is based on the Doppler phenomenon-reflected light changes its frequency when it interacts with moving objects such as red blood cells. The source of light is 2 mW He-Ne laser. The light penetrates into the tissue to the depth of 1 mm, and measures microvascular blood flow throughout it. This technique is objective, harmless even during prolonged exposition, repeatable, and very sensitive even to small changes in the blood flow. Because of difficulties with determination of the perfusion normal values and several factors disturbing microcirculation, the most objective results are obtained with dynamic tests. They measure a response of microcirculation to local ischemia, cooling or given medicines. A disadvantage is its high sensitivity to motion-produced disturbances. Laser Doppler flowmetry may be used not only in scientific investigations. It is of diagnostic value in plastic surgery, vascular surgery, dermatology, internal medicine, dentistry, and neurology.

Equipment Design↗

PubMedDate not supplied

[Nailfold capillaroscopy in the study of microcirculation in childhood].

The nailfold capillaroscopy allows to study the microcirculation: for its simple and rapid execution it can be used also in children. We examined the nailfold capillaroscopy features in childhood and valued the maturation of microcirculation in connection to age and presented some pathologic patterns. We studied nailfold capillaroscopy patterns in sixty-six children without chronic cutaneous diseases. Our results showed that development of microcirculation during childhood is incomplete. In connection to age we observed the capillaries are arranged as arches in children younger than six months, there are disposed as saddles between 12 and 24 months and they became similar to those of the adult at about 10-11 years. We observed immature capillaries in one child with hypothyroidism and one's delay growth. The cutaneous hemorrhages were rarely found in children who bit the in nails. The capillaroscopy is helpful to value the maturation of the capillaries from the birth to the adolescence. Moreover we would like to underline how our children took part to this exam almost like as if it were a game.

Adolescent↗

PubMed1996

[Effect of LHRH agonists on testicular microcirculation with Doppler laser flowmetry].

The purpose of this paper is to present the changes that take place in testicular microcirculation measured by DLF during systemic administration of LHRH agonists. The essay includes a comparison with the variations registered in the volume of testicular interstitial fluid, the anatomopathological changes and the associated leucocyte demyeloperoxidase levels. We also examine the relationship between testicular microcirculation changes and plasma testosterone levels. To do this, 50 male Wistar rats were randomly divided into 5 groups, using 10 as control group and the remaining 40 distributed in 4 groups. Measurements were done at 2, 4, 8 and 24 hours after administration of Tryptorelin 0.4 mg i.v. We found that acute administration of an LHRH agonist causes a series of significant changes on testicular microcirculation. Testicular rhythmic microcirculatory flow, i.e., vasomotion, disappears. In turn, accumulation of PMN leucocytes associated to increased venular permeability takes places. Such pre- and postcapillary vascular changes lead to increased vascular permeability which results in increased volume of testicular interstitial fluid. This increased capillary permeability is responsible for the extensive interstitial oedema that would explain the serious histological changes seen on the seminiferous tubule with these drugs.

Animals↗

PubMed1997

Prednisolone, platelet-activating factor receptor antagonist, or superoxide dismutase reduced leukocyte entrapment induced by interferon alpha in retinal microcirculation.

PURPOSE: Interferon (IFN) alpha has been suggested as a possible treatment for choroidal neovascularization. However, the pathogenesis of retinal complications after IFN therapy still is unknown. Previously, we have shown that IFN alpha induced leukocyte entrapment in retinal microcirculation. The current study was designed to determine if leukocyte entrapment can be reduced by the agents that modulate leukocyte-endothelial adherence. METHODS: Interferon alpha was administered intravenously in rats. Simultaneously, prednisolone (PSL), platelet-activating factor receptor antagonist (CV-6209), or superoxide dismutase (SOD) was given to the rats. Leukocyte dynamics were observed with acridine orange (AO) digital fluorography, which uses a nuclear fluorescent dye of AO and scanning laser ophthalmoscopy. The number of trapped leukocytes in each group was assessed with a personal computer-based image analysis. RESULTS: Interferon alpha induced leukocyte entrapment in retinal microcirculation and increased leukocyte adherence to the vessel walls. The simultaneous administration of PSL, CV-6209, or SOD inhibited leukocyte adherence to the venous walls and significantly reduced the number of trapped leukocytes. CONCLUSIONS: Acridine orange digital fluorography was helpful to quantitate leukocyte-endothelial interactions in retinal microcirculation. The results suggested that increased leukocyte adherence after IFN alpha administration was reduced significantly by PSL, CV-6209, or SOD. These agents may be useful to prevent IFN-induced microcirculatory disturbances.

Acridine Orange↗

PubMed1997

Effect of host microenvironment on the microcirculation of human colon adenocarcinoma.

It is generally accepted that the host microenvironment influences tumor biology. There are discrepancies in growth rate, metastatic potential, and efficacy of systemic treatment between ectopic and orthotopic tumors. Liver is the most common and critical site of distant metastasis of colorectal carcinoma. Tumorigenicity and efficacy of chemotherapeutic agents in colorectal tumors are different in liver and subcutaneous sites. Thus, we hypothesize that the liver (orthotopic) versus subcutaneous (ectopic) microenvironment would have different effects on the angiogenesis and maintenance of the microcirculation of colorectal tumor. To this end, we developed a new method to monitor and to quantify microcirculatory parameters in the tumor grown in the liver. Using this approach, we compared the microcirculation of LS174T, a human colon adenocarcinoma, metastasized to the liver with that of the host liver vessels and that of the same tumor grown in the subcutaneous space. In the liver metastasis model, 5 x 10(6) LS174T cells were injected into the spleen of nude mice. Four to eight weeks later, the liver with metastatic tumors was exteriorized and placed on a special stage and observed under an intravital fluorescence microscope. The dorsal skinfold chamber model was used to study the subcutaneous tumors. Red blood cell velocity, vessel diameter, density, permeability, and leukocyte-endothelial interactions were measured using fluorescence microscopy and image analysis. Vascular endothelial growth factor/ vascular permeability factor (VEGF/VPF) mRNA expression was determined by the Northern blot analysis. LS174T tumor foci in the liver had tortuous vascular architecture, heterogeneous blood flow, significantly lower vascular density, and significantly higher vascular permeability than normal liver tissue. Tumors grown in the liver had significantly lower vessel density, especially in the center coincident with central necrosis, than the subcutaneous tumors. The frequency distribution of vessel diameters of liver tumor was slightly shifted to smaller size compared with that of subcutaneous tumor. Leukocyte rolling in liver tumor was twofold lower than that in subcutaneous tumor. These physiological findings were consistent with the measurement of VEGF/VPF in that the VEGF/VPF mRNA level was lower in the liver tumor than that in the subcutaneous tumor. However, macromolecular vascular permeability in the liver tumor was significantly higher than in the subcutaneous tumor. Liver sinusoidal endothelial cells, the origin of liver tumor vessel endothelium, are known to be fenestrated and not to have a basement membrane, suggesting that the difference in endothelial cell origin may explain the difference in tumor vascular permeability in two sites. These findings demonstrate that liver microenvironment has different effects on some aspects of the tumor angiogenesis and microcirculation compared with the subcutaneous tissues. The new model/method described in this paper has significant implications in two research areas: 1) the liver microenvironment and its effect on tumor pathophysiology in conjunction with cytokine/ growth factor regulation and 2) the delivery of drugs, cells, and genes to liver tumors.

Adenocarcinoma↗

PubMedDate not supplied

Effects of glucagon administration on microcirculation and blood rheology.

It has been reported that some rheologic abnormalities are associated with diabetes. However, it is difficult to realize the condition of microcirculation in men. We developed an intra-vital video-microscopic system (IVVMS) to observe microcirculation directly on the bulbar conjunctiva. Using this system, we investigated the effect of intravenous glucagon administration on microcirculatory parameters such as the internal diameter of venules, flow velocity and flow volumes in diabetic patients. Blood viscosity and rheology factors were also examined before and after glucagon administration. The time required for erythrocytes to pass through pores of 5 microm diameter, as well as whole blood viscosity were decreased significantly after glucagon administration. Flow volumes of venules were increased significantly by glucagon. Leukocyte counts, platelet counts and fibrinogen did not change after glucagon administration. However, plasma glucose, insulin, C-peptide and cyclic-AMP were increased. In conclusion, glucagon administration improved blood fluidity and modified the microcirculation in patients with diabetes mellitus.

Blood Coagulation Factors↗

PubMed1998

Fenofibrate improves microcirculation in patients with hyperlipidemia.

In order to investigate the effect of fenofibrate on microcirculation, 16 patients (5 female, 11 male, age 58 +/- 8 years) were studied with the aid of nailfold capillaroscopy before and after treatment with 200 mg fenofibrate per day over six weeks. Fenofibrate resulted in a significant decrease in triglycerides, total and LDL-cholesterol and apolipoprotein B and an increase in apolipoprotein A. As a parameter of an improved microcirculation the time to peak capillary blood cell velocity during postreactive hyperemia (occlusion of the lower arm for 2 minutes, 200 mmHg) decreased markedly from 45 +/- 5 to 16 +/- 3 s, p < 0.0001). Fibrinogen levels were significantly decreased (p < 0.04) in contrast to other parameters with a possible impact on microvascular perfusion (hemoglobin, hematocrit, mean platelet volume, total protein) and to blood pressure and heart rate. These findings suggest that fenofibrate treatment improves microcirculation in patients with hyperlipidemia. This beneficial effect of fenofibrate may arise from two leading mechanisms. One of these might be the decrease in fibrinogen levels reducing plasma viscosity, the other mechanism might be an indirect effect on functional abnormalities of the vascular endothelium arising from hyperlipdidemia. By lowering plasma lipids fenofibrate is likely to restore the impaired formation or efficacy of the endothelium derived relaxing factor (nitric oxide, NO).

Adult↗

PubMed1998

Microcirculation in lower limbs during laparoscopic cholecystectomy.

To study the influence of venous hypertension, which develops in lower limbs under pneumoperitoneal pressure, on microcirculation, plethysmographic measurements were performed in patients before and during laparoscopic and traditional (open) cholecystectomy. During laparoscopy, isovolumetric venous pressure (estimate of capillary pressure), and filtration coefficient (estimate of patent capillary surface) decreased, which was not the case during open surgery. These results indicates that venous hypertension during laparoscopic surgery does not extend to the microcirculation; vasoconstriction is a result of protective mechanisms, which disable excessive fluid filtration in microcirculation. Parameters of macrocirculation (ambient venous pressure, compliance of calf tissue) changed intraoperatively in both groups similarly, irrespectively of the surgical technique.

Blood Pressure↗