Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Microcirculation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 37 records · Page 2Linked to original sources
PubMed1997

[Effect of topically applied isopropyl unoprostone on microcirculation in the human ocular fundus evaluated with a laser speckle microcirculation analyser].

The effect of topically applied 0.12% isopropyl unoprostone (unoprostone, Rescula) on the circulation of optic nerve head (ONH) and choroid-retina was studied using a laser speckle tissue circulation analyser in 9 normal human eyes. Normalized blur (NB), a quantitative index of blood flow velocity, was measured every 0.125 sec and averaged over 5 pulses in the temporal site of ONH free of surface vessels and in the middle site of the choroid-retina between ONH and macula. Intraocular pressure (IOP), blood pressure (BP), and pulse rate (PR) were also measured. On the first day, NB, IOP, BP, and PR were measured before and every 90 minutes for 6 hours after a 30 microliters instillation of placebo in both eyes (control eyes). The measured values were used as controls. On the other day one week later, a 30 microliters instillation of unoprostone was performed in one randomly chosen eye and the placebo in the other eye (treated and untreated eye). The above parameters were measured as the first day in a double masked manner. In the control experiment, no significant change occurred in any parameter. After topical application of unoprostone, NB in ONH showed no significant change. NB in the choroid-retina significantly increased at 3 (8%) and 4.5 (11%) hours in the treated eyes compared with the control eyes. After topical application of unoprostone, the IOP significantly decreased at 1.5 and 4.5 hours in the treated eyes compared with the control eyes. BP and PR showed no significant change. These results suggest that instillation of unoprostone can increase blood flow in the choroidretna in human eyes.

Adult↗
PubMed2002

Regulation of blood flow and microcirculation resistance in rabbit bladder.

PURPOSE: Human and animal studies have shown that filling, contraction and emptying produce cyclical changes in bladder blood flow. The mechanism of these hemodynamic changes remains unclear. We studied the regulation of bladder blood flow in the rabbit model. MATERIALS AND METHODS: A total of 18 male New Zealand White rabbits were anesthetized. Arterial pressure, intravesical pressure, and dome and base blood flow were measured simultaneously in the empty bladder, at 25 and 50 ml. intravesical volume, and after draining. These measurements were recorded before and then after intravenous administration of atropine, phentolamine, propranolol, L-arginine or N-nitro-L-arginine. Changes in dome and base microcirculation resistance, and blood flow after treatment were compared with those recorded before treatment. RESULTS: In the empty bladder dome microcirculation resistance was greater than at the base and base blood flow was greater than at the dome. Filling increased dome microcirculation resistance, decreased dome blood flow and increased base blood flow without changing base microcirculation resistance. Emptying produced much greater reactive hyperemia at the dome than at the base. Atropine did not alter microcirculation resistance or blood flow. Phentolamine had no effect on dome or base microcirculation resistance, blood flow in the empty bladder or at 25 ml. intravesical volume but it decreased dome microcirculation resistance at 50 ml. intravesical volume. Propranolol caused dome contraction, increased dome microcirculation resistance and decreased dome blood flow in the empty bladder, and at 25 and 50 ml. intravesical volume. Propranolol increased base blood flow without changing base microcirculation resistance. N-nitro-L-arginine increased dome microcirculation resistance in the empty bladder and at 25 ml. intravesical volume but decreased dome blood flow in the empty bladder alone. N-nitro-L-arginine increased base microcirculation resistance and decreased base blood flow in the empty bladder and at 25 ml. intravesical volume but not at 50 ml. intravesical volume. L-arginine decreased dome and base microcirculation resistance, and increased blood flow in the empty bladder, and at 25 and 50 ml. intravesical volume. Reactive hyperemia decreased after N-nitro-L-arginine and increased after L-arginine. CONCLUSIONS: Our studies show large variations in bladder dome and base microcirculation resistance and blood flow. Bladder blood flow appears to be largely regulated locally by nitric oxide mediated changes in bladder microcirculation resistance. beta-adrenergic receptors may regulate bladder blood flow indirectly by modulating dome tension and shifting blood flow between the dome and base. Mechanical changes in bladder wall and vasculature shape may also contribute to changes in microcirculation resistance.

Animals↗
PubMed2001

Imaging the microcirculation of untreated and treated human choroidal melanomas.

INTRODUCTION: Histologically demonstrable microcirculation patterns (microcirculation pattern) of human choroidal melanomas have prognostic significance for the patient. We report on our experience in imaging these microcirculation pattern in vivo using simultaneous confocal Fluorescein (FA)- and Indocyaninegreen (ICG) angiography before and after brachytherapy. PATIENTS AND METHODS: The simultaneously procured confocal FA- and ICG angiograms of 50 patients with untreated choroidal melanomas were studied for the visibility of microcirculation pattern. Patients were also followed with simultaneous FA/ICG after brachytherapy. RESULTS: Confocal FA disclosed signs of tumor vascularization in 12 (24%) of the 50 examined patients but microcirculation pattern only in 3 patients (6%). In contrast, simultaneously obtained confocal ICG disclosed microcirculation pattern in 47 patients (94%). In 10 (77%) of the 13 patients the tumor microcirculation changed considerably after brachytherapy: Distortion, thickening, thinning, as well as complete obliteration of vessels could be observed. CONCLUSION: Histologically demonstrated microcirculation pattern can be imaged in vivo. This offers the possibility to assess the likely biologic behavior of the individual tumor without the need for obtaining a cytologic or histologic specimen via enucleation or fine-needle biopsy. Confocal ICG angiogiography images microcirculation pattern better than FA which can be explained by the different absorption-, fluorescence- and exudation-characteristics ICG. Follow-up with confocal ICG of choroidal melanomas after brachytherapy shows different features and allows for visualization of the microcirculation reaction to the treatment which might be a useful tool for studying the effects of future anti-angiogenesis based tumor therapies.

Adult↗
PubMed1996

Sepsis/septic shock: participation of the microcirculation: an abbreviated review.

OBJECTIVE: An overview of the importance of understanding mechanisms occurring in the microcirculation during septic and endotoxic shock. The thesis of the paper is to place emphasis on this important vascular network to ultimately benefit the patient. DATA SOURCES: Early descriptions of vascular reactions to endotoxin which suggest that the microcirculation is a major site of attack during shock. More recent studies were sought out and examined as to their possible impacts on the microcirculation. STUDY SELECTION: Early comprehensive studies concerning vascular reactions in the microcirculation during shock were selected. Subsequent studies identified from the mainstream scientific medical literature describe the actions of blood, cells, and the emerging significant role of the vascular endothelium among other factors. A consensus view is identified, pointing to the causes of a malfunctioning microcirculation during shock. DATA EXTRACTION: Data gathered from reports in the mainstream, well-established basic and clinical literature, from reviews and forum reports, from studies by well-established investigators, and from more recent reports of excellent quality. DATA SYNTHESIS: The microcirculation undergoes massive alterations during sepsis/septic shock. There are numerous changes, including slowing of capillary blood flow due to depressed perfusion pressure as a result of systemic pressure reduction and local arteriolar constriction. Observations suggest that the microcirculation is shut off early in severe sepsis, allowing the effects of hypoperfusion and attacks by microorganisms to prevail in their destructive capabilities. Widespread capillary dilation may ultimately occur. However, with blood flow diverted through some arteriovenous channels, important areas of capillary exchange are bypassed. Decreased capillary blood flow during shock results from failure to allow normal passage of cellular elements, including erythrocytes and neutrophils. This defect occurs, in part, because of decreased perfusion pressure, decreased deformability of red and white cells, constricted arterioles, circulating obstructive fragments (including hemoglobin), and plugging of microvessels with "sludge." Other factors are adherence of cells to capillary and venular epithelial membranes creating increased resistance to flow, loss of fluid through abnormal transcapillary exchange, differential vascular resistance changes between various beds (e.g., intestinal vs. muscle), and the relative absence of regulatory neurohumoral control of small vessel segments of the circulation. During sepsis/septic shock, endothelial cells are reported to modulate vascular tone, control local blood flow, influence the rate of leakage of fluids and plasma proteins into tissues, modulate the accumulation and extravasation of white cells into tissues, and influence white cell activation. As a result of the predominance of many destructive factors, a subsequent round of tissue damage may occur. Because of prolonged capillary vascular stasis, deficient flow, and factors released from injured cells, the microcirculation becomes a trap for uncontrolled bacterial growth enhanced by sustained hypoxemia, acidosis and toxemia. These events may combine to contribute to the loss of normal cell integrity and death of the host. CONCLUSIONS: The purpose of this review is to draw the readers' attention to the growing list of adverse factors occurring in the microcirculation during sepsis/septic shock. A further aim is to point to the realization of the complexity of factors which may contribute to the importance of a well-functioning microcirculation.

Animals↗
PubMed1999

Evaluation of the human choroidal melanoma rabbit model for studying microcirculation patterns with confocal ICG and histology.

The aim of this study was to develop consistently focal elevated choroidal masses of human choroidal melanoma in immunosuppressed rabbits and to correlate the visualization of prognostically significant microcirculation patterns from confocal indocyanine green angiography with histologic microcirculation patterns. A human choroidal melanoma cell line (OCM1) was implanted in the choroid of 40 rabbit eyes using three different techniques: transscleral choroidal injection of a cell suspension, injection of a cell suspension in a surgically induced cyclodialysis cleft, and implantation of solid tumor fragments in a surgically induced cyclodialysis cleft. The rabbits were immunosuppressed with daily injections of Cyclosporin A to prevent host versus graft reaction. The eyes were studied weekly with indirect ophthalmoscopy and fundus photography to monitor tumor growth and indocyanine green angiography using a confocal scanning laser ophthalmoscope to identify microcirculation patterns in vivo and correlate these findings with the histologic demonstration of tumor microcirculation patterns. A tumor mass was identified by indirect ophthalmoscopy in 16 of the 40 implanted rabbit eyes (40%). Each of these tumors was confirmed histologically to represent a focal elevated choroidal mass. All 16 elevated choroidal masses grow in eyes in which solid tumor fragments were implanted. In total, a melanoma was identified histologically in 28 of the implanted 40 eyes (70%). In addition to the 16 eyes where the melanoma appeared as a focal elevated choroidal mass, 4 eyes contained a focal elevated mass in the sclera and 8 eyes contained a flat choroidal tumor. Histologically, microcirculation patterns were identified only in the 16 eyes with focal elevated choroidal masses. Confocal indocyanine green angiography imaged microcirculation patterns in 13 of these 16 eyes (81%). The surgical implantation of small solid fragments of human choroidal melanoma in immunosuppressed rabbit eyes provides the best method to consistently obtain focal elevated choroidal masses. These focal elevated choroidal masses resemble booth the localization and the growth pattern of choroidal melanomas in humans. In addition, they also contain microcirculation patterns similar to those seen in humans that are detectable with confocal indocyanine green angiography. The use of indocyanine green angiography with this animal model may be especially useful in designing and evaluating anti-microcirculation treatments directed at uveal melanoma.

Angiography↗
PubMedDate not supplied

Small vessel phenomena in the coronary microcirculation: phasic intramyocardial perfusion and coronary microvascular dynamics.

To place the characteristics of the coronary microcirculation in perspective to another muscular organ system, we have compared various parameters from exchange vessels in the heart and red skeletal muscle. The major differences between cardiac and skeletal muscle microcirculations relate to the larger density of capillaries in the heart. This increased density is responsible primarily for a greater capillary filtration coefficient-permeability-surface area product to various solutes, surface area, and decreased intercapillary distances. These features most likely represent an adaptation of the microcirculation of the heart to the very high, continual metabolic demands. Interestingly, capillary permeabilities and reflection coefficients of different solutes are in the same range (although the heart tends to have higher capillary permeabilities). Thus, the adaptation of the coronary circulation to facilitate exchange of nutrients and solutes is mediated via an increase in the numbers of exchange vessels, rather than modifications of the membrane characteristics of these exchange vessels. Within the last decade, there has been much information assimilated on the regulation of the coronary microcirculation. Most of the knowledge has been the result of many indirect approaches to studying the coronary microcirculation (indicator-dilution techniques, nuclide-labeled microspheres, plasma-lymph concentration of solutes). There are relatively few direct observations on regulation of the coronary microcirculation. This is primarily due to difficulties in techniques. Exploration of the phasic nature of intramyocardial perfusion is handicapped by the location of these intramuscular vessels. Visualization of the coronary microcirculation is hampered by movements of the heart, and such measurements are restricted to the superficial layers of the myocardium. It is worth emphasizing that direct observations of red cell velocities in epicardial capillaries, measurements of microvascular caliber, and the pressure profiles in the coronary microcirculation are restricted to the superficial, epicardial layer. It is not unreasonable to speculate that microvascular events and regulation occurring in the subepicardium may be quite different than that in the subendocardium. There are several salient points in this review that are worth emphasizing.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Effect of different methods of thermotherapy on skin microcirculation.

OBJECTIVE: The purpose of the study was to compare the effects of different methods of thermotherapy on skin microcirculation, skin temperature, and core temperature in patients with rheumatoid arthritis and in healthy persons. DESIGN: In 20 patients with rheumatoid arthritis and 20 healthy controls, the skin microcirculation was measured by means of laser-Doppler flowmetry before, at the end of, and 30 mins after completion of local thermotherapy (infrared light, paraffin, peat) in the lumbar area. In addition, skin and core temperature were recorded at the same point in time. The influence of previous intake of acetylsalicylic acid on skin microcirculation during thermotherapy was investigated. The controlled trial was conducted in an air-conditioned laboratory. RESULTS: All methods caused a significant increase in skin microcirculation (flow and vasomotion), skin temperature, and core temperature. The skin temperature showed the highest increase when infrared light was applied. The microcirculation became more intense when paraffin fango was used. There were no differences between the reactions of rheumatoid arthritis patients and healthy persons. The additional intake of 500 mg acetylsalicylic acid before treatment did not affect skin temperature or skin microcirculation. A tendency toward a sinusoidal rhythmization of vasomotion was detected. CONCLUSIONS: The effects of the three methods of thermotherapy differ quantitatively due to their physical attributes. The effects on circulation differ depending on the method chosen, and this is significant when selecting the least stressful method for a particular patient. Rheumatoid arthritis patients and healthy controls have the same increase of skin microcirculation in the lumbar area. Findings in the distal limbs might differ. All used therapies cause a rhythmization of the vasomotion and, as a consequence, a qualitative improvement of the microcirculation.

Adult↗
PubMed1998

Long-term measurement of liver microcirculation in dogs and humans.

BACKGROUND: We verified the possibility of using laser Doppler fluxmetry for prolonged monitoring of hepatic perfusion; we confirm the ability of an implantable laser Doppler microprobe to be in constant 'optical contact' with the liver and thus to transmit a stable microcirculatory signal for a prolonged period of time, and we correlate the response of liver microcirculation to the hepatic artery blood flow reduction in order to estimate this flow by continuous monitoring of microcirculation. METHOD: Hepatic microcirculation was recorded by a single-fiber microprobe implanted in the livers of 8 dogs and of 5 surgical ICU patients. In another 7 dogs, liver microcirculation as well as hepatic artery blood flow were recorded digitally, while an occluder was used to decrease hepatic artery flow. RESULTS: Analysis of the initial data of microcirculation revealed a nonsignificant variation between consecutive time segments, a finding confirming the hypothesis that laser Doppler gives a very stable signal over a long period of time. Polynomial regression analysis, performed on data pairs obtained from microcirculation and hepatic artery blood flow revealed a regression coefficient y = -54.22 + 1.07x + 0.0046x2 (y = hepatic artery blood flow, x = liver microcirculation). CONCLUSION: This finding means that it is possible to watch the hepatic artery flow values continuously by the use of this equation and simple monitoring of liver microcirculation. Thus, the use of laser Doppler fluxmetry with implantable microprobes seems promising as a novel method for continuous assessment of hepatic artery blood flow.

Animals↗
PubMed1998

[An animal experiment and clinical investigation on the protective effect of selenium on the microcirculation induced by free radical damaged RBCs].

UNLABELLED: Fluorescent labeling image analysis was used to evaluate the changes in cerebral arteriole and veinlet diameters (D), circulation velocities (FV) and permeability (VP) in rats; while in clinics, a laser-doppler device was used for assessing changes of skins and muscles microcirculation. The results show that in control rats, equal volume perfusion of free radical damaged RBCs resulted in decreases of D and FV significantly but VP was increased, whereas in the case when free radical damaged RBCs were perfused together with selenium, no disturbances in the D and VP were observed with FV even improved. In the human control group, either average skin microcirculative perfusions (ASMP) at 25 degrees C or maximal skin microcirculative perfusions (MSMP) at 42 degrees C were evidently decreased during myocardial ischemia/reperfusion period, while ASMP at 24th hour of post-surgery was kept reducing. At the same time, the changes in muscles microcirculative perfusions (MMP) tended to be similar to the skin, but overloaded than the pre-surgery levels at 24th hour of post-surgery period. In the selenium group before surgery, the ratio of MSMP to ASMP was obviously increased than the control group (3.95 in Se group vs 1.74 in control group, P < 0.05), but did not have significantly differences in ASMP, MSMP and MMP between the two groups during surgery period. RBC deformabilities were not changed. At 24th hour post-surgery, the ASMP were almost restored to pre-surgery levels. However, MMP were still lower than the pre-surgery levels. CONCLUSIONS: (1) free radical damaged RBC perfusion leads to damage of microcirculation; (2) selenium is highly efficient in protecting microcirculation from free radical damaged RBC disturbance; and (3) Oral administration of selenium may improve pre-surgery maximal skin microcirculative perfusion and promote recovery of the worsened skin microcirculation in addition to prevent the occurrence of RBC deformability.

Adolescent↗
PubMed2002

[Direct visualization of microcirculation in burn wounds with OPS imaging--is determination of depth of burns possible?].

Adjunct diagnostic techniques might help surgeons to accurately analyse the depth of a burn. However, despite all technical innovations an ideal device for such an application has not been established for routine use as yet. OPS imaging implemented into the CYTOSCAN A/R is a new, recently introduced technique which allows to obtain high contrast images of the microcirculation without the necessity for fluorescent dyes. The aim of the study was to validate OPS imaging as a tool to study microcirculation in skin after burn injury. OPS imaging was applied by no-touch technique and capillary blood flow was videotaped. Subsequent measurements of the microcirculation were performed at the identical site of the burn. Quantitative analysis of the microcirculation was performed off-line using CapImage. OPS imaging produces high quality images of the microcirculation in a burn wound. Data is given as the number of perfused capillaries per observation area (functional capillary density; FCD) [n/cm2]. OPS imaging allows for direct in vivo visualization and quantification of the microcirculation in burned skin. Our preliminary results of the use of OPS imaging in assessing the microcirculation in burns appear promising, and we hope that this novel technique will allow to improve the knowledge of the dynamics of the microcirculation in the pathophysiology of thermal injury.

Blood Flow Velocity↗