Microvascular research
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Microvascular research · Jan 1996
Randomized Controlled Trial Comparative Study Clinical TrialSpontaneous laser doppler flux distribution in ischemic ulcers and the effect of prostanoids: a crossover study comparing the acute action of prostaglandin E1 and iloprost vs saline.
The flux distribution within ischemic ulcers and adjacent skin and its change by prostanoids was investigated using laser Doppler flux scanning. A prostanoid-induced increase in ulcer flux could be a rationale for the improved wound healing. In a single-blind prospective study 18 patients received prostaglandin E1 (PGE1) (333.3 ng/min.), iloprost (41.7 ng/min final dose), and 0.9% saline in a randomized order. ⋯ Simultaneously, LFS was not significantly changed when pretreatment values were compared with mean flux at 120 min: PGE1 2.13 +/- 0.27 vs 2.54 +/- 0.34, iloprost 2.03 +/- 0.26 vs 1.94 +/- 0.21, and saline 1.74 +/- 0.27 vs 1.92 +/- 0.30 (P > 0.05, each), respectively. The laser Doppler flux scanning technique might be a tool to study the distribution of laser Doppler flux within ischemic ulcers. This might be useful to study the physiological or pathophysiological control of flux within ischemic ulcers as well as possible therapeutic approaches.
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Microvascular research · Jul 1994
Spatial heterogeneity in normal skin perfusion recorded with laser Doppler imaging and flowmetry.
Spatial and temporal variations in forearm skin perfusion captured by laser Doppler perfusion imaging (LDI) have been compared with topographic maps recorded by laser Doppler flowmetry. In order to determine the shortest LDI sampling time required at each measurement site, with an adequate signal-to-noise ratio and with the ability to display the heterogeneity in skin perfusion, the noise-limited resolution of the LDI system as well as various sampling times were tested. The noise-limited resolution for medium and high light intensities were less than 0.5% (temporal) and 0.3% (spatial) of full scale. ⋯ Small spots were selected in the areas and plotted versus time. Without provocation, the total perfusion changes at each spot showed large variations, but the relative perfusion levels between neighboring spots persisted. Provocation with heat increased the perfusion in all spots.
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Microvascular research · Mar 1994
Infrared videoangiofluorography of the skin with indocyanine green--rat random cutaneous flap model and results in man.
We report a new technique for visualizing and measuring skin perfusion on a macroscopic scale using low doses of indocyanine green (0.3 mg/kg body weight). The method was first evaluated in the rat random cutaneous flap model and subsequently applied to determine skin perfusion in a patient with peripheral arterial occlusive disease (PAOD), a patient with forefoot necrosis due to diabetic microangiopathy, and a healthy volunteer. ⋯ In PAOD reduced skin perfusion in the tissue surrounding the arterial ulcer could be clearly demonstrated, whereas skin perfusion in diabetic microangiopathy seems to be unaffected. Other potential clinical applications for the technique in dermatology and vascular and reconstructive surgery are briefly discussed.
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Microvascular research · Nov 1987
Model analysis of the enhancement of tissue oxygenation by hemodilution due to increased microvascular flow velocity.
The effect of hemodilution on oxygen delivery to the tissue was investigated analytically by taking into consideration the oxygen loss that occurs along the arterial microvasculature due to diffusion into the tissue and shunting to parallel running venules. The theoretical findings were related to experimental data on microvascular oxygen distribution and the blood flow weighted by the oxygen-carrying capacity of plasma and red blood cells (Q) during hemodilution. It was found that at 30-33% hematocrit, the amount of oxygen brought to the tissues is increased by 5% when diffusion is the only mechanism of oxygen loss, and by 15% when the loss is due to arteriole-venule (A-V) shunting. ⋯ The analysis was extended to conditions of low oxygen tension and flow condition, characteristic of ischemia. In the case of severe ischemia the total increase in oxygen delivery at hematocrit 30-33% was 38% for tissues with diffusion losses only, and 66% when shunting losses are predominant. These results suggest that hemodilution is particularly effective in increasing oxygenation in ischemic tissue, while it has a comparatively small effect in normal conditions.
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Microcirculatory blood flow and transport are controlled to meet local and systemic demands for material exchange and body fluid balance. Control mechanisms act through effectors (smooth muscle cells) at many sites within the microvascular bed. ⋯ However, knowledge of how these principles are integrated at the microcirculatory level requires the variability and heterogeneity to be taken into account. Indeed, there is much reason to believe that heterogeneity is an important part of microcirculatory control.