Injection Of Sodium Fluorescein Research Articles

Adenosine agonist regulation of outward active transport of fluorescein across retinal pigment epithelium in rabbits

To investigate the effect of an adenosine agonist, 2-5′- N-ethylcarboxamidoadenosine (NECA), on the outward active transport of fluorescein across the retinal pigment epithelium (RPE) in rabbits. High (5×10 −4–2×10 −3 m) and low (1×10 −5–1×10 −4 m) concentrations of NECA or phosphate buffered saline (PBS) were intravitreously injected into Dutch-belted rabbits. Sodium fluorescein was injected intravenously 180 min after NECA. Differential vitreous fluorophotometry was performed 3 hr after the sodium fluorescein injection and the vitreal fluorescein/fluorescein monoglucuronide (F/FG) ratio then was calculated. The F/FG ratios are inversely proportional to the outward active transport of fluorescein across the RPE. Retinal detachments were induced by injection of PBS into the subretinal space after the intravitreous injection of low- or high-dose NECA or PBS, and the size of the blebs was monitored. In eyes that received a low-dose injection of NECA, the F/FG ratio was higher compared with controls ( P<0·05); in eyes that received a high-dose intravitreal injection, the F/FG ratio was significantly lower compared with controls ( P<0·05). The effect of low-dose NECA on the F/FG ratio was suppressed by the A2 receptor antagonist, ZM241385, and the effect of high-dose NECA was suppressed by the A1 receptor antagonist, 8-cyclopentyl-1, 3-dipropylxanthine. The A3 receptor antagonist MRS1191 did not influence the effect of low- or high-dose NECA. Intravitreal injection of high-dose NECA enhanced the reabsorption of subretinal fluid compared with PBS; however, low-dose NECA inhibited reabsorption of subretinal fluid ( P<0·02 and 0·05, respectively). Intravitreous injection of high-dose NECA accelerates the active outward transport across the RPE via A1 receptors and low-dose NECA decelerates it via A2 receptors.

Fluorescence-guided resection of glioblastoma multiforme by using high-dose fluorescein sodium. Technical note.

The authors have recently performed a fluorescence-guided tumor resection procedure by using high-dose fluorescein sodium without any special surgical microscopes for the intraoperative visualization of glioblastoma multiforme (GBM), and they report on the actual procedure and clinicopathological findings. Thirty-two patients with GBMs underwent tumor resection during which this fluorescence-guided procedure was used. Fluorescein sodium (20 mg/kg) was intravenously injected after dural opening at the craniotomy site. The tumor was stained almost homogeneously yellow and the color was intense enough to be readily perceived for resection. The center of the solid lesion was stained a deep yellow and surrounded by a transition zone that was faintly stained. The colored lesion was clearly distinguishable from the unstained zone outside the GBM, particularly in the white matter. Both the deeply and faintly stained regions included endothelial proliferation and dense tumor cells. In the unstained region, less dense tumor cells were consistently revealed; however, no endothelial proliferation could be seen. Gross-total resection (GTR) was successful in 84.4% of the patients who received an injection of fluorescein sodium, which accounted for 100% of those in whom all the visible yellow color (both the deeply and faintly stained regions) was judged to have been resected during operation. Gross-total resection was performed in 100% of the patients who underwent the fluorescence-guided procedure and assigned to Stage I, a GBM stage in which, as a therapeutic policy, the tumor should be resected as radically as possible. The GTR rates in patients who received fluorescein sodium were significantly higher than those in patients who did not (73 patients with GBMs who underwent tumor resection without the fluorescence-guided procedure). Although the extent of surgery was revealed to be one of the significant and independent prognostic factors for GBM, the fluorescein sodium-guided resection procedure was not a significant or independent prognostic factor in this series. This surgical procedure does not require any special surgical microscopic equipment and is simple, safe, useful, readily accomplished, and universally available for resection of GBMs. Its efficacy simplifies the surgical procedure of navigating the stained lesion from the unstained area to achieve GTR of GBMs, which can be demonstrated on magnetic resonance images.

Effects of Latanoprost on Blood-Retinal Barrier Permeability in Rabbits

Purpose: To investigate the effect of latanoprost (LP) on the inward and outward permeability (P_in and P_out) of the blood-retinal barrier (BRB). Methods: Four New Zealand white rabbits received topical LP (0.005%) once daily for 3 weeks in one eye and phosphate-buffered saline (PBS) in the fellow eye (topical group). Five New Zealand white rabbits were injected intravitreously with LP (0.1 ml, 0.005%) in one eye and PBS (0.1 ml) in the fellow eye (injection group). In the injection group, vitreous fluorophotometry (VFP) to estimate the P_in and differential vitreous fluorophotometry (DVF) to estimate the P_out were performed 60 min after LP was injected. After the baseline measurements, VFP and DVF were performed 60 and 180 min after intravenous injection of sodium fluorescein, respectively. Fluorescein (F) and fluorescein monoglucuronide (FG) concentrations were obtained by DVF, and the F/FG ratio was calculated as an index of the P_out. Results: In the topical group, there were no significant differences in the P_in or F/FG ratio between the LP- and the PBS-treated eyes. In the injection group, the P_in in the LP-treated eyes was significantly higher than in PBS-treated eyes (p < 0.05). There was no significant difference in the F/FG ratio between the two groups. Conclusion: Although we cannot exclude the effect of differences in species, the physiologic effect of LP, which increased the P_in, was seen in experimental studies. Because antiglaucoma drugs are generally used over an extended period, further clinical studies of the effect of LP on the BRB should be performed in patients who have BRB breakdown, such as in uveitis, and in patients who are pseudophakic and aphakic.

Vascular permeability to fluorescent substance in human cranial nerves.

It has recently been reported that in the facial canal, the facial nerve shows enhancement on gadolinium-enhanced magnetic resonance imaging in patients with clinically normal facial nerves. However, the mechanism of this enhancement has not yet been sufficiently clarified. The present study investigated the permeability of blood vessels in human cranial nerves that were obtained from surgically treated patients. The patients received an intravenous injection of sodium fluorescein 45 minutes before nerve resection. For histologic observation, the nerves were removed and frozen at -70 degrees C, and the sections were then cut at 4-microm thickness with a freezing microtome. The localization of the tracers was examined with a fluorescence microscope. Fluorescence was observed in the external nerve sheath and slightly in the endoneurium of these nerves, but was not observed within nerve fibers. These findings indicate that the vascular barrier in human peripheral nerves is incomplete.

Laparoscopic Fluorometry: A New Minimally Invasive Tool for Investigation of the Intestinal Microcirculation

The aim of this study was to develop and establish a new system of laparoscopic fluorometry for the purpose of investigating the intestinal microcirculation. In 25 pigs (German Landrace, 16-25 kg body weight), ischemia was established in two segments (A, irreversible; B, reversible ischemia; C, internal control) of the small intestine by a laparoscopic technique. Microcirculation in the segments was assessed by laparoscopy at a second-look operation 24 h later by means of the fluorescence system Endoscan. The fluorescence of the three bowel segments was measured by arbitrary dye fluorescence units (DFU) 15 min after starting reperfusion, before and after injection of sodium fluorescein (NaFlu, 0.25 mg/kg body weight). The dividing line between viable and nonviable bowel tissue was established from the inflow and outflow rates of NaFlu with the aid of ROC (receiver operating characteristic) curves. The specificity and sensitivity of the new method were evaluated by correlating the results with the viability of each intestinal segment as predicted by three laparoscopically experienced surgeons and by histological examination. By means of the calculated separation sharpness (fluorescence index at 2 min >0.5, outflow factor of NaFlu at 10 min >20%), the overall predictions of intestinal viability in all 25 animals achieved a sensitivity of 93.5% and a specificity of 94.1% by laparoscopic fluorometry, versus a sensitivity of 70.8% and a specificity of 87.5% for the prediction of bowel viability by ordinary laparoscopic technique. Used as an adjunct to conventional laparoscopy, laparoscopic fluorometry brought significant gains in sensitivity and specificity in the distinction between reversible and irreversible intestinal ischemia.

Inhibitory effects of bucillamine on increased blood-retinal barrier permeability in streptozotocin-induced diabetic rats

Purpose. To investigate the effect of bucillamine for prevention of increasing blood-retinal barrier (BRB) permeability in streptozotocin (STZ)-induced diabetic rats. Methods. The groups included control and STZ-induced diabetic rats treated with or without bucillamine. Six months after intervention, the concentrations of reduced and oxidative glutathione (GSH and GSSG) in the retina were measured biochemically. In addition, vitreous fluorescein, which leaks from the vessels after intravenous injection of fluorescein sodium, was measured to evaluate BRB permeability. To evaluate the scavenging ability against the reactive oxygen species (ROS) in vitro, the second-order rate constant for the reaction of bucillamine with ROS was estimated from the kinetics based on the rate constant for the reaction of ROS. Results. The BRB permeability was significantly higher (p = 0.01) in diabetic rats not treated with bucillamine, and bucillamine inhibited the BRB permeability. The GSH concentration and the GSH/GSSG ratio in the retinas decreased in diabetic rats not treated with bucillamine; bucillamine inhibited the decrease of the GSH concentrations. The ROS scavenging activity of bucillamine was similar with that of GSH. Conclusions. In diabetic retinas, oxidative stress might increase, which may be one of the causes of BRB breakdown. The antioxidant effects of bucillamine might take part in inhibition of increased permeability of the BRB in diabetes.

Mathematical morphology in computerized analysis of angiograms in age-related macular degeneration.

This paper deals with image processing of numerical retinal angiograms in order to facilitate diagnosis and follow-up in age-related macular degeneration (AMD) which is currently the main cause of blindness in industrialized countries. A computerized scheme using principally mathematical morphology operators is proposed for detecting and counting drusen, which are precursor lesions of the ocular fundus. In order to check the feasibility of this approach, results relative to 58 retinal images are compared with those given by three retinal specialists independently. From manual counting measures it is found that interobserver correlation coefficients lie in the range 0.71-0.78. On the other hand, a correlation coefficient of 0.89 is obtained when the average of the three expert countings is compared with the drusen number given by the computerized method. This coefficient is improved from 0.89 to 0.93 by processing only frames captured immediately after the appearance of a dye consecutive to intravenous sodium fluorescein injection. Compared to the manual analysis which is, among other things, tedious and time consuming, the computerized analysis is both quicker and more objective. Validation by the practitioner is however necessary, given possible detection errors. The proposed computerized scheme for detecting and counting drusen may be easily automated and so should prove useful in clinical studies which involve high volume analysis of retinal angiograms.

Study of Temporal and Perfusion Physiology of Skin Capillaries in the Dorsum of the Foot

The aim of this study was twofold: firstly, to study the nature of any temporal variation in capillary numbers, and secondly to determine the proportion of perfused to total nutritional capillaries in normal skin. Using in vivo microscopy, the temporal behaviour of the number of visible capillaries in the skin of the dorsum of foot was observed over periods of time varying from 5 min to 55 days in 15 healthy subjects. Capillary perfusion was then studied by comparing capillary numbers before and after intravenous injection of sodium fluorescein. The mean percent difference in the number of visible capillaries over a mean period of 25.3 days was 5.5%. The percentage ratio of perfused to total capillaries was 54.2%. This study shows that there is little quantitative change in capillary numbers over periods of up to 50 days, and that under physiological conditions, about half of the nutritional capillaries of skin are not perfused.

Hepatic neovascularization after partial portal vein ligation: novel mechanism of chronic regulation of blood flow.

The present study was undertaken to investigate hepatic microcirculatory response following partial portal vein ligation (PPVL) in rats. Portal pressure was markedly increased 2-6 wk after PPVL, but no significant reduction in sinusoidal perfusion and hepatocellular injury were detected. However, marked neovascularization was observed in PPVL rats using intravital microscopy and scanning electron microscopy (SEM). Extremely high red blood cell velocity (2,000-4,900 microm/s) was seen in these vessels. Injection of fluorescein sodium via the carotid artery revealed that the neovessels originated from the hepatic arterial vasculature. This was further confirmed by clamping the common hepatic artery and phenylephrine injection from the carotid artery. These vessels maintained sufficient flow after massive sinusoidal shutdown elicited by the portal infusion of endothelin receptor B agonist IRL-1620. SEM also showed extensive neovascularization at the hilum. Additionally, clamping the portal vein decreased sinusoidal perfusion only by 9.5% in PPVL, whereas a 71.2% decrease was observed in sham. These results strongly suggest that the liver maintains its microcirculatory flow by vascular remodeling from the hepatic arterial vasculature following PPVL.

Effect of acetazolamide on outward permeability of blood-retina barrier using differential vitreous flyorophotometry

Purpose. To measure fluorescein (F) and fluorescein monoglucuronide (FG) concentrations in the vitreous and evaluate the effect of acetazolamide (AZM) on the outward permeability of the blood-retina barrier (BRB) using differential vitreous fluorophotometry (DVF). Methods. DVF was performed 180 minutes after intravenous injection of AZM (5 mg/kg) and 50 mg of sodium fluorescein in six rabbits (AZM group). DVF also was performed in six rabbits injected intravenously with only 50 mg of sodium fluorescein (control group). The F/FG ratio was calculated based on the concentrations of F and FG obtained by DVF. DVF also was performed 180 minutes after 50 mg of intravenous injection of sodium fluorescein in five rabbits given probenecid (150 mg/kg) intraperitoneally (probenecid group). Results. The average F/FG ratio was 0.36 ± 0.17 (range, 0.22–0.66) in the AZM group, which was significantly smaller than the control value of 0.74 ± 0.22 (range, 0.50–1.60). The average F/FG ratio at 180 minutes after injection was 1.51 ± 0.46 (range, 0.94–2.00) in the probenecid group, which was significant higher (p < 0.05) than that of the AZM or control group. Conclusions. This study showed that the F/FG ratio might be a good indicator of the estimated outward permeability of the BRB using DVF and that AZM may accelerate the outward active transport function of the BRB.

Computerized analysis of video fluorescein imaging (VFI) of the skin

Video fluorescein imaging (VFI) is a new technique to continuously follow the development of fluorescence in the skin, i.e. blood inflow and perfusion, after intravenous injection of sodium fluorescein. The method is supplementary to other microcirculatory techniques for evaluation of peripheral arterial occlusive disease, particularly in critical ischaemia. In the present article we describe a totally computerized digital imaging processing system for evaluation and present results from a comparison between the evaluations of the appearance and development of the fluorescence in the sole of the foot using the computerized and the previously used manual techniques. With the computerized system the images are stored and correlated with the start of the injection. Regions of interest are then marked and a mean value of fluorescence intensity is calculated for each image. Using this computerized system the time required for evaluation has been shortened to about 10 min. The results of the comparison between the manual and computerized evaluations of appearance times showed that a significant correlation existed in all examined parts of the feet between the two techniques. The methods gave approximately the same results in regions with fluorescence appearance times between 20 and 50 s. With longer appearance times than approximately 50 s a systematic difference between the two techniques seemed to exist. In this interval shorter appearance times were measured with the computerized technique than with the manual technique. However, the clinical information with regard to prognosis would be relatively unchanged when the new computerized assessment technique and a new cut-off level for the appearance time are used. Also, regarding the development of fluorescence after the appearance time, expressed by the slope, a significant correlation was found between the manual and the computerized evaluation.

A neurocutaneous island flap model: an experimental study in rats.

Neurocutaneous flaps have been popularized recently in clinical reconstructive surgery. However, controversies exist concerning their anatomy and physiology. The particular role of neural vasculature in the survival of these skin flaps is also quite undefined in the experimental setting, and additional studies on this subject are necessary. The goal of this study was to describe a neurocutaneous flap in a rat model and to investigate its blood supply. Thirty male Sprague-Dawley rats weighing 300 to 350 g were used in this study, which was conducted in two stages. During the first stage, the lower extremities of 10 rats were dissected for the anatomic study of the neurocutaneous flap. A constant cutaneous nerve innervating the anterolateral thigh skin was exposed. It arose either from the saphenous nerve or the superficial epigastric nerve and was accompanied by a constant longitudinal arterial plexus. The tiny neural vessels were conveyed by the superficial fascia along their course. A 30 x 30-mm cutaneous island flap, which was based only on the cutaneous nerve with its accompanying vessels and a strip of superficial fascia, was raised on the anterolateral thigh skin using an operating microscope. The well-perfused skin territory was marked after sodium fluorescein injection. The stained skin territory was located centrally and medially on the whole island flap, and it was approximately 10 x 20 mm. This finding was confirmed by the qualitative assessment of the vascularity for this skin territory in microangiography. After studying the pedicle anatomy and determining the optimal viable skin island, the second stage of the study was performed. The remaining 20 rats were divided into two groups. In the experimental group (N = 10), a neurocutaneous island flap (10 x 20 mm) was outlined on the anterolateral aspect of the thigh at its middle third. It was designed in such a way that its short and long axes lay in the center of the distance between the anterior superior iliac spine and the anterior aspect of the knee joint. After identification and dissection of the neurovascular pedicle, the flap was raised in a lateral-to-medial direction without including the deep fascia. At this point the flap remained connected only by the pedicle and a strip of superficial fascia surrounding it. It was sutured in the same place. In the control group (N = 10), the pedicle of the flap was severed and the skin island was sutured back as a composite graft. All the experimental flaps survived well. In the control group, none of the flaps survived except one that was partially viable. The flaps in the experimental group were reelevated as neurocutaneous island flaps on day 7 for microangiographic study, and specimens were processed for histologic staining. Microangiography revealed the extent of neural vasculature and vascularization of the skin through cutaneous perforators. Histologic investigation demonstrated the neural vessels that were related closely to the superficial fascia. The authors propose a neurocutaneous island flap model in the lower extremity of the rat in which the survival of the flap depended mainly on the neural arterial supply. It was also demonstrated that the superficial fascia played a role as a connective tissue framework for conveying tiny neural blood vessels to reach the skin. This model may serve as a reproducible and reliable neurocutaneous island flap model for additional studies in this field.

In vivo Microscopic Study of Microcirculatory Perfusion of the Skin of the Foot in Peripheral Vascular Disease

Objectives: the aim of this study was to determine the proportion of perfused capillaries in the skin of the foot in patients with peripheral vascular disease, and compare it with that in normal subjects. Design: experimental study comparing capillary perfusion in nine patients with severe peripheral vascular disease (group 2) with seven age- and sex-matched control subjects (group 1). Materials and methods: using in vivo video microscopy, a method was developed to measure the ratio of perfused to total capillaries, by comparing the numbers of corresponding capillaries before and after intravenous injection of sodium fluorescein. Results: the mean percentage ratio of perfused to total capillaries was 54.7% (range 41–87%, standard deviation 16.5) in group 1, and 86.0% (range 62–100%, standard deviation 13.2) in group 2 (p<0.001, t-test). Conclusion: a significantly higher proportion of capillaries is perfused in the skin of the foot of patients with severe peripheral vascular disease than in that of normal subjects. This is of important pathophysiological significance and may have clinical implications with regard to the role of pharmacological intervention in severe limb ischaemia.

A new minimally invasive technique to show nerve ischaemia in diabetic neuropathy.

Experimental studies have shown that abnormalities of nerve microcirculation are important factors in the pathogenesis of diabetic neuropathy but there have been few clinical studies. We have applied microlightguide spectrophotometry to measure intravascular oxygen saturation (HbO2%) and blood flow in human sural nerve. We studied ten patients with mild-moderate sensory motor diabetic neuropathy, nine patients without neuropathy and nine control subjects. We took 300 measurements of oxygen saturation under direct visual control through a 1.9 mm rigid endoscope over three regions of the nerve. Spectrophotometric measurements of nerve fluorescence were taken after an intravenous injection of sodium fluorescein and the rate of increase in nerve fluorescence (rise time) was used as an indicator of nerve blood flow. Nerve oxygen saturation was reduced in patients with neuropathy compared with control subjects (67.1 +/- 2.2% vs 76.7 +/- 2.1%, p = 0.006). Fluorescein rise time was prolonged in patients with neuropathy compared with the control group (48.5 +/- 7.0 s vs 14.0 +/- 3.1 s, p = 0.001) suggesting impaired nerve blood flow. There was a correlation between rise time, nerve oxygen saturation, glycaemic control and sural nerve sensory conduction velocity (p < 0.01). The combination of microlight-guide spectrophotometry and micro-endoscopy provides a valuable minimally invasive technique for clinical investigation of nerve microcirculation. We have shown reduced nerve oxygenation and impaired blood flow in diabetic neuropathy and these findings strongly support a central role of microvascular disease in the pathogenesis of diabetic neuropathy.

Fluorescein Kinetics in Interstitial Fluid Harvested from Diabetic Skin during Fluorescein Angiography: Implications for Glucose Monitoring

Glucose monitoring based on sampling skin interstitial fluid (ISF) is being developed as an alternative to fingerstick blood glucose monitoring. Time delays between rapidly changing levels of glucose in blood and interstitial fluid have been reported in the literature to be between 5 and 20 minutes. This study investigated the time delay between the injection of a small molecular weight fluorescent tracer into the circulation and interstitial fluid. Diabetic subjects undergoing fluorescein angiography were studied. Skin ISF was sampled using a proprietary microporation and harvesting process. ISF was drawn through micropores created in the stratum corneum. After intravenous injection of sodium fluorescein, samples of ISF were drawn from 2 sites for 30 seconds over a period of 20 minutes. Fluorescence levels in ISF were measured with a fluorometer and used to create ISF fluorescein concentration versus time profiles. The ISF fluorescein versus time profiles were characterized by a rapid rise followed by a slow decay. The time to peak of the ISF fluorescein concentration ranged from 2-4 minutes for the patients studied. Intravenous injection of a bolus of low molecular weight fluorescent tracer was used to estimate the time delay between changing glucose levels in blood and ISF. The results indicate that the ISF sampling technology utilized here is capable of tracking rapidly rising levels of blood glucose.

Efficacy and safety of fluorescein angiography with orally administered sodium fluorescein

PURPOSE: To report the efficacy and safety of fluorescein angiography after oral administration of fluorescein solution in a large number of patients during a period of 8 years. METHODS: A total of 1,787 patients (2,625 eyes) underwent fluorescein angiography after oral administration of sodium fluorescein at Hara Eye Hospital, Utsunomiya, Japan, between January 1989 and March 1997. The ingestible solution was 10 ml of 10% sodium fluorescein, the same material generally used for injection in conventional fluorescein angiography. Retinal photography began 15 minutes after ingestion and continued for 1 hour. The camera and the photography and film processing techniques were the same as those used for conventional fluorescein angiography using injected sodium fluorescein. RESULTS: In 2,554 (97.3%) of 2,625 eyes, photographs adequate for clinical use were obtained. In 1,787 patients, no anaphylactic or other severe adverse effects were observed, and only 31 patients (1.7%) experienced minimal itching, discomfort, or nausea after oral sodium fluorescein intake. For conditions such as central serous chorioretinopathy, retinal vein occlusion, diabetic retinopathy, and cystoid macular edema, sufficient information for clinical use was obtained. CONCLUSIONS: Fluorescein angiography using orally administered sodium fluorescein is generally effective and safe in standard clinical practice.

Flap Prefabrication

A new experimental model of a vascular carrier to prefabricate a "secondary" island flap, the popliteal musculovascular pedicle, was developed in the rat. Using quantitative skin-surface fluorometry 30 minutes after sodium fluorescein injection and a flap survival area in the prefabricated 8 x 2.5-cm abdominal composite island flap, we compared the revascularization ability of our muscular carrier to nonrevascularized controls: the skeletonized arteriovenous pedicle and the fasciovascular pedicle. The free composite graft with no vascular carrier exhibited near-total necrosis. The skeletonized vascular pedicle demonstrated 15.2% +/- 7.8% perfusion of normal skin on dye fluorescence index measurements and 50% flap survival. The fasciovascular pedicle exhibited better revascularization, with a dye fluorescence index of 36.2 +/- 15.5 (p < 0.01) and 90% +/- 10% flap survival (p < 0.001). India ink injection study and histological examination of our model provided visual evidence of revascularization from the musculovascular pedicle, along with preservation of the carrier's muscular architecture. The musculovascular pedicle is a reliable carrier for making new, vascularized composite flaps.

The revascularization interface in flap prefabrication: a quantitative and morphologic study of the relationship between carrier size and surviving area.

To make a quantitative assessment of the relationship between size of vascular carrier and surviving area in a prefabricated flap, vascular carriers composed of the superficial epigastric arteriovenous bundles and a surrounding fascial patch with varying sizes were transferred under a 7- x 7-cm bipedicled abdominal skin flap in a rat model. Seven days later, the abdominal flaps were raised as composite island flaps connected only by the superficial epigastric vascular pedicle, transferred, and then sutured back into place. Immediately after replacement, the degree of revascularization was assessed using quantitative skin fluorometry, after intravenous injection of sodium fluorescein. At 7 days after elevation as an island flap, the area of skin flap surviving was recorded and plotted on a map depicting the original flap surface. High levels of fluorescence appeared on the flap surface where the carrier was tacked underneath. The prefabricated island flaps survived with a circular shape up to approximately 4 times the radius of the vascular carrier. When the distance was converted into area, theoretically, an area 13 times the area of the vascular carrier survived, regardless of its size in this experimental model. Histologic examination revealed connections of fine capillaries between the carrier and flap.

Microvascular changes in arterial occlusive disease: target for pharmacotherapy.

The main techniques which have been used to study skin microcirculation in patients with peripheral arterial occlusive disease include intravital microscopy with and without the use of fluorescent dyes, laser Doppler fluxmetry and transcutaneous oximetry. In patients with severe ischaemia (rest pain or incipient gangrene) the number of perfused skin capillaries is reduced. Parallel to the decreased number of microvessels containing blood, transcutaneous oxygen tension is low or even approaches the zero level. The tendency to oedema formation is documented by increased leakage of intravenously injected sodium fluorescein at the capillary apex of foot skin ('candlelight phenomenon'). Laser Doppler flux at rest may still be within the normal range even in advanced disease, since the sample volume of these instruments also contains non-nutritive shunt vessels. However, reactive hyperaemia after arterial occlusion is decreased and delayed in peripheral ischaemia. Whereas rhythmic low-frequency vasomotion is significantly enhanced in patients with intermittent claudication, vasoparalysis with no flux fluctuations prevails in patients with critical ischaemia.

Hyperventilation enhances transcapillary diffusion of sodium fluorescein.

Voluntary hyperventilation (HV) provokes hemoconcentration due to a loss of fluid from the intravascular space. In 10 healthy male volunteers the hypothesis was tested whether HV increases transcapillary fluid shift into the interstitial compartment. For this purpose, fluorescent light intensity (FLI) alterations after intravenous injection of sodium fluorescein (Na fluorescein) before and during 3 min of HV were determined. Concomitantly, temperature and microvascular skin flux (laser Doppler fluxmetry, LDF) were recorded continuously. Hematocrit and serum proteins, as markers of hemoconcentration, increased significantly from 41.2 +/- 2.3 to 42.7 +/- 2.0% (p = 0.0023) and from 69.5 +/- 3.4 to 72.9 +/- 3.0 g/l (p = 0.0005, respectively). Skin temperature and LDF showed no changes during HV compared to baseline levels. Interstitial FLI indicating transcapillary diffusion of Na fluorescein was significantly higher (p < 0.001) during HV compared to the values recorded during the baseline period. The exact mechanism of enhanced transcapillary diffusion of Na fluorescein is not known. The distinct increase in FLI without a significant change in microvascular skin flux suggests an HV-induced increase in capillary pressure or an enhancement in capillary permeability for water and small solutes.