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PubMed1996

The use of enzyme activated milk for in vitro simulation of prosthetic valve thrombosis.

BACKGROUND AND AIM OF THE STUDY: Thrombosis remains a serious risk for patients with artificial heart valves and may be attributed in part to adverse blood flow patterns. Although the final assessment of a valve must follow years of clinical experience, in vitro flow analyses give valuable information prior to implantation. Laser Doppler velocimetry and computational fluid dynamics enable quantitative flow analyses to be made in vitro. Whilst these techniques highlight features such as areas of stasis, turbulence and high shear which may predispose to thrombus formation, the complex and time varying nature of the flow through valves makes it difficult to predict accurately potential sites of thrombus deposition and accumulation. METHODS: A technique is described which uses enzyme activated milk as a coagulable blood analogue to indicate flow related clotting. Milk flowing past a test valve or object was activated to clot downstream of the test piece after a certain time period. Milk clot was deposited clot at sites determined by the local flow disturbances. Milk clotting patterns produced on and around standard objects were compared with the transient flow patterns predicted around identical configurations to test the validity of computational flow analyses for predicting flow disturbances leading to clotting. Milk clots on valves were compared with examples of thrombus found on explanted valves of the same design. RESULTS: The sites of deposition were consistent with the predicted flow patterns around the two configurations of flow obstruction studied. Milk clotting patterns on valves corresponded with the early stages of thrombus on explanted valves of the same design. CONCLUSIONS: Whilst a coagulable milk mixture may be used to evaluate the risk of flow induced clot adherence, care must be taken when extrapolating to the clinical situation as other factors such as material properties, blood chemistry and concomitant disease must also be considered.

Animals↗
PubMed1996

Prostaglandin E1 ameliorates decreased tracheal blood flow after esophagectomy and aggressive upper mediastinal lymphadenectomy for esophageal carcinoma.

BACKGROUND: Aggressive upper mediastinal lymphadenectomy contributes to a better survival rate after esophageal resection to treat esophageal carcinoma, but it also increases postoperative respiratory complications. Devascularization of the airways because of mediastinal dissection is considered to be a cause of respiratory dysfunction. The present study attempts to clarify whether or not tracheal blood flow (TBF) deteriorates after esophagectomy and, if so, whether or not intravenous prostaglandin E1 (PGE1) attenuates the deterioration. STUDY DESIGN: Patients undergoing esophagectomy and aggressive upper mediastinal lymphadenectomy for the treatment of esophageal carcinoma (EC group, n = 12) or abdominal surgery (control group, n = 6) were enrolled in this study. Measurement of TBF was performed using a laser Doppler flowmeter. Changes in TBF induced by surgery and postoperative intravenous PGE1 were studied in both groups. RESULTS: The TBF deteriorated significantly in the EC group (21.78 +/- 9.60 to 11.24 +/- 4.45 mL/minute/10(-1) kg, p = 0.002) but did not change in the control group (26.13 +/- 6.84 to 26.61 +/- 4.69 mL/minute/10(-1) kg, p = 0.7371). Postoperative intravenous PGE1 partially, but significantly, reversed the deterioration in TBF in the EC group (11.53 +/- 4.58 to 14.87 +/- 6.30 mL/minute/10(-1) kg, p = 0.0207) but did not effect the control group (29.41 +/- 7.89 to 29.41 +/- 8.79 mL/minute/10(-1) kg, p = 0.9989). CONCLUSIONS: Esophagectomy and aggressive upper mediastinal lymphadenectomy cause a deterioration in TBF that is partially attenuated by PGE1.

Alprostadil↗
PubMed1996

[Skin circulation--measurements with laser-doppler].

The change in the skin blood flow (SkBF) due to vasoconstriction or vasodilation of the cutaneous vessels is a thermoregulative response during cold or heat stress, respectively. SkBF is estimated in different ways, for instance by measuring body and skin temperature, by venous occlusion plethysmography or by radioactive xenon 133 clearance. The application of laser light based on Doppler shift is a relatively new method for SkBF measurement. At present, several companies operating throughout the world produce laser-Doppler flowmeters. The laser-Doppler method is designed particularly for cutaneous tissues and it facilitates monitoring of the blood flow, however, the measurement results are relative. Depending on the wavelength, the laser light penetrates into the tissue at different depths (from 0.6 to 1.5 mm). The laser light with the wavelength of 632.8 nm enables the measurement of thermoregulative and nutritional blood flow in the skin. The range of the measurement and application of the device provide an opportunity for developing a universal standard. The European Community has published a guide for laboratory quality assurance aimed at improving the standard of measurement records.

Body Temperature Regulation↗
PubMed1996

Urinary bladder blood flow changes during the micturition cycle in a conscious pig model.

PURPOSE: To develop a method using laser Doppler flowmetry in conscious pigs, which allows the accurate simultaneous measurement of cystometric and cardiovascular parameters together with changes in vesical blood flow. The animal model was then used to investigate the changes in blood flow in the urinary bladder which occur during the micturition cycle. MATERIALS AND METHODS: Seven large white female pigs were subjected to chronically implanted vascular access and urodynamic catheters as well as an intramural vesical laser Doppler probe. The animals underwent repeated conscious urodynamics with simultaneous measurement of cardiovascular, urodynamic and vesical blood flow parameters. RESULTS: The model shows both compliant and low-compliance behavior and allows greater investigation of the effects of intravesical pressure on blood flow. Blood flow is not altered, during compliant filling and voiding transiently decreases flow to 38% of resting levels, with a rapid return to normal. Low-compliance filling results in a progressive fall in blood flow to a minimum of 45% of normal. At all times an inverse relationship between intravesical pressure and blood flow is maintained. CONCLUSIONS: The pig model proved to be well suited to the experimental conditions and provided reproducible results. The principal determinant of blood flow within the wall of the bladder is the pressure within its lumen. During normal filling the blood supply of the bladder is able to adapt to the large increase in surface area which occurs, maintaining blood flow until the pressure increases.

Animals↗
PubMed1995

Effect of a short course of indomethacin on gastric mucosal blood flow using endoscopic laser-Doppler velocimetry.

OBJECTIVE: To assess the effect of a short course of indomethacin on gastric mucosal blood flow (GMBF). METHODS: Patients with musculo-skeletal pain of recent origin and were prescribed a short course of therapy with indomethacin (25 mg tid for 7 days) were studied Baseline measurements of GMBF were carried out using endoscopic laser-Doppler velocimetry prior to starting indomethacin. At sites on the antrum, incisura, lesser and greater curvatures, and fundus. GMBF measurements were repeated after indomethacin therapy, as above and also on sites of erosions, it any. RESULTS: Baseline GMBF at sites on the antrum, incisura, greater and lesser curvatures, and fundus were (mean) 8.6, 7.9, 8.8, 8.5 and 8.7 volts, respectively. Post-therapy values did not differ from the corresponding baseline values (8.7, 8.5, 8.6, 8.6 and 8.3 volts, respectively). However, ten of the 16 patients developed gastric mucosal erosions and the mean GMBF on these sites of erosion was significantly reduced (6.6 +/- 1.3 volts, p < 0.05). CONCLUSIONS: A short course of indomethacin therapy produces a patchy decrease in blood flow in the gastric mucosa and erosions were seen in these areas.

Adult↗
PubMedDate not supplied

Influence of endotoxemia on hepatic energy metabolism in rats with obstructive jaundice.

BACKGROUND/AIMS: A secondary insult in patients with obstructive jaundice can lead to multiple system organ failure. We evaluated the influence of endotoxin on hepatic energy metabolism and hepatic tissue blood flow in obstructive jaundiced rats. MATERIAL AND METHODS: Male Sprague-Dawley rats were divided into a control group, an endotoxin administration group, an obstructive jaundice group, and an obstructive jaundice with endotoxin administration group. To evaluate hepatic energy metabolism, we have measured arterial blood ketone body ratio, and arterial blood total ketone body concentration. Hepatic tissue blood flow was determined by laser Doppler velocimetry. RESULTS: In the endotoxin administration group, no change was observed in hepatic energy metabolism. However, the obstructive jaundice group was associated with decreased hepatic tissue blood flow shortly after the outset of jaundice, while no change was observed in hepatic energy metabolism until 3 weeks later. In the obstructive jaundice with endotoxin administration, a significant decrease in hepatic tissue blood flow and an increase in hepatic energy metabolism were measured. CONCLUSION: Endotoxin administration alone had no influence on hepatic energy metabolism, while endotoxin administration in the presence of obstructive jaundice results in a rapid decrease in hepatic energy metabolism. This occurred as a result of the secondary insult of endotoxin in the setting of decreased hepatic tissue blood flow caused by obstructive jaundice.

Animals↗
PubMedDate not supplied

Comparative effects of exposure to different light sources (He-Ne laser, InGaAl diode laser, a specific type of noncoherent LED) on skin blood flow for the head.

BACKGROUND AND OBJECTIVE: This study assessed the effects of optic stimuli emitted by three different light sources on head skin blood flow. MATERIALS AND METHODS: The irradiation effects of the He-Ne laser (632.8 nm, 10 mW, total energy appr. 9.4 J), the InGaAl diode laser (670 nm, 60 mW, appr. 108 J) and monochromatic light (635 nm, 112.5 mW, appr. 202.5 J) were measured using laser Doppler technology. The corresponding fluences (energy densities) varied from 0.01 J/cm2 (He-Ne) to a range of 0.12-0.72 J/cm2 (InGaAl) and 0.22-1.36 J/cm2 (LED). The investigation was completed under single-blind, placebo-controlled conditions where the subjects (10 male healthy volunteers) were exposed on two occasions to the placebo (LED)-device against the laser (He-Ne or InGaAl). RESULTS: A short lasting vasodilation, a 54 per cent increase (p < 0.05) in skin blood flow was seen after the InGaAl irradiation (fluences between 0.12-0.36 J/cm2) whereas the non-coherent monochromatic irradiation (0.68-1.36 J/cm2) used in this particular study decreased blood flow by 36 per cent (p < 0.05). The He-Ne irradiation (0.01 J/cm2) had no effect. Skin temperature changes were insignificant. CONCLUSIONS: Skin blood flow changes seemed to be related more on radiant exposures then coherency.

Adult↗
PubMed1996

The effect of aminophylline on pharmacological stress with intravenous adenosine.

Myocardial perfusion imaging with adenosine pharmacological stress may be useful in patients with obstructive lung disease who are unable to exercise. However, these patients are often treated with medications containing theophylline, which is an adenosine antagonist. This study assessed the effect of aminophylline on coronary vasodilation produced by intravenous adenosine as commonly used during cardiac imaging. Changes in coronary flow velocity (measured by intracoronary Doppler catheter) heart rate, arterial pressure and changes in coronary resistance were measured during intravenous infusion of adenosine at 140 micrograms/kg/min before and after aminophylline, 6 mg/kg intravenously in 12 patients. After aminophylline infusion, the theophylline level averaged 14 +/- 1 microgram/mL. The coronary hemodynamic effects of adenosine were markedly attenuated by aminophylline. Adenosine increased coronary blood flow velocity by 192 +/- 39% at control and 78 +/- 16% after aminophylline (P < .05 v control). Adenosine produced a 63 +/- 5% decrease in coronary vascular resistance at control and 40 +/- 6% (P < .05) after aminophylline. The utility of myocardial imaging techniques using coronary vasodilation with intravenous adenosine may be reduced in patients treated with theophylline-containing preparations.

Adenosine↗
PubMed1996

Left ventricular cavitary geometry and dynamic intracavitary left ventricular obstruction during dobutamine stress echocardiography.

To investigate the relationship between left ventricular cavity geometry and dynamic intracavitary left ventricular obstruction occurring during dobutamine stress echocardiography, we evaluated 44 patients who underwent dobutamine stress echocardiography. Dynamic intracavitary left ventricular obstruction appeared in 10 (23%) patients (Group 1), and was absent in the remaining 34 patients (Group 2), during dobutamine stress echocardiography. The ratio of the apicalto-narrowest mid-left ventricular minor-axis dimension (D1/D2), as an index of the left ventricular cavitary geometry, was measured in the baseline two dimensional apical long-axis view. The left ventricular out-flow blood Doppler velocity was measured in the apical long-axis or five-chamber view at each stage during dobutamine infusion. Left ventricular end-systolic dimension was smaller (21 +/- 4 mm v 29 +/- 6 mm; p< .01), percent fractional shortening of the left ventricle was greater (51 +/- 4% v 39 +/- 8%, P>.01), and D1/D2 was greater (1.13 +/- 0.08 v.0.96 +/- 0.09; p < .0001) in Group 1 than in Group 2 in the baseline echocardiogram. Maximal out flow blood Doppler velocity during dobutamine infusion correlated moderately with percent fractional shortening of the left ventricle (r = .53; P < .01) and D1/D2 (r = .60; P < .0001). Dynamic intracavitary left ventricular obstruction, defined as an elevated intracavitary Doppler flow velocity with late-systolic peaking, was not related to the presence of left ventricular hypertrophy or the development of hypotension during dobutamine infusion. We conclude that dynamic left ventricular intracavitary obstruction during dobutamine infusion is associated with a characteristic (narrower-waisted) left ventricular cavitary geometry and increased contractility.

Adult↗
PubMed1996

Laser Doppler vibrometer (LDV)--a new clinical tool for the otologist.

We describe a laser Doppler system (LDS) that can be used clinically for the measurement of tympanic membrane (TM), malleus and prosthesis head displacement in response to sound inputs of 80-to 100-dB sound-pressure level (SPL). It also has the potential for use in the operating room to perform measurements of prosthesis and stapes displacement. The information provided by such testing gives the otologist knowledge of TM and ossicular function that is unique in evaluating middle ear function; it should help select the best type of reconstruction in a given case and direct us toward new and better methods of TM and ossicular reconstruction. The results of umbo displacement measurements in 95 human ears are reported. Examples are provided of LDS measurements in representative ears and how they can be of help to the clinician. The potential of multisite TM-displacement testing is demonstrated in two temporal bones, including before and after partial ossicular replacement prosthesis (PORP) insertion.

Audiometry, Pure-Tone↗
PubMed1996

[Effects of beta-adrenergic blockers on retinal circulation].

We evaluated the effects of 0.5% betaxolol hydrochloride and 0.5% timolol maleate on retinal blood flow. We measured the diameter of the retinal artery (Da) and vein (Dv), and retinal venous blood flow rate (V) in 8 healthy young volunteers by laser speckle velocimetry before and after the application of betaxolol or timolol topically to both eyes daily for one week. There were no any significant changes. Da before and after the application of betaxolol was 114.2 +/- 6.3 (mean +/- standard deviation) microns and 115.6 +/- 6.7 microns and before and after the application of timolol, 117.5 +/- 12.7 microns and 101.3 +/- 9.5 microns. Dv before and after the application of betaxolol was 149.5 +/- 11.1 microns and 148.4 +/- 13.3 microns, and before and after the application of timolol 148.5 +/- 9.2 microns and 146.2 +/- 10.3 microns. V before and after the application of timolol was 12.3 +/- 2.6 mm/s and 12.6 +/- 2.4 mm/s, and before and after the application of betaxolol, 11.6 +/- 1.5 mm/s and 11.4 +/- 2.1 mm/s. Thus one-week application of the beta-blockers, betaxolol and timolol did not change the retinal arterial or venous blood flow.

Adolescent↗
PubMed1996

Age-related changes in gastric blood flow in rats.

The present study was designed to examine the influence of aging on the gastric blood flow, a major mucosal protective mechanism against experimental gastric mucosal injury, basally and after treatment with acid, a known stimulant of gastric blood flow. Our data demonstrated that aging was associated with a significant decline in basal gastric blood flow (both mucosal and serosal). However, there were no significant differences in acid-induced increases in gastric blood flow between the young and aged animals. These findings suggest that aging is associated with selective and specific reductions in mucosal protective mechanisms that may predispose aged animals to gastric mucosal injury.

Aging↗
PubMed1996

The accuracy of magnetic resonance phase velocity measurements in stenotic flow.

Nuclear magnetic resonance (MR) can be used to measure velocities in fluid flow using the technique of phase velocity mapping. Advantages of MR velocimetry include the simultaneous mapping of the entire flow field through a non-contacting, magnetic window. The phase velocity mapping technique assumes that velocity is constant over the measurement time (typically around 10 ms). For many fluid flows, this assumption is not valid. The current study showed that MR phase velocity measurements of velocity through stenotic flow can be in error by over 100% immediately upstream and downstream of the stenosis throat and by 20% far downstream of the throat in comparison with laser Doppler anemometer measurements taken at the same location. Highly turbulent flow also led to significant errors in velocity measurement. These errors can be attributed to several sources including low signal-to-noise ratio, additional phase shifts due to non-constant velocities, and non-stationary transit-time effects. Velocity measurement errors could be reduced to under 30% at all measurement locations through the use of MR sequences with high signal-to-noise ratios, low echo times, and thick slices.

Arterial Occlusive Diseases↗
PubMed1992

[Microcirculatory changes in mitral prolapse as an expression of a systemic change in the connective tissue].

Many authors hypothesize that mitral valve prolapse (MVP) can be, in most cases, only a clinical sign of a primitive and systemic disorder of the connective tissue, like in Marfan Syndrome (MS). In our previous works we supported the presence of morphological and functional alterations of the microcirculation in patients affected by MS. In order to characterize a possible common denominator between these pathologies we have studied the cutaneous microcirculation in a group of patients affected by MVP, divided into 2 groups: anatomic MVP (MVP) and MVP syndrome (MVPS). The morphologic parameters have been investigated by nailfold capillaroscopy while digital laser-Doppler was used to study skin flowmetry. The results have been compared with a control group. Capillaroscopic remarkers showed an architecturally disorganized microvasculature with aspects related to a reduced compactness of the microvasculature unit with a significatively higher score compared with controls (7.3 +/- 2.9 vs 3.6 +/- 1 p less than 0.0005). Laser-Doppler flowmetry showed a significatively reduced rest flow; ischemic test showed: spike time 48.9 +/- 36.9 vs 15.3 +/- 7.7 s (p less than 0.0005), hyperemic acme 6.6 +/- 2.7 vs 12.5 +/- 8.4 UP (p less than 0.002); % increase 32.1 +/- 20.2 vs 51.5 +/- 15.4 (p less than 0.002). Thermic test showed a significatively higher thermic acme 8.7 +/- 4.2 vs 12.6 +/- 9.11 UP (p less than 0.05). These results appeared to be correlated with stage pathology as it was observed a severe microvasculature disorders in MVPS. Therefore we suppose that a phenotypic continuum may exist between MS and MVP.

Adult↗
PubMed1994

Effects of neural blockade and general anesthesia on the laser-Doppler skin blood flow waves recorded from the finger or toe.

Effects of neural blockade and general anesthesia on the basic wave (BW) and the reflex wave (RW) among the laser-Doppler (L-D) skin blood flow waves recorded on the finger or toe were studied in 2 volunteers and 42 patients. The BW was continuous, rhythmic and independent of respiratory movements. The RW, which was induced by a deep inspiration or a snapping sound, was a transient marked reduction in blood flow. The BW was almost flattened and the RW was no longer induced at the finger under complete wrist block (n = 2), or under cervical or upper thoracic epidural anesthesia extended caudally over T7 (n = 2). On the other hand, the BW was still detected with reducing frequency and the RW could be provoked with one exception at the finger on the side with a sympathetic ganglion block at the C6 vertebral level (n = 14). The BW and RW at the toe were retained under lumbar subdural anesthesia (n = 6) as well. However, under the combination of lumbar subdural anesthesia and lower thoracic epidural anesthesia extending rostrally over T4 (n = 6), both the BW and the RW disappeared at the toe. In the course of deepening nitrous oxide/enflurane anesthesia (n = 10), the BW gradually reduced in frequency until it was almost flattened, and it became difficult to provoke the RW. L-D flowmetry of the finger or toe could be a useful clinical measure for detecting the presence or absence of sympathetic function controlling cutaneous vasomotion.

Adult↗
PubMed1982

Current status of noninvasive tests in the diagnosis of peripheral arterial disease.

In this review of the current status of the vascular laboratory, the major emphasis has been upon those tests that have become well-established and documented, including resting pressure, pulse volume measurements, velocity studies, and three stress measurements--exercise ankle pressure, postocclusive reactive hyperemia, and the toe pulse reappearance time. Additional technology that may have application to peripheral arterial disease includes photoplethysmography, transcutaneous oxygen tension, laser-Doppler velocimetry, fluorescein angiography, infrared thermography, and transcutaneous electromagnetic flowmetry. These techniques, which are currently in development and experimental trial, were not discussed but are likely to provide significant additional information. The future role of the vascular diagnostic laboratory in the area of peripheral arterial occlusive disease appears clear. It has already become a standard resource of the community hospital and tertiary referral center. Its functions will become more and more generally accepted with time as newly graduating physicians who have been exposed to this technology enter the practice of medicine. It should permit obtaining an evaluation of all patients at the expert level, aid in the education of all physicians concerned with peripheral arterial disease, and play an important part in guaranteeing a higher level of patient care than has heretofore been available.

Arterial Occlusive Diseases↗
PubMed1988

Partitional measurement of capillary and arteriovenous anastomotic blood flow in the human finger by laser-Doppler-flowmeter.

This study was made to see whether changes in blood flow through the capillaries and arteriovenous anastomoses (AVA's) of the human finger can be measured by noninvasive flowmetry. Total finger blood flow (FBF) was measured by venous occlusion plethysmography; blood flow was measured by a laser-Doppler flowmeter (ADVANCE, ALF-2100, Tokyo, Japan) using probes with optic fiber separations of 0.3 mm (LDF-0.3) and 0.7 mm (LDF-0.7). The maximum sensitivities for LDF-0.3 and LDF-0.7 were at depths of 0.8 and 1.2 mm from the tissue surface respectively. Two series of experiments were performed on separate days. In the first series the test hand was immersed in a water bath whose temperature (Tw) was 25 degrees C at an ambient temperature (Ta) of 25 degrees C. Tw was raised to 35 degrees C (local hand warming), which was then followed by an increase in Ta to 35 degrees C (whole body warming). FBF, LDF-0.3, and LDF-0.7 increased during these thermal stimulations. However, the relationship of FBF to LDF-0.3 showed two different regression lines. In contrast, the relationship of FBF to LDF-0.7 showed a single regression line. In the second series, with Ta at 35 degrees C, the test hand was immersed in a water bath at Tw 35 degrees C. Tw was then raised every 10 min by 2 degrees C steps from 35 to 41 degrees C. At Tw 39-41 degrees C, FBF and LDF-0.7 in the test hand were significantly decreased compared with those at Tw 35 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗