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Results for “Laser-Doppler Flowmetry”

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PubMed1996

[Influence of hemodialysis on changes in cerebral artery blood flow velocity in patients with chronic renal failure].

The effect of hemodialysis on the cerebral circulation have been inadequately studied. Because of repeatability, safety and non-invasiveness transcranial Doppler sonography is well suited for evaluation of cerebral circulation and for estimation of cerebral blood flow during hemodialysis as well. The aim of our study was to find out whether hemodialysis affects the velocity of blood flow in extra- and intracranial arteries and in what way. 41 patients aged 18-71 (mean 43.9 +/- 13) years suffering from chronic renal failure made up the investigation group. We investigated 17 men and 24 women. Doppler examination was done to each dialized patient immediately before and then 120 and 240 minutes after the onset of hemodialysis. We used pulsed wave Doppler (TC2-64B, EME). Mean blood flow velocities were obtained from extracranial (CCA, ICA, ECA) and intracranial vessels (MCA, ACA, PCA). Simultaneously the series of biochemical blood parameters and arterial blood pressure were monitored. On the basis of investigation results the following conclusion have been drawn: Hemodialysis significantly affects on changes of blood flow velocities in extra-an intracranial arteries. Above mentioned changes consist in decrease of blood flow velocity in both CCA, left ICA, both MCA and PCA and right ACA.

Adolescent↗
PubMed1996

Multimodal monitoring and assessment of cerebral haemodynamic reserve after severe head injury.

This article contains an overview of selected clinical techniques employed for neurointensive care monitoring and testing of cerebral autoregulation of patients following severe head injury. Multiple modalities are used for monitoring of cerebral haemodynamic reserve, including intracranial pressure, cerebral perfusion pressure (CPP), blood flow velocity (FV) in the middle cerebral artery (MCA), jugular bulb oxygen saturation, laser-Doppler cortical flowmetry, near infrared spectroscopy of cerebral cortex, tissue oxygenation, and microdialysis. Large volumes of information demand specialised computer support for sensible interpretation and filtration of artifacts. Methods of testing of cerebral autoregulatory reserve based on transcranial Doppler ultrasonography are reviewed. Repetitive or continuous assessment is important in practice as autoregulatory reserve may fluctuate in time. Static and dynamic rates of autoregulation show sensitivity to carbon dioxide-induced vasodilatation, but fail to correlate with outcome following head injury. The carotid artery compression test, useful for assessment of patients after subarachnoid haemorrhage, has yet to prove its usefulness in head injury. Continuous waveform analysis of MCA FV and CPP correlates with coma score after resuscitation and outcome and hence may be considered as a robust method for the assessment of autoregulation in ventilated head trauma patients.

Cerebrovascular Circulation↗
PubMedDate not supplied

Laser Doppler perfusion imaging of proximal interphalangeal joints in patients with rheumatoid arthritis.

OBJECTIVE: A non-invasive imaging technique (laser Doppler perfusion imaging-LDI) based on measurement of backscattered Doppler-broadened near infra-red laser radiation was used to provide two-dimensional images of perfusion over the proximal interphalangeal (PIP) joints of a group of normal subjects compared to a group of patients with rheumatoid arthritis (RA). RESULTS: Some PIP joints of the RA group showed areas of increased perfusion whereas normal subjects showed much less variation in perfusion between joints. These hyperaemic areas arose from the underlying joint, as scans taken with a less penetrating red laser did not show such areas. CONCLUSION: Apart from its obvious dermatological uses, LDI could be employed to image hyperaemia associated with a variety of inflammatory conditions affecting subcutaneous structures.

Adult↗
PubMed1996

Measurement of optic nerve head circulation: comparison of laser speckle and hydrogen clearance methods.

Microcirculation in the optic nerve head (ONH) in the ocular fundus was measured noninvasively using the recently developed laser speckle circulation analyzer. Results were compared with capillary blood flow (CBF) measurements made by the hydrogen clearance method. The ONH blood flow of six normal rabbits was measured simultaneously by both methods. Inhalation of 10% carbon dioxide (CO2) increased the CBF by 22% (hydrogen clearance method). Intravenous injection of endothelin-1 (ET-1) (10(-10) mol/kg) decreased the CBF by 19%. Significant correlations were found between the NB (normalized blur) value by the laser speckle method and CBF (r = 0.38, P < 0.05, n = 30) and also between the relative change of NB and CBF (r = 0.92, P < 0.01, n = 30) in the ONH. This indicates that evaluation of the NB change in the ONH is as accurate with the laser speckle method as with the hydrogen clearance method, giving a basis for the clinical application of the laser speckle method of measuring ONH circulation.

Administration, Inhalation↗
PubMedDate not supplied

[Comparative hydrodynamic evaluation of variants of the cavopulmonary anastomosis].

An analysis of the range of postoperative complications following cavapulmonary anastomosis reveals a number of medical engineering problems in surgery techniques. The severity of the surgery due to the nonphysiological rearrangement of blood circulation makes it necessary to search for the most optimal types of anastomosis in terms of the hemo- and hydrodynamics of circulation. To optimize the performance of cavapulmonary anastomosis, namely to define the mutual localization and orientation of the implanted anastomoses against the axes of inflow and outflow, hemo- and hydrodynamic studies were made by Doppler laser anemometry. From the hydrodynamic point of view, the findings indicate the most optimal type of cavapulmonary anastomosis-cruciform anastomosis by displacing 0.5 d from the outflow axis at an angle of 60ë5 degrees.

Anastomosis, Surgical↗
PubMed1996

Role of AT1 receptors in the central control of sympathetic vasomotor function.

1. In a number of species, high concentrations of angiotensin II (AngII) receptors have been found in the rostral ventrolateral medulla (RVLM) in the hindbrain, which is an important region involved in the modulation of sympathetic vasomotor tone. The present review describes studies in which the contribution of angiotensin receptors in the brainstem to cardiovascular regulation, in particular sympathetic vasomotor reflexes, has been examined in conscious and anaesthetized rabbits. 2. In conscious rabbits, fourth ventricular infusions of AngII produced dose-dependent pressor responses as does 400 times less than equipressor intravenous doses. Chronic baroreceptor denervation increased the sensitivity to AngII by 1000-fold. Administration of prazosin i.v. blocked the pressor response, suggesting that the mechanism involved sympathetic vasoconstriction. 3. The pattern of haemodynamic changes in response to AngII injected into the fourth ventricle (4V) involved decreased total peripheral conductance and mesenteric conductance, but a rise in hindlimb conductance. Sinoaortic denervation changed the hindlimb fall in conductance to an increase, suggesting that muscle vasomotor pathways were particularly inhibited by baroreceptor feedback mechanisms. 4. In anaesthetized rabbits, infusion of AngII into the RVLM increased blood pressure and transiently increased resting renal sympathetic nerve activity. The renal sympathetic baroreflex curves were shifted to the right and the upper plateau of the sympathetic reflex increase was markedly increased. 5. The pressor actions of 4V AngII were blocked by administration of a peptide antagonist injected into the RVLM or by the angiotensin AT1 antagonist losartan injected into the 4V. These results suggest that mainly AT1 receptors are involved and that the RVLM is a likely candidate site for the modulation of the renal sympathetic baroreflex. 6. Losartan administration into the 4V in conscious rabbits increased resting renal sympathetic tone and enhanced renal sympathetic baroreflex and chemoreflexes. 7. Our studies suggest that there are sympathoexcitatory AT1 receptors in the RVLM accessible to AngII from the cerebrospinal fluid. In addition, an AT1 receptor pathway normally inhibits the sympathoexcitation produced by baroreceptor unloading or chemoreceptor activation. The effect of losartan suggests that there is greater tonic activity within the sympathoinhibitory pathways. These two actions suggest that angiotensin receptors in the brainstem modulate sympathetic responses to specific afferent inputs, thus forming part of a potentially important mechanism for the integration of characteristic autonomic response patterns.

Analysis of Variance↗
PubMed1996

[The new laser Doppler velocimetry for the measurement of retinal circulation and its clinical application].

We developed a new laser Doppler instrument to measure retinal blood flow. This instrument is equipped with an eye tracking system, which maintains the laser beam on the retinal vessel, thus enabling the measurement of patients with poor visual acuity and poor fixation. In diabetic patients even those without retinopathy, the retinal blood flow decreased compared to the control subjects. This was mainly the result of decreased retinal blood speed and no significant change in the arterial diameter. In diabetic patients requiring panretinal photocoagulation, we studied the regional changes in retinal blood flow following superior or inferior half fundus argon laser treatment, which produced a significant retinal blood flow decrease only in the treated area. We also studied the retinal circulatory changes in retinal branch vessel occlusion. In retinal branch view occlusion, the blood flow in arteries supplying the affected lesion showed 80-90% decrease compared to the arteries supplying the unaffected region. In retinal branch artery occlusion, the retinal blood flow in occluded arteries showed 40-50% decrease compared to the non-occluded arteries. In one patient with retinal branch vein occlusion in whom we measured the retinal blood flow over 18 months, the blood flow increased with the development of collateral vessels. The results showed that retinal circulatory abnormalities can be also evaluated quantitatively during the course of retinal vascular occlusive disease by our newly developed laser Doppler instrument, which proved that this instrument is a clinically very useful tool.

Adult↗
PubMed1996

[Macro- and microcirculation study in diabetic patients].

In diabetics, vascular examination may consider great and medium arteries and microcirculation. The aim of this study is correlation between stenosis in carotid and femoral bifurcation, ultrasound biopsy, and laser-Doppler measurements of distal microcirculation in diabetics. During a six month period, we have examined 90 diabetics in the diabetological service of the Civita Castellana Hospital (Viterbo, Italy), asymptomatic for any vascular distal, cerebral or coronary disease. Subjects were 49 +/- 20 years old with 15 +/- 5 years of diabetes; glycosilate haemoglobin was 7% (mean). 70% of diabetics (62% type I, 38% type II) had an altered veno-arteriolar reflex and 30% of these an ultrasound biopsy value of more than 25. These data demonstrate that most diabetic subjects develop an early, preclinical neuropathy that is directly proportional to the arterial wall condition.

Adult↗
PubMed1996

Postocclusive reactive hyperemia estimating peripheral vascular resistance: a noninvasive method to predict outcome of infrainguinal vascular reconstructions?

OBJECTIVE: The peripheral vascular resistance is an important factor determining the outcome of infrainguinal revascularizations. When measured intraoperatively, it correlates to graft patency, but to select patients to surgery a preoperative, preferably noninvasive, method is necessary. The aim of the present study is to test if parameters recorded during postocclusive reactive hyperemia can be used for that purpose. EXPERIMENTAL DESIGN: This prospective study compares patients with occluded grafts within 30 days postoperatively to patients with patent grafts. SETTING: University Hospital. PATIENTS: Thirty patients with critical ischemia scheduled for infrainguinal bypass surgery. MEASURES: Correlations between intraoperatively measured peripheral resistance and preoperatively recorded parameters of postocclusive reactive hyperemia. The ability of the values to predict outcome. RESULTS: Peripheral resistance correlated significantly to two parameters during postocclusive reactive hyperemia recorded after thigh occlusion, flux reappearance time (r=0.47, p=0.01) and time to peak flux (r=0.41, p=0.03). Intraoperative peripheral resistance predicted graft occlusion at 30 days with a 90% accuracy, while parameters obtained during reactive hyperemia, only tended to predict adverse outcome. CONCLUSIONS: Several parameters during reactive hyperemia show weak correlation to intraoperatively measured peripheral resistance, but none was able to accurately predict graft failure. Further studies are needed to evaluate its capability for patient selection.

Aged↗
PubMedDate not supplied

[Local cerebral ischemia in rats induced by ligation of the middle cerebral artery].

A model of local cerebral ischemia induced by ligation of the middle cerebral artery, which is a modification of the techniques proposed by A. Tamura and others, is suggested. It allows experiments to be conducted on conscious animals with appraisal of the morpho-functional state of the nervous system. Ligation of the middle cerebral artery caused a marked decrease (by 85 +/- 9%) in the blood flow in the temporal area of the cerebral cortex. The use of this method will promote a purposeful search for drugs for the treatment of patients with ischemic disorders of cerebral circulation.

Animals↗
PubMed1996

[The Laser-Doppler microcirculation technique in the study of the orthosympathetic system in obese and non-insulin-dependent diabetic patients].

Parasympathetic as well as cardiovascular sympathetic activity is perturbed in the heart of diabetic and obese subjects. The aim of this work was to assess the effect of sympathetic control on variations in skin blood flow in 14 controls, 42 subjects with non-insulin-dependent diabetes and 57 obese subjects without diabetes. All subjects had normal blood pressure and had no other disease state which might modify skin blood flow. Laser-Doppler measurement of skin blood flow on the palmar aspect of the right first finger was performed at rest and during three tests which activate sympathetic tone: deep respiration (R), active orthostatism (O) and Valsalva's manoeuvre (V). In all 113 subjects, there was a negative correlation between age and the standard deviation of blood skin flow at rest (p = 0.001) and rate of blood skin flow decline during R (p = 0.002), O (p < 0.0001) and V (p = 0.005). The standard deviation and slope of decline in blood skin flow during R was lower than the initial levels in controls in 11 diabetes patients and 6 obese subjects and in 15 diabetic patients and 12 obese subjects respectively. The slope of decline in skin blood flow during O was positively correlated with plasma cholesterol (p = 0.002), red cell aggregation index (p = 0.013) and negatively with hematocrit, glucose control and creatininemia. The respective effects of these factors were analyzed in each of the three groups of subjects. These preliminary results suggest that 1) the variation in skin blood flow at rest is regulated by the sympathetic system and the drop in skin blood flow during the three tests activating the sympathetic system decreases with age, 2) sympathetic control of peripheral vasoconstriction is reduced in many diabetic and obese subjects, 3) red cell aggregability and different metabolic parameters and renal function have an effect.

Diabetes Mellitus, Type 2↗
PubMed1996

Electrophysiological evaluation of peripheral autonomic function in leprosy patients, leprosy contacts and controls.

Since there is immunocytochemical evidence that the initial damage in leprosy is directed at distal, small, unmyelinated nerve fibers, we investigated several electrophysiological methods for their potential value in detecting peripheral autonomic dysfunction in leprosy contacts and leprosy patients. Fingertip blood flow velocity and its control by vasomotor reflexes (VMR) with a laser Doppler flowmeter, fingertip skin temperature, and the sympathetic skin response (SSR) to exosomatic stimuli were studied in 89 leprosy patients, 36 leprosy contacts and 47 normal subjects. Whereas there were no significant differences between the groups in fingertip skin temperature and resting blood flow velocity measurements, there were significant differences in the prevalence of impaired fingertip VMR and absent SSR. The prevalence of absent SSR in leprosy patients was 60.9%, in contacts 13.8%, in controls 6.3%. The prevalence of abnormal VMR in leprosy patients was 61.2%, in contacts 34.7% and in controls 10.6%. VMR testing is a more sensitive test method for autonomic dysfunction compared with the SSR. The implication of impairment in vasomotor and sudomotor function in leprosy contacts needs yet to be determined. However, we propose this to be a response to exposure to Mycobacterium leprae, which represents either ongoing nerve damage or nonprogressive residual autonomic nerve damage. We suggest that VMR testing and SSR are valuable methods to evaluate early leprous neuropathy.

Adolescent↗
PubMed1997

Superficial blood flow following photodynamic therapy of malignant non-melanoma skin tumours measured by laser Doppler perfusion imaging.

Laser Doppler perfusion imaging offers a new modality for in vivo monitoring of the superficial blood perfusion in biological tissue. In this study, the superficial blood perfusion of malignant non-melanoma skin tumours and the surrounding normal skin was measured in conjunction with photodynamic therapy (PDT) using topical delta-aminolaevulinic acid (ALA)-induced protoporphyrin IX as a photosensitizer. The results clearly show that, in contradiction to PDT with the intravenously administered photosensitizer Photofrin, no direct vascular damage can be seen. With the topical sensitization the blood perfusion is increased immediately after the treatment irradiation. The increased blood flow is seen up to a week after treatment, in a similar way as for an inflammatory reaction. Despite this, all basal cell carcinoma and squamous cell carcinoma in situ lesions in this study healed without any sign of residual tumour after the treatment, suggesting an efficient direct tumour cell destruction induced by PDT.

Adult↗
PubMedDate not supplied

Laser-Doppler imaging assessment of skin hyperemia as an indicator of trauma after adhesive strip removal.

The effect of adhesive tape and dressing removal on skin integrity is particularly important for patients who have increased risk for skin damage or impaired physiological responses to skin trauma. Visual observation of skin erythema does not always provide an adequate assessment of acute injury; detection of trauma is limited by the naturally occurring wide range of skin color and tones. This study had two purposes: (1) to assess the sensitivity and objectivity of laser-Doppler perfusion imaging (LDI) in measuring skin blood perfusion in forearm skin before and after removal of adhesive strips and (2) to determine the relationship between skin perfusion levels after adhesive-strip removal and the peel force required to remove the strips. Variations in peel-force levels were obtained in two ways: first, from naturally occurring skin differences; and second, by using an adhesive remover product (ARP) developed to reduce skin trauma. In 10 subjects, acrylic adhesive strips (13 x 70 mm) were placed in pairs on standardized sites on both volar forearms and peeled off 24 hours later at a constant velocity of 5 mm/sec while the peel force was recorded. During peeling, an ARP was used with one strip; nothing was used on the adjacent paired strip (CONTROL). Skin blood perfusion was measured at 5 and 20 minutes after strip removal by non-contact LDI under the ARP and CONTROL conditions simultaneously. Results show that (1) hyperemia after strip removal is linearly related to peel force (r2 = 0.55, p < .01): (2) use of an ARP, as indexed by the hyperemic response, significantly reduces skin trauma (1.02 [SD = 0.11] versus 1.47 [SD = 0.11], p < .01) with a mean CONTROL/ARP ratio of 1.56; and (3) the peel force required is reduced by using an ARP. These findings indicate that LDI is a useful, sensitive tool for assessment of skin trauma and that reducing peel forces has a positive effect.

Adhesives↗
PubMed1995

Measurement of pulpal blood flow in humans using laser Doppler flowmetry: a technique allowing stability and repeatability of pulpal blood flow measurement during surgical manipulations.

This study was undertaken to validate the repeatability of pulpal blood flow in human teeth with the laser Doppler flowmetry technique using a repeatable method of attachment of the laser Doppler probe. The variation in laser Doppler flowmetry measurements was evaluated over time periods that ranged from hours to days. In a prospective study, the pulpal blood flow was recorded from a maxillary central incisor (randomly selected) at a site directly gingival to the orthodontic bracket of three subjects. Measurements were made eight times over a 2-week period and every 30 minutes over 4 hours for eight recordings. The results indicated that there was only a slight difference between the temporal variability of the laser Doppler measurements over the course of 4 hours (intraday variability) or 2 weeks (interday variability). Furthermore, it appeared that subjects varied in their mean value recordings and may have varied widely in their respective signal-to-noise ratios.

Adult↗
PubMed1997

Intratemporal facial nerve blood flow in guinea pigs.

HYPOTHESIS: To investigate the effect of interruption of the stylomastoid artery and the petrosal artery on the facial nerve blood flow with the use of a laser Doppler flowmeter. BACKGROUND: Ischemia of the facial nerve is thought to be one of the most possible causes in idiopathic facial palsy. The blood supply in the facial nerve has been studied morphologically in considerable detail; however, we have little information on its hemodynamics. METHODS: The animals used were 20 guinea pigs. The blood flow in the facial nerve at the geniculate ganglion was measured using a laser Doppler flowmeter, and the change in the facial nerve blood flow between before and after interruption of the stylomastoid artery and the petrosal artery was investigated. The interruption of both arteries was carried out by electrical cauterization with a bipolar coagulator. RESULTS: Interruption of the petrosal artery resulted in almost complete ischemia of the facial nerve at the geniculate ganglion. This decrease in the facial nerve blood flow was significant statistically (p < 0.001). But, interruption of the stylomastoid artery caused no change. CONCLUSIONS: The blood flow in the geniculate ganglion of the facial nerve is thought to come not from the stylomastoid artery but mainly from the petrosal artery. Peripheral facial palsy following ligation of the middle meningeal artery or embolization of the maxillary artery or intra-arterial infusion of anticancer drug into the maxillary artery is likely to be attributed to facial nerve ischemia at the level of the geniculate ganglion.

Animals↗