Laser Doppler Flowmetry Measurements Research Articles

Pulse transit times to the capillary bed evaluated by laser Doppler flowmetry

The pulse transit time (PTT) of a wave over a specified distance along a blood vessel provides a simple non-invasive index that can be used for the evaluation of arterial distensibility. Current methods of measuring the PTT determine the propagation times of pulses only in the larger arteries. We have evaluated the pulse arrival time (PAT) to the capillary bed, through the microcirculation, and have investigated its relationship to the arterial PAT to a fingertip. To do so, we detected cardiac-induced pulse waves in skin microcirculation using laser Doppler flowmetry (LDF). Using the ECG as a reference, PATs to the microcirculation were measured on the four extremities of 108 healthy subjects. Simultaneously, PATs to the radial artery of the left index finger were obtained from blood pressure recordings using a piezoelectric sensor. Both PATs correlate in similar ways with heart rate and age. That to the microcirculation is shown to be sensitive to local changes in skin perfusion induced by cooling. We introduce a measure for the PTT through the microcirculation. We conclude that a combination of LDF and pressure measurements enables simultaneous characterization of the states of the macro and microvasculature. Information about the microcirculation, including an assessment of endothelial function, may be obtained from the responses to perturbations in skin perfusion, such as temperature stress or vasoactive substances.

Hemodynamic Parameters Change Earlier Than Tissue Oxygen Tension in Hemorrhage

Untreated hypovolemia results in impaired outcome. This study tests our hypothesis whether general hemodynamic parameters detect acute blood loss earlier than monitoring parameters of regional tissue beds. Eight pigs (23-25 kg) were anesthetized and mechanically ventilated. A pulmonary artery catheter and an arterial catheter were inserted. Tissue oxygen tension was measured with Clark-type electrodes in the jejunal and colonic wall, in the liver, and subcutaneously. Jejunal microcirculation was assessed by laser Doppler flowmetry (LDF). Intravascular volume was optimized using difference in pulse pressure (dPP) to keep dPP below 13%. Sixty minutes after preparation, baseline measurements were taken. At first, 5% of total blood volume was withdrawn, followed by another 5% increment, and then in 10% increments until death. After withdrawal of 5% of estimated blood volume, dPP increased from 6.1% +/- 3.0% to 20.8% +/- 2.7% (P < 0.01). Mean arterial pressure (MAP), mean pulmonary artery pressure (PAP) and pulmonary artery occlusion pressure (PAOP) decreased with a blood loss of 10% (P < 0.01). Cardiac output (CO) changed after a blood loss of 20% (P < 0.05). Tissue oxygen tension in central organs, and blood flow in the jejunal muscularis decreased (P < 0.05) after a blood loss of 20%. Tissue oxygen tension in the skin, and jejunal mucosa blood flow decreased (P < 0.05) after a blood loss of 40% and 50%, respectively. In this hemorrhagic pig model systemic hemodynamic parameters were more sensitive to detect acute hypovolemia than tissue oxygen tension measurements or jejunal LDF measurements. Acute blood loss was detected first by dPP.

Strategies for reducing variance in laser Doppler flowmetry measurements

Scattering of blood flow data as assessed with laser Doppler flowmetry (LDF) in humans is a problem in many studies using this technique. We set out to reduce variability in LDF data by eliminating the effect of the total returning light level (DC) on LDF parameters in the choroid through partial regression analysis. In 20 healthy subjects, choroidal blood flow parameters were measured at different DC values using a portable confocal LDF device. We used two different strategies to reduce scattering of data eliminating the effect of yield, which is defined as DC/gain. On the one hand, we used a previously described method based on a third-order polynomial fit, which combines all obtained data. On the other hand, we applied a new method based on a linear fit for each individual subject. Variability of data during changes in DC is higher for LDF parameters volume and flow than for velocity. Both methods were successful in reducing scattering of LDF parameters with varying DC. The present study indicates that both methods to correct for changes in yield were successful in reducing the variability of LDF measurements. When systematic changes in DC occur after an intervention, one needs to be careful in interpreting the obtained data and it remains to be shown if either of the two techniques is capable of correcting for this effect. The approach presented here may, however, represent an effective, easily applicable and valid approach to reduce scattering of data from using LDF to assess blood flow in the posterior pole of the human eye.

Effects of photodynamic therapy on subfoveal blood flow in neovascular age‐related macular degeneration patients

Abstract Purpose To assess the short‐term changes in choroidal blood flow after photodynamic therapy (PDT) in patients with neovascular age‐related macular degeneration (AMD). Methods Fourteen patients with exudative AMD were included after complete ophthalmologic examination, fluorescein and indocyanine green angiography and optical coherence tomography. Subfoveal choroidal blood flow was assessed using laser Doppler flowmetry (LDF) in both treated (n=14) and nontreated controlateral (n=8) eyes, 1 h and 1 week after PDT. Ocular perfusion pressure was calculated. Results The detection sensitivity of the LDF measurements at 2‐min intervals before PDT in treated eyes was 7.4% for volume, 6.3% for velocity, and 10.4% for choroidal blood flow. Initial mean visual acuity was 0.68±0.3 logMar. Macular thickness at baseline as measured by OCT3 was at median [interquartile range], 326.5 mm[188–367]. One hour and 7 days after PDT, a significant increase in velocity (15.8% and 24.4%, respectively) and a significant decrease in volume (11% and 17.9%, respectively) were noted in treated eyes. Choroidal blood flow and ocular perfusion pressure remained similar during follow‐up. No significant change in flow parameters was reported in untreated eyes. Conclusion The LDF technique provides feasible and reliable measurements of blood flow parameters before and after PDT in a selective population of patients with exudative AMD. The prognostic value of these early blood flow parameter changes also needs to be assessed.

Outcomes of dental fracture injury as related to laser Doppler flow measurements of pulpal blood‐flow level

Laser Doppler flowmetry (LDF) is a non-invasive method to assess pulpal blood flow (PBF). Dental fracture injuries have been associated with significant PBF reduction The purpose of this study was: (i) to evaluate whether the severity of outcomes of dental fracture injuries may be related to LDF measurements of PBF, and (ii) to investigate whether outcomes of dental fracture injuries may predict PBF levels. The relationship between outcomes and PBF measurements was analyzed in 72 permanent maxillary incisors of 52 consecutive dental trauma patients. The diagnostic outcome group comprised 72 incisors with a type I (absence of sensitivity, periapical radiolucency, and grey discoloration of crown) (n = 42), type II (loss of sensitivity) (n = 16), or type III (loss of sensitivity, periapical radiolucency, and/or grey discoloration of crown) diagnosis. At each session, when an injured permanent maxillary incisor was recorded, a contralateral homologous tooth was used as a control. An ordinal stepwise regression was completed to assess the degree of association between PBF measurements and diagnostic outcomes. A logistic regression analysis was used to compute the odds ratios for the outcome features for incisor non-injury controls vs two outcome groups: type II (n = 16) and type III (n = 14). PBF measurements that were significantly associated with more severe outcome were PBF levels of <or=6 perfusion units (PU) (106.70 odds ratio) (P = 0.000). Significant increase in the risk of a PBF level of <or=6 PU occurred with a type III outcome (32.49 odds ratio) (P = 0.004). PBF measurements were related to the severity of adverse outcomes. Diagnoses of treatment outcomes predicted the presence of specific PBF levels.

Dynamics of oxygen delivery and consumption during evoked neural stimulation using a compartment model and CBF and tissue P O2 measurements

The dynamics of blood oxygen delivery and tissue consumption produced by evoked stimulation of the rat somato-sensory cortex were investigated. Tissue oxygen tension (P O2) and laser Doppler flowmetry (LDF) measurements were recorded under two experimental conditions: normal, which represented both oxygen delivery and consumption, and suppressed CBF (achieved using a vasodilator), which only represented tissue oxygen consumption. Forepaw stimulation for 10 s produced increases of 27.7% and 48.8% in tissue P O2 and LDF signal under normal conditions, respectively. The tissue P O2 response peaked 9.8 s after stimulation onset and did not show any early transient decreases indicating that measurable oxygen deficits are not required to increase the delivery of oxygen by blood flow. Under suppressed CBF conditions, the LDF signal was mostly suppressed while the tissue P O2 decreased by 11.7% and reached a minimum 10.8 s after stimulation onset. These data were analyzed using a dynamic model that described the transport of oxygen from blood to tissue. In order to explain the differences between the model prediction of the tissue P O2 changes and the experimental data, several hypothetical scenarios were considered, such as changes in the vascular volume, permeability–surface area or arterial oxygenation. The increase in tissue P O2 was found to probably require the recruitment of upstream oxygen from larger arteries as well as increases in the vascular volume at the oxygen exchange sites. The amplitude of the estimated tissue tension of oxygen delivered was about 2.7x larger than the estimated consumption under normal conditions (45.7% vs. 17.1%, respectively).

Characteristics of pulpal blood flow levels associated with non-segmented and segmented Le Fort I osteotomy

Laser Doppler flowmetry (LDF) is a noninvasive method to assess pulpal blood-flow (PBF). The purpose of this study was (1) to test whether Le Fort I (LF-I) osteotomy may show tooth type-related effects on LDF measurements, and (2) to investigate whether LF-I and tooth type may predict adverse PBF outcomes. PBF was recorded bilaterally in maxillary incisors, canines, and first premolars in a surgical group of patients who underwent a segmented (n = 14) or nonsegmented LF-I osteotomy (n = 12), and in a nonsurgical group of control subjects (n = 12) who did not undergo orthodontic treatment. PBF measurements were made before surgery (session I), and at intervals between 3 and 5 days (session II), and 55 and 59 days after surgery (session III). The nonsurgical control subjects were tested at similar intervals. An adverse outcome was defined as the presence of "PBF reduction of > 40%." Statistical analysis consisted of univariate analysis of variance for repeated measurements. A multiple logistic regression analysis was used to compute the odds ratio for LF-I and tooth type for adverse outcome versus nonadverse outcome. For the LF-I osteotomy study group there was a significant change in PBF values (P = .000). Analysis of session-related measurements revealed a significant difference between session I- and II-related measurements for the canine (P = .004) of the segmented LF-I osteotomy. Significant increase in risk of a session II-related adverse outcome occurred with a nonsegmented (16.6 odds ratio) (P = .009) and segmented LF-I osteotomy (59.2 odds ratio) (P = .000). The odds ratio that a patient with a segmented LF-I osteotomy might belong to the session III-related adverse outcome group was strong (20.6) and significant (P = .007). LF-I osteotomy type proved to be linked to changes in tooth type-related LDF measurements; it was an important prognostic determinant of adverse PBF outcomes.

In vivo vasodilating mechanisms: who's NOS involved?

appreciate the importance and difficulty of identifying cellular mechanisms in physiological conditions. Indeed, 7-NI was administrated by intradermal microdialysis (2 mm) allowing large local drug concentration with local effects at the site of administration and thus avoiding systemic effects. Data were normalized to the SNP-induced maximal vasodilatation performed at the end of each protocol. Changes in skin blood flow were monitored by laser‐Doppler flowmetry (LDF) that gives continuous beat-to-beat information specific to cutaneous microvascular perfusion in a non-invasive manner. LDF measurements provide a robust approach to evaluate mechanisms of microvascular dilatation and their modification by physiological perturbations. The study reported that during nNOS inhibition, the skin vasodilatation due to whole-body heating was attenuated (∼30%) in contrast to local skin heating. The authors demonstrated that, in vivo, the nNOS isoform is responsible for NO generation during centrally mediated, reflex cutaneous active vasodilatation in whole-body heating, but is not involved in increasing skin blood flow in response to axon reflex-mediated, local skin heating. This study also showed that the nNOS isoform generates NO from the very initial phase of cutaneous active vasodilatation and continues during prolonged whole-body heat stress. However, Kellogg et al. (2008) strongly suggest that NO acts to increase synergistically the vasodilating effects of other neurotransmitters rather than acting as a direct mediator of vasodilatation. Interestingly, they excluded any participation of eNOS in centrally mediated reflex cutaneous active vasodilatation since studies using l-NAME, a non-selective isoform NOS antagonist, reported approximately an identical attenuation of 30% of skin blood flow increases to that of 7-NI, a selective nNOS antagonist, highlighting the possibility that nNOS is the sole NOS

Characterization of autonomic dysfunction in patients with irritable bowel syndrome using fingertip blood flow

Fingertip blood flow (FTBF) as measured by laser Doppler flowmetry (LDF) measurement is considered an indicator of sympathetic nerve function. We evaluated autonomic function in patients with irritable bowel syndrome (IBS) by assessing FTBF with both LDF and continuous-wave (cw) Doppler sonography. Firstly, the two methods were compared in 40 healthy volunteers. Next, 59 patients with IBS as well as 118 healthy volunteer controls were studied. In the supine position, FTBF in the right index finger was measured with cw Doppler sonography, whereas FTBF in the left index finger was assessed with LDF. After baseline measurement for at least 5 min, the volunteers received sympathetic stimulation from cold stress applied without notification in the form of an icebag (0 degrees C) upon the left forearm for 1 min. The new cw Doppler sonography method can be used in place of the old LDF method for clinical purposes. FTBF velocity before stimulation (V(pre)) was significantly lower in the IBS group than that in the healthy volunteers (P < 0.01). In addition, the time required for FTBF to return to V(pre) after stimulation was significantly longer in the IBS group than that in the control group. (P = 0.02). Thus, measurement of FTBF with cw Doppler sonography can be useful in the assessment of sympathetic nerve function. The IBS patients showed an abnormal FTBF response suggesting the presence of excess sympathetic activity.

The effects of dorzolamide 2% and dorzolamide/timolol fixed combination on retinal and optic nerve head blood flow in primary open-angle glaucoma patients

To compare the effect of dorzolamide hydrochloride 2%, timolol maleate 0.5%, and their fixed combination on intraocular pressure (IOP)and retinal and optic nerve head haemodynamics in primary open-angle glaucoma patients. Twenty-eight patients with early moderate glaucomatous damage treated with β-blockers (>6 months) with IOP values ranging from 18 to 22 mmHg at trough participated in this trial. After a 4-week washout period,patients were randomised in two groups: group I started with dorzolamide 2% monotherapy and group II with timolol 0.50% monotherapy for 4 weeks. After this period, both groups switched to dorzolamide/timolol fixed combination for 4 weeks. IOP, ocular diastolic perfusion pressure, heart rate, and Scanning Laser Doppler Flowmetry measurements at the peripapillary retina and neuroretinal rim were taken at T0 (enrolment), T1 (wash out), T2(monotherapy), and T3 (dorzolamide/timolol).Data were compared between different study times. Statistical analysis was conducted using a paired t-test. Between T1 and T3, IOP decreased significantly in group I (-21.40%) (P<0.001)and in group II (-21.25%) (P<0.001). At the same time intervals, blood flow increased significantly at rim level for group I (+30.03%)(P<0.05) and also when all patients were considered (rim +20.81%) (P<0.05). Between T1 and T3, we also observed a significant increase of ODPP in group I (+7.24%) (P<0.01)and in group II (+6.08%) (P<0.05) and when all patients were considered (+6.71%)(P<0.001) [corrected]. Dorzolamide/timolol fixed combination increased blood flow significantly at the neuroretinal rim showing a combination of hypotensive and haemodynamic effects.

Optical microcirculatory skin model: assessed by Monte Carlo simulations paired with in vivo laser Doppler flowmetry

An optical microvascular skin model, valid at 780 nm, was developed. The model consisted of six layers with individual optical properties and variable thicknesses and blood concentrations at three different blood flow velocities. Monte Carlo simulations were used to evaluate the impact of various model parameters on the traditional laser Doppler flowmetry (LDF) measures. A set of reference Doppler power spectra was generated by simulating 7000 configurations, varying the thickness and blood concentrations. Simulated spectra, at two different source detector separations, were compared with in vivo recorded spectra, using a nonlinear search algorithm for minimizing the deviation between simulated and measured spectra. The model was validated by inspecting the thickness and blood concentrations that generated the best fit. These four parameters followed a priori expectations for the measurement situations, and the simulated spectra agreed well with the measured spectra for both detector separations. Average estimated dermal blood concentration was 0.08% at rest and 0.63% during heat provocation (44 degrees C) on the volar side of the forearm and 1.2% at rest on the finger pulp. The model is crucial for developing a technique for velocity-resolved absolute LDF measurements with known sampling volume and can also be useful for other bio-optical modalities.

Adverse outcomes of dental trauma splinting as related to displacement injury and pulpal blood flow level

Splinting of traumatically displaced permanent teeth has been described as an effective modality in the treatment of patients with dental injuries. The purpose of this study was to (i) investigate whether dental injury diagnosis may predict adverse outcomes occurring 96 weeks after splint removal, and (ii) evaluate whether the severity of adverse outcome is related to laser Doppler flowmetry (LDF) measurements of pulpal blood flow (PBF). In 206 trauma patients, 273 permanent maxillary incisors treated by repositioning and splinting, and the respective contralateral homologous control teeth were investigated clinically and radiographically, and by LDF to assess local PBF values. Dental displacement injuries were classified as grade I (subluxation), grade II (lateral or extrusive luxation) and grade III (avulsion or intrusive luxation). Outcomes were classified as 'absence of loss of sensitivity, periapical radiolucency, and/or grey discolouration of crown', type I (loss of sensitivity), type II (loss of sensitivity and periapical radiolucency or grey discoloration of crown) and type III (loss of sensitivity, periapical radiolucency and grey discoloration of crown). An adverse outcome was defined as the presence of 'periapical radiolucency and/or grey discoloration'. A multiple logistic regression analysis was used to compute the odds ratio (OR) for dental displacement injury for adverse outcome (n = 69) vs non-adverse outcome (n = 168). An ordinal stepwise regresssion was completed to assess the degree of association between PBF measurements and outcome groups. Significant increase in risk of an adverse outcome occurred with a grade II dental displacement injury (OR 14.3) (P = 0.000) and a grade III dental displacement injury (OR 19.9) (P = 0.000). PBF measurements that were significantly associated with more severe outcome were PBF levels of < or =3 perfusion units (PU) (OR 399.4) (P = 0.000), those of >3 PU and < or =6 PU (OR 100.5) (P = 0.000), and those of >6 PU and < or =9PU (OR 6.2) (P = 0.000). Diagnoses of displaced teeth predicted dental injury patients who went on to show adverse treatment outcomes of splinting. PBF measurements were related to the severity of adverse outcome.

Effect of forced-air heaters on perfusion and temperature distribution during and after open-heart surgery

After cardiopulmonary bypass, patients often show redistribution hypothermia, also called afterdrop. Forced-air blankets help to reduce afterdrop. This study explores the effect of forced-air blankets on temperature distribution and peripheral perfusion. The blood perfusion data is used to explain the observed temperature effects and the reduction of the afterdrop. Fifteen patients were enrolled in a randomised study. In the test group (n=8), forced-air warmers were used. In the control group (n=7), only passive insulation was used. Core and skin temperatures and thigh temperatures at 0, 8, 18 and 38 mm depth were measured. Laser Doppler flowmetry (LDF) was used to record skin perfusion from the big toe. Blood flow through the femoral artery was determined with ultrasound. Afterdrop in the test group was smaller than in the control group (1.2+/-0.2 degrees C vs 1.8+/-0.7 degrees C: P=0.04) whilst no significant difference in mean tissue thigh temperature was found between the groups. Local skin temperature was 2.5-3.0 degrees C higher when using forced-air heaters. However, skin perfusion was unaffected. Ultrasound measurements revealed that leg blood flow during the first hours after surgery was reduced to approximately 70% of pre- and peri-operative values. Forced-air blankets reduce afterdrop. However, they do not lead to clinical relevant changes in deep thigh temperature. LDF measurements show that forced-air heating does not improve toe perfusion. The extra heat especially favours core temperature. This is underlined by the decrease in postoperative leg blood flow, suggesting that the majority of the warmed blood leaving the heart flows to core organs and not to the periphery.

Strategies for improving intraindividual reproducibility in laser Doppler flowmetry measurements

Abstract Purpose: Scattering of blood flow data as assessed with laser Doppler flowmetry (LDF) in humans is a problem in many studies using this technique. We set out to reduce variability in LDF data by partializing out the effect of the total returning light level (DC) on LDF parameters in the choroid. Methods: In 20 healthy subjects choroidal blood flow was measured at different DC values using a portable confocal LDF device. To reduce scattering of data partializing out the effect of yield, defined as DC/gain, firstly a previously described method based on a third order polynomia fit using all obtained data was applied. Secondly a new method based on a linear fit obtained for each subject individually was used.In addition, these correction procedures were applied retrospectively to the data of a recent study investigating the effect of a nitric oxide (NO) synthase inhibitor on choroidal and optic nerve head blood flow parameters. Results: Both methods were successful in reducing scattering of LDF parameters in the choroid with varying baseline DC values. In addition, both methods minimized scattering of the effect of the NO synthase inhibitor on ocular blood flow parameters as analyzed retrospectively. Whereas, however, the previous approach altered the magnitude of the mean change induced by the NO synthase inhibitor to higher values, the new method preserved the originally reported effect. Conclusions: When systematic changes in DC occur after an intervention one needs to be careful in interpreting the obtained data. The approach presented here may represent an effective, easily applicable and valid way to reduce scattering of data from using LDF to assess blood flow in the posterior pole of the human eye.

Ocular hemodynamic effects of nitrovasodilators in healthy subjects

Abstract Purpose: Previous studies on the ocular hemodynamic effects of nitrates showed partially contradicting results. The aim of the present study was to investigate the effect of nitrovasodilators on choroidal and optic nerve head (ONH) blood flow. Methods: The study was performed in a randomized, placebo‐controlled, double masked, 4‐way crossover design in 12 healthy male subjects. Nitroglycerine, isosorbide dinitrate or sodium nitroprusside were administered intravenously in stepwise increasing doses on different study days. Physiologic saline solution was used as placebo control. To assess choroidal and ONH microcirculation, laser Doppler flowmetry measurements were performed. Laser interferometric measurements of fundus pulsation were used to assess pulsatile choroidal and ONH blood flow. Ocular perfusion pressure (OPP) was calculated as OPP=2/3MAP‐IOP. Thereafter a parameter of vascular resistance (R) for each measured blood flow parameter (BF) was calculated as R~OPP/BF. Results: Placebo administration did not change any of the measured parameters. We observed small but significant reduction of IOP during the infusion of sodium nitroprusside. The pulsatile choroidal blood flow decreased significantly during the infusion of isosorbide dinitrate (–8.1%) and sodium nitroprusside (–4.3%). The pulsatile ONH blood flow decreased significantly only during the infusion of sodium nitroprusside (–5.7%). In addition, we observed a significant reduction of all calculated parameters of vascular resistance during the infusion of each nitrovasodilator (maximal decrease: –16% to –29%). Conclusions: An intravenous infusion of nitroglycerine, isosorbide dinitrate or sodium nitroprusside caused a significant reduction of vascular resistance in the ONH and the choroid.

Variability of ocular perfusion measurements in glaucoma and healthy subjects

Abstract Purpose: Variability is a major problem in ocular blood flow measurements. It is an important determinant of sample size in clinical trials and may limit clinical usefulness if it is too high. We set out to compare the short‐term reproducibility of blood flow parameters assessed with scanning laser Doppler flowmetry and laser interferometric measurement of fundus pulsation between healthy young subjects and glaucoma patients. Methods: Measurements in 140 healthy male non‐smoking subjects and 140 patients with primary open angle glaucoma were included in this analysis. From two consecutive measurements performed within 5 minutes the coefficient of variation in an individual was calculated for each outcome parameter. These included the fundus pulsation amplitude (FPA), the flow, volume and velocity in the rim and the cup. Results: Mean coefficients of variation were between 3.2% and 23.8 % for all outcome parameters in healthy subjects and between 4.9% and 34.3% in the patients. FPA showed the highest reproducibility although individual coefficients of up to 22.5% and 34.7% were observed in healthy subjects and glaucoma patients, respectively. With scanning laser Doppler flowmetry velocity was better reproducible than volume or flow. Individual coefficients of variation for flow values were as high as 87.5% in healthy subjects and 132.2% in glaucoma/ocular hypertension patients. Conclusions: Our data indicate that in healthy subjects the selected techniques provide better reproducibility than in patients with ocular disease. This needs to be considered in sample size calculation for clinical trials. In addition, the high individual differences in flow parameter readings observed in some subjects limit the use of the techniques in clinical practice.

Treatment outcomes of dental injury diagnoses as related to blood flow measurements from teeth

The purpose of this study was to investigate whether dental injury diagnoses may predict adverse outcomes occurring 102 weeks after trauma, and to evaluate whether the severity of adverse outcome is related to laser Doppler flowmetry (LDF) measurements of blood flow from teeth. In 309 trauma patients, 404 permanent maxillary incisors and the respective contralateral homologous control teeth were investigated clinically and radiographically, and by LDF to assess local blood flow values. Dental displacement injuries were classified as grade I (subluxation), grade II (lateral or extrusive luxation), and grade III (avulsion or intrusive luxation). Dental fracture injuries were classified as uncomplicated crown fractures, complicated crown fractures, and root fracture. An adverse outcome was defined as the presence of 'periapical radiolucency and/or grey discolouration'. Significant increase in risk of an adverse outcome occurred with a grade II dental displacement injury (15.07 odds ratio; P = 0.000), a grade III dental displacement injury (28.33 odds ratio; P = 0.000), and a root fracture (106.25 odds ratio; P = 0.000). Blood flow measurements that were significantly associated with more severe outcome were blood flow levels of < or =3 perfusion units (PU; 170.72 odds ratio; P = 0.000), and those of >3 PU and < or =6 PU (76.71 odds ratio; P = 0.000). Diagnoses of displaced and root fractured teeth predicted dental injury patients who went on to show adverse treatment outcomes of splinting. Blood flow measurements from teeth were related to the severity of adverse outcome.

CT Perfusion for Determination of Pharmacologically Mediated Blood Flow Changes in an Animal Tumor Model1

To prospectively compare single- and multisection computed tomographic (CT) perfusion for tumor blood flow determination in an animal model. All animal protocols and experiments were approved by the institutional animal care and use committee before the study was initiated. R3230 mammary adenocarcinoma was implanted in 11 rats. Tumors (18-20 mm) were scanned with dynamic 16-section CT at baseline and after administration of arsenic trioxide, which is known to cause acute reduction in blood flow. The concentration of arsenic was titrated (0-6 mg of arsenic per kilogram of body weight) to achieve a defined blood flow reduction (0%-75%) from baseline levels at 60 minutes, as determined with correlative laser Doppler flowmetry. The mean blood flow was calculated for each of four 5-mm sections that covered the entire tumor, as well as for the entire tumor after multiple sections were processed. Measurements obtained with both methods were correlated with laser Doppler flowmetry measurements. Interobserver agreement was determined for two blinded radiologists, who calculated the percentage of blood flow reduction for the "most representative" single sections at baseline and after arsenic administration. These results were compared with the interobserver variability of the same radiologists obtained by summing blood flow changes for the entire tumor volume. Overall correlations for acute blood flow reduction were demonstrated between laser Doppler flowmetry and the two CT perfusion approaches (single-section CT, r=0.85 and r(2)=0.73; multisection CT, r=0.93 and r(2)=0.87; pooled data, P=.01). CT perfusion disclosed marked heterogeneity of blood flow, with variations of 36% +/- 13 between adjacent 5-mm sections. Given these marked differences, interobserver agreement was much lower for single-section CT (standard deviation, 0.22) than for multisection CT (standard deviation, 0.10; P=.01). Multisection CT perfusion techniques may provide an accurate and more reproducible method of tumor perfusion surveillance than comparison of single representative tumor sections.

Effects of dopamine on retinal and choroidal blood flow parameters in humans

Aim:To investigate the effect of dopamine on retinal and choroidal blood flow in humans.Methods:We investigated the effect of two doses of intravenous dopamine (5 and 10 µg/kg/min) via a randomised...

An evaluation of the reliability and validity of capillary refill time test

Background While capillary refill time test (CRTT) has been commonly used as a quick and convenient clinical vascular assessment of the lower limb, the validity of this test has not been established. Objectives There were three aims to this study: the first was to evaluate the reliability of CRTT, the second to investigate the premise that CRTT represents skin perfusion, and thirdly to determine whether CRTT can detect lower limb vascular disease. Method Intra- and inter-tester reliability was evaluated for five experienced physicians who used CRTT on 10 participants. Criterion validity for measurement of skin perfusion was investigated by comparison with laser Doppler flowmetry on 49 participants, and for this same group the usefulness of detecting those persons with peripheral arterial disease and a state of impaired healing was evaluated. Results CRTT had reasonable intra-tester reliability (ICC = 0.72) but poorer inter-tester reliability (ICC range = 0.12–0.81). For measurement of skin perfusion, CRTT was predictive of only 38% of the variance in laser Doppler flowmetry measures ( r 2 = 0.38, P < 0.001). Finally, CRTT was not able to discriminate between patients with and without peripheral arterial disease ( z = −1.86, P = 0.062), nor could it discern between patients with and without impaired lower extremity healing ( z = −0.21, P = 0.830). Laser Doppler flowmetry was also unable to predict the presence of peripheral arterial disease ( t 96 = 0.27, P = 0.787) and impaired healing ( t 96 = 1.95, P = 0.054). Conclusion These results question the usefulness of capillary refill time test for assessment of vascular status in the lower limb.