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Quantification of residual limb skeletal muscle perfusion with contrast-enhanced ultrasound during application of a focal junctional tourniquet.

ABSTRACT: Focal junctional tourniquets (JTs) have been developed to control hemorrhage from proximal limb injuries. These devices may permit greater collateral perfusion than circumferential tourniquets. We hypothesized that JTs eliminate large-vessel pulse pressure yet allow a small amount of residual limb perfusion that could be useful for maintaining tissue viability.Ten healthy control subjects were studied. Transthoracic echocardiography, Doppler ultrasound of the femoral artery (FA) and posterior tibial artery, and contrast-enhanced ultrasound (CEU) perfusion imaging of the anterior thigh extensor and calf plantar flexor muscles were performed at baseline and during application of a JT over the common FA. Intramuscular arterial pulsatility index was also measured from CEU intensity variation during the cardiac cycle.FA flow was eliminated by JTs in all subjects; posterior tibial flow was eliminated in all but one. Perfusion measured in the thigh and calf muscles was similar at baseline (0.33 ± 0.29 vs 0.29 ± 0.22 mL/min/g). Application of the JT resulted in a reduction of perfusion (P < .05) that was similar for the thigh and calf (0.08 ± 0.07 and 0.10 ± 0.03 mL/min/g). On CEU, microvascular flux rate was reduced by ?55%, and functional microvascular blood volume was reduced by ?35%. Arterial pulsatility index was reduced by ?90% in the calf. JT inflation did not alter left ventricle dimensions, fractional shortening, cardiac output, or arterial elastance as a measure of total systolic load.Application of a JT eliminates conduit arterial pulse and markedly reduces intramuscular pulse pressure, but thigh and calf skeletal muscle perfusion is maintained at 25% to 35% of basal levels. These data suggest that JTs that are used to control limb hemorrhage allow residual tissue perfusion even when pulse pressure is absent.

SUBMITTER: Davidson BP

PROVIDER: S-EPMC4344419 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Quantification of residual limb skeletal muscle perfusion with contrast-enhanced ultrasound during application of a focal junctional tourniquet.

Davidson Brian P BP Belcik J Todd JT Mott Brian H BH Landry Gregory G Lindner Jonathan R JR

Journal of vascular surgery 20140724 1

<h4>Objective</h4>Focal junctional tourniquets (JTs) have been developed to control hemorrhage from proximal limb injuries. These devices may permit greater collateral perfusion than circumferential tourniquets. We hypothesized that JTs eliminate large-vessel pulse pressure yet allow a small amount of residual limb perfusion that could be useful for maintaining tissue viability.<h4>Methods</h4>Ten healthy control subjects were studied. Transthoracic echocardiography, Doppler ultrasound of the fe ...[more]

PMID: 25065582

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Project description:BACKGROUND:In patients with peripheral artery disease (PAD), the severity of symptoms correlates poorly with ankle-brachial index (ABI). The aim of this study was to test the hypothesis that limb perfusion assessed using contrast-enhanced ultrasound (CEU) during contractile exercise varies according to functional class in patients with PAD, particularly those with ABIs in the 0.4 to 0.6 range whose symptoms vary widely. METHODS:Bilateral quantitative CEU perfusion imaging of the calf was performed in normal control subjects (n = 10) and patients with PAD who had at least one limb with a moderately reduced ABI (0.4-0.6; n = 17). Imaging was performed at rest and immediately after 30 sec of modest periodic (0.3-Hz) plantar flexion (10 W). RESULTS:In patients with PAD, Rutherford symptom classification for each limb varied widely, including in limbs with ABIs of 0.4 to 0.6 (n = 6 with mild or no symptoms, n = 14 with moderate to severe symptoms). CEU perfusion imaging parameters at rest were similar between control subjects and patients with PAD irrespective of ABI. In normal control subjects, limb flow increased on average by > 20-fold after only 30 sec of moderate exercise. In patients with PAD, muscle exercise perfusion for all limbs was reduced compared with control subjects and decreased according to the severity of ABI reduction, primarily from reduced microvascular flux rate. Even limbs with ABIs > 0.9 in patients with PAD had lower exercise perfusion than in control subjects (P = .03). In subjects with PAD, exercise perfusion was lower in those with moderate to severe versus mild symptoms when analyzed for all limbs (median, 30 IU/sec [interquartile range (IQR), 21-52 IU/sec] vs 84 IU/sec [IQR, 36-177 IU/sec]; P = .01) and limbs with ABIs of 0.4 to 0.6 (median, 26 IU/sec [IQR, 14-41 IU/sec] vs 54 IU/sec [IQR, 31-105 IU/sec]; P = .05). CONCLUSIONS:In patients with PAD, CEU exercise perfusion imaging detects differences in limb muscle perfusion that are likely to be responsible for differences in symptom severity and can detect the flow abnormalities from microvascular dysfunction even in limbs with normal ABIs.

Project description:PurposeContrast-enhanced ultrasound imaging has expanded the diagnostic potential of ultrasound by enabling real-time imaging and quantification of tissue perfusion. Several perfusion models and curve fitting methods have been developed to quantify the temporal behavior of tracer signal and standardize perfusion quantification. While the least-squares approach has traditionally been applied for curve fitting, it can be inadequate for noisy and complex data. Moreover, previous research suggests that certain perfusion models may be more relevant depending on the organ or tissue imaged. We propose a multi-model framework to select the most appropriate perfusion model and curve fitting method for each diagnostic application.MethodsOur multi-model approach uses a system identification method, which estimates perfusion parameters from the model with the best fit to a given time-intensity curve. We compared current perfusion quantification methods that use a single perfusion model and curve fitting method and our proposed multi-model framework on bolus 3D dynamic contrast-enhanced ultrasound (DCE-US) in vivo images obtained in mice implanted with a colon cancer, as well as on simulation data. The quality of fit in estimating perfusion parameters was evaluated using the Spearman correlation coefficient, the coefficient of determination (R2 ), and the normalized root-mean-square error (NRMSE) to ensure that the multi-model framework finds the best perfusion model and curve fitting algorithm.ResultsOur multi-model framework outperforms conventional single perfusion model approaches with least-squares optimization, providing more robust perfusion parameter estimation. R2 and NRMSE are 0.98 and 0.18, respectively, for our proposed method. By comparison, the performance of the traditional approach is much more dependent upon the selection of the appropriate model. The R2 and NRMSE are 0.91 and 0.31, respectively.ConclusionsThe proposed multi-model framework for perfusion modeling outperforms the current approach of single perfusion modeling using least-squares optimization and more robustly estimates perfusion parameters when using empiric data labeled by an expert as the gold standard. Our technique is minimally sensitive to issues affecting the accuracy of perfusion parameter estimation, including rise time, noise, region of interest size, and frame rate. This framework could be of key utility in modeling different perfusion systems in different tissues and organs.

Project description:BACKGROUND:The uteroplacental vascular supply is a critical determinant of placental function and fetal growth. Current methods for the in vivo assessment of placental blood flow are limited. OBJECTIVE:We demonstrate the feasibility of the use of contrast-enhanced ultrasound imaging to visualize and quantify perfusion kinetics in the intervillous space of the primate placenta. STUDY DESIGN:Pregnant Japanese macaques were studied at mid second trimester and in the early third trimester. Markers of injury were assessed in placenta samples from animals with or without contrast-enhanced ultrasound exposure (n = 6/group). Human subjects were recruited immediately before scheduled first-trimester pregnancy termination. All studies were performed with maternal intravenous infusion of lipid-shelled octofluoropropane microbubbles with image acquisition with a multipulse contrast-specific algorithm with destruction-replenishment analysis of signal intensity for assessment of perfusion. RESULTS:In macaques, the rate of perfusion in the intervillous space was increased with advancing gestation. No evidence of microvascular hemorrhage or acute inflammation was found in placental villous tissue and expression levels of caspase-3, nitrotyrosine and heat shock protein 70 as markers of apoptosis, nitrative, and oxidative stress, respectively, were unchanged by contrast-enhanced ultrasound exposure. In humans, placental perfusion was visualized at 11 weeks gestation, and preliminary data reveal regional differences in intervillous space perfusion within an individual placenta. By electron microscopy, we demonstrate no evidence of ultrastructure damage to the microvilli on the syncytiotrophoblast after first-trimester ultrasound studies. CONCLUSIONS:Use of contrast-enhanced ultrasound did not result in placental structural damage and was able to identify intervillous space perfusion rate differences within a placenta. Contrast-enhanced ultrasound imaging may offer a safe clinical tool for the identification of pregnancies that are at risk for vascular insufficiency; early recognition may facilitate intervention and improved pregnancy outcomes.

Dataset Information

Quantification of residual limb skeletal muscle perfusion with contrast-enhanced ultrasound during application of a focal junctional tourniquet.

Publications

Quantification of residual limb skeletal muscle perfusion with contrast-enhanced ultrasound during application of a focal junctional tourniquet.

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