Pain management options for the equine orthopedic patient are limited and can have harmful systemic effects. Methods of local drug delivery such as intravenous regional limb perfusion (IVRLP) are able to provide more focal therapy with a decreased risk of systemic side effects. The primary goal of the present study was to develop a novel, targeted pain management approach able to mitigate the complications encountered with systemic opioid administration. There were two main objectives with respect to elucidating the usefulness of a butorphanol IVRLP. The first of these was to evaluate the feasibility of IVRLP to deliver butorphanol to the treated limb, and the second was to develop a method for evaluating the analgesic efficacy of the procedure. The findings suggest butorphanol IVRLP is well tolerated, results in measurable levels of butorphanol in the treated limb and may be of analgesic benefit.

No description available.

No description available.

<p>The pathophysiology of how a maternal infection induces fetal inflammation and subsequently premature birth is a growing area of research. The <em>ex-vivo</em> dual closed-loop placental perfusion model has been widely used to study placental physiology. To address the association between bacterial chorioamnionitis and fetal inflammation, TNF-α induction following lipopolysaccharide (LPS) challenge – a pyrogen of Gram-negative origin – was measured in the perfusion model. Preliminary analysis of perfusates unexpectedly revealed markedly elevated levels of TNF-α in control and LPS-treated groups indicating contamination of material(s) capable of activating innate immune responses.</p> <p>To identify source(s) driving high background TNF-α expression in perfusates, bovine serum albumin (BSA) – the chief component of the perfusion media – the perfusion system and the materno-feto-placental unit were independently examined. To validate a cleaning protocol effective in LPS removal, acid-base and oxidative depyrogenation techniques were also additionally assessed in the perfusion system.</p> <p>Using TNF-α as a surrogate marker of contamination, high background TNF-α expression in previously conducted placental perfusions were attributed to (1) LPS contaminated perfusion media and (2) LPS build up in the perfusion system. Additionally, results from depyrogenation experiments revealed both acid-base and oxidative techniques effectively reduced LPS buildup in the perfusion system to levels that were in accordance with FDA guidelines for medical equipment (< 0.5 EU/mL). Thus, to circumvent LPS-derived contamination placentas should be perfused using endotoxin-free perfusion media and the perfusion system should be cleaned with acid-base or oxidative depyrogenation techniques prior to its use.</p> / Master of Science (MSc)

This work represents the next step in the ongoing development of a system to noninvasively estimate blood perfusion using thermal methods. A combination thermocouple/thermopile sensor records heat flux and temperature measurements on the tissue of interest (in this case skin) for a given period of time. These data, in combination with other experimental parameters, are read into a computer program that compares them to a biothermal finite difference model of the system. The program uses an iterative process incorporating Gauss Minimization to adjust parameters in the biothermal model until the predicted system behavior satisfactorily approximates the real world data. The result is an estimation of blood perfusion in the tissue being measured, as well as an estimate of the thermal contact resistance between the probe and tissue. The system is tested on human forearms, canine legs during laparoscopic spay surgery, and on a canine medial saphenous fasciocutaneous free tissue flap model. Experimental measurements, especially those performed on the tissue flap model, show distinct correlation between blood perfusion and bioprobe output. This research demonstrates the accuracy of the biothermal model and the parameter estimation technique, as well as the usability of the system in a clinical setting. / Master of Science

The vascular system, responsible for the transport of nutrients, oxygen, and waste removal, overcomes the limitations of oxygen diffusion in solid tissues through blood perfusion, thereby preventing necrosis. The mechanical stimuli from blood flow are pivotal for vascular development and engineering, influencing endothelial cell morphology and vessel remodeling via mechanosensing. Current organ-on-chip systems, while successful in applying dynamic flow to endothelial cells, have limitations, including dependency on pumps and confinement to closed microfluidic channels. Additionally, the interaction between immune cells and these systems under long-term recirculating flow conditions has not been adequately demonstrated. This thesis introduces a novel biofabrication and device manufacturing technique that utilizes a flexible, patternable sacrificial material on a 2D surface. This material morphs in response to an aqueous hydrogel and then degrades, forming perfusable vascular networks within a natural hydrogel matrix. We achieved perfusion using a rocker mechanism that periodically changes tilt direction, while the open-well design facilitates the visualization of perfusable tubular tissues via clinical ultrasound imaging and the construction of complex, vascularized hepatic tissues embedded in gel matrices (Chapter 2). To mimic the unidirectional recirculating flow characteristic of blood vessels, we created the UniPlate platform, combining injection molding with 3D printing (Chapter 3). This innovation allows for the perfusion and recirculation of monocytes through vascular channels without compromising cell viability or eliciting an inflammatory response. Furthermore, by integrating cancer spheroids into the vascular tissues on UniPlate, we developed a vascularized cancer spheroid model that exhibited temporally dependent and tissue-specific macrophage recruitment toward tumor sites with continuous monocyte recirculation (Chapter 4). Collectively, this series of research work introduces a versatile and robust platform capable of replicating vascular functions and immune responses, offering a substantial advancement in the investigation of vascular biology and the mechanism of disease progression. / Thesis / Doctor of Philosophy (PhD) / Vascular networks of the circulatory system are crucial organs in the body, determining the life and death of tissues and organisms by distributing nutrients and oxygen throughout the body. Dysfunction in blood vessel systems is closely related to clinical diseases such as stroke, atherosclerosis, tumor angiogenesis, and cancer metastasis. Mechanical stimuli in blood vessels play a crucial role in regulating the structure and function of endothelial cells during in vivo embryonic development and in vitro vascular tissue formation. Understanding and mimicking the complex environment of blood vessels is vital for studying diseases related to endothelial dysfunction. In this thesis, we introduce a novel subtractive manufacturing method to create three-dimensional (3D) perfusable tubular tissues within a hydrogel. Unidirectional recirculating flow, stromal cells and spheroids, as well as circulating immune cells, were then introduced to the engineered vascular tissues to develop more complex tissue models. These models reproduce the cell diversity, 3D structure, mechanical stimuli, and immune components found in the native tissue microenvironment, providing a valuable tool for the study of vascular diseases and the development of potential treatments.

The development of an organ preservation system (primarily kidneys and livers, but could be adapted to fit hearts, lungs, and even limbs in the future) that can provide surgeons and doctors with real-time quantitative feedback on the health of the organ would be a significant improvement on current transplant practices. This organ transport system will provide surgeons and doctors the opportunity to make more educated decisions towards whether or not to proceed with organ transplantation. Here, we discuss the use Smart Perfusion's organ preservation system as a platform for determining the optimal perfusion temperature of an organ. Porcine kidneys were procured and perfused with a modified PBS solution on the Vasowave™. While on this organ preservation system, a heart emulating pressure waveform (90/50 mmHg) was generated and sent to the specimen. The pressure response, flow rate, temperature, pH, dissolved oxygen content, and conductivity of the fluid stream were all monitored throughout the duration of experimentation. In addition to inline sensors, IR imaging captured the surface temperature of the organ while on the system. Lastly, the use of a combined heat flux-temperature (CHFT) sensor, previously developed at Virginia Tech, was applied for the first time to monitor and measure local tissue perfusion of an explanted organ. A total of 12 experiments were performed (6 at a set fluid temperature of 15°C, and 6 at 20°C). All system data was collected, statistically evaluated and finally compared against blind histological readings (taken at the termination of each experiment at the hilum and pole) to investigate the effects of temperature on organ vasculature. The results of this experiment indicated that the effects of temperature on explanted kidneys can be affectively measured using a non-invasive bioheat perfusion sensor. Specifically, the lower temperature group of kidneys was measured to have lower perfusion. Furthermore, an enhancement to the CHFT sensor technology (CHFT+) was developed and tested for compliance. A controllable thin filmed heat resistor was added to the CHFT assembly to replace the current convective thermal event. This enhancement improved the measured heat flux and temperature signals and enables autonomy. Also, the thin and semi-flexible nature of the new CHFT+ sensor allows for perfusion measurements to be taken from the underside of the organ, permitting a quantitative measure of pressure ischemia. Results from a live tissue test illustrated, for the first time, the effects of pressure ischemia on an explanted porcine kidney. / Master of Science

Many medical therapies, such as thermal tumor detection and hypothermia cancer treatments, utilize heat transfer mechanisms of the body. The focus of this work is the development and experimental validation of a method to simultaneously estimate thermal conductivity, volumetric specific heat, and perfusion of in-vivo tissue. The heat transfer through the tissue was modeled using a modified Pennes' equation. Using a least-squares parameter estimation method with regularization, the thermal properties could be estimated from the temperature response to the known applied heat flux. The method was tested experimentally using a new agar-water tissue phantom designed for this purpose. A total of 40 tests were performed. The results of the experiments show that conductivity can be successfully estimated for perfused tissue phantoms. The values returned for volumetric specific heat are lower than expected, while the estimated values of perfusion are far greater than expected. It is believed that the mathematical model is incorrectly accounting between these two terms. Both terms were treated as heat sinks, so it is conceivable that it is not discriminating between them correctly. Although the method can estimate all three parameters simultaneously, but it seems that the mathematical model is not accurately describing the system. In the future, improvements to the model could be made to allow the method to function accurately. / Master of Science

Les propriétés microvasculaires de la moëlle osseuse (MO) sont mal connues chez l’être humain. L’IRM de perfusion en permet une évaluation quantitative non invasive. La hanche a été choisie, car elle est la cible de pathologies fréquentes et handicapantes, qu’il est nécessaire de diagnostiquer plus précocement telle la coxarthrose. Nous avons d’abord implémenté une séquence IRM volumique à voxels isotropiques, avec une couverture large et une résolution spatiale élevée. Celle-ci a ensuite permis l’étude d’une série de 60 patients âgés de 18 à 60 ans, sans antécédent de pathologie osseuse et présentant une MO d’aspect normal en IRM. Les paramètres de perfusion semi-quantitatifs et pharmacocinétiques ont été mesurés dans 15 régions d’intérêt chez chaque patient. Tous les paramètres de perfusion diffèrent entre les zones de MO rouge et de MO jaune. La perfusion est différente entre les MO acétabulaire (squelette axial) et fémorale intertrochantérienne (squelette appendiculaire). Plusieurs paramètres sont corrélés de manière négative à l’âge. Plusieurs paramètres sont différents entre les hommes et les femmes. La perfusion de la tête fémorale est hétérogène, probablement en raison de l’exposition aux contraintes mécaniques. Les paramètres Ktrans, Kep et TTP sont corrélés à l’indice de masse corporelle, ce qui suggère que l’obésité influence le métabolisme de la MO. Enfin, le tabagisme et l’hypercholestérolémie ont une incidence sur ces mêmes paramètres dans certaines zones. Ils pourraient donc être le reflet d’altérations de la microvascularisation osseuse. Ces travaux ouvrent de nouvelles perspectives de recherche sur la physiologie et la pathologie de la MO. / Bone Marrow (BM) microvascular properties are insufficently known in humans. Dynamic-Contrast Enhanced (DCE) MRI allows its non-invasive quantitative assessment. We concentrated on the hip because this joint is frequently affected by debilitating pathologies such as osteoarthritis. Their early diagnosis is a current medical challenge. We implemented a 3D DCE-MRI sequence with isotropic voxels, high spatial resolution and a large coverage. It was used in a study of 60 patients aged 18 to 60, with no previous history of bone disease and with normal-appearing BM on MR images. Semi-quantitative and pharmacokinetic parameters were measured in 15 regions of interest in each patient. All the parameters were different between red and yellow BM. Perfusion was different between acetabular (axial skeleton) and femoral intertrochanteric (appendicular skeleton) BMs. Several parameters were negatively correlated with age. Perfusion was different in men and women. The femoral head perfusion was heterogeneous, likely because of mechanical load exposure. Ktrans, Kep and TTP were correlated with body mass index. This suggests that obesity influences BM metabolism. Smoking and hypercholesterolemia influenced these same parameters in several zones. We hypothesized that these parameters might reflect BM microvascular aletrations. Our results open new research perspectives both in the physiology and pathology of BM.

Heidelberg, Univ., Diss., 2005.