Outflow Tube Research Articles

Discovery of delayed gas production after implantation of a continuous-flow left ventricular assist device and a preliminary exploration of the mechanisms of its occurrence.

To characterize the gas production phenomenon in the animal model of left ventricular assist device (LVAD), and study its mechanism. An in vitro bubble precipitation experiment was conducted, and the blood samples of Parma spp. animals were divided into ordinary group and oxygen-enriched group according to whether they were oxygenated or not at the time of blood collection, and a static control group was set up respectively. Blood gases were drawn and analyzed before and after the experiment. Activate the pump, and the number of air bubbles in the loop was measured by ultrasound at different rotational speeds; CFD was applied to simulate the flow field in the blood pump, and pressure, fluid velocity vector and shear force diagrams were plotted, and a thrombus model was constructed and the flow field was simulated and plotted as a cloud diagram. There was a statistical difference in the number of bubbles in the inflow and outflow tubes of the blood pump (P values of 0.04 and 0.023, respectively), and the number of bubbles in the outflow tubes of both groups was significantly higher than the number of bubbles in the inflow tubes. The number of bubbles in the tubes of both the oxygen-enriched and normal groups was significantly higher than that in the inflow group. In both the normal and oxygen-enriched groups, more gas was produced at higher speeds than at lower speeds. Blood gas analysis showed that the reduced gas composition in the blood was mainly oxygen. Flow field simulation results: the high rotation speed group had lower central pressure and greater scalar shear. The thrombus simulation group was more prone to turbulence, sudden pressure changes, and greater shear than the normal group. Blood gas production is associated with higher partial pressures of blood oxygen, higher rotation speed, and intrapump thrombosis, and the mechanism of pump gas production is degassing of dissolved gases rather than cavitation of water, and the gas released is most likely to have oxygen. The degassing phenomenon is an warning factor for pump thrombosis.

Treatment of intractable septic ankle arthritis with a continuous closed irrigation system.

The study aimed to evaluate the efficacy of a continuous closed irrigation system (CCIS) after open debridement for patients with intractable septic ankle arthritis. The retrospective study analyzed the intractable septic arthritis of 12 (6 males, 6 females; mean age: 64.1±14.7 years; range, 33 to 80 years) patients managed by CCIS between July 2015 and July 2020. All patients had previously undergone operations to treat septic ankle arthritis without resolution of the infection. After open debridement, the CCIS was usually equipped with two outflow tubes and one inflow tube. Saline inflow was about 1 L per day. The mean follow-up period was 30.8±14.9 (range, 15 to 70) months. The CCIS was maintained for a mean of 5.1±2.1 (range, 3 to 7) days. The mean number of operations the patients had previously undergone was 2.83±1.5 (range, 1 to 6). For 11 (91.6%) out of 12 patients, infection did not recur after one-time CCIS, and laboratory test results remained normal. Six patients had previously undergone total ankle replacement arthroplasty. These patients underwent antibiotics-mixed cement arthroplasty after CCIS. For five of six with infected total ankle replacement arthroplasty, infection did not recur after CCIS. However, one patient without the removal of both implants experienced recurrence at the same site after four postoperative months. In the reoperation, after the removal of both implants and the application of antibiotics-mixed cement arthroplasty, the infection was cleared. Use of CCIS after open debridement for intractable septic ankle arthritis is a good treatment option since it is relatively simple and safe, with good results.

Case Report on CAKUT Syndrome with Known Case of Chronic Kidney Disease

Background: Congenital abnormalities of the kidneys and urinary tracts (CAKUT) are conditions brought on by errors in the growth of the kidneys and the outflow tubes that drain the kidneys. Although the issue may not become apparent until later in life, CAKUT is a congenital abnormality brought on by improper urinary system development. Case presentation: We are presenting the case of a 23-year-old man who has chronic kidney disease and is undergoing maintenance hemodialysis. The patient was apparently alright 2 weeks back when he had complained of breathlessness. fever 2 episodes, lower which was insidious in onset and gradually progressive. On arrival, the patient was provided oxygen therapy via a face mask for breathlessness and to make him feel comfortable with the head elevation. On laboratory investigation, the patient’s blood values are altered. The patient underwent computed tomography of the kidney-ureter-bladder (CT-KUB), and Ultrasonography of the kidneys (USG). A permanent tunnel hemodialysis catheter under local anesthesia was placed and he received 2 cycles of hemodialysis. During the course in the hospital, the patient’s condition was improving and was stable clinically and vitally hence, the patient was discharged. Conclusion: CAKUT can occur alone or in conjunction with heart and cardiovascular malformations, gastrointestinal tract malformations, central nervous system malformations, skeletal system malformations, lung, face, genito-reproductive system malformations, abdominal wall malformations, chromosomal abnormalities, MCA, and other organ system malformations.

A fluidic relaxation oscillator for reprogrammable sequential actuation in soft robots

A fluidic relaxation oscillator for reprogrammable sequential actuation in soft robots

An Improved Device Clears Blockages in the Tube of Irrigation and Drainage Systems

The outflow tube may be blocked during continuous irrigation for the treatment of septic joints. Although multiple solutions have been applied to clear the blockage, there are still many disadvantages. The success rate is difficult to guarantee, and bacteria may enter the joint cavity and cause secondary infection. We designed an improved irrigation and drainage system that avoids these disadvantages and is particularly convenient to use. In addition, the improved system provides more thorough lavage and drainage and prevents joint adhesion.

Increasing the pulsatility of continuos flow VAD: comparison between a valvulated outflow cannula and speed modulation by simulation

To investigate by a lumped parameter model the feasibility of increasing the pulsatility of a continuous flow VAD,implanting an active valvulated outflow cannula and tocompare the resultswith the haemodynamic outcome given by speed modulation methods.The concomitant presence of speed modulation and the active valvulated outflow conduit is also simulated. A lumped parameter model was adopted. VAD was modeled starting from its pressure flow characteristics with a second order polynomial equation. The valvulated outflow conduit was modeled as an active resistance described by a square function. Starting from pathological condition we simulated: VAD; VAD and valvulated outflow conduit in copulsation, counterpulsation and asynchrony work with the heart; VAD and active valvulated outflow tube and speed modulation. Copulsation 1:1 andasynchrony 0.3s valve close-0.7s valve open configurationsmaximised the haemodynamic benefits with the highest increment in pulsatility. The valvulated outflow conduit causes a decrement of the left ventricular unloading and of VAD flow that can be counteracted by increasing the VAD speed without affecting pulsatility. The concomitant use of the speed modulation and the active valvulated outflow conduit can further increase the pulsatility without altering left ventricular unloading and VAD flow. The valvulated outflow tube provide similar increase in pulsatility to speed modulation method but causes a decrement of left ventricular unloading and VAD flow that can be counteracted increasing the VAD speed or allowing a partial support. A valvulated outflow tube can be potentially applied to all continuous flow VADs.

Designing an Active Valvulated Outflow Conduit for a Continuous-Flow Left Ventricular Assist Device to Increase Pulsatility: A Simulation Study.

The purpose of this work was to investigate, using a lumped parameter model, the feasibility of increasing the pulsatility of a continuous-flow ventricular assist device (VAD) by implanting an active valvulated outflow cannula. A lumped parameter model was adopted for this study. VAD was modeled, starting from its pressure-flow characteristics. The valvulated outflow conduit was modeled as an active resistance described by a square function. Starting from pathologic condition, the following simulations were performed: VAD, VAD and valvulated outflow conduit in copulsation and counterpulsation with different ratios between the VAD valve opening rate and the heart rate, and asynchrony work with the heart with different VAD valve opening intervals. The copulsation 1:1 configuration and the asynchrony 0.3s-close-0.7s-open configurations permit to maximize the hemodynamic benefits provided by the presence of the active VAD outflow valvulated conduit providing an increase of arterial pulsatility from 1.86% to 14.98% without the presence of left ventricular output. The presence of the active VAD valve in the outflow conduit causes a decrement of the left ventricular unloading and of VAD flow and, that can be counteracted by increasing the VAD speed without affecting arterial pulsatility. The valvulated outflow tube provides an increase in arterial pulsatility; it can be driven in different working modality and can be potentially applicable to all types of VADs. However, the valvulated outflow conduit causes a decrement of left ventricular unloading and of the VAD flow that can be counteracted, increasing the VAD speed.

A prototype non-invasive urodynamic test to estimate voiding reserve in normal adult males

ABSTRACTObjective: To propose a prototype non-invasive test to estimate voiding reserve in normal adult men; identifying its feasibility, limitations, and initial results.Subjects and methods: In all, 30 adult healthy male volunteers aged <40 years were included in the study. Initial free uroflowmetry was done with post-void residual urine volume (PVR) assessment using ultrasonography. The men were later asked to void into a uroflowmeter through a condom catheter attached to the glans penis and connected to an outflow tube with specific vertical heights (10, 20, 30, 40, 50 and 60 cm) on different days. The mean maximum urinary flow rate (Qmax) and PVR at each height were compared with the Qmax and PVR at the initial free uroflowmetry. The maximum height at which the Qmax and PVR remained normal was considered the normal voiding reserve for that age group.Results: All the men completed the study without any complications. At zero level, the mean Qmax was 27.6 mL/s, which then dropped gradually to reach 17.8 mL/s at 60 cm, where still 83% of the men had a normal Qmax. The PVR was nil at zero level and started to exceed the normal range at 50 and 60 cm height (58 and 65.7 mL, respectively). So, the maximum height resistance at which the men could have a normal Qmax and normal PVR was 40 cm.Conclusions: The use of the tube height-resistance test to assess voiding reserve is feasible, non-invasive and has no complications. A 40-cm height resistance can be considered a reference level that a young adult male should be tested against to estimate his voiding reserve.Abbreviations: NPV: negative predictive value; PdetQmax: maximum detrusor pressure at maximum urinary flow; PPV: positive predictive value; PVR: post-void residual urine volume; ROC: receiver operating characteristic

Harvesting the Liver From a Donor With a Biventricular Assist Device (BiVAD)—An Unexpectedly Challenging Procedure: A Case Report

BackgroundOrgan procurement from deceased donors is usually a standard procedure. Nevertheless, the performing surgeon is often confronted with demanding situations, such as atherosclerotic or aneurysmatic aortic disease or even other pathologies, which may alter the surgical steps. We report on an interesting case of solid organ harvesting from a donor with a biventricular assist device (BiVAD) due to global heart failure. Case ReportA 42-year-old male donor with a BiVAD, enlisted for heart transplantation, died of intracerebral hemorrhage. Dressing the surgical field was challenging because the extracorporal portions of all 4 tubes and the pump device rested on the donor's body, covering his whole abdomen. To ensure enough space, the pump and tubes had been covered with sterile swabs and drapes. The second surgical assistant was tasked with holding the device slightly deviated to the left and the ankle elevated at 45°, to avoid any tube kinking. The dissection of the main vessels distally was performed using the standard technique. No encirclement of the proximal aorta beneath the diaphragm was necessary, as the cardiac output could be arrested by clamping the left ventricle's outflow tube. Once the perfusion was completed, the procedure continued in the standard fashion. ConclusionSo far, the literature has no data on organ harvesting from deceased donors with BiVAD. Although such a retrieval is quite challenging and requires an experienced team, the transplantation of the corresponding organs can be performed without any further special technical problems.

The Subacromial Bursa is a Viable Source of Autologous Mesenchymal Stem Cells for Rotator Cuff Repair

Objectives: Chronic rotator cuff tears still represent a significant source of morbidity and functional decline in the general population. The purpose of this study was to establish protocols for isolation and expansion of bursa-derived mesenchymal stem cells (BDSCs) and to evaluate their differentiation capacity, including tenogenesis. We hypothesized that BDSCs would be capable of multilineage differentiation (including tenogenesis) and represent an important source for autologous stem cells for patients undergoing rotator cuff repair. Methods: After IRB approval, 10 patients (ages 43-65 years) scheduled to undergo arthroscopic repair for chronic rotator cuff tears were enrolled. During diagnostic arthroscopy, subacromial bursa tissue was harvested using an arthroscopic shaver and collected by attaching the outflow tubing to a specialized specimen cup. Tissue specimens were transported to our laboratory for analysis. BDSCs were isolated via adherent culture and plated in Dulbecco’s Modified Eagle’s Medium (DMEM) supplemented with 10% Fetal Bovine Serum (FBS). Chondrogenic, adipogenic, and osteogenic induction media were used to induce differentiation. Tenogenic induction was performed using DMEM supplemented with varying concentrations of BMP-12, ascorbic acid, and human tenocyte-conditioned media. Alcian Blue staining was used to evaluate chondrogenesis, Oil Red O staining for adipogenesis, and Alkaline Phosphatase staining for osteogenesis. Gene expression markers for adipogenesis (ADIPOQ, FABP4, PPARγ), chondrogenesis (COL2A1 and SOX5), and osteogenesis (osteocalcin, osterix), along with primary antibodies to tenogenic markers (scleraxis, tenomodulin), were used to verify each cell lineage. Results: BDSCs isolated by adherent culture without collagen exhibited a spindle-shaped morphology characteristic of mesenchymal stem cells (MSCs), formed colonies, and demonstrated great expandability for six to eight passages without morphology changes (Figure 1A). After 3 weeks of culture, 95% (p&lt;0.0001) of the BDSCs expressed the MSC surface marker CD90 and were negative for non-MSC cell markers (CD45, CD146, CD31, and CD34) (Figure 1B and C). These BDSCs demonstrated a capacity for adipogenesis (positive Oil Red O staining, ADIPOQ, FABP4, PPARγ expression), osteogenesis (positive alkaline phosphatase staining, positive osteocalcin and scleraxis expression), chondrogenesis (positive Alcian Blue staining, positive COL2A1 and SOX5 expression), and tenogenesis (scleraxis and tenomodulin expression) (Figure 2). The results indicate that BDSCs are multipotent as evidenced by their differentiation into fat, bone, cartilage, and tendon cells. For tenogenesis, we found that 7-day incubation in DMEM supplemented with 100 ng/mL of BMP-12 and 50 μg/mL of ascorbic acid produced superior tenogenic induction. These BDSCs adapted an elongated morphology combined with the expression of both scleraxis and tenomodulin - a unique characteristic of native tenocytes. Conclusion: Our results demonstrate that subacromial bursa represents a viable source of mesenchymal stem cells. We developed a reliable protocol for isolation of BDSCs from patient bursa samples. We show that BDSCs in the presence of BMP-12 and ascorbic acid can differentiate toward a tenogenic lineage. Our work provides strong evidence that BDSCs may be a potent tool for cellular therapy and may benefit future patients who undergo surgical repair of chronic rotator cuff tears. [Figure: see text][Figure: see text]

Death in a Carbon Dioxide Therapy Bath: A Case Report and Review of the Literature.

Carbon dioxide (CO2) therapy is the subcutaneous or transcutaneous administration of CO2 for therapeutic purposes. Carbon dioxide therapy is used for localized lipolysis, to treat chronic skin conditions, and is a safe treatment. Full-body CO2 baths are offered in European spa centers, in which the clients are placed into full body bags infused with CO2 at an optimal concentration range between 1000 and 1400 mg/L (516 000-722 500 ppm). Commercially manufactured, air-tight bags and accompanying apparatus designed to provide CO2 baths can be purchased for home use. Few human CO2-related deaths have been reported. They have been mostly accidental, consisting of persons trapped in a closed environment in the presence of "dry ice" or solid CO2. There have been no reported deaths of a human undergoing a CO2 therapy at home. We present a case of a middle-aged male found at home completely inside an air-sealed bag wrapped tightly around his body. The bag was connected to a working pump and a CO2 gas tank. The pump was connected through an inflow and outflow circuit to the bag. The inflow tubing for CO2 gas delivery was partially disrupted, while the outflow tubing was intact. The autopsy and toxicology were unremarkable. The cause of death was determined to be asphyxia by vitiated atmosphere as evident by the displacement of oxygen by CO2 and low pressure created inside a "CO2 therapy bath." The manner of death was accidental.

A novel method for sampling the suspended sediment load in the tidal environment using bi-directional time-integrated mass-flux sediment (TIMS) samplers

Identifying the source and abundance of sediment transported within tidal creeks is essential for studying the connectivity between coastal watersheds and estuaries. The fine-grained suspended sediment load (SSL) makes up a substantial portion of the total sediment load carried within an estuarine system and efficient sampling of the SSL is critical to our understanding of nutrient and contaminant transport, anthropogenic influence, and the effects of climate. Unfortunately, traditional methods of sampling the SSL, including instantaneous measurements and automatic samplers, can be labor intensive, expensive and often yield insufficient mass for comprehensive geochemical analysis. In estuaries this issue is even more pronounced due to bi-directional tidal flow. This study tests the efficacy of a time-integrated mass sediment sampler (TIMS) design, originally developed for uni-directional flow within the fluvial environment, modified in this work for implementation the tidal environment under bi-directional flow conditions. Our new TIMS design utilizes an ‘L’ shaped outflow tube to prevent backflow, and when deployed in mirrored pairs, each sampler collects sediment uniquely in one direction of tidal flow. Laboratory flume experiments using dye and particle image velocimetry (PIV) were used to characterize the flow within the sampler, specifically, to quantify the settling velocities and identify stagnation points. Further laboratory tests of sediment indicate that bidirectional TIMS capture up to 96% of incoming SSL across a range of flow velocities (0.3–0.6 m s−1). The modified TIMS design was tested in the field at two distinct sampling locations within the tidal zone. Single-time point suspended sediment samples were collected at high and low tide and compared to time-integrated suspended sediment samples collected by the bi-directional TIMS over the same four-day period. Particle-size composition from the bi-directional TIMS were representative of the array of single time point samples, but yielded greater mass, representative of flow and sediment-concentration conditions at the site throughout the deployment period. This work proves the efficacy of the modified bi-directional TIMS design, offering a novel tool for collection of suspended sediment in the tidally-dominated portion of the watershed.

Effect of an intervention in storm drains to prevent Aedes aegypti reproduction in Salvador, Brazil

BackgroundAedes aegypti, the principal vector for dengue, chikungunya and Zika viruses, is a synanthropic species that uses stagnant water to complete its reproductive cycle. In urban settings, rainfall water draining structures, such as storm drains, may retain water and serve as a larval development site for Aedes spp. reproduction. Herein, we describe the effect of a community-based intervention on preventing standing water accumulation in storm drains and their consequent infestation by adult and immature Ae. aegypti and other mosquitoes.MethodsBetween April and May of 2016, local residents association of Salvador, Brazil, after being informed of water accumulation and Ae. aegypti infestation in the storm drains in their area, performed an intervention on 52 storm drains. The intervention consisted of placing concrete at the bottom of the storm drains to elevate their base to the level of the outflow tube, avoiding water accumulation, and placement of a metal mesh covering the outflow tube to avoid its clogging with debris. To determine the impact of the intervention, we compared the frequency at which the 52 storm drains contained water, as well as adult and immature mosquitoes using data from two surveys performed before and two surveys performed after the intervention.ResultsDuring the pre-intervention period, water accumulated in 48 (92.3%) of the storm drains, and immature Ae. aegypti were found in 11 (21.2%) and adults in 10 (19.2%). After the intervention, water accumulated in 5 (9.6%) of the storm drains (P < 0.001), none (0.0%) had immatures (P < 0.001), and 3 (5.8%) contained adults (P = 0.039). The total number of Ae. aegypti immatures collected decreased from 109 to 0 (P < 0.001) and adults decreased from 37 to 8 (P = 0.011) after the intervention. Collection of immature and adult non-Aedes mosquitoes (mainly Culex spp.) in the storm drains also decreased after the intervention.ConclusionThis study exemplifies how a simple intervention targeting storm drains can result in a major reduction of water retention, and, consequently, impact Ae. aegypti larval populations. Larger and multi-center evaluations are needed to confirm the potential of citywide structural modifications of storm drains to reduce Aedes spp. infestation level.

1614not just 2d but also 4d flow measurements in pulsatile phantom are accurate and reproducible

Introduction: 4DFlow is an emerging technique with high potential in the evaluation of congenital and acquired heart diseases. The validation of accuracy and reproducibility of flow measurements in 4DFlow is of key importance for the clinical use of this technique. Here, we compare 2D and 4DFlow using a robust pulsatile flow phantom setup with different tube configurations and heart rates. Methods:Acquisition: A closed-circuit pulsatile flow phantom was built; composed by an industrial membrane flow pump, two counter-flow parallel silicone tubes (inflow tube at isocenter and center of FoV and outflow tube out of isocenter) and a Coriolis flow meter (Endress + Hauser), to measure a ground-truth net flow measure with a precision of about ±1ml/s. Two configurations were tested: 1) with tubes parallel to the z axis of the scanner (axial), and 2) with tubes placed in a double oblique. Flow phantom scans were performed on a GE 3T MR750w MR scanner (Waukesha, WI). Retrospectively gated PC; “breathhold” and “free-breathing” (with 3 averages) 2D through-plane FastCINE and kat ARC 4D Flow were scanned [1]. Table 1 summarizes the flow phantom configuration setups and the main MRI protocol parameters. Analysis: PC net flow measurements were evaluated using CVI42 software (Calgary, Canada) for 2D and Arterys (San Francisco, CA) for 4DFlow. For both, background phase correction (BPC) using static phantom correction [2] and image-based correction [3] was applied. Statistical analyses were performed in Microsoft Excel. Intraclass Correlation Coefficients (ICC) was used to evaluate reproducibility. The Bland-Altmann plot was used to compare the obtained net flow results using MR to the ground-truth value measured by the flow meter in percentage difference as a measure of accuracy. Results: At the position of the outflow tube (>8cm from isocenter) before BPC the highest background phase error of 13% for the lower VENC was found. However, Figure 1 shows a mean percentage error of less than 8% (less than 6% for 4DFlow) with respect to the ground-truth flow for both tubes and for all configurations after BPC. Reproducibility was excellent obtaining ICC = 0.97 for 20 datasets. Discussion: 2D PC and 4DFlow across multiple imaging conditions and setup configurations for a pulsatile flow phantom setup are reliable and accurate.

Development of a flow rate monitoring method for the wearable ventricular assist device driver.

Our research institute has been working on the development of a compact wearable drive unit for an extracorporeal ventricular assist device (VAD) with a pneumatically driven pump. A method for checking the pump blood flow on the side of the drive unit without modifying the existing blood pump and impairing the portability of it will be useful. In this study, to calculate the pump flow rate indirectly from measuring the flow rate of the driving air of the VAD air chamber, we conducted experiments using a mock circuit to investigate the correlation between the air flow rate and the pump flow rate as well as its accuracy and error factors. The pump flow rate was measured using an ultrasonic flow meter at the inflow and outflow tube, and the air flow was measured using a thermal mass flow meter at the driveline. Similarity in the instantaneous waveform was confirmed between the air flow rate in the driveline and the pump flow rate. Some limitations of this technique were indicated by consideration of the error factors. A significant correlation was found between the average pump flow rate in the ejecting direction and the average air flow rate in the ejecting direction (R2 = 0.704-0.856), and the air flow rate in the filling direction (R2 = 0.947-0.971). It was demonstrated that the average pump flow rate was estimated exactly in a wide range of drive conditions using the air flow of the filling phase.

New type of pump for the heart-lung bypass system

Objective: Complications arising from roller pump usage in modern heart-lung bypass (HLB) systems are widely known. Alternative to roller pumps has existed as various devices. This work is dedicated to developing new, considerably simpler and less expensive pump device for HLB systems, which provides maximally physiological pulsating blood flow. Material and Method: We used pediatric cardiotomy reservoirs of HLB systems as blood chambers. Two such reservoirs were placed in front of the oxygenator, with their in-flow tubes connected to the venous blood tubes, and the outflow tubes – to the entry to the oxygenator. In each reservoir, 2 air outlets tubes were connected to pneumo-receivers of positive and negative pressure. We filled up one of the reservoirs whith closed of exit blood tube by creating negative pressure in it. Simultaneously, with closed entry blood tube of the second reservoir, we ejected blood from it by created positive pressure. Used external pulsator. Results: In stand testing under re-circulation regime, productivity of the device was 12,5 liters/minute. Pressure on exit blood pump was within 0 to 300mm.Hg. The pump operating system enabled laminar, as well as pulsating flow of liquid, with frequency of 0-200 pulses/minute. Research is based on experiments conducted on 14 mongrel dogs weighing 20 kg. Standard methodology was used to cannulate Venae cavae and aorta, and to connect perfusion system to body. Duration of complete HLB reached 2 hours. Systolic pressure was maintained within 120-130mm.Hg.; diastolic – 70-80 mmHg. Velocity of blood flow in the aorta arc fluctuated within 950-1100 ml/min; in the femoral artery – within 60-80 ml/min. Conclusion: Preliminary tests of the new pump indicate that its hemodynamic characteristics are maximally approximated to physiological ones. In comparison to modern machines, a perfusion system with new pump type has minimal volume of fill-up and does not damage formative elements of blood.

A27 Session 8: Gastrointestinal Cryotherapeutic Indications : Local hypothermia: A potential multimodal reversible therapy for acute pancreatitis

The observations that the pancreas is hyper-metabolic on positron emission tomography during acute pancreatitis (AP), that multiple signaling cascades are activated during AP, and that several pharmacologic approaches tested in patients with AP have been unsuccessful in changing outcomes of the disease; suggest that a multimodal approach deserves consideration. Hypothermia is known to reduce metabolic demand, cell death and inflammation in other disease states; however generalized hypothermia can potentially compromise vital systems. We therefore aimed at learning the temperatures that would significantly slow deleterious signaling in pancreatic acinar cells (in which AP is initiated and which are damaged as a consequence of AP), and also explored approaches to induce pancreatic hypothermia without causing generalized hypothermia. Trypsin, cathepsin B activities and cathepsin B mediated trypsinogen activation to trypsin (TGA) were studied at 37 °C, 23 °C and 4 °C. In a separate set of experiments, pancreatic acinar cells were exposed to agents that induce AP i.e. caerulein (100nM; CER) or the bile salt sodium taurocholate (4 mM; STC), and TGA, up-regulation of mRNA levels of the chemokines CXCL1, 2, cell injury (LDH leakage, propidium iodide uptake) were studied at 37 °C, 34 °C, 31 °C, 28 °C and25 °C in response to the above stimuli. For in vivo studies, a collapsible gastric balloon attached to inflow and outflow tubing was placed in the stomach and perfused with ice cold water. Rectal, pancreas body and tail temperatures were measured. While trypsin and cathepsin B activities at 23 °C were respectively 53% and 64% of 37 °C, a temperature of 23 °C reduced cathepsin B mediated TGA to 26% of that at 37 °C. This was equal to the reduction in trypsin activity noted at 4 °C compared to 37 °C. There was a >80% reduction in CER induced TGA, CXCL1, 2 mRNA increase at 28 °C compared to 37 °C. The amount of cell injury induced by CER and STC at 37 °C was reduced by >80% at 34 °C and 31 °C respectively. Therapeutic induction of hypothermia 1 h after exposure to CER or STC required temperatures 3 °C lower than those needed to prophylactically reduce cell injury. Perfusion of the gastric balloon reduced pancreatic, but not rectal temperatures from 37.8±1.1 °C to 26.7±2.8 °C within 1 h, which normalized rapidly on discontinuing cooling. Hypothermia slows deleterious signaling in AP by sequentially slowing consecutive step in a synergistic manner, and also by slowing mechanistically distinct pathways which are simultaneously operating in AP. The pancreatic temperatures achieved by transgastric cooling in vivo , are in the range to sufficiently slow deleterious outcomes induced in acinar cells by agents that cause AP. These temperatures can be achieved in vivo without causing generalized hypothermia, and rapidly normalize on cessation of the cooling. Therefore Transgastric pancreatic hypothermia may be a better option than drug therapy in AP, by virtue of its being multimodal, rapid and reversible. Its efficacy in improving outcomes of AP needs to be tested in future studies.

Outcomes of Shunt Tube Coverage With Glycerol Preserved Cornea Versus Pericardium

Pericardium is a biomaterial widely used for covering the outflow tubes of glaucoma drainage devices. Recently, glycerol preserved cornea has been introduced as an alternative that offers durability and improved cosmesis because of its clarity. We retrospectively reviewed 262 patients in the University of Alabama Birmingham Glaucoma Service who underwent shunt procedures using either cornea tissue or pericardium to cover the tube. The primary outcome measure was the number of erosions of the covering material. Nine out of 101 (8.9%) patients in the pericardium covered group experienced an erosion compared with 3 out of 161 (1.9%) in the cornea covered group. A significant difference was reached with P=0.0125. Median follow-up was 440 days for the cornea group and 331 days for the pericardium group. The type of glaucoma (primary open-angle glaucoma vs. secondary glaucoma) was not associated with the risk of erosion (odds ratio, 0.501; 95% confidence interval, 0.204-1.234). The median time to exposure was 252 days in the pericardium group and 440 days in the cornea group (P=0.0017).

Acoustic analysis of a mechanical circulatory support.

Mechanical circulatory support technology is continually improving. However, adverse complications do occur with devastating consequences, for example, pump thrombosis that may develop in several parts of the pump system. The aim of this study was to design an experimental clot/thrombosis model to register and analyze acoustic signals from the left ventricular assist device (LVAD) HeartMate II (HMII) (Thoratec Corporation, Inc., Pleasanton, CA, USA) and detect changes in sound signals correlating to clots in the inflow, outflow, and pump housing. Using modern telecom techniques, it was possible to register and analyze the HMII pump-specific acoustic fingerprint in an experimental model of LVAD support using a mock loop. Increase in pump speed significantly (P < 0.005) changed the acoustic fingerprint at certain frequency (0–23 000 Hz) intervals (regions: R1–3 and peaks: P1,3–4). When the ball valves connected to the tubing were narrowed sequentially by ∼50% of the inner diameter (to mimic clot in the out- and inflow tubing), the frequency spectrum changed significantly (P < 0.005) in P1 and P2 and R1 when the outflow tubing was narrowed. This change was not seen to the same extent when the lumen of the ball valve connected to the inflow tube was narrowed by ∼50%. More significant (P < 0.005) acoustic changes were detected in P1 and P2 and R1 and R3, with the largest dB figs. in the lower frequency ranges in R1 and P2, when artificial clots and blood clots passed through the pump system. At higher frequencies, a significant change in dB figs. in R3 and P4 was detected when clots passed through the pump system. Acoustic monitoring of pump sounds may become a valuable tool in LVAD surveillance.

Volume quantification by contrast-enhanced ultrasound: an in-vitro comparison with true volumes and thermodilution

BackgroundContrast-enhanced ultrasound (CEUS) has recently been proposed as a minimally- invasive, alternative method for blood volume measurement. This study aims at comparing the accuracy of CEUS and the classical thermodilution techniques for volume assessment in an in-vitro set-up.MethodsThe in-vitro set-up consisted of a variable network between an inflow and outflow tube and a roller pump. The inflow and outflow tubes were insonified with an ultrasound array transducer and a thermistor was placed in each tube. Indicator dilution curves were made by injecting indicator which consisted of an ultrasound-contrast-agent diluted in ice-cold saline. Both acoustic intensity- and thermo-dilution curves were used to calculate the indicator mean transit time between the inflow and outflow tube. The volumes were derived by multiplying the estimated mean transit time by the flow rate. We compared the volumes measured by CEUS with the true volumes of the variable network and those measured by thermodilution by Bland-Altman and intraclass-correlation analysis.ResultsThe measurements by CEUS and thermodilution showed a very strong correlation (rs = 0.94) with a modest volume underestimation by CEUS of −40 ± 28 mL and an overestimation of 84 ± 62 mL by thermodilution compared with the true volumes. Both CEUS and thermodilution showed a high statistically significant correlation with the true volume (rs = 0.97 (95% CI, 0.95 - 0.98; P<0.0001) and rs = 0.96 (95% CI, 0.94 - 0.98; P<0.0001, respectively).ConclusionsCEUS volume estimation provides a strong correlation with both the true volumes in-vitro and volume estimation by thermodilution. It may therefore represent an interesting alternative to the standard, invasive thermodilution technique.