How does saline backflow affect the treatment of saline-infused radiofrequency ablation?

BACKGROUND AND OBJECTIVE

Saline infusion is applied together with radiofrequency ablation (RFA) to enlarge the ablation zone. However, one of the issues with saline-infused RFA is backflow, which spreads saline along the insertion track. This raises the concern of not only thermally ablating the tissue within the backflow region, but also the loss of saline from the targeted tissue, which may affect the treatment efficacy.

METHODS

In the present study, 2D axisymmetric models were developed to investigate how saline backflow influence saline-infused RFA and whether the aforementioned concerns are warranted. Saline-infused RFA was described using the dual porosity-Joule heating model. The hydrodynamics of backflow was described using Poiseuille law by assuming the flow to be similar to that in a thin annulus. Backflow lengths of 3, 4.5, 6 and 9 cm were considered.

RESULTS

Results showed that there is no concern of thermally ablating the tissue in the backflow region. This is due to the Joule heating being inversely proportional to distance from the electrode to the fourth power. Results also indicated that larger backflow lengths led to larger growth of thermal damage along the backflow region and greater decrease in coagulation volume. Hence, backflow needs to be controlled to ensure an effective treatment of saline-infused RFA.

CONCLUSIONS

There is no risk of ablating tissues around the needle insertion track due to backflow. Instead, the risk of underablation as a result of the loss of saline due to backflow was found to be of greater concern.

Changing the syringe pump: A challenging procedure in critically ill patients

INTRODUCTION

In the literature, the change of a syringe pump is described as a dangerous situation, especially in the case of vasoactive drug administration.

METHODS

Different variables have been studied (central venous pressure, pump displacement in relation to the patient position, utilization of a stopcock, or a neutral displacement needle-free connector between the syringe and the infusion tubing) to understand their influence on medication administration in terms of backflow or bolus creation when changing the syringe.

RESULTS

We performed 576 measurements with different combinations. With respect to all the observations, in comparison with "time zero," we found the following differences expressed in microliters: 0 (±1) at the plunger opening; 0 (±3) at the syringe extraction from the pump; 0 (±7) at the syringe disconnection from the infusion tubing; 0 (±11) at the syringe reconnection to the infusion tubing; 1 (±7) at the syringe insertion in the pump; 3 (±23) at the plunger closing; 8 (±33) at the stabilization at the maneuver end.

CONCLUSION

The syringe change can be a very critical moment given different influencing variables. Syringe pump position, displaced higher than the patient level, always generates a medication bolus that is higher at the lowering of the central venous pressure value. The presence of a neutral displacement needle-free connector reduces the incidence of boluses. When the pump is placed at the patient level, the presence of neutral displacement needle-free connector reduces the establishment of boluses, even in a central venous pressure of -5 mmHg simulations.

Accuracy comparisons of intra-articular knee injection between the new modified anterolateral Approach and superolateral approach in patients with symptomatic knee osteoarthritis without effusion

Background

Intra-articular knee injection with steroid or various other agents have been used to control the local inflammation and relieve pain in the osteoarthritis knee. To achieve the maximal potential therapeutic worth and decrease the complications from the inaccurate knee injection, these medications should be delivered directly into the intra-articular space. Injection technique is one of the most important factors for accuracy of knee injection. Therefore, this study was aimed to propose the new modified anterolateral injection technique for higher accuracy of knee injection in symptomatic osteoarthritis knee without effusion.

Material and methods

Patients with symptomatic osteoarthritis without effusion were included prospectively from May 2014 to May 2015 and randomized into 2 groups for knee injection: Modified anterolateral (MAL), Standard superolateral (SL). Knee injection was performed by one experienced orthopaedic. Accuracy of injection was test by mini air-arthrography technique. The pain from injection were evaluated by visual analog scale (VAS).

Result

132 knees were included, 66 knees were modified anterolateral group same as superolateral group. The modified anterolateral injection was significantly yield the higher accuracy rate than the standard superolateral injection (89% vs 58%, P < 0.05). The pain visual analog scale was not significantly different between the modified anterolateral and standard superolateral injection technique (2.61 vs 2.65, P = 0.917) No adverse events were occurred.

Conclusion

The new modified anterolateral injection yields the higher pooled accuracy rate. From the accuracy and the advantage of the new modified anterolateral injection, this is the preferred injection technique for the symptomatic osteoarthritis without knee effusion.

A Novel Multi-objective Physiological Control System for Rotary Left Ventricular Assist Devices

Various control and monitoring algorithms have been proposed to improve the left-ventricular assist device (LVAD) therapy by reducing the still-occurring adverse events. We developed a novel multi-objective physiological control system that relies on the pump inlet pressure (PIP). Signal-processing algorithms have been implemented to extract the required features from the PIP. These features then serve for meeting various objectives: pump flow adaptation to the perfusion requirements, aortic valve opening for a predefined time, augmentation of the aortic pulse pressure, and monitoring of the LV pre- and afterload conditions as well as the cardiac rhythm. Controllers were also implemented to ensure a safe operation and prevent LV suction, overload, and pump backflow. The performance of the control system was evaluated in vitro, under preload, afterload and contractility variations. The pump flow adapted in a physiological manner, following the preload changes, while the aortic pulse pressure yielded a threefold increase compared to a constant-speed operation. The status of the aortic valve was detected with an overall accuracy of 86% and was controlled as desired. The proposed system showed its potential for a safe physiological response to varying perfusion requirements that reduces the risk of myocardial atrophy and offers important hemodynamic indices for patient monitoring during LVAD therapy.

DPM dispersion inside a single straight entry using dynamic mesh model

Three-dimensional simulations of diesel particulate matter (DPM) distribution inside a single straight entry for the Load-Haul-Dump loader (LHD)-truck loading and truck hauling operations were conducted by using ANSYS FLUENT computational fluid dynamics software. The loading operation was performed for a fixed period of 3 min. The dynamic mesh technique in FLUENT was used to study the impact of truck motion on DPM distribution. The resultant DPM distributions are presented for the cases when the truck were driving upstream and downstream of the loading face. Interesting phenomena were revealed in the study including the piston effect, layering of DPM in the roof region, and backflow of diesel exhaust against ventilation. The results from the simulation can be used to determine if the areas inside the face area and straight entry exceed the current U.S. regulatory requirement for DPM concentration (>160 µg/m³). This research can guide the selection of DPM reduction strategies and improve the working practices for the underground miners.

Evaluation of one-way valves used in medical devices for prevention of cross-contamination

BACKGROUND

One-way valves used in day use devices (used on multiple patients throughout a day without reprocessing between patients) are intended to reduce the potential for cross-contamination between patients resulting from the backflow of patient fluids. One-way valves are typically designed to withstand high levels of back pressure before failure; however, they may not be explicitly designed as a means of infection control as used in medical device applications.

METHODS

Five different medical grade one-way valves were placed in low pressure configurations. After flushing in the intended direction of flow, bacteriophage, bacteria, or dye was placed patient side for 24 hours. The upstream device side of the valve was then evaluated for microbial growth or presence of visible dye.

RESULTS

Leakage (ie, backflow) of the microorganisms occurred with a variety of one-way valve designs across a range of fluid properties tested.

CONCLUSIONS

This study describes testing of the one-way valves (component-level testing) for the potential of cross-contamination. Although day use medical device systems may use numerous other factors to prevent patient cross-contamination, this work demonstrates that one-way valves themselves may not prevent leakage of contaminated fluid if the fluid is able to reach the upstream side of the one-way valve.

Consequences of not relieving negative internal pressure of a medication vial: A survey and simulation study

STUDY OBJECTIVE

The glass vial of acetaminophen as an intravenous preparation (Acelio®, Terumo, Japan) has a strong internal negative pressure. The aim of our study was to determine if this negative pressure could result in medication administration errors if not released prior to connecting to the IV set.

DESIGN

Questionnaire survey and simulation study.

SETTING

University hospital and its affiliated hospitals.

SUBJECTS

Fifty-two anesthesiologists in 6 different hospitals in Yokohama.

MEASUREMENTS

A questionnaire on current practice was sent to the subjects. The authors then first calculated the internal pressure of the Acelio® vial followed by a simulation set-up. This set-up measured the amount of saline that could be aspirated from a syringe loaded on a syringe pump connected via a secondary IV line when the Acelio® vial was attached to the primary line without prior release of the internal pressure. The volume of aspiration was tested with two syringe sizes and with a fully open IV clamp vs partially closed.

MAIN RESULTS

Twenty-nine (56.9%) of 51 anesthesiologists who responded to the survey had connected the Acelio® vial at least once without releasing the internal negative pressure, and 21 experienced consequences such as backflow of the venous blood. The pressure inside the Acelio® vial was 81.8±19.6Torr. With the clamp of the simulated IV line fully open, the amount of saline aspirated before the alarm of the syringe pump went off was 1.5±0.1ml and 3.2±0.3ml when 20ml and 50ml syringes were used, respectively. When the clamp was partially closed to allow 2 drops per second, this value was 1.3±0.1ml and 2.3±0.1ml, respectively. After removing the plunger from the holder of the syringe pump, an additional 7ml (clamp partially closed) or 15-18ml (clamp fully open) was aspirated in the subsequent 1min.

CONCLUSIONS

A considerable number of anesthesiologists experienced consequences caused by the negative pressure inside the Acelio® vial. This can also cause aspiration of the contents of the syringe pump.

Evaluation of the delivered activity of yttrium-90 resin microspheres using sterile water and 5 % glucose during administration

BACKGROUND

The purpose of this study is to evaluate the impact of switching from sterile water to 5 % glucose (G5W) for the administration of yttrium-90 ((90)Y)-resin microspheres on the total activity of (90)Y administered (expressed as a proportion of the prescribed/calculated activity), as well as the number of cases of stasis and the reported incidence of discomfort during the selective internal radiation therapy (SIRT) procedure.

METHODS

In December 2013, we switched from sterile water to G5W for the administration of SIRT using (90)Y resin microspheres in all patients. This retrospective observational single-center case series describes our experience in the months preceding and after the switch. Apart from the change in administration medium, the protocol for SIRT was otherwise identical.

RESULTS

One hundred and four SIRT procedures were performed on 78 patients (45 male, mean age: 63 years, range: 31-87 years) with either unresectable hepatocellular carcinoma, cholangiocarcinoma, or chemorefractory liver-dominant metastatic cancer. Compared with sterile water, the whole prescribed activity was administered in significantly more procedures with G5W: 85 vs. 22 %; p < 0.0001. A significantly higher proportion of the calculated activity was administered with G5W: 96.1 ± 11.0 % vs. 77.4 ± 24.3 % (p < 0.0001). G5W procedures were also associated with a significantly lower incidence of stasis (28 vs. 11 % procedures; p = 0.02) and mild-to-moderate upper abdominal pain during the procedure (1.8 vs. 44 % procedures; p < 0.0001).

CONCLUSIONS

Replacing sterile water with isotonic G5W during administration favorably impacts on the safety of SIRT, eliminates and/or minimizes flow reductions and stasis/reflux during administration of (90)Y resin microspheres, improves percentage activity delivered, and reduces peri-procedural pain.

Morphometry of boar sperm head and flagellum in semen backflow after insemination

Once deposited in the female reproductive system, sperm begin their competition and undergo a selection to reach the site of fertilization. Little is known about the special characteristics of sperm that reach the oviduct and are able to fertilize, with even less information on the role of sperm dimension and shape in transport and fertilization. Here, we examine whether sperm morphometry could be involved in their journey within the uterus. For this purpose, sperm head dimension (length, width, area, and perimeter) and shape (shape factor, ellipticity, elongation, and regularity), and flagellum length were analyzed in the backflow at different times after insemination (0-15, 16-30, and 31-60 minutes). Sperm morphometry in the backflow was also analyzed taking into account the site of semen deposition (cervical vs. intrauterine). Finally, flagellum length was measured at the uterotubal junction. Sperm analyzed in the backflow were small (head and flagellum) with different head shapes compared with sperm observed in the dose before insemination. The site of deposition influenced head morphometry and tail size both being smaller in the backflow after cervical insemination compared with intrauterine insemination. Mean tail length of sperm collected in the backflow was smaller than that in the insemination dose and at the uterotubal junction. Overall, our results suggest that sperm size may be involved in sperm transport either because of environment or through sperm selection and competence on their way to encounter the female gamete.

Convection Enhanced Delivery: A Comparison of infusion characteristics in ex vivo and in vivo non-human primate brain tissue

Background

Convection enhanced delivery (CED) is emerging as a promising infusion toolto facilitate delivery of therapeutic agents into the brain via mechanically controlled pumps. Infusion protocols and catheter design have an important impact on delivery. CED is a valid alternative for systemic administration of agents in clinical trials for cell and gene therapies. Where gel and ex vivo models are not sufficient in modeling the disease, in vivo models allow researchers to better understand the underlying mechanisms of neuron degeneration, which is helpful in finding novel approaches to control the process or reverse the progression. Determining the risks, benefits, and efficacy of new gene therapies introduced via CED will pave a way to enter human clinical trial.

Purpose

The objective of this study is to compare volume distribution (Vd)/ volume infused (Vi) ratios and backflow measurements following CED infusions in ex vivo versus in vivo non-human primate brain tissue, based on infusion protocols developed in vitro.

Methods

In ex vivo infusions, the first brain received 2 infusions using a balloon catheter at rates of 1 μL/min and 2 μL/min for 30 minutes. The second and third brains received infusions using a valve-tip (VT) catheter at 1 μL/min for 30 minutes. The fourth brain received a total of 45 μL infused at a rate of 1 μL/min for 15 minutes followed by 2 μL/min for 15 minutes. Imaging was performed (SPGR FA34) every 3 minutes. In the in vivo group, 4 subjects received a total of 8 infusions of 50 μL. Subjects 1 and 2 received infusions at 1.0 μL/min using a VT catheter in the left hemisphere and a smart-flow (SF) catheter in the right hemisphere. Subjects 3 and 4 each received 1 infusion in the left and right hemisphere at 1.0 μL/min.

Results

MRI calculations of Vd/Vi did not significantly differ from those obtained on post-mortem pathology. The mean measured Vd/Vi of in vivo (5.23 + /-1.67) compared to ex vivo (2.17 + /-1.39) demonstrated a significantly larger Vd/Vi for in vivo by 2.4 times (p = 0.0017).

Conclusion

We detected higher ratios in the in vivo subjects than in ex vivo. This difference could be explained by the extra cellular space volume fraction. Studies evaluating backflow and morphology use in vivo tissue as a medium are recommended. Further investigation is warranted to evaluate the role blood pressure and heart rate may play in human CED clinical trials.

Ramped-rate vs continuous-rate infusions: An in vitro comparison of convection enhanced delivery protocols

Background

Convection enhanced delivery (CED) is a technique using infusion convection currents to deliver therapeutic agents into targeted regions of the brain. Recently, CED is gaining significant acceptance for use in gene therapy of Parkinson’s disease (PD) employing direct infusion into the brain. CED offers advantages in that it targets local areas of the brain, bypasses the blood-brain barrier (BBB), minimizes systemic toxicity of the therapeutics, and allows for delivery of larger molecules that diffusion driven methods cannot achieve. Investigating infusion characteristics such as backflow and morphology is important in developing standard and effective protocols in order to successfully deliver treatments into the brain. Optimizing clinical infusion protocols may reduce backflow, improve final infusion cloud morphology, and maximize infusate penetrance into targeted tissue.

Purpose

The purpose of the current study was to compare metrics during ramped-rate and continuous-rate infusions using two different catheters in order to optimize current infusion protocols. Occasionally, the infusate refluxes proximally up the catheter tip, known as backflow, and minimizing this can potentially reduce undesirable effects in the clinical setting. Traditionally, infusions are performed at a constant rate throughout the entire duration, and backflow is minimized only by slow infusion rates, which increases the time required to deliver the desired amount of infusate. In this study, we investigate the effects of ramping and various infusion rates on backflow and infusion cloud morphology. The independent parameters in the study are: ramping, maximum infusion rate, time between rate changes, and increments of rate changes.

Methods

Backflow was measured using two methods: i) at the point of pressure stabilization within the catheter, and ii) maximum backflow as shown by video data. Infusion cloud morphology was evaluated based on the height-to-width ratio of each infusion cloud at the end of each experiment. Results were tabulated and statistically analyzed to identify any significant differences between protocols.

Results

The experimental results show that CED rampedrate infusion protocols result in smaller backflow distances and more spherical cloud morphologies compared to continuous-rate infusion protocols ending at the same maximum infusion rate. Our results also suggest internal-line pressure measurements can approximate the time-point at which backflow ceases.

Conclusion

Our findings indicate that ramping CED infusion protocols can potentially minimize backflow and produce more spherical infusion clouds. However, further research is required to determine the strength of this correlation, especially in relation to maximum infusion rates.

Boar sperm with defective motility are discriminated in the backflow moments after insemination

During insemination, a large number of spermatozoa are deposited in the female genital tract, but a very low percentage is able to colonize the site of fertilization. The influx of neutrophils into the uterine lumen and semen reflux (backflow) are known mechanisms that decrease the number of spermatozoa within the uterus. No report has attempted to ascertain whether the backflow is a random or selective process of the spermatozoa. In this work, sows were inseminated using two populations of spermatozoa in the same proportion: (1) unstained spermatozoa with high motility and (2) stained spermatozoa with low, medium, or high motility. Volume, number, and percentage of stained spermatozoa were evaluated in the backflow (collected at 0-15, 16-30, and 31-60 minutes after insemination). This article provides evidence that (1) the motility characteristics of the spermatozoa do not influence the percentage of sows with backflow, the volume and number of spermatozoa in the backflow; (2) the discarding of spermatozoa in the backflow is not specific during the first moments after insemination (0-15 minutes), whereas later (16-60 minutes), spermatozoa with defective motility (low and medium groups) are discarded in a higher proportion than high group in the backflow ([16-30 minutes: low, 85.13 ± 4.32%; medium, 72.99 ± 5.05%; and high, 54.91 ± 2.38%; P < 0.0001; 31-60 minutes: low, 87.16 ± 6.01%; medium, 87.02 ± 4.01%; and high, 59.35 ± 2.86%; P = 0.001]). Spermatozoa with poor motility are discarded in the backflow probably as a selective process, on the part of the female genital tract or as a result of the intrinsic low spermatozoa motility.