Block Failure Research Articles

Failed Nerve Blocks: Prevention and Management

Failed Nerve Blocks: Prevention and Management

Assessment of irrigation reservoir levee impairment in Arkansas, United States

The use of surface water resources for irrigation in the state of Arkansas increased over the years following 2000 due to groundwater depletion. In order to reduce dependence on groundwater, irrigation reservoirs and tailwater recovery systems are used to capture and store water for irrigation. Irrigation reservoir levees are typically constructed from local soils that are often low in cohesion, and the use of rock armoring and geotextiles is limited due to high costs, resulting in levees that are susceptible to erosion. Wind-driven waves erode the exposed inner slopes of the levees, resulting in the need for frequent repairs, an added expense for agricultural producers. Evaluation of the status of irrigation storage reservoirs and identification of design factors that contribute to erosion are needed to address the problem. A survey was conducted in 2013 to 2015 to assess the current state of levee erosion and attempt to identify associated factors. It was found that 79% of the 584 homogeneous levee segments contained within 148 surveyed reservoirs had block failures and near-vertical slopes. Despite regional winds with preferential southerly and northerly directions, levees of all orientations were damaged by waves. For the surveyed irrigation reservoir levees, soil type, vegetation, inner slope, and berm presence were found to be poor predictors of the state of impairment. The most important variable associated with levee failure was maximum effective fetch length, such that longer fetches were more likely to have block failures and greater loss of top width.

Architecture-aware coding for distributed storage: Repairable block failure resilient codes

In large scale distributed storage systems (DSS) deployed in cloud computing, correlated failures resulting in simultaneous failure (or, unavailability) of blocks of nodes are common. In such scenarios, the stored data or a content of a failed node can only be reconstructed from the available live nodes belonging to the available blocks. To analyze the resilience of the system against such block failures, this work introduces the framework of Block Failure Resilient (BFR) codes, wherein the data (e.g., a file in DSS) can be decoded by reading out from a same number of codeword symbols (nodes) from a subset of available blocks of the underlying codeword. Further, repairable BFR codes are introduced, wherein any codeword symbol in a failed block can be repaired by contacting a subset of remaining blocks in the system. File size bounds for repairable BFR codes are derived, and the trade-off between per node storage and repair bandwidth is analyzed, and the corresponding minimum storage regenerating (BFR-MSR) and minimum bandwidth regenerating (BFR-MBR) points are derived. Explicit codes achieving the two operating points for a special case of parameters are constructed, wherein the underlying regenerating codewords are distributed to BFR codeword symbols according to combinatorial designs. Finally, BFR locally repairable codes (BFR-LRC) are introduced, an upper bound on the resilience is derived and optimal code construction are provided by a concatenation of Gabidulin and MDS codes. Repair efficiency of BFR-LRC is further studied via the use of BFR-MSR/MBR codes as local codes. Code constructions achieving optimal resilience for BFR-MSR/MBR-LRCs are provided for certain parameter regimes. Overall, this work introduces the framework of block failures along with optimal code constructions, and the study of architecture-aware coding for distributed storage systems.

Comparison of efficacy of different concentration of bupivacaine in ultrasound-guided transversus abdominis plane (TAP) block for postoperative pain relief in lower segment cesarean section

Comparison of efficacy of different concentration of bupivacaine in ultrasound-guided transversus abdominis plane (TAP) block for postoperative pain relief in lower segment cesarean section

МЕТОДИКА ЧИСЛЕННОГО ИССЛЕДОВАНИЯ ДИНАМИЧЕСКОЙ ПРОЧНОСТИ КИРПИЧНОЙ КЛАДКИ С УЧЕТОМ ФРАГМЕНТАЦИИ

A methodology for numerically analyzing a 3D problem of nonstationary deformation and damage accumulation in brickwork is presented. The defining equation set is formulated in Lagrange variables. The equation of motion is derived from the balance of virtual work power. Kinematic relations are determined in the metrics of the current state. Brickwork is modeled as a continual hetero-modular medium, the properties of which depend on the stressed-strained state type and the current level of damage of the material. To analyze fragmentation of the brickwork, a simplified model is used, accounting for deformability of the seams, tensile and shear strengths of the brick 108 and mortar, as well as the contact interaction of the brickwork fragments. The problem is analyzed using the moment scheme of the finite-element method and the “cross”-type explicit finite-difference time integration scheme. The discretization of the computational area is based on eight-node finite elements with poly-linear approximation of displacement velocity. The finite element methodology is verified by analyzing the problem of deformation and failure of a brickwork block under explosive loading. The results of the numerical analysis of the problem are compared with experimental data for the failure form of the brickwork and the displacement of its center. Good agreement with the experimental data corroborates the reliability of the computations and effectiveness of the developed numerical analysis methodology. Keywords: brickwork, dynamic effect, damage accumulation, fragmentation, finite-element method.

BMAQR: balanced multi attribute QoS aware replication in HDFS

The Hadoop distributed file system (HDFS) replicates data to ensure data availability in case of a failure caused by events such as data node crash, disk failure, switch/rack failure or corruption in the data block. The evolution of big data leads to large population of data stored and managed in the clusters of cloud. The degree of replication is directly proportional to availability of data with an increase in the replication cost and update cost of data blocks in cloud. The applications executed on the data nodes demand various QoS needs while a block of its data is replicated such as disk access latency, constant bandwidth, delay, jitter etc. Existing replication algorithms replicates data based on the replication factor and the specified QoS needs of application. At a given point of time we expect the types of replication request from different applications varies largely and there is a need to allocate replica based on the request type and the replication factor to achieve a balanced replication cost and availability of data with the available block spaces in the entire cluster. We propose a multi attribute QoS replica allocation algorithm to replicate data considering the different types of replica request, replication factor and the total available space to achieve a balanced replica allocation. The proposed algorithm satisfies different QoS needs of applications and reduces the number of QoS violated replicas when the request consists of different QoS types. We measure the performance of the proposed algorithm in allocating replica and the reduction in number of QoS violated replica count over the existing algorithms such as random replication. The simulation result shows a better performance over the existing algorithms with a slight increase in the computational time.

Role of endometrial cytokines of the female genital tract tuberculosis in the context of infertility

BACKGROUND: Nowadays, one of the most common vulnerable sites of extrapulmonary tuberculosis is female genital tract tuberculosis (FGTB) leading to infertility. As FGTB produce clinical symptom quite late, its detection is very difficult to the health-care providers and according to some experts in this field; FGTB has no confirmatory investigation procedure. FGTB can cause other form of reproductive failure through ectopic pregnancy, tubal block, and implantation failure. Their presence may alter the cytokines level in endometrium. METHODS: A total of 300 cases in our clinic had undergone polymerase chain reaction (PCR) for detection of tubercle bacillus (TB-PCR). Among of them, 91 individuals fulfilling all inclusion and exclusion criteria were included in this study. In our study, we measured cytokines, two from pro-inflammatory group (interleukin-6 [IL-6] and IL-10) and three from inflammatory group (IL-2, interferon gamma [IFNγ], and tumor necrosis factor alpha [TNFα]). RESULTS: Out of 91 participants, 45 (49.46%) cases were TB-PCR positive, and 46 (50.55%) cases were TB-PCR negative. It has been observed that the value of IL-10 and TNFα did not fit any statistical parameter. The result showed that pro-inflammatory indicators IL-6 and inflammatory indicators IL-2 and IFNγ had significant different values between TB-PCR- positive and TB-PCR-negative groups. P value of this cytokines has statistically significant. CONCLUSION: From our study, we conclude that cytokine study was undertaken, of which IFNγ showed a possibility to become an important clinical indicator of endometrial hostility followed by IL-2.

In response to-Quadratus lumborum block failure: "A must know complication".

In response to-Quadratus lumborum block failure: "A must know complication".

Aberrant femoral nerve anatomy: No longer a cause of block failure when using ultrasound guidance.

Aberrant femoral nerve anatomy: No longer a cause of block failure when using ultrasound guidance.

Response to comments: Quadratus lumborum block failure: 'A must know complication'.

Response to comments: Quadratus lumborum block failure: 'A must know complication'.

КОМПЛЕКСНОЕ РЕШЕНИЕ ПО СОКРАЩЕНИЮ КОЛИЧЕСТВА ОТКАЗОВ КОЛЕСНО-МОТОРНЫХ БЛОКОВ ТЯГОВЫХ АГРЕГАТОВ

КОМПЛЕКСНОЕ РЕШЕНИЕ ПО СОКРАЩЕНИЮ КОЛИЧЕСТВА ОТКАЗОВ КОЛЕСНО-МОТОРНЫХ БЛОКОВ ТЯГОВЫХ АГРЕГАТОВ

An analytical framework in LEO mobile satellite systems servicing batched Poisson traffic

The authors consider a low earth orbit (LEO) mobile satellite system (MSS) that accepts new and handover calls of multirate service-classes. New calls arrive in the system as batches, following the batched Poisson process. A batch has a generally distributed number of calls. Each call is treated separately from the others and its acceptance is decided according to the availability of the requested number of channels. Handover calls follow also a batched Poisson process. All calls compete for the available channels under the complete sharing policy. By considering the LEO-MSS as a multirate loss system with ‘satellite-fixed’ cells, it can be analysed via a multi-dimensional Markov chain, which yields to a product form solution (PFS) for the steady-state distribution. Based on the PFS, they propose a recursive and yet efficient formula for the determination of the channel occupancy distribution, and consequently, for the calculation of various performance measures including call blocking and handover failure probabilities. The latter are much higher compared to the corresponding probabilities in the case of the classical (and less bursty) Poisson process. Simulation results verify the accuracy of the proposed formulas. Furthermore, they discuss the applicability of the proposed model in software-defined LEO-MSS.

Morphological alterations in the position of the mandibular foramen in dentate and edentate mandibles.

The technique of inferior alveolar nerve (IAN) block must be based on precise anatomical knowledge regarding the correct position of the mandibular foramen (MF). The aim of the investigation reported here was to determine the anatomic and topographic localization of the MF according to mandibular ramus anatomic landmarks and to identify morphological alterations in the position of the MF and size and shape of the ramus in terms of the impact of tooth socket loss in the molar and premolar region. Seventy-three dry human adult mandibles were divided into two groups according to dental status. These were measured to determine the distances from the anterior and posterior ramus border (AB, PB) to the midpoint of the MF fossa, and from the mandibular notch (MN) and inferior ramus border (IB) to the MF entering point. A number of relevant ramus anatomic features were analyzed, such as ramus width (RW), height (RH), and thickness (RT). The MF was closer to the PB and IB in edentate mandibles (right/left mean PB-MF 10.66±1.84/11.06±2.05mm; right/left mean IB-MF 21.77±3.23/21.8±2.27mm) compared to dentate mandibles (right/left mean PB-MF 11.87±2.08/12.04±1.94mm; right/left mean IB-MF 22.94±3.09/22.74±3.74mm). Edentate mandibles demonstrated reduced RW (right/left mean RW 26.03±3.53/26.49±3.90mm), significantly reduced (p=0.03) right RH (right/left mean RH 43.56±4.74/45.43±4.86mm), and significantly reduced (p<0.05) RT in the area of the MF fossa depression (right/left mean RT 5.52±1.21/5.21±0.91mm) compared to dentate mandibles (right/left mean RW 27.34±3.84/27.48±3.80mm; right/left mean RH 46.33±4.52/47.40±4.20mm; right/left mean RT 7.86±1.98/8.10±1.92mm). Alterations in MF position and mandibular ramus anatomic features in edentate mandibles increase the potential risk of complications and failure of IAN block.

Ultrasound-guided pudendal nerve block in children: A new technique of ultrasound-guided transperineal approach.

Transperineal pudendal nerve block guided by nerve stimulator is used in pediatric anesthesia as an alternative to caudal analgesia in perineal surgery. The risk of rectal puncture or intravascular injection is inherent to this blinded technique. We described a new technique of transperineal pudendal nerve block, with ultrasound guidance, to improve safety of the technique. The first goal of this study was to describe this new technique and to test its feasibility. The second objective was to evaluate intra operative effectiveness and postoperative pain control. After parental and children consent, this prospective descriptive study included children aged 1-15 years, ASA status I-III, scheduled for general anesthesia associated with bilateral pudendal nerve block for an elective perineal surgery. After standardized general anesthesia, the anesthesiologist performed pudendal nerve block under ultrasound guidance with "out of plane" approach and evaluated the visualization of anatomical structures (ischial tuberosity, rectum, and pudendal artery), of the needle and of the local anesthetic spread. Pudendal nerve block failure was defined as an increase in mean arterial blood pressure or heart rate more than 20% compared to baseline values after surgical incision. In the postoperative period, the need for rescue analgesia was noted. During the study period, 120 blocks were performed in 60 patients, including 59 boys. Quality of the ultrasonographic image was good in 81% of blocks, with easy visualization of ischium and rectum in more than 95% of cases. Localization of the tip of the needle was possible for all pudendal nerve blocks, directly or indirectly. The spread of local anesthetic was seen in 79% of cases. The block was effective in 88% of cases. The new technique of ultrasound-guided pudendal nerve block, described in this study, seems to be easy to perform with a good success rate, and probably improves safety of the puncture and of the injection by real-time visualization of anatomical structures and local anesthetic spread.

Rational Use and Pitfalls of Regional Anesthesia for Orthopedic Surgery

Surgeons often are reluctant to support the use of regional anesthesia for orthopedic surgery. This is because of the perceived “slowing down” of the surgical process, our poor understanding of conditions such as acute compartment syndrome, an alleged block failure rate, especially secondary block failure (all addressed elsewhere in this Symposium), and the perceived (or real) potential of added morbidity caused by regional anesthesia. This reluctance of surgeons, especially toward continuous nerve blocks, is furthered even more by the common perception that patients call their surgeons, not their anesthesiologists, postoperatively when a block is not working. The potential for added morbidity and surgeon reluctance toward its use can only be minimized by performing the appropriate block for the appropriate surgery when properly indicated with the correct equipment and technique, while avoiding situations prone to causing morbidity. This article discusses in some detail when it is appropriate to perform blocks, but perhaps more important, when not to perform blocks, and how to carefully calculate the risks and benefits so the latter outweigh the former.

Why Continuous Peripheral Nerve Blocks Fail

Continuous nerve blocks (CNBs), compared with other forms of postoperative analgesia, are less frequently utilized, although postoperative pain control may be improved with their use. Further, it has been demonstrated that the safety and side-effect profiles of opioids and other analgesics are inferior to well-performed CNBs. For CNB success, however, several principles must be adhered to: application of appropriate indications, selection of the correct nerve to block, performance of correct CNB technique, and utilization of correct equipment. Although these are simple concepts, they are often violated and can result in block failure, especially secondary block failure, which occurs once the primary bolus block has worn off. Almost all secondary block failures and medico-legal challenges originate from the violation of ≥1 of these principles. Hilton Law of Anatomy and Fick Law of Diffusion underpin common reasons for CNB failures. In addition, novel developments in our understanding of the macroneuroanatomy and microneuroanatomy may further explain CNB failures.

Abstract 21385: Presenting Features in Suspected Cardiac Sarcoid

Background: Sarcoidosis is multi-system disease characterized by non-caseating granulomas, often presenting with pulmonary involvement. However, in the United States at least one-fourth of sarcoid patients have cardiovascular involvement. Sarcoid can also present as isolated cardiac sarcoidosis (CS), with symptoms that include heart failure (HF), advanced atrioventricular (AV) nodal block, ventricular tachycardia (VT), or sudden cardiac death. Consequently, it has been suggested that CS should be considered in patients presenting with high grade AV block, VT, or heart failure, with a non-ischemic presentation. Here, we present the CS experience at a tertiary medical center. Methods: Patients who underwent 18 F-FDG (2-deoxy-2-[fluorine-18]fluoro-D-glucose) PET/CT to assess perfusion and inflammation for clinical suspicion of CS between 2009-2015 at a tertiary referral center were included in the study. These patients were retrospectively assessed for frequency of presenting features. Results: Inclusion criteria were met by 71 patients. VT was the most common presenting symptom seen in 40 of 71 patients (56%). High grade AV block was seen in 24 of 71 patients (34%). VT and high grade AV block was seen concomitantly in 9 (13%). An abnormal PET result was seen in 51 out of 71 patients (72%) with 30 of 51 having VT (59%) and 21 of 51 having AV block (41%). Of the patients with both VT and AV block, 8 of 9 had abnormal PET studies. In 34 of 71 (47%) patients with known extracardiac sarcoid, 18 (53%) had VT and 11 (32%) had AV block. HF symptoms (New York Heart Association class II-IV) were seen in 24 (34%). An abnormal resting ECG was seen in 64 out of 71 patients (90%). Conclusions: In our retrospective cohort VT is the most common presenting symptom in patients with suspicion of CS, and the combination of AV block with VT should raise concerns for an infiltrative process. In patients with extracardiac sarcoid and rhythm disturbance, cardiac involvement should be suspected and screened. Early identification of cardiovascular involvement is critical to ensure that appropriate management of the source of rhythm disturbance or heart failure is addressed before cardiovascular dysfunction is sustained.

Probabilistic fatigue S-N curves derivation for notched components

Europe has a number of ancient riveted metallic bridges, constructed during the second half of the 19th century up to the middle of the 20th century, which are still in operation. In this paper, a unified approach is presented to generate probabilistic S-N curves to be applied to structural components, accounting for uncertainties in material properties. The approach is particularly demonstrated for a plate with a circular hole, made of puddle iron from the Portuguese Eiffel Bridge. This paper presents an extension of the local strain-based fatigue crack propagation model proposed by Noroozi et al. The latter model is applied to derive the probabilistic fatigue crack propagation field (p-S-Np field). The probabilistic fatigue crack initiation field (p-S-Ni field) is determined using a notch elastoplastic approach, to calculate the fatigue failure of the first elementary material block ahead of the notch root.

A comparison of the application of block theory and 3D block-cutting analysis

In hard rock masses, rock destruction is often manifested in the form of the local failure of the blocks formed due to fracturing. In this paper, we compare the application of block theory and three-dimensional (3D) block-cutting analysis to underground caverns. Using block theory, we can determine both the type of removable block and key block for different excavation surfaces. We can then identify ‘support-required’ blocks from the key blocks by drawing and analyzing the shapes of the maximum likely blocks (i.e. the largest blocks likely to be formed when the fractures are extended indefinitely in a definite-sized cavern). Subsequently, 3D block-cutting analysis is used to identify all the spatial blocks cut by all the finite-sized fractures in the rock mass region. Based on the geometrical information gathered about each spatial block, we carry out an analysis of the progressive failure of the block system. The simulation results allow us to explore the statistical laws governing the distribution of progressive failure blocks. This is a very important aspect which can be used to determine the spacing and length of the rock bolts required, or to check the design of the intended rock support regime. Overall, if we can understand the shortcomings of classic block theory (due to, for example, the assumptions made) and properly utilize the benefits gained from 3D block-cutting analysis, we can deal with more complicated issues. Thus, we hope to gain a more intensive and extensive understanding of block failure analysis.

Tunnel stability assessment by 3D DDA-key block analysis

The key block theory is often the first analysis carried out in assessing potential instability caused by tunneling through jointed rock masses. This study suggests that it is beneficial to include it as the first step for a detailed design analysis by discrete numerical modeling, such as 3D DDA. The procedure is illustrated with an example which is simplified but is general and contains both primary and secondary key blocks. The agreement of the identified key blocks from 3D DDA and the key block theory provides credence for the DDA study, while the DDA, in turn, gives insights on how the failure of the unstable blocks evolves and complements the key block analysis.