Failure Of Drainage Research Articles

Incidence, Risk Factors and Management of Symptomatic Lymphoceles after Radical Retropubic Prostatectomy

IntroductionWe investigated the incidence, clinical course and risk factors for symptomatic lymphoceles after radical retropubic prostatectomy with pelvic lymph node dissection. Moreover, we explored parameters for the failure of percutaneous lymphocele drainage. MethodsThe incidence of symptomatic lymphoceles in patients with prostate cancer who underwent radical retropubic prostatectomy with pelvic lymph node dissection in our department between 2008 and 2013 was investigated retrospectively. The occurrence of lymphoceles was correlated with several clinical and histopathological parameters. In addition, logistic regression analysis was performed to assess the value of independent variables with regard to the development of symptomatic lymphoceles and failure of percutaneous drainage. ResultsA total of 599 consecutive patients treated with radical retropubic prostatectomy with pelvic lymph node dissection were included in the study, of whom symptomatic lymphocele had developed in 5%. Median time to diagnosis of symptomatic lymphocele was 22.5 days. Median time of percutaneous drainage was 16 days. Overall 43% of patients required surgical unroofing. On multivariate analysis age greater than 67 years (OR 3.27, p=0.005) and removal of more than 10 lymph nodes (OR 2.57, p=0.018) were independent predictors for the development of symptomatic lymphoceles. A significantly increased risk of percutaneous drainage failure was observed in patients who had a body mass index greater than 27 kg/m2 (OR 7.0, p=0.03), followed by a trend for those with a drainage volume of more than 375 ml 24 hours after puncture (OR 3.89, p=0.12). ConclusionsSymptomatic lymphocele will develop in 1 of 20 patients after radical retropubic prostatectomy with pelvic lymph node dissection. The number of lymph nodes removed constitutes an independent risk factor. Percutaneous drainage failure is associated with high body mass index and high drainage volume within the first 24 hours after puncture.

Study of pigtail catheter and chest tube in management of secondary spontaneous pneumothorax

BackgroundThe initial management for a large and symptomatic secondary spontaneous (SSP) pneumothorax is to remove the air from the pleural space, but recommended methods varied across guidelines, from a large bored chest tube toward less invasive management with the use of smaller catheters. So the aim of this study is to elucidate the effectiveness, safety and tolerability of small bore catheter in draining (SSP). Patients and methodsThis study is a prospective randomized controlled trial (RCT) which was carried out at Chest Department, Zagazig University Hospitals and included 22 patients with SSP. The cases were enrolled into the study according to the following criteria: first episode of SSP, large size pneumothorax, SSP with circulatory and respiratory distress (tension pneumothorax) irrespective of the size of pneumothorax. The patients were randomly assigned into two groups into: test group including 11 patients who underwent small bore pigtail catheter drainage (14 Fr) and a control group including 11 patients who underwent conventional large bore chest tube drainage (30 Fr). Follow up of patients and extubation after resolution of pneumothorax was applied. Success of drainage was considered with full lung reexpansion and extubation with hospital discharge. ResultsThe frequency of success rate in the pigtail group and ICT group is nearly comparable (72.7%) and (63.6%) without significant difference. The frequency of complications following SSP drainage in patients of both studied groups was 36.7%. The more frequent complications among the failed cases was tube displacement and sepsis followed by surgical emphysema. The frequency of drainage complications was more frequent in failed cases of ICT than failed cases of the pigtail group with a significant difference. Among patients with successful outcome, pigtail catheter drainage of SSP was associated with significant and highly significant reduction in drainage duration and length of hospital stay in comparison to ICT drainage. ConclusionPigtail catheter drainage is nearly effective as ICT drainage of first episode of SSP. Pigtail catheter offers a safe, tolerable method for draining SSP with a shorter duration of drainage and hospital stay more than ICT. Increasing BMI is associated with drainage failure of SSP, where obesity is considered as a risk factor with high specificity for pigtail catheter drainage failure.

Incidence, Management, and Outcome of Symptomatic Postoperative Posterior Fossa Pseudomeningocele: A Retrospective Single-Institution Experience.

Pseudomeningocele is a source of considerable morbidity after posterior fossa surgery, but incidence and optimal management strategies are unclear. To define risk factors, evaluate management strategies, and identify predictors of resolution. A prospectively maintained database of 687 consecutive posterior fossa operations at a single institution was analyzed to identify cases of symptomatic postoperative pseudomeningocele. Retrospective analysis of treatment strategies and outcome was performed. Overall rate of symptomatic postoperative pseudomeningocele was 14.1% (97 cases). The highest rate was for midline posterior fossa surgery (16.5%), and the lowest rate was for retrosigmoid surgery (11.9%). Multivariate logistic regression analysis revealed that the presence of increased ventricle size on postoperative imaging predicted significantly higher risk of failure of lumbar drainage (odds ratio, 6.57; 95% confidence interval [CI], 1.18-36.59; P < .05). Cox proportional hazards analysis revealed that time to clinical resolution was significantly associated only with use of temporary lumbar drainage (hazards ratio, 2.28; 95% CI, 1.04-5.00; P < .05), and time to radiographic resolution was associated only with placement of a ventricular shunt (hazards ratio, 2.84; 95% CI, 1.19-6.78; P < .05). Pseudomeningocele is a common complication after posterior fossa surgery, but incidence is not related to age or medical comorbidity. Postoperative ventriculomegaly portends failure of temporary cerebrospinal fluid diversion, and early consideration of shunting might be appropriate in such cases. In the absence of ventriculomegaly, temporary use of a lumbar drain leads to earlier clinical resolution, but complete radiographic resolution is rare when a permanent shunt is not implanted. Further research should be performed to establish the most effective treatment strategy.

Lymphatic Clearance of the Brain: Perivascular, Paravascular and Significance for Neurodegenerative Diseases.

The lymphatic clearance pathways of the brain are different compared to the other organs of the body and have been the subject of heated debates. Drainage of brain extracellular fluids, particularly interstitial fluid (ISF) and cerebrospinal fluid (CSF), is not only important for volume regulation, but also for removal of waste products such as amyloid beta (Aβ). CSF plays a special role in clinical medicine, as it is available for analysis of biomarkers for Alzheimer’s disease. Despite the lack of a complete anatomical and physiological picture of the communications between the subarachnoid space (SAS) and the brain parenchyma, it is often assumed that Aβ is cleared from the cerebral ISF into the CSF. Recent work suggests that clearance of the brain mainly occurs during sleep, with a specific role for peri- and para-vascular spaces as drainage pathways from the brain parenchyma. However, the direction of flow, the anatomical structures involved and the driving forces remain elusive, with partially conflicting data in literature. The presence of Aβ in the glia limitans in Alzheimer’s disease suggests a direct communication of ISF with CSF. Nonetheless, there is also the well-described pathology of cerebral amyloid angiopathy associated with the failure of perivascular drainage of Aβ. Herein, we review the role of the vasculature and the impact of vascular pathology on the peri- and para-vascular clearance pathways of the brain. The different views on the possible routes for ISF drainage of the brain are discussed in the context of pathological significance.

A Simulation Model of Periarterial Clearance of Amyloid-β from the Brain

The accumulation of soluble and insoluble amyloid-β (Aβ) in the brain indicates failure of elimination of Aβ from the brain with age and Alzheimer's disease (AD). There is a variety of mechanisms for elimination of Aβ from the brain. They include the action of microglia and enzymes together with receptor-mediated absorption of Aβ into the blood and periarterial lymphatic drainage of Aβ. Although the brain possesses no conventional lymphatics, experimental studies have shown that fluid and solutes, such as Aβ, are eliminated from the brain along 100 nm wide basement membranes in the walls of cerebral capillaries and arteries. This lymphatic drainage pathway is reflected in the deposition of Aβ in the walls of human arteries with age and AD as cerebral amyloid angiopathy (CAA). Initially, Aβ diffuses through the extracellular spaces of gray matter in the brain and then enters basement membranes in capillaries and arteries to flow out of the brain. Although diffusion through the extracellular spaces of the brain has been well characterized, the exact mechanism whereby perivascular elimination of Aβ occurs has not been resolved. Here we use a computational model to describe the process of periarterial drainage in the context of diffusion in the brain, demonstrating that periarterial drainage along basement membranes is very rapid compared with diffusion. Our results are a validation of experimental data and are significant in the context of failure of periarterial drainage as a mechanism underlying the pathogenesis of AD as well as complications associated with its immunotherapy.

Patterns of failure and morbidity associated with palliative intervention in patients with malignant biliary obstruction.

71 Background: Outcome for patients with malignant biliary obstruction is poor. While endoscopic or percutaneous procedures provide palliative benefit, stents often occlude or migrate, and drains frequently fail requiring repeat procedures in medically fragile patients. As part of a multidisciplinary effort to improve outcomes in this population, we undertook an investigation to determine rates of stent and drain failure and morbidity to identify areas of potential improvement. Methods: After Institutional Review Board approval, retrospective review of all cancer registry patients undergoing percutaneous or endoscopic intervention for biliary obstruction from 1/2004-10/2014 and billing reports from 11/2012-10/2014 identified 230 patients. Cases of biliary obstruction due to malignancy requiring intervention were selected, resulting in 94 evaluable patients. Charts were reviewed to determine dates and cause for stent and/or drain replacement and morbidity. Results: Of 94 analyzable patients, median age was 60 years and 49 were male (52%). Malignant cause of obstruction was gastric/colorectal in 16 (17%), biliary in 37 (39%), hepatocellular in 7 (7%), and pancreatic in 34 (36%). Stenting was part of the initial procedure in 47 (50%), and drain placement in 49 (52%). Ultimately 60 (64%) patients underwent stent procedures and 82 (87%) patients required drains. Of the stented patients, 27 (45%) required repeat stenting, and 13 (22%) required &gt; 1 stent replacement. Of the patients who underwent drainage procedures, 68 (83%) required repeat drainage, and 52 (63%) required &gt; 1 repeat drainage procedure. Cholangitis was observed following stent in 5 (5%) of patients, 60% in patients undergoing &gt; 1 stent procedures. Median survival after initial procedure was 12 months; for patients requiring repeat procedures, median survival was 4.5 months. Conclusions: Malignant biliary obstruction is a morbid disease with high rates of reocclusion requiring repeat procedures, which may negatively impact outcome and increase healthcare cost. Efforts to reduce the rates of repeat procedures are critical to address this clinical need.

Acute pancreatitis.

To summarize recent data on classification systems, cause, risk factors, severity prediction, nutrition, and drug treatment of acute pancreatitis. Comparison of the Revised Atlanta Classification and Determinant Based Classification has shown heterogeneous results. Simvastatin has a protective effect against acute pancreatitis. Young black male, alcohol, smoldering symptoms, and subsequent diagnosis of chronic pancreatitis are risk factors associated with readmissions after acute pancreatitis. A reliable clinical or laboratory marker or a scoring system to predict severity is lacking. The PYTHON trial has shown that oral feeding with on demand nasoenteric tube feeding after 72 h is as good as nasoenteric tube feeding within 24 h in preventing infections in predicted severe acute pancreatitis. Male sex, multiple organ failure, extent of pancreatic necrosis, and heterogeneous collection are factors associated with failure of percutaneous drainage of pancreatic collections. The newly proposed classification systems of acute pancreatitis need to be evaluated more critically. New biomarkers are needed for severity prediction. Further well designed studies are required to assess the type of enteral nutritional formulations for acute pancreatitis. The optimal minimally invasive method or combination to debride the necrotic collections is evolving. There is a great need for a drug to treat the disease early on to prevent morbidity and mortality.

Deposition of amyloid β in the walls of human leptomeningeal arteries in relation to perivascular drainage pathways in cerebral amyloid angiopathy

Deposition of amyloid β (Aβ) in the walls of cerebral arteries as cerebral amyloid angiopathy (CAA) suggests an age-related failure of perivascular drainage of soluble Aβ from the brain. As CAA is associated with Alzheimer's disease and with intracerebral haemorrhage, the present study determines the unique sequence of changes that occur as Aβ accumulates in artery walls. Paraffin sections of post-mortem human occipital cortex were immunostained for collagen IV, fibronectin, nidogen 2, Aβ and smooth muscle actin and the immunostaining was analysed using Image J and confocal microscopy. Results showed that nidogen 2 (entactin) increases with age and decreases in CAA. Confocal microscopy revealed stages in the progression of CAA: Aβ initially deposits in basement membranes in the tunica media, replaces first the smooth muscle cells and then the connective tissue elements to leave artery walls completely or focally replaced by Aβ. The pattern of development of CAA in the human brain suggests expansion of Aβ from the basement membranes to progressively replace all tissue elements in the artery wall. Establishing this full picture of the development of CAA is pivotal in understanding the clinical presentation of CAA and for developing therapies to prevent accumulation of Aβ in artery walls. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Genetic programming and floating boom performance

In this paper the performance of floating booms under waves and currents is investigated by means of genetic programming (GP). This artificial intelligence (AI) technique is used to establish a mathematical expression of the significant effective draft, an essential parameter in predicting the containment capability of floating booms, and more specifically the occurrence of drainage failure. Obtained by applying GP to a comprehensive dataset of wave–current flume experiments, the expression makes the relationships among the relevant variables explicit – an advantage relative to other AI techniques such as artificial neural networks (ANN). The expression was selected as the most adequate to represent this physical problem from various expressions generated in two different stages in which dimensional and dimensionless variables were considered as input and output variables respectively. The most representative expressions obtained in both stages are presented and compared taking into account their goodness-of-fit, physical meaning, coherence and complexity. In addition, the adjustment with the experimental data obtained with these expressions is also discussed and compared with a previously developed ANN model.

Failed glaucoma drainage implant: long-term outcomes of a second glaucoma drainage device versus cyclophotocoagulation

Background/aimsTo evaluate long-term efficacy of a second glaucoma drainage device (GDD) versus cyclophotocoagulation (CPC) after failure of primary drainage implant.MethodsThis is a non-randomised, retrospective cohort study. A chart review was...

Percutaneous drainage for giant pyogenic liver abscess—is it safe and sufficient?

BackgroundLarge size is a predictor of failure of percutaneous drainage (PD) for pyogenic liver abscess (PLA). This article serves to establish the safety and sufficiency of PD in giant PLA (GPLA). MethodsA retrospective review of all GPLA patients treated at a tertiary care academic hospital from 2001 to 2011 was performed. A GPLA is defined as an abscess greater than or equal to 10 cm size based on imaging. ResultsForty patients (24 men, 60%) were treated for GPLA. All but 1 patient (98%) was managed with PD and the mean duration of drainage was 9 days (range 1 to 23 days). One patient underwent operative drainage. Three patients (7.7%) needed secondary procedures after the initial PD. One patient (2.6%) failed PD and subsequently underwent operative drainage. Among the patients who underwent PD, the overall morbidity was 25%; the median length of hospital stay was 13 days (range 5 to 31 days) and 1 (2.6%) mortality. ConclusionsLarge size itself is not a contraindication for PD. PD is safe and sufficient even in GPLA patients.

Amputation of the peritoneal dialysis catheter in the abdominal cavity

An 83-year-old female patient with a 3-year history of peritoneal dialysis (PD) for diabetic nephropathy presented to our clinic with abrupt dialysate drainage failure. The Tenckhoff catheter inserted 3 years ago was a two-cuffed, straight-type flexible silicone tube. Before presentation, she had no abnormal sensation in the abdomen, had not performed any vigorous exercises, or received external force to the abdomen that could have caused catheter damage. No crack or fracture was observed in the PD catheter outside the exit site.

Prenatal high-fat diet alters the cerebrovasculature and clearance of β-amyloid in adult offspring.

Alzheimer's disease (AD) is characterized by the accumulation of β-amyloid (Aβ) peptides in the extracellular spaces of the brain as plaques and in the walls of blood vessels as cerebral amyloid angiopathy (CAA). Failure of perivascular drainage of Aβ along cerebrovascular basement membranes contributes to the development of CAA. Mid-life hypercholesterolaemia is a risk factor for the development of AD. Maternal obesity is associated with the development of obesity, hypertension and hypercholesterolaemia in adulthood, suggesting that the risk for AD and CAA may also be influenced by the early-life environment. In the present study, we tested the hypothesis that early-life exposure to a high-fat diet results in changes to the cerebrovasculature and failure of Aβ clearance from the brain. We also assessed whether vascular Aβ deposition is greater in the brains of aged humans with a history of hyperlipidaemia, compared to age-matched controls with normal lipidaemia. Using a mouse model of maternal obesity, we found that exposure to a high-fat diet during gestation and lactation induced changes in multiple components of the neurovascular unit, including a down-regulation in collagen IV, fibronectin and apolipoprotein E, an up-regulation in markers of astrocytes and perivascular macrophages and altered blood vessel morphology in the brains of adult mice. Sustained high-fat diet over the entire lifespan resulted in additional decreases in levels of pericytes and impaired perivascular clearance of Aβ from the brain. In humans, vascular Aβ load was significantly increased in the brains of aged individuals with a history of hypercholesterolaemia. These results support a critical role for early dietary influence on the brain vasculature across the lifespan, with consequences for the development of age-related cerebrovascular and neurodegenerative diseases.

Intrapleural Tenecteplase Therapy in Treatment of Loculated Parapneumonic Pleural Effusions and Empyema

BackgroundThoracic empyema (TE) and loculated parapneumonic effusions (CPE) cause considerable morbidity and mortality, with an estimated case-fatality rate of 15%. Intrapleural administration of recombinant tissue plasminogen activators (r-TPA) such as tenecteplase (TNKase) has been recently employed to lyse the fibrinous structures of multiloculated pleural space with reduction of surgical intervention. Yet, there is no enough data concerning intrapleural TNKase in treating patients with CPE or TE. Thus, the objective of this study is to determine the safety and efficacy of TNKase for the treatment of loculated parapneumonic pleural effusions and thoracic empyema after failure of complete drainage using pigtail catheter. Patients and methodsThis study was done at Respirology and Interventional Radiology Departments, Farwaniya Hospital, Alrashid Respiratory Centre and Thoracic Surgery Department, Chest Hospital, Ministry of Health, State of Kuwait, between January 2012 and November 2013. 58 patients were admitted with loculated pleural effusions {22 patients (37.9%) with thoracic empyema and 36 patients (62.1%) with complicated parapneumonic effusion}. All patients received intrapleural TNKase after failure of complete drainage of pigtail catheter, which was inserted under chest ultrasound guidance. The evaluation was made according to imaging, laboratory, and clinical status. Adverse effects and hemorrhagic complications were also reported. ResultsThe overall intrapleural TNKase effectiveness in achieving complete drainage of pleural collections was 49 of 58 cases (84.5%). Intrapleural TNKase was successful in 70% (14 of 20) of patients with TE, and 92.1% (35 of 38) of patients with CPE. The total number of TNKase instillations ranged from 2 to 5 (mean, 3.2). The mean volume of pleural fluid increased significantly after TNKase administration (P<0.001). White blood cell count (WBC) and C-reactive protein (CRP) were significantly improved after TNKase instillations (both P<0.05). Complications observed were mild and local bleeding occurred in only 4 patients (6.9%). ConclusionIntrapleural TNKase is an effective therapy in improving drainage of loculated CPE and TE not drained with pigtail catheters alone and can prevent surgical interventions. Intrapleural TNKase is well tolerated with infrequent adverse events.

Predictors of postoperative outcomes for patients with diverticular abscess initially treated with percutaneous drainage

BackgroundThe aim of our study was to evaluate factors associated with percutaneous drainage (PCD) failure, complications, and stoma creation for patients undergoing sigmoidectomy for diverticular abscess. MethodsData for patients with diverticular abscess greater than or equal to 3 cm in diameter treated with initial PCD from 1994 to 2012 were identified. ResultsOne hundred fourteen patients (54% male) with a mean age of 57 years and a mean abscess diameter of 7.1 ± 2.4 cm were identified. American Society of Anesthesiologists 4 was the only independent factor associated with PCD failure (P < .001). On multivariate analysis, factors associated with postoperative morbidity (n = 42, 37%) included PCD failure (P = .02) and older age (P = .04), while risk for stoma creation was associated with PCD failure (P < .001), multiple PCD attempts (P = .002), older age (P < .001), Hinchey II (P = .03), and increased body mass index (P = .01). American Society of Anesthesiologists 4 was the only factor associated with permanent stoma (P = .02). ConclusionsIn patients with large diverticular abscess, a successful PCD is associated with reduced postoperative morbidity. However, a large proportion of patients require stoma creation. Significant comorbidity is associated with both failure of PCD and permanent stoma risk.

Failure of perivascular drainage of β-amyloid in cerebral amyloid angiopathy.

In Alzheimer's disease, amyloid-β (Aβ) accumulates as insoluble plaques in the brain and deposits in blood vessel walls as cerebral amyloid angiopathy (CAA). The severity of CAA correlates with the degree of cognitive decline in dementia. The distribution of Aβ in the walls of capillaries and arteries in CAA suggests that Aβ is deposited in the perivascular pathways by which interstitial fluid drains from the brain. Soluble Aβ from the extracellular spaces of gray matter enters the basement membranes of capillaries and drains along the arterial basement membranes that surround smooth muscle cells toward the leptomeningeal arteries. The motive force for perivascular drainage is derived from arterial pulsations combined with the valve effect of proteins present in the arterial basement membranes. Physical and biochemical changes associated with arteriosclerosis, aging and possession of apolipoprotein E4 genotype lead to a failure of perivascular drainage of soluble proteins, including Aβ. Perivascular cells associated with arteries and the lymphocytes recruited in the perivenous spaces contribute to the clearance of Aβ. The failure of perivascular clearance of Aβ may be a major factor in the accumulation of Aβ in CAA and may have significant implications for the design of therapeutics for the treatment of Alzheimer's disease.

Comparison of Video-Assisted Thoracoscopic Surgery and Intrapleural Urokinase as an Initial Treatment for Parapneumonic Effusion and Thoracic Empyema

Introduction: The treatment of complicated parapneumonic effusion (PPE) and thoracic empyema (TE) is controversial; and the choice of treatment after confirming the failure of simple drainage remains unclear. The purpose of this study was to compare the outcomes of intrapleural urokinase (UK) administration and video-assisted thoracoscopic surgery (VATS) as initial treatment options for PPE and TE. Materials and Methods: We retrospectively reviewed and compared the data of 20 patients with PPE and TE diagnosed between January 2010 and December 2012 at our hospital, dividing them on the basis of the initial treatment into a video-assisted thoracoscopic surgery (VATS) group (n=9) and UK group (n=11). Results: Age was the only statistically different parameter between both groups (P=0.025); with the mean age of the VATS and UK groups being 64 and 76 years, respectively. There was no significant difference in the duration of drainage or success rate between the UK or VATS groups. Although no statistically significant differences (P=0.20) were observed, duration of hospital stay was longer in the UK group (21 and 28 day for VATS and UK, respectively). Conclusion: VATS for PPE and TE may shorten the duration of hospital stay.However, UK administration may be used for selective patients because it is considered to yield outcomes similar to VATS.

Second Glaucoma Drainage Devices in Refractory Pediatric Glaucoma: Failure by Fibrovascular Ingrowth

To evaluate initial glaucoma drainage device failure and subsequent glaucoma drainage device placement for refractory pediatric glaucoma. Retrospective interventional case series. The Duke University surgical records from a single surgeon from 1997 to 2012 were reviewed for patients having at least 2 glaucoma drainage devices for refractory pediatric glaucoma. Data collected included glaucoma diagnosis, age at surgery, surgical interventions, preoperative/postoperative IOP and medications, and complications. Failure was defined as having an IOP >21 mm Hg (or clinically inadequate), and/or IOP-reducing surgery/devastating complication. Forty-three eyes (37 patients) had 2 or more glaucoma drainage devices. Mean age at second glaucoma drainage device implantation was 9.2 ± 7.1 years, with mean IOP 30 ± 11 mm Hg, on 3 ± 1 IOP-lowering medications. Fibrovascular ingrowth was documented during second glaucoma drainage device surgery in 12 of 43 eyes (28%), occurring only in Ahmed devices, at a mean of 70 months (range 11-153) after initial implantation. Failure of the second glaucoma drainage device surgery occurred in 18 of 43 eyes (42%) at mean 26.1 ± 32.2 months (median 19.3 months). Surgical success of second glaucoma drainage devices (Kaplan-Meier analysis) at 1 year, 2 years, and 3 years was 81%, 62%, and 50%, respectively. Single glaucoma drainage device surgery fails to control IOP in some eyes with refractory pediatric glaucoma. Second glaucoma drainage device implantation offers a treatment option with modest success over time. Fibrovascular ingrowth should be suspected as a relatively common cause of IOP elevation and failure after Ahmed device implantation.

Afferent and efferent immunological pathways of the brain: anatomy, function and failure (84.1)

Immunological privilege appears to be the result of two major processes: (a) unique lymphatic drainage systems for the brain; and (b) highly regulated specialised passage of inflammatory cells through the blood‐brain barrier. Most organs of the body have well‐defined lymphatic vessels that carry extracellular fluid to regional lymph nodes. The brain has no such conventional lymphatics. Instead, it has perivascular pathways that drain interstitial fluid (ISF) from the brain parenchyma and cerebrospinal fluid (CSF) from the subarachnoid space to cervical lymph nodes. Solutes and ISF drain along narrow, ~100 nm‐thick basement membranes within the walls of cerebral capillaries and arteries to cervical lymph nodes. This pathway does not allow traffic of cells from the parenchyma to lymph nodes. CSF drains into blood through arachnoid villi and through channels in the cribriform plate of the ethmoid bone into nasal lymphatics, permitting cells to travel from CSF to cervical lymph nodes. Efferent pathways by which lymphocytes enter the brain are regulated by integrins on lymphocytes and selective receptors on endothelial cells. I will review: (a) the functional morphology of lymphatic drainage of the brain; (b) mechanisms involved in the pathways by which lymphocytes enter the brain; and (c) the failure of lymphatic drainage of the brain parenchyma in Alzheimer's disease.

Application of in-seam directional drilling technology for gas drainage with benefits to gas outburst control and greenhouse gas reductions in Daning coal mine, China

Gas outburst disasters are becoming more serious as the underground coal mines become deeper in China, and a thick zone of deformed coal provides conditions favorable to coal and gas outbursts. The Daning coal mine’s main mining seam is the No. 3 coal seam with coal and gas outburst hazard, which often contains two normal coal sub-layers and one deformed sub-layer. Considering both the geological conditions of the coal seam and applications of the in-seam directional longhole drilling technology, a new schematic diagram of in-seam directional longholes for gas drainage is developed. The two borehole layout models of longwall panel and main entries for gas outburst disasters control have been successfully applied. The gas drainage rates of both models are >70 %, and the residual gas contents are both <8 m3/t, which can be considered that the gas outburst disasters were effectively controlled. To better guide gas drainage, gas drainage normal and failure modes have been obtained. Although in-seam directional longhole technology has been successfully applied for regional gas drainage with benefits to gas outburst control, there are also some problems that are detrimental to greenhouse gas reductions in gas drainage and gas utilization. The three main problems are air leakage failure in gas drainage, decreasing gas concentration and a low gas utilization ratio. To address the problems mentioned above, five improvements are suggested.