Predicting wind-driven spatial deposition through simulated color images using deep autoencoders.

For centuries, scientists have observed nature to understand the laws that govern the physical world. The traditional process of turning observations into physical understanding is slow. Imperfect models are constructed and tested to explain relationships in data. Powerful new algorithms can enable computers to learn physics by observing images and videos. Inspired by this idea, instead of training machine learning models using physical quantities, we used images, that is, pixel information. For this work, and as a proof of concept, the physics of interest are wind-driven spatial patterns. These phenomena include features in Aeolian dunes and volcanic ash deposition, wildfire smoke, and air pollution plumes. We use computer model simulations of spatial deposition patterns to approximate images from a hypothetical imaging device whose outputs are red, green, and blue (RGB) color images with channel values ranging from 0 to 255. In this paper, we explore deep convolutional neural network-based autoencoders to exploit relationships in wind-driven spatial patterns, which commonly occur in geosciences, and reduce their dimensionality. Reducing the data dimension size with an encoder enables training deep, fully connected neural network models linking geographic and meteorological scalar input quantities to the encoded space. Once this is achieved, full spatial patterns are reconstructed using the decoder. We demonstrate this approach on images of spatial deposition from a pollution source, where the encoder compresses the dimensionality to 0.02% of the original size, and the full predictive model performance on test data achieves a normalized root mean squared error of 8%, a figure of merit in space of 94% and a precision-recall area under the curve of 0.93.

Prediction of the Evolution to Brain Death in the Neurocritical Patient: SPN Model Showed Better Performance Than Simplified Acute Physiology Score II and Acute Physiology and Chronic Health Evaluation II.

The detection of brain death (BD) plays a fundamental role in the management of hospital donation. Delayed diagnosis of BD is the main cause of donor loss. A tool for monitoring and prognosis in the neurocritical patient is essential to meet these objectives. The most used prognostic scores in intensive care units are Simplified Acute Physiology Score (SAPS) II and Acute Physiology and Chronic Health Evaluation (APACHE) II. A predictive model of good performance (ModSPN) in predicting BD in neurocritical patients with Glasgow Coma Scale score < 8 was published in 2014. With the objective of analyzing the predictive capacity of ModSPN and comparing it with SAPS II and APACHE II, 2307 patients admitted to the neurocritical patient monitoring (SPN) program of the INDT were analyzed. The predictive capacity for death and brain death of SAPS II, APACHE II, and ModSPN was compared using receiver operating characteristic curves. The area under the curve showed a better APACHE II performance for the prediction of death and the ModSPN being a better predictor of the probability of dying in BD. Therefore, for the prediction of death in the neurocritical patient, APACHE II was superior, but for the prediction of encephalic death, the ModSPN presented the best predictive power for all causes of brain injury.

Addressing a Diagnosis of Brain Death in Hypernatremia Situation.

Hypernatremia and the state of plasma hypertonia are part of the alterations of insipid diabetes that are integrated to the brain death (BD) syndrome. Hypernatremia should be corrected as early as possible to make the clinical diagnosis of BD and to avoid its potential deleterious effect on the subsequent operation of the liver graft. Transcranial Doppler is a very valuable tool for the diagnosis of cerebral circulatory arrest associated with BD. The correction of natremia is made through the use of hypotonic solutions, and using of pyrogen-free distilled water intravenously in special cases, which controls the possibility of hemolysis in the donor. In our study, isolated severe hypernatremia corrected before ablation was not associated with liver graft failure in the recipient.

Organ Use Rate: A New Indicator of Donation and Transplantation Efficiency.

The conversion rate has emerged as a good indicator of the effectiveness of the transplantation process by showing the percentage of potential donors who become real donors, but it overestimates the number of organs that are actually used for transplantation in recipients. The incorporation of organ use rate, a new quality indicator that reflects the actual number of organs used for transplantation excluding those that are discarded in the surgical block, provides complementary information of great value when comparing transplantation in different regions. This new variable allows more accurate prediction of the waiting time for the transplantation of a certain organ in patients with nonreversible organic insufficiencies, while providing the national authorities a real response in relation to the percentage of the demand for organs that can be satisfied.

Organ Donation and Primary Central Nervous System Tumors.

Primary central nervous system tumors can be the cause of brain death. Not all of them contraindicate the donation of organs and tissues for transplant. A survey of cases was carried out in our country in which it was observed that the number of brain deaths caused by primary tumors was low, of the order of 2%, with an x (media) of 3 by year, which would increase the potential for donation. Medical records, an anatomopathologic study, and a detailed physical examination will be fundamental when applying the donor selection criteria. Nuclear magnetic resonance in expert hands has a sensitivity of 96% to catalog the benignity or malignancy of this type of tumors.

Intensive Care Unit Approach to the Diagnosis of Brain Death in Infratentorial Neurologic Pathology: Case Reports.

The ischemic and primary vascular injury of the brainstem (BS) can determine, among other serious conditions, the brain death (BD) of the individual. We present 2 cases of individuals with primary ischemic vascular disease of the BS who evolved to BD and were donors of solid organs and tissues. In both cases, the clinical examination was positive for the diagnosis of BD, and transcranial Doppler did not confirm the pattern of cerebral circulatory arrest that accompanies BD. The magnetic resonance angiography performed on 1 patient confirmed the lesion etiology and the presence of vascular obstruction. Both patients were real and effective organ and tissue donors. In these cases, we suggest not to resort to transcranial Doppler as an auxiliary diagnostic test.

Does Traumatic Brain Injury by Firearm Injury Accelerates the Brain Death Cascade? Preliminary Results.

Brain death (BD) triggers a series of pathophysiological events similar to multiple-organ dysfunction. Traumatic brain injury (TBI) due to firearm injury (FAI) causes lesions that could lead to BD. Patients admitted to the ICU due to severe TBI that evolved to BD were studied, including those caused by FAI; the 2 groups were compared with the objective of demonstrating that the support of the deceased donor by TBI due to FAI is more unstable and of shorter duration than the one related to TBI by another cause. Preliminary results demonstrated that the individuals with TBI by FAI died in BD in a higher percentage than the individuals with TBI caused by accidents (83% vs 41%). The donor treatment period was lower in individuals who presented TBI by FAI. These individuals needed higher doses of noradrenaline as vasopressor support for their treatment, without showing a statistically significant difference (P = .15), compared with individuals whose BD cause was TBI caused by accident.

Utility of Transcranial Doppler in the Coordination of Transplants: 10 Years of Experience.

Transcranial Doppler (TCD) integrated to multimodal neuromonitoring of neurocritical patients is a useful tool in the clinical follow-up. A retrospective and descriptive study of 194 patients who were admitted into the intensive care unit (ICU) was carried out from December 2007 to February 2017. We analyzed the distribution of study frequencies with respect to the pathologies that motivated them, the characteristics of patients who evolved to brain death (BD), and most frequent patterns of cerebral circulatory arrest. Ninety-four of the patients that evolved to BD required 126 studies during their follow-up. The insonation of the 2 middle cerebral arteries and the basilar artery was the most frequent combination (30%). Most frequent reasons of request for a TCD included apnea test intolerance and reduction of waiting time and sedation analgesia. These 10 years of experience have enabled a deeper understanding of the cerebral hemodynamics and the identification of common patterns of high resistance to different pathologies (subarachnoid hemorrhage, severe skull trauma, anoxic ischemia, ammonia encephalopathy) that explain the severity of the acute brain injury, related to the increase of brain volume and its deleterious consequence: the elevation of intracranial pressure (ICP). In the same way, because invasive ICP monitoring is not available in all cases, with a tomographic scan of the skull we have been able to observe a correlation of some imaging signs suggestive of intracranial hypertension with patterns of high resistance obtained by the TCD in the pathologies mentioned. We recommend that each ICU that assists neurocritical patients should have TCD equipment and the skilled personnel to carry out the technique.

Systodiastolic Separation Expresses Cerebral Circulatory Arrest?

There is a situation before the cerebral circulatory cessation phase, the systodiastolic separation in transcranial Doppler (TCD), which may raise doubts to the operator technician who performs it. A total of 266 studies were performed in 188 neurocritical patients over a 9-year period: 88 cases (77%) corresponded to cerebral circulatory arrest (CCA) which accompanies brain death (BD); 9 (5%) presented the systodiastolic separation pattern. In 1 of those 9 there was persistence of cough reflex and spontaneous breathing; in 5, CCA was not reached; only 3 evolved to CCA. The finding of a minimal persistent neurologic semiology is a categoric fact that would rule out the clinical correlation between this pattern and BD diagnosis.

Complicaciones de la reparación artroscópica del ligamento cruzado anterior sin ingreso hospitalario / Postoperative complications of anterior cruciate ligament reconstruction after ambulatory surgery

Objetivo: Estudiar las complicaciones postoperatorias de la ligamentoplastia artroscópica del LCA realizada ambulatoriamente (CMA) comparándola con la realizada mediante hospitalización (no-CMA). Material y método: Cohorte histórica sobre 342 pacientes (115 CMA vs. 227 no-CMA) intervenidos de ligamentoplastia primaria artroscópica del LCA (2004-2012). Revisión de variables sociodemográficas, quirúrgicas y de hospitalización. Estudio de complicaciones precoces (primeros 60 días) incluyendo visitas a urgencias hospitalarias y reingresos. Análisis descriptivo y bivariado de distribución entre grupos: realización de la técnica en CMA o no. Test Chi-Cuadrado para variables cualitativas y test U-Mann-Whitney para cuantitativas. Límite significación p < 0,05. Resultados: Un 13,2% de visitas a urgencias (media de 1,24 visitas), demora media de 8,22 días tras el alta. Complicaciones: dolor no controlado con analgesia (6,7%), hemartros a tensión precisando artrocentesis evacuadora (4,4%), sensación febril (3,2%), trombosis venosa profunda (0,6%), celulitis (0,6%), artritis séptica con desbridamiento artroscópico (0,3%) y otras (1,2%) como problemas con la inmovilización. Un 2,3% de ingresos para vigilancia y seguimiento de la herida quirúrgica. En el análisis bivariado no se encontraron diferencias estadísticamente significativas entre ambos grupos en las características sociodemográficas de los pacientes ni en las complicaciones registradas. Discusión: Las complicaciones más frecuentes registradas fueron el dolor agudo, el hemartros y la sensación febril. Las graves (trombosis venosa profunda, artritis séptica o necesidad de reingreso hospitalario) fueron excepcionales. La CMA de reparación artroscópica del LCA es una técnica frecuente que se puede realizar de forma segura mediante cirugía sin ingreso hospitalario con una tasa global de complicaciones bajas sin diferencias entre hospitalización o sin ingreso (AU)

Objective: To study postoperative complications of arthroscopic anterior cruciate ligament (ACL) reconstruction performed as an outpatient compared with same surgery performed as a regular admission (inpatient). Material and method: A study was conducted on a historical cohort of 342 patients (115 outpatients vs 227 inpatients) who underwent arthroscopic ACL primary ligamentoplasty (2004-2012). A review was performed on the demographic, surgical and hospital variables. A study was made of early complications (60 days postoperative) including visits to emergency department and readmissions. A descriptive and bivariate distribution analysis was performed between groups, with the grouping criterion: performing of the surgery with or without admission. The Chi-square test was used for qualitative variables and Mann-Whitney U test for quantitative. Limit significance p < 0.05. Results: Overall, there were 13.2% emergency department visits (mean of 1.24 visits) with an average delay of 8.22 days after discharge. Complications: pain not controlled with analgesia (6.7%), hemarthrosis that required arthrocentesis (4.4%), fever (3.2%), deep vein thrombosis (0.6%), cellulitis (0.6%), septic arthritis that required arthroscopic debridement (0.3%), and others (1.2%) including problems with immobilization. The hospital readmissions (2.3%) were for surveillance and monitoring of the surgical wound. In the bivariate analysis no statistically significant differences were found between groups as regards the sociodemographic characteristics of the patients or the complications recorded. Discussion: The most frequent complications recorded were acute pain, hemarthrosis and fever. Serious complications (deep vein thrombosis, septic arthritis or need for hospital readmission) were rare. Outpatient arthroscopic ACL repair is a common technique that can be performed safely by surgery without admission, with an overall low complication rate with no differences between outpatients and inpatients (AU)

Luxación traumática del tendón tibial posterior por avulsión del retináculo flexor. Reconstrucción con suturas con anclajes / Traumatic dislocation of posterior tibial tendon by avulsion of flexor retinacular release. Reconstruction with suture anchors

Introducción: La luxación traumática del tendón tibial posterior (TTP) es una entidad con muy baja prevalencia. Debuta con dolor y resalte retromaleolar medial tras un traumatismo en inversión del tobillo con la práctica deportiva. El diagnóstico se basa en la exploración clínica, apoyado en pruebas de imagen. El tratamiento debe ser quirúrgico. Caso clínico: Varón de 28 años que presenta giro forzado del tobillo en inversión del pie y dorsiflexión del tobillo, mientras realizaba una carrera. Es atendido en urgencias donde se trata como esguince de tobillo con vendaje elástico. Una vez recuperado comienza la práctica deportiva notando un resalte con dolor en el tobillo. En la exploración física se reproduce el resalte del TTP con maniobras de inversión y dorsiflexión forzada. Se completa el estudio con ecografía y RMN. El paciente se interviene quirúrgicamente mediante reinserción del retináculo flexor, quedando un tobillo estable y sin resalte. A los 3 meses postoperatorios el paciente reinicia su práctica deportiva. Conclusión: Tras el diagnóstico clínico de luxación del TTP, el tratamiento quirúrgico mediante reinserción del retináculo flexor consiguió un excelente resultado funcional (AU)

Introduction: Traumatic dislocation of the posterior tibial tendon (PTT) has a very low prevalence. It presents with pain and recurrent snapping on the posterior side of the medial malleolus after an ankle sprain while practicing sports. The diagnosis is based on clinical examination, supported by imaging techniques. The treatment must be always surgical. Case report: A 28 year old man sprained ankle his ankle while jogging. He was treated in an emergency department with an elastic bandage. Once he recovered, he went back to running, noticing a projection with ankle pain. In the physical examination the PTT was reproduced with inversion maneuvers and forced dorsiflexion. Ultrasound and MRI were performed on the ankle. The patient was operated on, leaving a stable ankle with no projection. Three months later he had no pain and restarted his physical activities. Conclusion: Surgical treatment of PTT dislocation by re-anchoring the flexor retinacula provides an excellent functional outcome (AU)

Postoperative complications of anterior cruciate ligament reconstruction after ambulatory surgery.

OBJECTIVE: To study postoperative complications of arthroscopic anterior cruciate ligament (ACL) reconstruction performed as an outpatient compared with same surgery performed as a regular admission (inpatient). MATERIAL AND METHOD: A study was conducted on a historical cohort of 342 patients (115 outpatients vs 227 inpatients) who underwent arthroscopic ACL primary ligamentoplasty (2004-2012). A review was performed on the demographic, surgical and hospital variables. A study was made of early complications (60 days postoperative) including visits to emergency department and readmissions. A descriptive and bivariate distribution analysis was performed between groups, with the grouping criterion: performing of the surgery with or without admission. The Chi-square test was used for qualitative variables and Mann-Whitney U test for quantitative. Limit significance p<0.05. RESULTS: Overall, there were 13.2% emergency department visits (mean of 1.24 visits) with an average delay of 8.22 days after discharge. COMPLICATIONS: pain not controlled with analgesia (6.7%), hemarthrosis that required arthrocentesis (4.4%), fever (3.2%), deep vein thrombosis (0.6%), cellulitis (0.6%), septic arthritis that required arthroscopic debridement (0.3%), and others (1.2%) including problems with immobilization. The hospital readmissions (2.3%) were for surveillance and monitoring of the surgical wound. In the bivariate analysis no statistically significant differences were found between groups as regards the sociodemographic characteristics of the patients or the complications recorded. DISCUSSION: The most frequent complications recorded were acute pain, hemarthrosis and fever. Serious complications (deep vein thrombosis, septic arthritis or need for hospital readmission) were rare. Outpatient arthroscopic ACL repair is a common technique that can be performed safely by surgery without admission, with an overall low complication rate with no differences between outpatients and inpatients.

Traumatic dislocation of posterior tibial tendon by avulsion of flexor retinacular release. Reconstruction with suture anchors.

INTRODUCTION: Traumatic dislocation of the posterior tibial tendon (PTT) has a very low prevalence. It presents with pain and recurrent snapping on the posterior side of the medial malleolus after an ankle sprain while practicing sports. The diagnosis is based on clinical examination, supported by imaging techniques. The treatment must be always surgical. CASE REPORT: A 28 year old man sprained ankle his ankle while jogging. He was treated in an emergency department with an elastic bandage. Once he recovered, he went back to running, noticing a projection with ankle pain. In the physical examination the PTT was reproduced with inversion maneuvers and forced dorsiflexion. Ultrasound and MRI were performed on the ankle. The patient was operated on, leaving a stable ankle with no projection. Three months later he had no pain and restarted his physical activities. CONCLUSION: Surgical treatment of PTT dislocation by re-anchoring the flexor retinacula provides an excellent functional outcome.

Donation rates: what matters?

INTRODUCTION: The increase in the number of donors is the main objective of all transplantation organizations around the world. Further understanding of the factors involved in increasing donation rates is very important for planning future strategies to improve outcomes in each country. OBJECTIVE AND METHOD: With this purpose we analyzed the relationship between social and economic factors of the countries and organizational aspects of health systems and institutions dedicated to transplantation in relation to the number of actual donors per million population. We analyzed rates of deceased donors per million population of Latin America, North America, and Europe (20 countries) and correlated them with the human development index and its most important indicators. We also studied the correlation with spending on health and organizational aspects of the health system. RESULTS: On the one hand, we found that donation rates (DRs) per million population (pmp) were not statistically significantly correlated with the human development index (significant correlation 0.61 and 0.181). There is a correlation, albeit weak, between observed donation rates and gross domestic product (GDP) of each country (significance, 0.04; correlation, 0.46). On the other hand, there exists a strong correlation between the percentage of GDP spent on health and DRs pmp (significance, 0.01; correlation, 0.53). Those countries with an integrated national health system (P = .01) and a higher percentage of hospitals with intrahospital transplantation coordinators (P = .001) had higher DRs pmp. CONCLUSIONS: The best DRs are closely linked to organizational aspects of the donation system in particular and the health system in general. There is a weak correlation between observed DRs and socio-economic and development indicators of countries. These data should be taken into account in planning future strategies to increase DRs, health plan policies, and investments.

Transcranial Doppler in the diagnosis of cerebral circulatory arrest: cases of the National Institute of Donation and Transplantation of Uruguay.

BACKGROUND: Transcranial Doppler (TCD) is an auxiliary method for the diagnosis of cerebral circulatory arrest (CCA). The objective of this work was to appreciate the efficiency of the method in the diagnosis of the CCA and its outcome in situations such as decompressive craniectomy (DC). METHODS: In this descriptive, retrospective study, conducted between 2000 and 2012, variables considered were causes of brain death (BD), age, sex, application reason, CCA patterns, and CCA patterns in DC. As a statistical approach, Pearson χ(2) distribution was used. A total of 522 cases were analyzed; mean patient age was 30 ± 19 years, and 61% were men. RESULTS: The principal causes of BD were traumatic brain injury, 44%; subarachnoid hemorrhage, 20%; and post-cardiac arrest anoxic ischemic injury, 17%. TCD was requested by contraindication to apnea testing in 84% of cases, and it diagnosed CCA in 79%. The most frequent pattern of CCA was the systolic spike (70%). CCA was diagnosed in patients with DC in 43% (23/54) compared with 79% (369/468) in those patients without this procedure (P = .0001), with the systolic spike being the most frequent pattern (48%). CONCLUSIONS: TCD is a useful and highly specific tool for the diagnosis of CCA that occurs with BD, diminishing its performance significantly in patients with DC.

A model to predict progression in brain-injured patients.

INTRODUCTION: The study of brain death (BD) epidemiology and the acute brain injury (ABI) progression profile is important to improve public health programs, organ procurement strategies, and intensive care unit (ICU) protocols. The purpose of this study was to analyze the ABI progression profile among patients admitted to ICUs with a Glasgow Coma Score (GCS) ≤8, as well as establishing a prediction model of probability of death and BD. MATERIALS AND METHODS: This was a retrospective analysis of prospective data that included all brain-injured patients with GCS ≤8 admitted to a total of four public and private ICUs in Uruguay (N = 1447). The independent predictor factors of death and BD were studied using logistic regression analysis. A hierarchical model consisting of 2 nested logit regression models was then created. With these models, the probabilities of death, BD, and death by cardiorespiratory arrest were analyzed. RESULTS: In the first regression, we observed that as the GCS decreased and age increased, the probability of death rose. Each additional year of age increased the probability of death by 0.014. In the second model, however, BD risk decreased with each year of age. The presence of swelling, mass effect, and/or space-occupying lesion increased BD risk for the same given GCS. In the presence of injuries compatible with intracranial hypertension, age behaved as a protective factor that reduced the probability of BD. CONCLUSIONS: Based on the analysis of the local epidemiology, a model to predict the probability of death and BD can be developed. The organ potential donation of a country, region, or hospital can be predicted on the basis of this model, customizing it to each specific situation.

[Bankart repair. Comparative study with and without suction drainage to assess shoulder pain and functional limitation]. / Reparación de Bankart. Estudio comparativo con y sin drenaje aspirativo para valorar dolor y limitación funcional del hombro.

UNLABELLED: The purpose of this study is to compare two patient cohorts with Bankart lesion, one with intraarticular drainage after surgery and another group without drainage. MATERIAL AND METHODS: We designed a study cohort for patients with Bankart repair due to relapsing shoulder dislocation; they underwent arthroscopy and were stabilized with suture anchors; intraarticular drainage was used in one group and no drainage was used in a control patient cohort. Thirty-one consecutive patients were operated by the same team. All patients were evaluated at the office using the Rowe, Constant and UCLA scales. The statistical tests used included chi-square, the student-t test or the Wilcoxon rank sum test (nonparametric version). RESULTS: The UCLA median value was 35 (34.5-35) in group B and 33 (32.5 -35) in group A, with p = 0.13. The Rowe test score was 100 (95;100) in group B and 100 in group A (85;100), with p = 0.913. The Constant test score was 96 (88.8-98) in group B and 96 (90.5-100) in group A with p = 0.535 and no differences. DISCUSSION: This comparative study includes two groups that underwent arthroscopic Bankart repair, one with drainage and another one without drainage. Good results were obtained in both groups. In this study the placement of a postoperative intraarticular drainage did not improve clinical results, as no statistically significant differences were observed between both groups.

Binding and removal of sulfate, phosphate, arsenate, tetrachloromercurate, and chromate in aqueous solution by means of an activated carbon functionalized with a pyrimidine-based anion receptor (HL). Crystal structures of [H3L(HgCl4)]·H2O and [H3L(HgBr4)]·H2O showing anion-π interactions.

Binding of anions of great environmental concern such as SO(4)(2-), PO(4)(3-), AsO(4)(3-), HgCl(4)(2-), and CrO(4)(2-) by the protonated forms of a tren-like (tren = tris(2-aminoethyl)amine) ligand (HL) functionalized with a pyrimidine residue was studied by means of potentiometric measurements and isothermal titration calorimetry (ITC) affording log K, ΔH°, and TΔS° values for the formation of the relevant complexes. The complexes show high to very high stability due to the particular topology and electronic properties of the ligand which is able to use two separated coordination environments to host the anions, the protonated tren site where electrostatic and hydrogen bond interactions are operating, and the pyrimidine ring which may act via anion-π interaction. A contribution of -8.9 ± 0.4 kJ/mol for pyrimidine-anion interaction in water was derived for SO(4)(2-) binding. The crystal structures of [H(3)L(HgCl(4))]·H(2)O (1), [H(3)L(HgBr(4))]·H(2)O (2), and that previously reported for [H(3)L(CdI(4))], clearly show these binding features in the solid state. A hybrid AC-HL material obtained by adsorption of HL on commercial activated carbon (AC) was used to study the removal of these anions from water. AC-HL shows enhanced adsorption capacity toward all the anions studied with respect to AC. This behavior is ascribed to the stronger interaction of anions with the HL function of AC-HL than with the Cπ-H(3)O(+) sites of the unfunctionalized AC.

Ventricular dysfunction associated with brain trauma is cause for exclusion of young heart donors.

OBJECTIVE: Ventricular dysfunction (VD) in the context of brain death (BD) is one medical cause that may be reversed to extend the range of donors for cardiac transplant programs. The aim of this study was to identify and quantify the causes for exclusion of potential heart donors and to define risk factors for VD among the BD population. MATERIALS AND METHODS: This study of 100 heart-beating potential donors defined subjects as those younger than 50 years. We defined hemodynamic dysfunction (HD) as failure to achieve hemodynamic objectives despite the use of inotropic agents by protocol or upon diagnosing VD. RESULTS: Among 246 BD subjects were 100 potential heart donors. Of these, 75 were transformed into real donors (RD) including 13 heart RD and 62 noncardiac RD. The conversion rate of BD subjects younger than 50 years to heart RD was 17%. When we analyzed the medical reasons for exclusion of the 62 donors who were not converted to heart RD, we observed that HD was the major cause (34%). When we analyzed the causes for exclusion related to cause of death, cranial trauma predominated (52%; P = .01; relative risk 3.5; 95% confidence interval 1.4-8.5). CONCLUSION: Hemodynamic dysfunction represented the major cause for loss of heart donors; it was associated with younger patients with cranial trauma.

Study of the internal morphology of cation-exchange membranes by means of electroosmotic permeability relaxations.

The effect of an ac sinusoidal perturbation of known amplitude and frequency superimposed to the usual dc applied electric voltage difference on the electroosmotic flow through three cation-exchange membranes with different morphology has been studied. A dispersion of the electroosmotic permeability on the frequency of the applied ac signal has been found for the three membranes investigated, observing that the electroosmotic permeability reaches maximum values for some characteristic values of the frequency. These characteristic frequency values, which are related to relaxation processes in heterogeneous media, depend on the membrane system and permit to obtain information about the different structures of the membrane system. Thus, the study of the electroosmotic permeability relaxation can be used as a method to study the internal morphology of a cation-exchange membrane in a given electrolyte medium.