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Biomedical subjects

R Vicente

Publications and source records attributed to R Vicente.

At least 37 records · Page 2Linked to original sources
PubMed2000

Synthesis, structural characterisation, and Monte Carlo simulation of the magnetic properties of the 3D-stacked honeycomb Cs(n)

Two new polymeric manganese-azido systems with formula Cs(n)-[[Mn(N3)3]n] (1) and [[N(C2H5)4]n][[Mn2-(N3)5(H2O)]n] (2) were synthesised and structurally characterised. Compound 1 crystallises in the P2(1)/n group and consists of a three-dimensional system with end-to-end and end-on azido bridges with the caesium atoms in the holes of the net. Magnetically, compound 1 is a rare case of a three-dimensional network with alternate ferro-antiferromagnetic interactions. Compound 2 crystallises in the P1 group and consists of double chains of manganese atoms bridged by end-on and, the exceptional, (mu-1,1,1)-azido bridges. Magnetically, compound 2 shows net ferromagnetic behaviour. Exact fit of the magnetic data was performed for the two compounds by means of Monte Carlo simulations based on the Metropolis algorithm on sets of 10 x 10 x 10 (1) and 1 x 1 x 320 (2) S = 5/2 classical spin centres.

Journal Article↗
PubMed2000

Statistical physics of regular low-density parity-check error-correcting codes

A variation of Gallager error-correcting codes is investigated using statistical mechanics. In codes of this type, a given message is encoded into a codeword that comprises Boolean sums of message bits selected by two randomly constructed sparse matrices. The similarity of these codes to Ising spin systems with random interaction makes it possible to assess their typical performance by analytical methods developed in the study of disordered systems. The typical case solutions obtained via the replica method are consistent with those obtained in simulations using belief propagation decoding. We discuss the practical implications of the results obtained and suggest a computationally efficient construction for one of the more practical configurations.

Journal Article↗
PubMed2000

[Lesion caused by ischemia-reperfusion in lung transplantation].

OBJECTIVES: To assess the existence or not of a relation between the characteristics of lung donor and/or recipient and the development of ischemia-reperfusion injury (IRI). We also review the latest experimental findings on the biophysical conditions pf graft preservation. PATIENTS AND METHOD: A retrospective study of 74 lung transplants performed in our hospital from 1993 to 1998. Donor and recipient screening and anesthetic and surgical techniques were performed following established protocols. Various degrees of IRI were determined according to hemodynamic and gasometric criteria. We analyzed the statistical relation between donor and recipient variables and IRI. Statistical significance was set at p < 0.05. RESULTS: The incidence of IRI was 70.2% (52 cases), with 12 cases categorized as mild, 22 as moderate and 18 as severe. IRI was significantly related only to the start of extracorporeal circulation. CONCLUSIONS: The development of IRI in lung transplantation is linked to such donor and/or recipient characteristics as the biophysical conditions of graft preservation. At present, greater prevention of this type of early dysfunction of the lung graft requires not only use of adequate screening criteria for donors and receivers but also adequate measures for graft preservation with the use of drugs and handling that have been shown to be effective.

Adolescent↗
PubMed2000

[Lung transplantation and hemophilia. Preoperative considerations].

Lung transplantation is indicated in certain patients with terminal pulmonary disease. We report a case in which a single lung (left) was transplanted to a 16-year-old girl with hemophilia B; she also suffered idiopathic pulmonary fibrosis and had a history of malnutrition, osteoporosis, severe scoliosis, hepatitis C positivity and recurrent bilateral pneumothorax. Treatment with pure factor IX was started the moment the donor lung was available and was continued for 37 days after surgery. Plasma levels of factor IX were kept at 100% during surgery and in the early postoperative period, and over 40% after that time. Correct hemostasis was thus achieved throughout the procedure, with no need for blood products. Patient outcome was satisfactory. The stay in the intensive care recovery ward was 17 days and discharge was 40 days after transplantation. We discuss aspects of hemophilia and lung transplantation, and the influence on malnutrition, chronic steroid treatment and osteoporosis.

Adolescent↗
PubMed1999

[Application of selection criteria in sequential double lung transplantation].

Since the first sequential double lung transplant was performed in 1986, such procedures have been increasing in number and the criteria used as indications for this type of surgery have broadened. Our aim was to reflect on the application of selection criteria and to describe the anesthetic and surgical techniques and postoperative follow-up of 72 patients who underwent this type of transplant surgery between March 1993 and December 1998. Actuarial survival five years after surgery was 74.4%. Among patients requiring transplantation after septic disease, actuarial survival was 90.8% for cystic fibrosis and 88.2% for bronchiectasis. Of the preoperative risk factors analyzed (prior surgery, pachypleuritis, multiresistant germs, poor nutrition, mechanical ventilation and corticoid therapy), only prior treatment with high doses of corticoids proved significant. Eleven patients have been diagnosed of bronchiolitis obliterans, four have died and only two continue to experience difficulties in daily living. The high survival rate and the restriction-free life after recovery lead us to consider sequential double lung transplantation to be the treatment of choice for all pulmonary diseases.

Adult↗
PubMed1999

Educational level, voluntary private health insurance and opportunistic cancer screening among women in Catalonia (Spain).

Health care services in Catalonia (Spain) are organized in a national health service with universal population coverage and include preventive services such as mammography and Pap tests. In addition to a national health service (NHS) coverage, 22% of the population is enrolled in a voluntary private health insurance (VPHI), leading to a double coverage. This situation offers an opportunity to study the impact of this organizational aspect of health care with regard to cancer screening access. The source of data was the Catalan Health Survey (CHS), a cross-sectional survey conducted in a random sample of non-institutionalized population carried out in 1994. Variables analysed were age, educational level and voluntary private health insurance (VPHI). Women were asked if they had ever had a mammography and Pap test for preventive purposes. Logistic regression was used to study the relationship between these variables and the mammography or Pap test participation. The study sample was 5865 women aged 20 years and older. A Pap test and mammography were carried out on 42% and 25% of women, respectively. Participation had a peak between the ages of 30 and 39 years in Pap test and between 40 and 49 years in mammography; it decreased in older women. The percentage of Pap test practice increases according to a higher educational level than it does in mammography. Women who had a VPHI showed a higher percentage of screening tests than the rest of the population. There is also an increase in the mammography practice related to the educational level in older groups, but this fact is not observed in women younger than 40 years . Multivariate logistic regression analysis showed an increase in the likelihood of ever had a mammography and a Pap test according to age and to educational level, although this situation is less pronounced in older age groups. Both variables (educational level and age) remained significant after introducing the VPHI into the model (women who reported having a VPHI were more likely to have had a Pap test and a mammography than the rest of the women). In conclusion the opportunistic screening is associated with age, educational level and VPHI. Educational level is also associated with participation in both screening tests after adjusting by age. Furthermore, screening for cervical cancer shows a higher educational gradient than for breast cancer screening. The influence of VPHI after adjusting by age and by educational level poses the question about the role of private health insurances with regard to preventive practices in the context of a national health service aimed at promoting equity of health care access.

Adult↗
PubMed1999

Finite-connectivity systems as error-correcting codes.

We investigate the performance of parity check codes using the mapping onto Ising spin systems proposed by Sourlas [Nature (London) 339, 693 (1989); Europhys. Lett. 25, 159 (1994)]. We study codes where each parity check comprises products of K bits selected from the original digital message with exactly C checks per message bit. We show, using the replica method, that these codes saturate Shannon's coding bound for K-->infinity when the code rate K/C is finite. We then examine the finite temperature case to assess the use of simulated annealing methods for decoding, study the performance of the finite K case, and extend the analysis to accommodate different types of noisy channels. The connection between statistical physics and belief propagation decoders is discussed and the dynamics of the decoding itself is analyzed. Further insight into new approaches for improving the code performance is given.

Journal Article↗
PubMed1999

Antifungal prophylaxis during the early postoperative period of lung transplantation. Valencia Lung Transplant Group.

INTRODUCTION: Fungal infections occur frequently in lung transplant patients, with the highest risk being in the early postoperative period (the initial hospitalization after lung transplantation). Aspergillus is responsible for more than half of all fungal infections, and Aspergillus has even been considered a contraindication for lung transplantation because of its difficult therapy and frequently fatal outcome. The aim of this article is to evaluate the success of an antifungal prophylaxis protocol to prevent fungal infection in the immediate postoperative period in lung transplant recipients. MATERIAL AND METHODS: From March 1994 to March 1997, we performed 52 lung transplants in 31 men and 21 women who received antifungal prophylaxis with fluconazole, 400 mg/d, and aerosolized amphotericin B, 0.6 mg/kg/d, during the postoperative period. RESULTS: The mean (+/- SD) postoperative period duration was 49 +/- 27.5 days. No fungal infections were observed during this period, and all patients provided negative cultures. We also found no toxicity related to antifungal drugs. The dose of cyclosporine was easily adjusted in every recipient according to blood levels so that effective immunosuppression was not compromised. DISCUSSION: In our study, the removal of the lungs and antifungal prophylaxis with fluconazole and aerosolized amphotericin B prevented fungal infection in the postoperative period in all 52 lung transplant recipients.

Adolescent↗
PubMed1999

[The first simultaneous double unilateral lung transplantation in Spain: clinical course and results. Transplantation Group].

Unilateral lung transplantation of two organs allows two patients to benefit from a single donor. We report the first and only such transplants--carried out simultaneously in the same surgical unit--to be performed in Spain to date. The diagnosis was idiopathic pulmonary fibrosis in both cases and the donor came from the same hospital. No complications developed during the subsequent hospital stay. Two years later, both patients are asymptomatic and carrying out normal activities with no limitations.

Female↗
PubMed1999

[Lung transplantation in cystic fibrosis. The results of the Clínica Puerta de Hierro (Madrid) and the Hospital La Fe (Valencia)].

UNLABELLED: Retrospective analysis of cystic fibrosis patients who underwent pulmonary transplantation at Clínica Puerta de Hierro, Madrid, and at Hospital La Fe, Valencia. Since the beginning of the programme and until March 1998, a total of 63 patients with cystic fibrosis were studied. Among transplanted patients, 18 were males and 16 females, with a mean age of 18.9 years. All patients underwent sequential bilateral pulmonary transplantation. After transplantation, the most common complication was bacterial pneumonia which affected all patients. Six patients had dehiscence or stenosis of the bronchial suture. Other specific complications of this condition by frequency were intestinal obstruction and diabetes mellitus. Six patients developed obliterans bronchiolitis and one of them underwent a repeat transplantation. Three out of the 34 patients died, and the likelihood of survival after one and three years was 94%. Respiratory function tests and PaO2 peaked at sixth post-transplantation month. CONCLUSION: Pulmonary transplantation is a therapeutic option to be considered for the patient with cystic fibrosis and severe involvement of his/her pulmonary disease.

Adolescent↗
PubMed1999

[Paraplegia after surgery for aneurysm of the descending thoracic aorta].

Postoperative paraplegia caused by ischemic injury of the spinal cord is the most disabling complication of thoracoabdominal surgery, particularly when repair of the descending thoracic aorta is involved. We describe the case of a 59-year-old man who underwent emergency surgery for placement of a Dacron prosthesis to repair a ruptured descending thoracic aorta aneurysm, using an aortic cross-clamping technique plus aortic-femoral partial bypass with normothermia and an ischemic time of 165 minutes. The early postoperative course included complete spinal syndrome with motor and sensory loss below T5, with consequent respiratory insufficiency of neuromuscular origin. The result was a difficult postoperative course including prolonged mechanical ventilation and recurrent respiratory infections. Possible causes include prolonged time of ischemia, inadequate monitoring of distal aortic pressure and inappropriate surgical technique related to the absence of angiographic data on spinal vascularization. We conclude that ischemic time should be kept to under 30 minutes whenever possible. In cases of prolonged ischemia, bypass techniques with outflow to the distal aortic segment are more effective whenever mean blood pressure at this point rises to 60 mmHg or more. Vasodilator use should be reserved for cases of severe arterial hypertension and left ventricular failure and/or life-threatening increases in aortic wall stress even if not leading to dangerous decreases in distal aortic pressure. Finally, angiographic study to obtain anatomical details of spinal blood flow is advisable.

Aortic Aneurysm, Thoracic↗
PubMed1998

Prognostic factors in a series of 297 patients with gastric adenocarcinoma undergoing surgical resection.

BACKGROUND: Gastric cancer has a poor prognosis. The aim of this study was to determine the influence of several clinicopathological variables on outcome in a series of 297 Western patients undergoing surgical resection for gastric adenocarcinoma. METHODS: The results were analysed retrospectively and prognostic factors were identified in a univariate and Cox proportional hazards regression model. Mean patient age at the time of operation was 61.9 years; 65.7 per cent were men. Mean follow-up was 7.8 (range 1-15) years. Of the 297 patients undergoing surgery, 70 per cent had subtotal gastrectomy, 26.3 per cent underwent total gastrectomy and 3.7 per cent had proximal gastrectomy. RESULTS: The overall survival rate was 38.9 per cent at 5 years. In th univariate analysis, survival-related factors were weight loss (P < 0.05), abdominal mass (P < 0.01), dysphagia (P < 0.001), type of gastrectomy (subtotal gastrectomy versus total gastrectomy, P < 0.001), intention of resection (curative versus palliative resection, P < 0.001), tumour site (P < 0.001), histopathological grade (low versus high grade, P < 0.05), tumour diameter less than 3 cm (P < 0.001), degree of gastric wall invasion (P < 0.001), degree of lymph node invasion (P < 0.001) and stage of the neoplasia (P < 0.001). Other variables had no significant influence. In the multivariate analysis, degree of gastric wall invasion, lymph node invasion, tumour size and dysphagia at presentation were the only independent prognostic variables. CONCLUSION: From these data it was possible to derive a prognostic index with which patients could be classified as at low, intermediate or high risk.

Adenocarcinoma↗
PubMed1997

[Smoking prevalence trends in Catalonia, Spain, 1982-1994].

BACKGROUND: Smoking prevalence trends from 1982 to 1994 of adult population in Catalonia (Spain) are described. SUBJECTS AND METHODS: Four population surveys have been carried out periodically using the same questionnaires and definitions for smoking status. Surveys in 1982, 1986 and 1990 have been implemented taking samples of Catalonia population through a multistage sampling with random stratified selection by province and habitat. Individuals were chosen through a random route process. In 1994, a survey with a complex probabilistic sample design with 8 geographical areas (health regions) and 2 basic units (towns and individuals) was implemented. RESULTS: Among the 15-64 years old adults, a decrease of 6.9% in smoking prevalence has been observed. The initial prevalence in 1982 was 37.9% (CI 95%: 35.4; 40.3); in 1994 this prevalence was 35.3% (CI 95%: 34.4; 36.2). In 1994, the prevalence of current smokers in population over 14 years old was 30.6% (CI 95%: 29.8; 31.4). We have observed a significant decrease in smoking prevalence in all age groups among male population (-20.6% for the 12-year period) whereas prevalence has increased among female (+28.0%) mainly among those between 25 and 54 years old. The main percentual decrease in smoking prevalence has been observed among young people aged 15-24 years old for both genders. The proportion of former smokers has remained stable (11.4% in 1982, 12.9% in 1994) during the period studied. The proportion of former smokers increases with age among man over 25 years. CONCLUSIONS: Smoking habit is still very prevalent in Catalonia, even higher than in other Western European countries. In spite of the increase among women, the significant dectines of smoking prevalence among men and youngsters (of both genders) could represent encouraging findings in order to pursue the efforts aimed at reducing the morbi-mortality burden of smoking in our society.

Adolescent↗
PubMed1997

[Primary pulmonary hypertension: treatment with prostacyclin before lung transplantation].

We report our experience with two patients diagnosed of primary pulmonary hypertension who later received lung transplants, with treatment with short-acting pulmonary vasodilators (epoprostenol) provided as a bridge to transplantation. Continuous intravenous perfusion at a dose of 6 ng/kg/min was provided to the first patient, a 19-year-old man, for 26 days. An initial dose of 4 ng/kg/min followed by 6 ng/kg/min was given to the second patient, a 49-year-old woman, for 6 months. Symptoms were drastically reduced in both patients, significantly improving their quality of life.

Adult↗