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Biomedical subjects

J M Pons

Publications and source records attributed to J M Pons.

15 recordsLinked to original sources
PubMed2001

C-C versus C-O anionic domino cycloalkylation of stabilized carbanions: facile one-pot stereoselective preparation of functionalized bridged bicycloalkanones and cyclic enol ethers.

alpha,alpha'-Diactivated cyclic- or acyclic ketones undergo a chemoselective base promoted (K2CO3, DBU) one-pot C-C cycloalkylation, with 1,3- and 1,4-dihalides having a cis-like fixed configuration. This reaction gives highly functionalized bicyclo[3.2.1]octan-9-one and bicyclo[4.2.1]nonan-9-one derivatives, which are easily transformed to seven- and eight-membered rings through a high yield retro-Dieckmann cleavage. Starting from trans-1,4-dibromo-2-butenes, the transformation is governed by stereoelectronic factors and leads, through a chemo- and stereoselective C-O cycloalkylation, to synthetically valuable monocyclic or fused polycyclic functionalized enol ethers of high synthetic value. Semiempirical calculations showed a small difference in energy and the late character of the transition states leading to cis and trans isomers of the corresponding fused polycyclic enol ethers. These results, although minimizing the influence of a destabilizing 1,3-interaction on the outcome of the reaction, are qualitatively in agreement with the experimental results.

Journal Article↗
PubMed2000

Scoring system has better discriminative value than Helicobacter pylori testing in patients with dyspepsia in a setting with high prevalence of infection.

OBJECTIVE: To prospectively assess the accuracy of a scoring system to predict organic diseases in dyspeptic patients in an area of South Europe, and to compare it with that of Helicobacter pylori testing in patients with dyspepsia in an environment with high prevalence of H. pylori infection. METHODS: Symptoms and demographic data were recorded in 501 consecutive dyspeptic patients referred to an outpatient gastroenterology clinic. A simple scoring system was constructed from the predictive factors obtained in a multi-variate logistic regression analysis. Overall predictive accuracy was assessed with the c statistic. The model was validated using bootstrap techniques. The accuracy of clinical judgement and H. pylori testing to predict endoscopic diagnosis was also assessed. RESULTS: Organic dyspepsia (peptic ulcer, oesophagitis or malignancies) was diagnosed in 45% of the patients. The test for H. pylori was positive in 68%, and 29% of infected patients had an ulcer. The organic dyspepsia predictive model had an accuracy of 0.79, which decreased to 0.77 after validation adjustment. The predictive accuracies for clinical judgement and H. pylori testing were 0.69 and 0.61, respectively. The addition of H. pylori testing to the scoring system resulted in a minor improvement of the predictive accuracy. CONCLUSION: In an environment with a high rate of H. pylori infection and a low prevalence of peptic ulcer among infected patients, a scoring system has higher predictive accuracy for the diagnosis of organic disease than H. pylori testing. Moreover, in this setting, H. pylori testing adds a minimum value to the predictive capability of the scoring system.

Adolescent↗
PubMed1999

Subjective versus statistical model assessment of mortality risk in open heart surgical procedures.

BACKGROUND: The aim of this study was to compare the predictive accuracy for open heart surgical mortality between a statistical model based on collection of clinical data and surgeons' subjective risk assessment. METHODS: Predictive discrimination of both risk assessments (surgeons' and model) was compared through the area under the receiver operating characteristic curve. Logistic regression analysis was used to assess the relation between surgeons' and model predictions to actual outcomes. Calibration of the subjective estimates was evaluated with a chi2 test. RESULTS: Overall, the area under the receiver operating characteristic curve was 0.76 for the statistical model and 0.70 for the subjective assessment. Logistic regression analysis showed that the statistical model remained significant after accounting for the subjective assessment. Calibration of subjective mortality predictions was poor. CONCLUSIONS: Surgeons' risk assessment tends to cluster in the middle ranges of risk. Subjective assessment seems accurate in identifying the two extremes of risk but is inaccurate for intermediate risk levels. A multivariate statistical model improves the accuracy of subjective predictions.

Aged↗
PubMed1998

Cardiac surgical mortality: comparison among different additive risk-scoring models in a multicenter sample.

OBJECTIVE: To compare the performance of several risk-scoring models to predict surgical mortality following open heart surgery. DESIGN: A prospective observational study. SETTING: Seven tertiary cardiac centers (3 private and 4 public and teaching hospitals) in Catalonia (Spain). PATIENTS: A consecutive sample of 1287 patients submitted to open heart surgery during a 6 1/2-month period (February 14, 1994, to August 31, 1994). INTERVENTION: None. MAIN OUTCOME MEASURE: Model discrimination capability was assessed with the c-statistic. A chi(2) test to compare observed and predicted mortality rates was used as a measure of model calibration. Performance of centers was evaluated through the standardized mortality ratio and using the center as an indicator variable in a logistic regression model. The agreement among models for individual predictions was tested using weighted K statistics. RESULTS: Models developed in other health care contexts showed, as expected, lower c-statistics and an inappropriate calibration. There were no statistically significant differences among hospitals after adjusting for baseline patients' risk factors with the use of any of the different models. Models also agree in the standardized rank of centers. Weighted K statistics indicated poor agreement among models for individual patient risk prediction. CONCLUSIONS: Models can be a useful tool to compare providers' performance and to give a more in-depth look at the process of care when appropriately customized to the context. Severity-adjusted models can also play a role in supporting the informed and subjective surgeon's assessment, but it is inappropriate to use them for individual predictions.

Cardiac Surgical Procedures↗
PubMed1998

[Activity and morbimortality of coronary surgery in Spain].

The goal of the study is to describe the current knowledge about coronary artery by-pass surgery in Spain related to activity, institutions, and clinical outcomes. A search in the MEDLINE (1982-97) and IME (1976-97) databases and manual search in medical journals, official publications of scientific societies was performed. References whose authors or institutions in charge were located in Spain, and including data on activity, mortality and morbidity of coronary artery bypass surgery alone or in combination with other procedures. In 1995, 7,936 coronary procedures were carried out (alone or in combination) in 51 Spanish centres, representing an increase of 123% in those procedures registered and published in 1988. Hospital mortality, according to the Registry of the Spanish Society of Cardiovascular Surgery (1995), was 7.2%. Data from multicenter studies showed, allowing for variations among centres, 8.8% (1975-82) and 8.1% (1994) mortality in isolated coronary revascularization. Other studies refer to the particular experience in a centre, examining either predictive mortality factors or outcomes in specific clinical conditions. Surgical mortality has been only partially analysed in multicentre studies, although several groups refer to the incidence of their own specific complications. There are few multicentre studies assessing morbidity and mortality in coronary artery surgery and some results (quality of life, economical) have been poorly evaluated. An alternative to be considered is the creation of an advisory commission aimed at establishing health care standards and at supporting an information system on the patients characteristics, techniques applied, and results obtained in the provision of cardiological procedures that, due to their invasiveness, complexity and cost, can be considered as tertiary cardiological care.

Coronary Artery Bypass↗
PubMed1998

[The unequal clinical profile, quality of life and hospital mortality in patients undergoing aortocoronary bypass in the public and private centers of Catalonia. The CIRCORCA Study].

INTRODUCTION AND AIMS: The influence of the type of health care funding and management of hospital centres on hospital mortality in coronary artery bypass surgery (CABG) has not been analyzed in detail. We therefore assessed clinical and quality of life preoperative profiles and in-hospital mortality in public and private patients undergoing coronary bypass surgery in Catalonia. METHODS: Clinical questionnaires, Duke Activity Status Index (DASI) and SF-36 were preoperatively administered to all patients undergoing first coronary bypass surgery without associated procedures in Catalonia between November 1996-June 1997. In-hospital morbidity and mortality were recorded. RESULTS: Predictors of in-hospital death, including DASI, SF-36 and comorbidity scores, were significantly worse in public than in private patients. In-hospital mortality rate was more than ten times greater in public than in private patients (8.2% vs 0.7%; p < 0.001). Multivariate analysis identified private funding of health care, among others, as an independent predictor of in-hospital survival. Non evidence-based indications for surgery were significantly more common in private than in public patients (6% vs 0.7%, p < 0.001). CONCLUSIONS: a) In catalonia, the risk profile of public patients undergoing coronary bypass surgery was significantly higher than that of private patients, accounting, at least in part, for a remarkable mortality difference; b) non evidence-based indications for surgery were more common in private than in public patients; c) these unequal patterns raise questions about the adequacy of care and referral patterns in both private and public sectors.

Aged↗
PubMed1997

Assessing open heart surgery mortality in Catalonia (Spain) through a predictive risk model.

OBJECTIVE: To develop a risk stratification model to assess open heart surgery mortality in Catalonia (Spain) in order to use risk-adjusted hospital mortality rates as an approach to analyze quality of care. METHODS: Data were prospectively collected through a specific data-sheet during 6 1/2 months in consecutive adult patients subjected to open heart surgery. The dependent variable was surgical mortality, and independent variables included were presurgical (sociodemographic data, clinical antecedents, morphological and functional studies) and surgical. The model was built on a subsample (70% of study population) through univariate and logistic regression analysis and validated in the rest of the sample. RESULTS: The total sample was of 1309 procedures in seven hospitals; 47% of them were valve procedures. The overall crude mortality rate was 10.9% and varied among centers (range, 2.8-14.8%). Risk factors included in the model received a weight based on the logistic regression coefficient and a score was generated for each patient. The factors with the highest weight were patient older than 80 and second reoperation. Score was stratified in five categories of increasing risk. There was a good agreement between observed and predicted mortality rates in the validation group. Overall patient distribution was as follows: 52% low risk level, 16% fair, 13% high, 12% very high, and 6% extremely high risk level. Mortality rate increased from 4.2% in the low risk to 54.4% in the highest risk group. Case mix adjustment was performed through the risk score level. There were statistically significant differences in the risk profiles of patients admitted among centers. After adjustment by risk profiles, there were no differences in mortality by hospital. CONCLUSION: A risk stratification model through a multicentric, prospective and exhaustive collection of data in all types of open heart procedures was developed. In spite of wide differences on crude rates and in the risk profiles of patients admitted, we did not find statistically significant differences in adjusted mortality rates among centers. Timely and accurate information about surgical outcomes can lead to improvements in clinical practice and quality of care.

Adolescent↗
PubMed1985

Changes in body compartments on different types of haemodialysis.

Changes in plasma volume (PV), extracellular volume (ECV) and intracellular volume (ICV) were studied in seven patients on conventional haemodialysis (HD) and in six patients on stable hypertonic HD. Weight loss and ultrafiltration were similar in both groups. Before HD the spaces of 125RISA (PV), 35SO4Na2 (ECV) and 3H2) (total body water, TBW) were simultaneously determined ICV = TBW - ECV. At the end of HD the space of 35SO4Na2 was again tested. PV and ECV diminished more on conventional HD than on hypertonic HD, whereas ICV increased on conventional HD and decreased on hypertonic HD. The handling of plasma osmolality during HD is an effective method for modifying transcompartmental body fluid shifts in HD by distributing weight loss between intracellular and extracellular spaces allowing for a better maintenance of plasma volume.

Adult↗
PubMed1981

[Early diagnosis of renal ischemia in arterial hypertension by means of urine N-acetyl-beta-D-glucosaminidase (author's transl)].

Essential arterial hypertension, malignant hypertension and renovascular hypertension were studied in 64 patients, divided into 5 groups according to creatinine clearance (Ccreat) and ophthalmic fundus. Urine N-Acetyl-b-d-glucosaminidase (NAG) was expressed in units/mg creatinine in urine. Results were; Group A: Ccreat greater than 60, ophthalmic fundus less than II (n=33), NAG 13.5 + 4.5; Group B: CCreat. greater than 60, ophthalmic fundus III-IV (n=4) NAG 42.4 +/- 12.5; Group C: Ccreat. less than 60, ophthalmic fundus less than II (n = 14) NAG 31.2 +/- 10,5; Group D: (clinically malignant arterial hypertension) Ccreat. less than 60, ophthalmic fundus III--IV (n = 8), NAG 91.1 +/- 55.7 and Group E: (renovascular hypertension) Ccreat. greater than 60, ophthalmic fundus less than II (n = 5), NAG 35.5 +/- 12.9. Only the patients in Group A had NAG within normal limits. Differences were found between groups: A-B (p less than 0.001), A-D (p less than 0.001), A-E (p less than 0.001) and C-D (p less than 0.001). Urine NAG is considered to be an early sign of renal involvement in arterial hypertension, an indication of the severity and a sign of ischemia even when the involvement is unilateral only, and helpful in the management of renovascular hypertension.

Acetylglucosaminidase↗