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Biomedical subjects

Samer A M Nashef

Publications and source records attributed to Samer A M Nashef.

17 recordsLinked to original sources
PubMed2006

The impact of altitude on early outcome following the Fontan operation.

BACKGROUND: The success of a Fontan circulation depends on several factors including low pulmonary vascular resistance. Pulmonary vascular resistance rises in response to hypoxia. Hypoxia is associated with altitude. Therefore, we wondered whether altitude is a risk factor for early failure after the Fontan operation. The aim was to test this hypothesis. METHODS: Data were obtained from all published series of 'total cavopulmonary' Fontan operations since 1990. The early failure rate from each series and the altitude of the respective cities were recorded. Early failure was defined as death, takedown of Fontan, or transplantation during the same hospital admission. The association between altitude and failure rate was investigated by rank correlation and logistic regression. RESULTS: 24 series were identified from centres situated at altitudes ranging from sea level to 520 metres. The plot of failure rate versus altitude suggests that failure rate increases with altitude. Logistic regression did not fit the data adequately. This was possibly due to the influence of unmeasured and unknown factors affecting the results, as well as the fact that centres were not randomly chosen but were self-selected by virtue of publishing their results. However, Spearman's rank correlation was 0.74 (p = 0.001). CONCLUSION: The early outcome of the Fontan circulation appears to be adversely affected by altitude.

Altitude↗
PubMed2006

Total arterial revascularization is safe: multicenter ten-year analysis of 71,470 coronary procedures.

BACKGROUND: The purpose of this study was to assess the use of arterial revascularization and to compare the in-hospital mortality with other CABG grafting strategies. METHODS: A total of 71,470 CABG patients (1992-2001) in 27 centers in the United Kingdom were studied. The proportion of patients with arterial revascularization was compared. In-hospital mortality was compared for various grafting strategies: all-arterial (n = 5,401), all non-all-arterial patients (n = 66,069), one artery any number of veins (n = 49,801). The groups were compared for in-hospital mortality using multivariate logistic regression to assess the independent effect of the grafting strategies on mortality; logistic EuroSCORE-predicted mortality was compared to actual mortality, and all arterial and one artery and veins patients were compared with propensity score analysis. RESULTS: There was a significant increase in the proportion of all-arterial patients over time (3.2% to 11.7%, p < 0.001) with evidence of variability across centers. Crude mortality for all-arterial patients was 2% vs 3% for all non-all-arterial patients (p < 0.001). In multivariate analysis, all-arterial was associated with a slight but insignificant increase in in-hospital mortality (odds ratio [OR] 1.13; [95% confidence interval {CI} 0.86-1.48], p = 0.36). There was a trend toward higher mortality in the all-arterial group when compared with the one artery and veins group (OR 1.19 [95% CI 0.91-1.56], p = 0.10). The one artery and veins group was the only group where actual mortality was significantly lower than predicted by EuroSCORE (p < 0.001). In propensity analysis the mortality was 1.51% for one artery and veins and 1.74% of all-arterial patients (p = 0.56). CONCLUSIONS: The use of arterial grafting has increased over time, varies by center, and appears to be safe in terms of in-hospital mortality.

Aged↗
PubMed2006

Risk factor identification and mortality prediction in cardiac surgery using artificial neural networks.

OBJECTIVE: The artificial neural network model is a nonlinear technology useful for complex pattern recognition problems. This study aimed to develop a method to select risk variables and predict mortality after cardiac surgery by using artificial neural networks. METHODS: Prospectively collected data from 18,362 patients undergoing cardiac surgery at 128 European institutions in 1995 (the European System for Cardiac Operative Risk Evaluation database) were used. Models to predict the operative mortality were constructed using artificial neural networks. For calibration a sixfold cross-validation technique was used, and for testing a fourfold cross-testing was performed. Risk variables were ranked and minimized in number by calibrated artificial neural networks. Mortality prediction with 95% confidence limits for each patient was obtained by the bootstrap technique. The area under the receiver operating characteristics curve was used as a quantitative measure of the ability to distinguish between survivors and nonsurvivors. Subgroup analysis of surgical operation categories was performed. The results were compared with those from logistic European System for Cardiac Operative Risk Evaluation analysis. RESULTS: The operative mortality was 4.9%. Artificial neural networks selected 34 of the total 72 risk variables as relevant for mortality prediction. The receiver operating characteristics area for artificial neural networks (0.81) was larger than the logistic European System for Cardiac Operative Risk Evaluation model (0.79; P = .0001). For different surgical operation categories, there were no differences in the discriminatory power for the artificial neural networks (P = .15) but significant differences were found for the logistic European System for Cardiac Operative Risk Evaluation (P = .0072). CONCLUSIONS: Risk factors in a ranked order contributing to the mortality prediction were identified. A minimal set of risk variables achieving a superior mortality prediction was defined. The artificial neural network model is applicable independent of the cardiac surgical procedure.

Adolescent↗
PubMed2006

Outcomes of cardiac surgery in the elderly.

The elderly represent a rapidly growing and substantially under-treated sector in industrialized countries, with coronary artery disease and degenerative aortic stenosis rampant. The proportion of elderly patients undergoing cardiac surgery is rising steadily and outcomes continue to improve with the refinement of operative techniques and perioperative care. Advanced risk stratification models, such as the logistic European System for Cardiac Operative Risk Evaluation now offer validated prediction of operative mortality in these high-risk patients. Current trends towards off-pump coronary artery surgery, hybrid revascularization and mitral repair may have advantages in the elderly, who often have more diffuse cardiovascular disease and a lower tolerance to intervention. Recent advances may also provide surgical options for the emerging epidemics of cardiovascular disease affecting the elderly, atrial fibrillation and heart failure.

Aged↗
PubMed2004

Should surgeons take a break after an intraoperative death? Attitude survey and outcome evaluation.

OBJECTIVES: To investigate attitudes of cardiac surgeons and anaesthetists towards working immediately after an intraoperative death and to establish whether an intraoperative death affects the outcome of subsequent surgery. DESIGN: Questionnaire on attitudes to working after an intraoperative death and matched cohort study. SETTING: UK adult cardiac surgery centres and regional cardiothoracic surgical centre. PARTICIPANTS: 371 consultant cardiac surgeons and anaesthetists in the United Kingdom were asked to complete a questionnaire, and seven surgeons from one centre who continued to operate after intraoperative death. MAIN OUTCOME MEASURES: Outcome for 233 patients operated on by a surgeon who had experienced an intraoperative death within the preceding 48 hours compared with outcome of 932 matched controls. Hospital mortality and length of stay as a surrogate for hospital morbidity. RESULTS: The questionnaire response rate was 76%. Around a quarter of surgeons and anaesthetists thought they should stop work after an intraoperative death and most wanted guidelines on this subject. Overall, there was no increased mortality in patients operated on in the 48 hours after an intraoperative death. However, mortality was higher if the preceding intraoperative death was in an emergency or high risk case. Survivors operated on within 48 hours after an intraoperative death had longer stay in intensive care (odds ratio 1.64, 95% confidence interval 1.08 to 2.52, P = 0.02) and longer stay in hospital (relative change 1.15, 1.03 to 1.24, P = 0.02). CONCLUSION: Mortality is not increased in operations performed in the immediate aftermath of an intraoperative death, but survivors have longer stays in intensive care and on the hospital ward.

Anesthesiology↗
PubMed2004

Cardiac surgery risk models: a position article.

Differences in medical outcomes may result from disease severity, treatment effectiveness, or chance. Because most outcome studies are observational rather than randomized, risk adjustment is necessary to account for case mix. This has usually been accomplished through the use of standard logistic regression models, although Bayesian models, hierarchical linear models, and machine-learning techniques such as neural networks have also been used. Many factors are essential to insuring the accuracy and usefulness of such models, including selection of an appropriate clinical database, inclusion of critical core variables, precise definitions for predictor variables and endpoints, proper model development, validation, and audit. Risk models may be used to assess the impact of specific predictors on outcome, to aid in patient counseling and treatment selection, to profile provider quality, and to serve as the basis of continuous quality improvement activities.

Bayes Theorem↗
PubMed2003

What is a near miss?

Explore the source record for details and available documents.

Drug Hypersensitivity↗
PubMed2003

Logistic or additive EuroSCORE for high-risk patients?

OBJECTIVES: To assess whether the use of the full logistic European System for Cardiac Operative Risk Evaluation (EuroSCORE) is superior to the standard additive EuroSCORE in predicting mortality in high-risk cardiac surgical patients. METHODS: Both the simple additive EuroSCORE and the full logistic EuroSCORE were applied to 14,799 cardiac surgical patients from across Europe, of whom there were 4293 high-risk patients (additive EuroSCORE of 6 or more). The systems were compared for absolute prediction and discrimination (area under the receiver operating characteristic (ROC) curve). RESULTS: Actual mortality was 4.72%. The logistic model was closer to this than the additive model (4.84% (4.72-4.94) versus 4.21 (4.21-4.26)). Most of this difference was due to high-risk patients where actual mortality was 11.18% and predicted was 7.83% (additive) and 11.23% (logistic). Discrimination was similar in both systems as measured by the area under the ROC curve (additive 0.783, logistic 0.785). CONCLUSIONS: The additive EuroSCORE model remains a simple "gold standard" for risk assessment in European cardiac surgery, usable at the bedside without complex calculations or information technology. The logistic model is a better risk predictor especially in high-risk patients and may be of interest to institutions engaged in the study and development of risk stratification.

Aged↗
PubMed2003

Regional differences in surgical heart valve disease in Europe: comparison between northern and southern subsets of the EuroSCORE database.

BACKGROUND AND AIMS OF THE STUDY: Although rates for coronary and valve surgery vary between northern and southern Europe, differences in the features of valve disease leading to surgery in Europe are poorly documented. The study aim was to compare demographics, risk factors, procedures and outcome in valve surgery between European regions, using the EuroSCORE database. METHODS: Between September and December 1995, information on 98 variables (risk factors, procedures and outcome) were collected on valve surgery patients in 128 European centers. Patients were allocated to two geographic subgroups (north, n = 1,990; south, n = 3,682). The distribution of variables was assessed. Subsequently, the impact of preoperative and operative risk factors on mortality was analyzed in both groups using a bivariate analysis. Risk-adjusted outcomes were then compared according to the EuroSCORE. RESULTS: Significant differences were identified for clinical features, risk factors and procedures. In northern Europe, surgery was performed on older patients with more severe coronary or associated disease, whilst in the south the cardiac status seemed more severely compromised. Degenerative aortic disease prevailed in the north (aortic valve replacement in 72.7% of cases), whilst in the south mitral surgery accounted for 46.1% of procedures. Despite differences in crude mortality (6.9% north versus 5.7% south), outcomes (when adjusted to risks) seemed comparable (observed-to-expected mortality ratio 0.90 for north versus 0.84 for south). The impact of individual risk factors on mortality was similar, except for atrial fibrillation. CONCLUSION: Despite large epidemiological differences between northern and southern Europe in terms of valve surgery, performances and outcomes were similar when individual risk factors and overall risk profiles were taken into account.

Aged↗
PubMed2002

Preoperative risk prediction and intraoperative events in cardiac surgery.

OBJECTIVE: To examine the relationship between preoperative risk prediction and intraoperative events. METHODS: A total of 3118 patients operated in 1999 and 2000 at our institution were analysed, all of whom had their EuroSCORE collected prospectively. The intraoperative variables studied were consultant or trainee operating, long bypass time, long ischaemic time, return on bypass in theatre and use of intra-aortic balloon pump at the end of the procedure. The outcomes are reported as hospital mortality, prolonged length of stay in the intensive therapy unit (pLOS-ITU, >48 h) and death or pLOS-ITU. Risk models were constructed by logistic regression for predicting these three outcomes. RESULTS: With the exception of prolonged cross-clamp time, all variables analysed were independently predictive of a negative outcome. Trainee operating had an apparent protective effect. All risk models performed well. The area under the receiver operating characteristic (ROC) curve (95% CI) increased from 0.857 (0.81, 0.90) for EuroSCORE to 0.874 (0.83, 0.92) for the risk of death model. Similarly, the area under the ROC curve for the pLOS-ITU model increased from 0.687 (0.642, 0.732) to 0.734 (0.691, 0.777) and for the death or pLOS-ITU model from 0.717 (0.677, 0.756) to 0.757 (0.719, 0.795). CONCLUSIONS: Knowledge of adverse intraoperative events enhances preoperative risk prediction. This type of analysis could be used for identifying "near miss" outcomes in adult cardiac surgery.

Cardiac Surgical Procedures↗
PubMed2002

Validation of European System for Cardiac Operative Risk Evaluation (EuroSCORE) in North American cardiac surgery.

OBJECTIVE: To assess the performance of the European System for Cardiac Operative Risk Evaluation (EuroSCORE) when applied in a North American cardiac surgical population. METHODS: The simple additive EuroSCORE model was applied to predict operative mortality (in-hospital or 30-day) in 401684 patients undergoing coronary or valve surgery in 1998 and 1999 as well as in 188913 patients undergoing surgery in 1995 in the Society of Thoracic Surgeons (STS) database. RESULTS: The proportion of isolated coronary artery bypass grafting (CABG) was greater in STS patients (84%) than in Europe (65%). STS patients were also older (mean age 65.3 versus 62.5), and had more diabetes (30 versus 17%) and prior cardiac surgery (11 versus 7%). Other comorbidity was also significantly more prevalent in STS patients. EuroSCORE predicted overall mortality was virtually identical to the observed mortality (1998/1999: predicted 3.994%, observed 3.992%; 1995: observed and predicted 4.156%). Predicted mortality also closely matched observed mortality across the risk groups. Discrimination was good to very good for the population overall and for isolated CABG in both time periods, with the area under the receiver operating characteristic curve between 0.75 and 0.78. CONCLUSION: Despite substantial demographic differences between Europe and North America, EuroSCORE performs very well in the STS database, and can be recommended as a simple, additive risk stratification system on both sides of the Atlantic.

Cardiac Surgical Procedures↗
PubMed2002

A case-control analysis of readmissions to the cardiac surgical intensive care unit.

OBJECTIVE: To identify predictors of requirement for readmission to the intensive care unit (ICU) for patients undergoing cardiac surgery. METHODS: The setting was a 17-bedded ICU in a tertiary level institute for specialist adult cardiorespiratory disease. The case notes and ICU charts of 65 ICU readmissions and 65 controls, matched for day of initial ICU discharge, were analysed. Patient variables assessed included preoperative risk stratification, ICU admission APACHE III score and intensive therapy interventions, complications and indication for readmission if readmitted. RESULTS: Twenty of 65 patients (31%) readmitted to the cardiac ICU died, compared with no mortality among the control group. Significant univariate determinants of ICU readmission (odds ratio, 95% confidence interval) included worse angina (1.38, 0.99-1.91) and dyspnoea (1.70, 1.10-2.61) classes and corresponding non-elective surgery (2.04, 1.31-3.19), higher Parsonnet score (1.06, 1.01-1.11) or EuroSCORE (1.14, 1.01-1.28), APACHE III score (1.03, 1.00-1.05), body mass index>27 (4.25, 1.43-12.63), non-usage of beta-blockers (1.53, 1.03-2.26), emergency resternotomy (5.00, 1.10-22.79), and lower haemoglobin (0.75, 0.58-0.96), higher required inspiratory oxygen (1.05, 1.02-1.08), and higher respiratory rate upon ICU discharge (1.09, 1.01-1.18). Renal failure, respiratory failure and cardiac arrest were the most common indications for ICU readmission. Thirty-five of 65 patients readmitted to the ICU required ventilation for a mean of 7.1 days. The mean ICU readmission duration for all 65 cases was 5.7 days. CONCLUSIONS: Readmission of cardiac surgical patients to the ICU is associated with high morbidity and mortality, and substantial resource consumption. Parsonnet or EuroSCORE risk stratification models in combination with obesity, operative urgency, resternotomy and respiratory indices at time of intended ICU discharge are strongly associated with readmission to ICU.

APACHE↗