Development and internal validation of a clinical prediction model for serious complications after emergency laparotomy

Purpose Emergency laparotomy (EL) is a common operation with high risk for postoperative complications, thereby requiring accurate risk stratification to manage vulnerable patients optimally. We developed and internally validated a predictive model of serious complications after EL. Methods Data for eleven carefully selected candidate predictors of 30-day postoperative complications (Clavien-Dindo grade >  = 3) were extracted from the HELAS cohort of EL patients in 11 centres in Greece and Cyprus. Logistic regression with Least Absolute Shrinkage and Selection Operator (LASSO) was applied for model development. Discrimination and calibration measures were estimated and clinical utility was explored with decision curve analysis (DCA). Reproducibility and heterogeneity were examined with Bootstrap-based internal validation and Internal–External Cross-Validation. The American College of Surgeons National Surgical Quality Improvement Program’s (ACS-NSQIP) model was applied to the same cohort to establish a benchmark for the new model. Results From data on 633 eligible patients (175 complication events), the SErious complications After Laparotomy (SEAL) model was developed with 6 predictors (preoperative albumin, blood urea nitrogen, American Society of Anaesthesiology score, sepsis or septic shock, dependent functional status, and ascites). SEAL had good discriminative ability (optimism-corrected c-statistic: 0.80, 95% confidence interval [CI] 0.79–0.81), calibration (optimism-corrected calibration slope: 1.01, 95% CI 0.99–1.03) and overall fit (scaled Brier score: 25.1%, 95% CI 24.1–26.1%). SEAL compared favourably with ACS-NSQIP in all metrics, including DCA across multiple risk thresholds. Conclusion SEAL is a simple and promising model for individualized risk predictions of serious complications after EL. Future external validations should appraise SEAL’s transportability across diverse settings

The Hellenic emergency laparotomy study (HELAS): a prospective multicentre study on the outcomes of emergency laparotomy in Greece

Background Emergency laparotomy (EL) is accompanied by high post-operative morbidity and mortality which varies significantly between countries and populations. The aim of this study is to report outcomes of emergency laparotomy in Greece and to compare them with the results of the National Emergency Laparotomy Audit (NELA). Methods This is a multicentre prospective cohort study undertaken between 01.2019 and 05.2020 including consecutive patients subjected to EL in 11 Greek hospitals. EL was defined according to NELA criteria. Demographics, clinical variables, and post-operative outcomes were prospectively registered in an online database. Multivariable logistic regression analysis was used to identify independent predictors of post-operative mortality. Results There were 633 patients, 53.9% males, ASA class III/IV 43.6%, older than 65 years 58.6%. The most common operations were small bowel resection (20.5%), peptic ulcer repair (12.0%), adhesiolysis (11.8%) and Hartmann’s procedure (11.5%). 30-day post-operative mortality reached 16.3% and serious complications occurred in 10.9%. Factors associated with post-operative mortality were increasing age and ASA class, dependent functional status, ascites, severe sepsis, septic shock, and diabetes. HELAS cohort showed similarities with NELA patients in terms of demographics and preoperative risk. Post-operative utilisation of ICU was significantly lower in the Greek cohort (25.8% vs 56.8%) whereas 30-day post-operative mortality was significantly higher (16.3% vs 8.7%). Conclusion In this study, Greek patients experienced markedly worse mortality after emergency laparotomy compared with their British counterparts. This can be at least partly explained by underutilisation of critical care by surgical patients who are at high risk for death

Symbol error probability of decode and forward cooperative diversity in Nakagami-m fading channels

In this paper, we provide closed-form expressions for the symbol error probability of decode and forward cooperative diversity systems, when operating over independent but not necessarily identically distributed Nakagami-m fading channels. The results hold for arbitrary number of relays, and refer to the M-ary QAM and M-ary PSK modulations. © 2008 The Franklin Institute

Amplify-and-forward relay selection with outdated channel state information

10.1109/GLOCOM.2010.5683118GLOBECOM - IEEE Global Telecommunications Conference

Satellite Communications. Research Trends and Open Issues

A panoramic view on the study and design of digital satellite communication links is the focus of this paper. Starting from the characterization of satellite propagation channel in different application environments (from broadcast to fixed terminals, to broadband mobile satellite access), we address physical layer aspects related to satellite communications in the attempt of providing the Reader with an overview of the new trends and open issues in this field

Down regulation of epidermal growth factor receptors in liver proliferation induced by a mixture of triiodothyronine, amino acids, glucagon, and heparin (TAGH).

This study investigated the mechanisms by which TAGH solution (a mixture of triiodothyronine, amino acids, glucagon, and heparin) induces DNA synthesis in hepatocytes in the liver of intact rats, with particular reference to events at the epidermal growth factor (EGF) receptor. Both partial hepatectomy and infusion of TAGH stimulated DNA synthesis at 24 hours and both procedures resulted in a reduction of EGF receptors assessed in plasma membranes isolated from rat liver at this time. In cell cultures, while EGF strongly stimulated DNA synthesis and started EGF receptor down regulation, TAGH had only a minor effect (1.5 x basal) on DNA synthesis and did not interact with or down regulate the EGF receptor. Membrane phosphorylation studies, however, showed that TAGH induced phosphorylation of tyrosine residues in the EGF receptor. The in vivo action of TAGH seems to entail recruitment of similar changes in the EGF receptor to those that occur after partial hepatectomy

Galactosamine induced hepatitis induces a reduction in hepatocyte epidermal growth factor receptors.

The rapid regenerative response of the rat liver to partial hepatectomy is associated with a decline in liver epidermal growth factor receptor numbers which implies that ligand epidermal growth factor receptor interactions maybe important in initiating and/or modulating this process. The proliferative process in toxic hepatitis (where in contrast with partial hepatectomy the majority of hepatocytes have been exposed to damaging influences) has been less widely investigated. We studied the DNA synthetic response of rat livers to toxic injury induced by a 350 or 800 mg/kg ip injection of galactosamine and that caused by 70% hepatectomy, comparing the changes in epidermal growth factor receptor status. Both resulted in down regulation of epidermal growth factor receptors, suggesting similar ligand epidermal growth factor receptor binding occurs during the proliferative response after galactosamine administration and after partial hepatectomy. In vitro studies on isolated hepatocytes showed that epidermal growth factor receptor down regulation was not a direct effect of galactosamine on hepatocyte membranes