The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

Transmission of butanol isomers in pervaporation based on series resistance model

Pervaporation (PV) has shown great potential in the separation of butanol aqueous solutions due to their economic and environmental benefits. This work applies polydimethylsiloxane (PDMS) composite membrane to separate four butanol isomers (n-butanol, isobutanol, sec-butanol and tert-butanol) in aqueous solution. Based on physical and chemical properties of butanol isomers, such as solubility, polarity and interaction parameter, we systematically study the transmission difference in the pervaporation process. The influence of feed concentration, temperature and permeate pressure on membrane performance of PDMS composite membrane are investigated. The results show that the contact angles of butanol isomers on the PDMS layer are 51°, 42.7°, 37.7°, 29.1° and the fluxes at 40 °C are 237.6 g m-2 h-1, 245.4 g m-2 h-1, 224.1 g m-2 h-1, 169.4 g m-2 h-1 for n-butanol, isobutanol, sec-butanol, and tert-butanol, respectively. Moreover, the similar compatibility principle is introduced to the series resistance model so the process simulation matches well with the antagonistic effect of water molecules on mass transfer of butanol isomers. The permeation activation energy is negative, indicating that the dissolution dominates the dissolution and diffusion process. In addition, low vacuum is not conducive to the separation of n-butanol from water. The research on isomers separation through pervaporation may pave a way to separate other solvents of similar properties