The Cholecystectomy As A Day Case (CAAD) score: a validated score of preoperative predictors of successful day-case cholecystectomy using the CholeS data set

Background: Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods: Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results: Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions: The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Nuclear magnetic resonance study of spin relaxation and magnetic field gradients in maple leaves

1H Nuclear magnetic resonance techniques were used to measure the distributions of spin-spin relaxation times, T2, and of magnetic field gradients in both the chloroplast and nonchloroplast water compartments of maple leaves (Acer platanoides). Results showed that encounters between water molecules and membranes inside chloroplasts provide an inefficient relaxation mechanism; i.e., chloroplast membranes interact weakly with water molecules. Gradient measurements indirectly measured the sizes of chloroplasts by showing that water in the chloroplasts is confined to small compartments a few microns in diameter. A comparison between measured gradients and gradients calculated for a model leaf indicated that chloroplasts are somewhat more likely to occupy positions along cell walls adjacent to air spaces, but also they may be found in the interiors of cells

Combined effects of light and water stress on chloroplast volume regulation

A nuclear magnetic resonance technique was used to measure changes in the water content of Acer platanoides chloroplasts in leaf discs that had reached osmotic equilibrium with external solutions either in the dark or under exposure to light. Results showed that chloroplast volume regulation (CVR) maintained constant water content in the chloroplasts over a range of water potentials in the dark, but CVR failed when the water potential fell below a critical value. The critical potential was lower in the dark in sun leaves than in shade leaves. Upon exposure to intense light, CVR remained effective in sun leaves over the same range as in the dark, but it failed in shade leaves at all water potentials. Osmolytes are necessary for CVR, but KCl is relatively ineffective; increased concentrations of intracellular KCl did not fully support an increase in the range of CVR. The results indicate that leaves need reserve supplies of cytosolic osmolytes to maintain CVR at low water potentials, and a larger reserve supply is needed in leaves that are exposed to intense light

In vivo study of chloroplast volume regulation

This paper describes a new technique that can be used to study chloroplast volume regulation in vivo. Nuclear magnetic resonance spectroscopy was used to measure relative amounts of chloroplast water in Acer platanoides leaves as they dried in air, and also in leaf disks exposed to aqueous polyethylene glycol, sucrose, or glycerol. The chloroplasts retained a constant quantity of water as leaf water potentials varied between -0.05 and -1.90 MPa, indicating that volume regulation was effective throughout this range. The chloroplasts lost water when the water potential fell below -1.90 MPa, except when leaf disks were exposed to glycerol, suggesting that the lower limit of effective volume regulation is determined by physiological levels of osmotic solutes and that glycerol can be used for chloroplast osmoregulation

A theory and a model for interpreting the proton nuclear magnetic resonance spectra of water in plant leaves

Some plant leaves display complex, orientation-dependent, proton nuclear magnetic resonance (1H NMR) spectra. The spectral patterns vary as the angle between the leaf surface and the applied magnetic field is varied. They also vary with temperature and with the quantity of absorbed manganous ions, but they are independent of magnetic field strength. In this paper, we propose a theory to explain the origin of the spectra and a model from which the patterns can be calculated. The theory shows how heterogeneous magnetic susceptibilities and local dipolar magnetic fields in chloroplasts can shift the water-proton resonance field. The model describes a simplified leaf structure in which the chloroplasts are nonrandomly aligned with respect to the leaf surface. Model calculations are tested by comparison with experimental spectra from hawthorn leaves (Crataegus sp.)