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

TRANSFORMATION BEHAVIOR OF A Ti50Ni47Fe3 ALLOY : II. MARTENSITIC TRANSFORMATION

In-situ electron microscopy observations of the martensitic transformation and the martensitic phase in thin foils of a Ti50Ni47Fe3 alloy have been made. The Ms temperature in such thin foils is about -98°C. Below the Ms temperature, martensite plates nucleate and grow, and "consume" the previously formed needle-like domains and their matrix. The crystal structure of the martensite was determined to be of the B19' type (monoclinic). In addition to (111) internal transformation twins, stacking faluts on the (001) basal plane and antiphase domain boundaries (APB's) were observed within the martensite plates. The APB's in the martensite, which are a consequence of atomic ordering rather than electron ordering (CDW's), are different from those observed in the premartensitic phases. The "1/3" superlattice reflections characteristic of the prior charge density wave formation are not found in the martensite. The orientation relationships between the martensite, needle domains and matrix rhombohedral phase were also determined. The "premartensitic" effects found in the Ti50Ni47Fe3 alloy are suggested to be separate electronically driven structural changes and not precursory effects insofar as the martensitic transformation per se is concerned. The sequence of transformation events (upon cooling) in the Ti50Ni47Fe3 alloy is as follows : parent phase (B2) incommensurate phase (distorted cubic) commensurate phase (rhombohedral) martensitic phase (monoclinic, B19')

ELECTRON MICROSCOPY STUDIES OF LATH MARTENSITE

Crystallographic and substructural features of lath martensite formed in an Fe-20Ni-5Mn (wt.%) alloy containing small amounts of lath martensite in a matrix of austenite have been investigated using transmission electron microscopy. The average austenite/martensite orientation relationship determined by an accurate method is (111)f || (011)b and [[MATH]01]f 3.90 from [[MATH][MATH]1]b, while the habit plane of the laths is close to (575)f or ([MATH]54)b. Adjacent laths within a packet of laths adopt the same variant of the orientation relationship, but may be misoriented relative to each other by about 2°. The martensite laths contain screw dislocations in all four b directions, but one set of the four is clearly dominant. The martensite/austenite interface on one side of a lath is planar, while that on the opposite side is irregular. Dislocation tangles in the austenite associated with the irregular interface suggest that the laths thicken mainly in the direction away from the initial planar interface. The martensite/austenite interface contains a single set of dislocations with Burgers vector ab/2 [1[MATH]1] = af/2 [0[MATH]1], which form loops around the laths. The observed interface dislocation structure satisfies the requirements for a glissile semi-coherent interface