The power Lomax distribution with an application to bladder cancer data.

A three-parameters continuous distribution, namely, Power Lomax distribution (POLO) is proposed and studied for remission times of bladder cancer data. POLO distribution accommodate both inverted bathtub and decreasing hazard rate. Several statistical and reliability properties are derived. Point estimation via method of moments and maximum likelihood and the interval estimation are also studied. The simulation schemes are calculated to examine the bias and mean square error of the maximum likelihood parameter estimators. Finally, a real data application about the remission time of bladder cancer is used to illustrate the usefulness of the proposed distribution in modelling real data application. The characteristics of the fitting data using the proposed distribution are compared with known extensions of Lomax distribution. The comparison showed that the POLO distribution outfit most well-known extensions of Lomax distribution.

Technical aspects of composite arterial T-grafts: estimation of required conduit length by a simple formula.

BACKGROUND: When composite arterial T-grafts are used, uncertainty persists as to whether the RIMA will be long enough to reach the RCA. We present a formula for the preoperative estimation of the required conduit length. METHODS: The following formula was created to estimate the required conduit length for a sequential graft, starting from the proximal RIMA-LIMA T-graft anastomosis, passing the PLA, and ending at the PDA: 2.14 x ([2 x LV wall thickness [WT]) + end-diastolic diameter (EDD)]. The estimated length was compared to the measured length in 100 patients undergoing off-pump revascularisation with BIMA T-grafts. RESULTS: There were no hospital deaths, no major infarctions and no wound complications. The required conduit length varied from 11.5 cm to 19 cm (average 14.9 +/- 1.4 cm) and was excellently predicted by the formula (paired T-test: P < 0.001, r = 0.86, average overestimation: 0.55 cm). CONCLUSION: The formula reliably determines the minimum required conduit length. We recommend this formula for preoperative decision making when considering the choice of graft and the length of RIMA harvesting. To facilitate calculation a simplified version is useful: 2 x EDD + 4 x WD + 1. Avoiding uncertainty about the sufficiency of the RIMA length may contribute to the spread of this technique.

On-line variable live-adjusted displays with internal and external risk-adjusted mortalities. A valuable method for benchmarking and early detection of unfavourable trends in cardiac surgery.

OBJECTIVE: Benchmarking and early detection of unfavourable trends. METHODS: We implemented a dedicated project-orientated data warehouse, which continuously supplies data for on-line computing of the variable live-adjusted displays (VLADs). To calculate the expected cumulative mortality, we used the multi-variate logistic regression model of the EuroSCORE model. In addition to the external EuroSCORE standard, we calculated a centre-specific risk score for internal standards by analysing the data of 9135 patients, which enables both internal and external comparisons. The VLADs are embedded into the multi-purpose web-based information portal, so that the physicians can investigate several types of VLADs interactively: performance of different types of surgery and individual surgeons for different time intervals. We investigated clinically important events such as modification of operative techniques and personnel changes of the team by the VLADs. RESULTS: We found transient declines in the performance curves during major changes in patient management, indicating that systemic--rather than accidental or patient related factors--were involved in the mortality risk. The internal standard line represents these clusters more clearly than the external line. We evaluated examples of how periods of increased risk could be monitored by the VLAD curves: (1) the introduction of OPCAB surgery; (2) training of surgeons; (3) staff changes and staff-related management. CONCLUSIONS: On-line VLADs based on a day-to-day updated database, displaying both internal and external standards, are a helpful visualisation tool for earlier detection of unfavourable trends. They enable the surgeon teams and clinical management to take countermeasures at an early stage.

Continuous perfusion of donor hearts in the beating state extends preservation time and improves recovery of function.

OBJECTIVES: Improving methods of donor heart preservation may permit prolonged storage and remote procurement of cardiac allografts. We hypothesized that continuous, sanguineous perfusion of the donor heart in the beating, working state may prolong myocardial preservation. METHODS: We developed a portable perfusion apparatus for use in donor heart preservation. Contractile, metabolic, and vasomotor functions were monitored simultaneously in an isolated swine heart. The metabolic state was monitored by myocardial tissue pH. Vasomotor function was assessed in isolated coronary ring chambers. Hearts were randomized into 3 groups: group I (n = 5), cardioplegic arrest, 12-hour storage at 4 degrees C with modified Belzer solution, and 2-hour sanguineous reperfusion in the working state; group II (n = 6), 12-hour continuous perfusion in the beating working state, 30 minutes of arrest (to simulate re-implantation time), and 2 hours of reperfusion, as above; group III (n = 7), coronary ring control hearts. RESULTS: At 2 hours of reperfusion, left ventricular developed pressure in group II was higher than in group I (mean +/- standard deviation: 90 +/- 6 mm Hg, 53 +/- 15 mm Hg, P = .005). Significantly less myocardial edema was observed in group II than in group I (73% +/- 4%, 80% +/- 1% water content, P = .01). Significantly less myocardial acidosis was noted in group II than in group I during preservation (pH 7.3 +/- 0.01, 6.1 +/- 0.03, P < .001) and reperfusion (pH 7.3 +/- 0.008, 6.8 +/- 0.05, P < .001). Coronary endothelial vasomotor function was better preserved in group II than in group I as evidenced by dose-response relaxation of coronary rings to 10(-8) mol/L bradykinin (37%, 55% delta baseline, P = .01). CONCLUSION: This new method extends the current preservation limit and avoids time-dependent ischemic injury, thereby allowing for distant procurement of donor organs.