Reorganizing the system of care surrounding laparoscopic surgery: a cost-effectiveness analysis using discrete-event simulation.

PURPOSE: To determine the cost-effectiveness of a proposed reorganization of surgical and anesthesia care to balance patient volume and safety. METHODS: Discrete-event simulation methods were used to compare current surgical practice with a new modular system in which patient care is handed off between 2 anesthesiologists. A health care system's perspective, using hospital and professional costs, was chosen for the cost-effectiveness analysis. Outcomes were patient throughput, flow time, wait time, and resource use. Sensitivity analyses were performed on staffing levels, mortality rates, process times, and scheduled patient volume. RESULTS: The new strategy was more effective (average 4.41 patients/d [median = 5] v. 4.29 [median = 4]) and had similar costs (average cost/ patient/d = 5327 dollars v. 5289 dollars) to the current strategy with an incremental cost-effectiveness of 318 dollars/additional patient treated/d. Surgical mortality rate must be >4% or hand-off delay >15 min before the new strategy is no longer more effective. CONCLUSION: The proposed system is more cost-effective relative to current practice over a wide range of mortality rates, hand-off times, and scheduled patient volumes.     

Paramagnetic thermosensitive liposomes for MR-thermometry.

MR-thermometry methods have been developed for the guidance and control of thermal therapies such as thermal ablation or regional hyperthermia. However, they are limited to the measurement of temperature changes and, thus, cannot be used to assess absolute temperature values. Paramagnetic thermosensitive liposomes are innovative contrast agents offering the potential to overcome these limitations. They are composed of a gadolinium- or manganese-based compound enclosed by a phospholipid membrane with a distinct gel-to-liquid crystalline phase transition temperature (Tm). At this temperature, the phospholipid membrane changes from a gel-phase to a liquid-crystalline phase which is associated with an increased transmembrane permeability towards solutes and water. Under these conditions, both types of paramagnetic thermosensitive liposomes demonstrate a significant increase in longitudinal (T1) relaxivity, attributed to the release of paramagnetic material from the liposome and/or to the increased water exchange rate between the liposome interior and exterior. Paramagnetic thermosensitive liposomes have already been successfully studied in animal models and have demonstrated a clear correlation between tissue temperature changes and signal intensity changes in MRI. Nevertheless, before entering clinical trials they have to be studied in more detail with regard to dose, pharmacokinetics and toxicity.     

Lycopene oxidation product enhances gap junctional communication.

Carotenoids as well as their metabolites and oxidation products stimulate gap junctional communication (GJC) between cells, which is thought to be one of the protective mechanisms related to cancer-preventive activities of these compounds. Increased intake of lycopene by consumption of tomatoes or tomato products has been epidemiologically associated with a diminished risk of prostate cancer. Here, we report a stimulatory effect of a lycopene oxidation product on GJC in rat liver epithelial WB-F344 cells. The active compound was obtained by complete in vitro oxidation of lycopene with hydrogen peroxide/osmium tetroxide. For structural analysis high performance liquid chromatography, gas chromatography coupled with mass spectrometry, ultraviolet/visible-, and infrared spectrophotometry were applied. The biologically active oxidation product was identified as 2,7,11-trimethyl-tetradecahexaene-1,14-dial. The present data indicate a potential role of lycopene degradation products in cell signaling enhancing cell-to-cell communication via gap junctions.     

Determination of malondialdehyde-induced DNA damage in human tissues using an immunoslot blot assay

Malondialdehyde (MDA) is a product of lipid peroxidation and prostaglandin biosynthesis. It is mutagenic and carcinogenic and the major adduct formed by reaction with DNA, a highly fluorescent pyrimidopurinone (M1-dG), has been detected in healthy human liver and leukocyte DNA. Analytical methods used so far for the detection of M1- dG have not been applied to a large number of individuals or variety of samples. Often, only a few microg of DNA from human tissues are available for analysis and a very sensitive assay is needed in order to detect background levels of M1-dG in very small amounts of DNA. In this paper, the development of an immunoslot blot (ISB) assay for the measurement of MI-dG in 1 microg of DNA is described. The limit of detection of the assay is 2.5 adducts per 10(8) bases. A series of human samples were analysed and levels of 5.6-9.5 (n = 8) and 3.1-64.3 (n = 42) of M1-dG per 10(8) normal bases were detected in white blood cell and gastric biopsy DNA, respectively. Results on four human samples were compared with those obtained using an HPLC/32P-post- labelling (HPLC/PPL) method previously developed and indicated a high correlation between M1-dG levels measured by the two assays. The advantages of ISB over other assays including HPLC/PPL, such as the possibility of analysing 1 microg DNA/sample and the fact that it is less time-consuming and laborious, means that it can be more easily used for routine analysis of a large number of samples in biomonitoring studies.      

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