Optimization techniques: industrial production tools with applications in nurse staffing efficiency research

Registered nurses (RNs) are one of many inputs that produce patient outcomes at some level of quality for a price. Optimal levels of any input are those that produce the most efficient outcome with relation to quality and cost. Through the use of optimization techniques, efficient staffing levels can be calculated to either minimize negative outcomes or maximize positive outcomes. Thus, the value of RNs can be established empirically and be precisely measured against other staffing inputs.     

Enteral fluconazole population pharmacokinetics in patients in the surgical intensive care unit

STUDY OBJECTIVE: To determine the population pharmacokinetic parameters of enterally administered fluconazole in patients in a surgical intensive care unit (SICU). DESIGN: Population pharmacokinetics component of a prospective, randomized clinical study. SETTING: The SICU at a university hospital. PATIENTS: One hundred ten patients with an expected length of stay in the SICU of 3 or more days and a need for intubation, in whom at least one fluconazole plasma concentration-time measurement was available. Intervention. Patients received fluconazole as an 800-mg loading dose and as a 200- or 400-mg (depending on renal function) daily maintenance dose. Fluconazole suspension was administered enterally followed by a 30-ml free water flush. MEASUREMENTS AND MAIN RESULTS: Plasma samples were collected, and population pharmacokinetic analysis was performed with NONMEM software; a one-compartment pharmacokinetic model was used. Fluconazole clearance was dependent on creatinine clearance, and volume of distribution was dependent on body weight and age. In patients with creatinine clearance values greater than 80 ml/minute, between 30 and 80 ml/minute, and less than 30 ml/minute, geometric mean (percentage coefficient of variation) fluconazole clearance was 14.39 ml/minute (21%), 10.53 ml/minute (28%), and 5.47 ml/minute (30%), respectively. The geometric mean (percentage coefficient of variation) volume of distribution in all patients was 1.27 L/kg (28%) and decreased with increasing age. CONCLUSIONS: Fluconazole clearance values in patients in the SICU who had normal renal function and in those with renal impairment were in agreement with previously reported data. Fluconazole volume of distribution was larger and half-life was longer in the SICU population than in healthy subjects.     

Frequency and predictive value of a mammographic recommendation for short-interval follow-up

BACKGROUND: A recommendation for short-interval follow-up of "probably benign finding" is associated with up to 11% of screening mammograms, but its predictive value for breast cancer is unclear. We examined the predictive values (i.e., the percentage of women with a diagnosis of breast cancer 2 years after a short-interval follow-up recommendation) and likelihood ratios (derived from the pretest and post-test odds of breast cancer in the Women's Health Initiative sample) for breast cancer that are associated with a recommendation for short-interval follow-up among postmenopausal women. METHODS: We performed a longitudinal analysis of a prospective cohort of 68 126 postmenopausal women (aged 50-79 years) who were participating in clinical trials as part of the Women's Health Initiative at 40 centers across the United States. Eligible participants had screening mammograms at baseline and at least 2 years of follow-up that included a repeat mammography. Outcomes measured were breast cancer events at 1 and 2 years after baseline and the results of subsequent mammograms. All P values were two-sided. RESULTS: A total of 2927 (5%) of the 58 408 eligible women had baseline mammograms that included recommendations for short-interval follow-up. The incidence of breast cancer for women with a short-interval follow-up recommendation was 1.0% at 2 years after the baseline mammogram compared with breast cancer incidences of 0.6% and 0.5% for women whose baseline mammograms were described as "benign" and "negative," respectively. Across the 40 participating centers, the prevalence of short-interval follow-up recommendations among baseline mammograms varied from 1.2% to 9.8% (P<.001), even when the analysis was adjusted for key variables in regression models. Centers reporting higher frequencies of such recommendations did not have lower positive predictive values for breast cancer than centers reporting lower frequencies. The likelihood ratio for breast cancer after a recommendation for short-interval follow-up on a subsequent mammogram was 2.20 (95% confidence interval = 1.65 to 2.86). CONCLUSION: Having a mammographic recommendation for short-interval follow-up was associated with a low positive predictive value for breast cancer among postmenopausal women during a 2-year follow-up. This result suggests that the current criteria for this recommendation-repeat mammography within 6 months-should be reconsidered.     

Vasculogenic mimicry and tumour-cell plasticity: lessons from melanoma

The gene-expression profile of aggressive cutaneous and uveal melanoma cells resembles that of an undifferentiated, embryonic-like cell. The plasticity of certain types of cancer cell could explain their ability to mimic the activities of endothelial cells and to participate in processes such as neovascularization and the formation of a fluid-conducting, matrix-rich meshwork. This ability has been termed 'vasculogenic mimicry'. How does vasculogenic mimicry contribute to tumour progression, and can it be targeted by therapeutic agents?     

Maspin regulates different signaling pathways for motility and adhesion in aggressive breast cancer cells

Previous studies from our laboratory and others have demonstrated that treatment of breast cancer cells with exogenous maspin led to a significant decrease in cell motility, and an increase in cell adhesion to human fibronectin. However, the signaling mechanisms by which maspin, a putative tumor suppressor gene, might regulate cell motility and adhesion have not been previously addressed. In this study, we hypothesized that maspin could inhibit cell motility through the Rho GTPase pathway, specifically by affecting Rac activity. To test this intriguing hypothesis we utilized an experimental approach where invasive and metastatic MDA-MB-231 breast cancer cells were either treated exogenously with recombinant maspin protein, or stably transfected with maspin. The data revealed decreased Rac1 activity within 4 h, and a decrease in the Rac1 effector, PAK1, within 12 h. In addition, an increase in PI3K and ERK1/2 activities within 1 h of recombinant maspin (rMaspin) treatment was observed, which returned to baseline level after 12 h. ERK activity was shown to be downstream of PI3K, as pretreatment with the PI3K inhibitor, LY294002, inhibited the stimulation of ERK activity by rMaspin. Furthermore, rMaspintreated cells displayed approximately a 30% increase in cell adhesion which was abrogated by pretreatment with LY294002. Increased focal adhesions and stress fibers were observed after 12 h of rMaspin treatment, when the cells were least motile and had reverted to a more epithelial-like phenotype. These data suggest that maspin may inhibit cell motility by regulating Rac1 and subsequently PAK1 activity, and promote cell adhesion via PI3K/ERK pathways. This study provides new insights into the diverse signaling pathways affected by maspin to suppress the metastatic phenotype, and could contribute to novel therapeutic approaches for the treatment of invasive and metastatic breast cancer.