Trace elements in hemodialysis patients: a systematic review and meta-analysis

<p>Abstract</p> <p>Background</p> <p>Hemodialysis patients are at risk for deficiency of essential trace elements and excess of toxic trace elements, both of which can affect health. We conducted a systematic review to summarize existing literature on trace element status in hemodialysis patients.</p> <p>Methods</p> <p>All studies which reported relevant data for chronic hemodialysis patients and a healthy control population were eligible, regardless of language or publication status. We included studies which measured at least one of the following elements in whole blood, serum, or plasma: antimony, arsenic, boron, cadmium, chromium, cobalt, copper, fluorine, iodine, lead, manganese, mercury, molybdenum, nickel, selenium, tellurium, thallium, vanadium, and zinc. We calculated differences between hemodialysis patients and controls using the differences in mean trace element level, divided by the pooled standard deviation.</p> <p>Results</p> <p>We identified 128 eligible studies. Available data suggested that levels of cadmium, chromium, copper, lead, and vanadium were higher and that levels of selenium, zinc and manganese were lower in hemodialysis patients, compared with controls. Pooled standard mean differences exceeded 0.8 standard deviation units (a large difference) higher than controls for cadmium, chromium, vanadium, and lower than controls for selenium, zinc, and manganese. No studies reported data on antimony, iodine, tellurium, and thallium concentrations.</p> <p>Conclusion</p> <p>Average blood levels of biologically important trace elements were substantially different in hemodialysis patients, compared with healthy controls. Since both deficiency and excess of trace elements are potentially harmful yet amenable to therapy, the hypothesis that trace element status influences the risk of adverse clinical outcomes is worthy of investigation.</p

Evaluation of tension lap splices for code provisions

Six real-size beams were tested in order to examine the reliability of tension lap splices for the minimum requirements of clear cover, spacing between bars and transverse reinforcement. The beams were prepared in accordance with the minimum provisions of the American Concrete Institute building code requirements for structural concrete (ACI 318-08) and the Turkish standards on requirements for design and construction of reinforced concrete structures (TS 500). Results showed that all beams prepared in accordance with ACI 318-08 showed satisfactory behaviour. Since the specimen prepared according to TS 500 with 26 mm diameter bars failed due to bond, it can be concluded that the TS 500 clear cover is insufficient for spliced bars equal to or greater than 26 mm in diameter. In order to evaluate the ACI Committee 408 new proposal and Eurocode 2 provision for tension lap splices, a case study was also conducted. According to the results of the case study, while the ACI 318-08 requires unnecessarily longer splice lengths for bars of greater than 19 mm diameter, Eurocode 2 always gives the smallest lap splice length which leads to safety concerns