A new method for determining the insertion depth of tracheal tubes in children: a pilot study.

BACKGROUND: Choosing the correct insertion depth of tracheal tubes is crucial for successful airway management in paediatrics. Currently used formulas are based on patient characteristics such as age, body weight and height. The aim of the study is to devise and evaluate more suitable body surface area based diagrams for predicting the correct tracheal insertion depth. METHODS: Calculated insertion depth according to currently used formulas, primary insertion depth and insertion depth corrected by chest radiography ('gold standard') were collected from 237 children. Age, body weight, height and body surface area were noted. Body surface area based diagrams were devised and prospectively evaluated in another set of 123 paediatric patients. RESULTS: Tracheal tube position according to currently used formulas had to be corrected in 37% of all intubations. New body surface area based diagrams were created. In 20.3%, depth of the tracheal tube had to be corrected according to the new body surface area based diagrams. CONCLUSIONS: The body surface area based diagrams may be a reliable tool for predicting the correct tracheal insertion depth in children.

Cytotoxicity of mycotoxins evaluated by the MTT-cell culture assay.

The application of a modified colorimetric bioassay for the evaluation of the biological effects of mycotoxins is reported. Using three different monolayer cell lines (swine kidney, Madin Darby canine kidney, HeLa) the influence of nine different mycotoxins on the cellular methylthiazoltetrazolium (MTT)-cleavage activity was evaluated. The yellow tetrazolium salt MTT is converted by mitochondrial dehydrogenases of metabolically active cells to an insoluble purple formazan product, which was then solubilized with dimethylsulfoxide. The optical density of this homogeneous solution was suitable for a precise spectrophotometric measurement by a plate reader at a wavelength of 510 nm. Nine mycotoxins were simultaneously tested in all three cell lines, from which the swine kidney cell line proved to be the most sensitive. The effects of additional 35 mycotoxins were therefore tested using swine kidney monolayers as target cells. A total of 28 toxins of the 44 mycotoxins tested proved to be cytotoxic in the MTT-bioassay. Most of them belong to the group of trichothecene mycotoxins. Concentrations ranged between 0.01 micrograms and 100 micrograms/ml of cell culture medium. The MTT cleavage assay was found to be a quick (24 hours) and easy to perform system for the evaluation of the biological activity of many different mycotoxins and may also provide a useful tool for the testing of a large variety of sample materials.

In vitro transformation of the Fusarium mycotoxins deoxynivalenol and zearalenone by the normal gut microflora of pigs.

The biotransformation of the Fusarium mycotoxins deoxynivalenol and zearalenone by the normal bacterial gut flora of pigs was examined in this in vitro study. For that purpose, suspensions of intestinal contents (duodenum, jejunum, caecum, colon, rectum) of porcine origin were incubated anaerobically with deoxynivalenol (DON) or zearalenone (ZEA). DON and ZEA were degraded by the flora of the caudal segments (caecum, colon, rectum) of the gut--particularly the colon content--whereas the microorganisms of the cranial segments (duodenum, jejunum) exhibited no transforming activity. DON was showed to be deepoxidated, ZEA was hydrolyzed to alpha-zearalenol and an unknown metabolite. The transformation of DON was correlated with a loss of cytotoxicity, which could be demonstrated in the MTT(3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium++ + bromide)-cell-culture assay using swine kidney cells as target cells. The results of the study presented here correspond with the data found in in vivo studies. On the basis of these findings one could conclude that this in vitro method seems to be well suited to the study of the transformation of mycotoxins by the microflora of the gut. The in vitro study is cheaper than a feeding trial, and the preliminary information on the metabolism of mycotoxins obtained in such studies is helpful in designing feeding trials more clearly. Besides the simple and fast handling, reproducibility and the protection of the animals studied are further advantages of this in vitro method. In connection with the MTT-cell-culture assay, additional information about the cytotoxic potential of the bacterial transformation products can be obtained.