The combined effects of plasma and hydrogel coating on adhesion of Staphylococcus epidermidis and Staphylococcus aureus to polyurethane catheters.

The adhesion of three Staphylococcus epidermidis and three S aureus clinical isolates, to uncoated and hydrogel-coated polyurethane catheters was tested, following pretreatment of catheters with human plasma. Plasma significantly decreased the adhesion of S. epidermidis strains to uncoated polyurethane catheters, but had no significant effect on the adhesion to hydrogel-coated catheters. The influence of plasma on adhesion of S. aureus strains to catheters was strain dependent. Plasma significantly increased the adhesion of one strain (SA6) to uncoated catheters. For two other strains (SA3 and SA14) plasma produced no clear effect on their adhesion to uncoated catheters; adhesion values for each strain showed either a small but significant increase or a replicate-dependent increase or decrease. However, plasma significantly increased the adhesion of all S. aureus strains to hydrogel-coated polyurethane catheters. Overall, with the exception of one batch culture of S. epidermidis strain SE3 tested, attachment to plasma-treated hydrogel coated catheters was statistically significantly lower, by up to 85%, than attachment to plasma-treated uncoated catheters for both S. epidermidis and S. aureus.

Uptake of drugs by catheters: the influence of the drug molecule on sorption by polyurethane catheters.

The sorption of drugs by indwelling intravenous catheters may have clinical consequences both by alteration of the dose received by the patient and by physically affecting the catheter materials themselves which may lead to changes in mechanical properties and biocompatibility. Studies of drug sorption to new catheter materials are therefore important. Pellethane, a polyurethane increasingly used in vascular access catheters, is as yet little studied in terms of its capacity for drug sorption. In this work a range of drugs known to be sorbed by PVC infusion sets were studied with respect to their sorption by Pellethane catheters. Standard lengths of catheter were incubated with solutions of drugs and samples of the solution were taken at intervals, assayed spectrophotometrically and compared with control solutions incubated without catheter. Losses from solution of up to 93% were found after 24 h. A series of highly sorbing and clinically relevant drugs was identified and their uptake was studied until equilibrium had been reached. A correlation was evident between the octanol/water partition coefficient and the fraction of drug taken up from solution at equilibrium, with the more hydrophobic drugs being taken up to a greater extent by the catheter.

Adhesion of staphylococci to polyurethane and hydrogel-coated polyurethane catheters assayed by an improved radiolabelling technique.

Adhesion of Staphylococcus epidermidis NCTC 11047 to the external surface of polyurethane catheters was quantified by a radiolabelling assay. Maximum adhesion was achieved with an initial cell concentration of 3 x 10(8)/ml after incubation for 120 min. The assay was tested for reproducibility by analysis of variance. Adhesion of clinical strains of S. epidermidis and S. aureus to uncoated polyurethane and hydrogel (Hydromer)-coated polyurethane catheters was compared. Hydrogel coating significantly reduced adhesion for both S. epidermidis and S. aureus (mean percentage reduction 71% for S. epidermidis, 69% for S. aureus). Clinical isolates were also tested for adhesion to polystyrene by a modified microtitration well adhesion assay; there was no correlation between staphylococcal adhesion to polyurethane catheters and adhesion to polystyrene. Cell surface hydrophobicity values varied widely for both species. Positive correlations were found between cell surface hydrophobicity and adhesion to polystyrene and uncoated polyurethane catheters for S. epidermidis but not for S. aureus.

Granule secretion markers on fluid-phase platelets in whole blood perfused through capillary tubing.

The effect of material composition and shear rate on fluid-phase platelet activation was investigated using a capillary perfusion model. Citrated whole blood was perfused along the lumens of tubes constructed from silicone, PVC, Pellethane, W124 (an experimental polyetherurethane), and glass. Platelet activation was determined by measuring the increase in alpha-granule membrane protein P-selectin (GMP-140, CD62) and the lysosomal granule membrane protein GP-53 (CD63) on fluid-phase platelets by flow cytometry. All tubes caused an increase over the negative control in the number of P-selectin and GP-53 molecules detectable on the surface of these platelets. The activation response of platelets to changes in shear rate was also investigated. It was found that lysosomal release paralleled alpha-granule release in glass, but not in Pellethane, over a range of wall shear rates (100-1,000 s-1).

Failure of dialysis therapy in potassium dichromate poisoning.

A fatal case of oral ingestion of potassium dichromate is presented. Following an initial presentation of abdominal pain and vomiting, the patient had a rapid progression to coma with the development of methemoglobinemia, coagulopathy, gastrointestinal hemorrhage, and respiratory distress syndrome. A blood concentration of chromium on admission was 5,800 mcg/dL, 80% of which was found to be in the intracellular fraction. Supportive treatment was also initiated as a four-hour period of hemodialysis followed by a one-hour period of charcoal hemoperfusion. Neither of these treatment modalities was found to significantly remove chromium from whole blood and neither seemed to affect the progression or outcome of this intoxication. We conclude that the ingestion of potassium dichromate is highly toxic and may rapidly lead to death. Hemodialysis and charcoal hemoperfusion appear to have little role in the management of chromium intoxication.