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PubMedDate not supplied

The peritoneoscopic implantation of a polyurethane percutaneous access device for peritoneal dialysis. Preliminary experience.

The short-term experience with peritoneoscopic implantation of eight Dermaport devices is discussed. These eight devices were implanted using local anesthesia and utilizing a modification of the Y-TEC method of catheter implantation. Excellent immediate function was observed universally allowing catheter use for dialysis and good skin-device interface; however dialysate leakage occurred within 2 to 4 weeks in four patients. Lack of permanent bonding between the catheter and the adjustable proximal cuff, resulting in suboptimal or slow ingrowth of tissue around it, appears to be the cause of this phenomenon.

Adult↗
PubMedDate not supplied

A tricuspid polyurethane heart valve as an alternative to mechanical prostheses or bioprostheses.

The main disadvantages of today's heart valve prostheses are the need for lifelong anticoagulation for mechanical valves and problems with biodegradation for tissue valves. Therefore, a new valve type devoid of these problems would be a major step forward. In order to evaluate a new valve design made by dipmolding with different PU materials, an animal test series was carried out in which two valves from each material were implanted into the mitral position of growing Jersey calves. The surgical procedure and postoperative catheterization data are presented. The survival times ranged between 127 and 291 days. Organs and explanted valves were examined post mortem according to general pathology standards. Specifically, the valves were histologically examined for calcium deposits and investigated by light microscopy, REM and EDAX. All explanted valves showed calcification and immobilization, but the results suggest that at least two PU materials attain survival times which are far beyond the lifetime of bioprostheses under the same implant conditions, justifying further in vivo studies in adult animals.

Animals↗
PubMedDate not supplied

Influence of mold properties on surface structure of a polyurethane-siloxane block co-polymer. Implications for blood compatibility.

The authors studied the surface structure of organosiloxane-polyether urethane co-polymer films cast against low and high surface free energy materials (glass/ceramic and metal). A novel surface interaction parameter, the gold nucleus density distribution (GND), determined by partial gold decoration transmission electron microscopy, was used to indirectly assess the dispersive contribution to interfacial surface free energy. A water wetting assay was used to characterize the hydrophobic/hydrophilic balance of the polymer film surfaces. Two biological interaction parameters, one involving the kinetics of albumin and fibrinogen adsorption from plasma and the other a platelet adhesion index (RIPA), were used to estimate blood compatibility. Results indicate that mold properties influence the surface structure of this block co-polymer, sequestering polysiloxane groups at mold, and possibly air interfacial regions of the film. However, as shown by ESCA and FTIR analysis, specific chemical groups did not correlate with the blood compatibility indices. The GND correlate with initial albumin and fibrinogen adsorption rates. Initial protein adsorption was less well predicted by surface water wettability. Neither surface structure nor surface interaction data predicted later (60-120 min) protein sorption or platelet adhesion. Subsequent events may be influenced by protein turnover and cell-surface interactions, and are less influenced by polymer surface properties.

Adsorption↗