Biomer bladder

Figure 4. Chromatograph of CHCl3 extract of steam-sterilized Biomer bladder. Column conditions 1% Dexsil 300 100°-350°C at 8°C/min and carrier—30 mL/min helium.

In Vivo Analytical Results. Indications of the presence of lipids at or within the polymer surface of bovine-implanted Biomer LVAD bladders and calcified neointimal areas were observed in GC solvent-extraction analyses. In addition, concentrations of polymer-derived species extracted from the Biomer bladder were detected. Although analytical techniques were effective in selectively separating lipids from extracted polymer components,... 

Figure 3. Exploded view of the components of Baylor left ventricular bypass pump a) polycarbonate connectors, b) Lille-hei-Kaster tilting disc valves, c) top of polycarbonate pump housing, d) polyether urethane (Biomer) bladder, e) bottom of polycarbonate pump housing ("dome") with sensor electrode attached which monitors pump filling.

The experimental work described here relates to studies done to characterize the affinity of lipids for Biomer and to determine their role in observed calcification of AHD and LVAD elastomeric bladders in vivo. 

In Vivo Studies. Segments of bovine-implanted Biomer LVAD bladders were obtained from researchers at the Thermo Electron Corporation. Segments that possessed observed calcifications were also obtained. In addition, a control bladder sample, steam sterilized at 121.1°C for 3 h, was obtained. Samples were vacuum dried at 50°C for 24 h, followed by a 24-h CHC13 solvent extraction. Extract solutions were reduced to 1 mL prior to gas chromatographic (GC) analysis. 

A rapid calcification process on in vitro lipid-exposed Biomer samples occurred within a 1-week period. Strips exposed to the synthetic plasma for less than 2 weeks underwent a rapid surface calcium complexation following a 7-day exposure to a calcium-containing physiological medium (pH 7), whereas unexposed Biomer samples did not calcify. The development of calcium deposits as seen in in vivo bovine LVAD bladders probably would arise from this initial nucleation process. 

Polymer-derived monomeric and oligomeric species are readily extractable from Biomer LVAD bladders. Lipid sorption definitely occurs in vitro on/in various elastomers presently being used or considered for LVAD or AHD applications. Apparently, lipid sorption does occur in vivo, and may be involved in surface calcification observed on both smooth and textured... 

Poirier (10) at Thermoelectron Corporation investigated seven elastomers for blood pump bladder applications. The flex life of diaphragms from the elastomers showed that Hexsyn, Fellethane, and Biomer were significantly superior to Tecoflex HR, Tecothane B, Silastic, and SRI. 

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