Optimal gastric pouch reconstruction post-gastrectomy.

BACKGROUND: Gastric pouches have the potential to improve nutrition following total gastrectomy, compared with standard reconstruction. However, a consensus view of clinical benefit is not available, at least partly due to a lack of standardization of pouch design or size. This study was undertaken to identify optimal conditions for pouch design. METHODS: A mathematical model was established and a porcine model constructed to evaluate the pressure/volume dynamics of the pouch. A "J" pouch was constructed at anastomotic lengths of 5, 10, 15, and 20 cm. Each pouch was distended with saline and the pressure/volume relationship established. RESULTS: Mathematically, increasing the anastomotic length of the pouch to 15 cm increases the volume significantly; thereafter, there is minimal benefit of increasing the pouch length further. For smaller pouches (5 and 10 cm) a 350-to 400-ml volume (approximate meal volume in the elderly) is never achieved until higher pressures (45 cmH(2)O) are applied. However, in the larger pouches (15 and 20 cm) a 350-to 400-ml volume is readily achieved at basal pressures of 15 cmH(2)O. CONCLUSION: Smaller pouches never achieve adequate volumes at basal pressures; accordingly, it is unlikely that they will lead to any clinical benefit. Further in-vivo studies should therefore be based upon 15-cm pouch designs.

Activation energy-activation volume master plots for ion transport behavior in polymer electrolytes and supercooled molten salts.

We demonstrate the use of activation energy versus activation volume "master plots" to explore ion transport in typical fragile glass forming systems exhibiting non-Arrhenius behavior. These systems include solvent-free salt complexes in poly(ethylene oxide) (PEO) and low molecular weight poly(propylene oxide) (PPO) and molten 2Ca(NO3)2.3KNO3 (CKN). Plots showing variations in apparent activation energy EA versus apparent activation volume VA are straight lines with slopes given by M = DeltaEA/DeltaVA. A simple ion transport mechanism is described where the rate determining step involves a dilatation (expressed as VA) around microscopic cavities and a corresponding work of expansion (EA). The slopes of the master plots M are equated to internal elastic moduli, which vary from 1.1 GPa for liquid PPO to 5.0 GPa for molten CKN on account of differing intermolecular forces in these materials.