Holy crap.
Knee-jerk smart-aleck option: RSI general anesthesia for plastics to remove the blasted polypropylene implants and the fluid they absorbed. After she heals from reduction, THEN proceed with the Nissen. The implant device has been banned in the EU and US.
In seriousness, those things are a huge reservoir of fluid. A hefty fluid shift is concerning.
For induction; RSI. With 24kg extra on her chest, I don't think she would tolerate being apneic for more than a few seconds.
At 12kg per, there is a problem with maintaining tidal volume. The surgeons would be screaming for such high pressures to maintain pneumoperitoneum that I would think it would increase the risk of CO2 embolism, in addition to restricting ventilation even further. I am thinking 18 to 20cm H2O of pressure and up.
I never understood augmentation beyond a D cup. Personally, I think they are hideous, and more of a freak show than a sex status at that size. And the back pain has got to be excruciating.