But as a first-year medical student, I often wondered why the solutions doctors infuse through patients’ IVs were always salty. After all, human life seems dependent on fresh water with virtually no salt in it. Fresh water is the only kind of fluid that quenches our thirst, waters our crops, and bathes our bodies. But if I infused the same fresh, saltless water into my patients’ veins, it would be toxic, quickly causing blood cells to burst and the brain to swell, leading to seizure, coma, and death.
