The glucose is important because it enables the _enteric_ sodium-glucose cotransport mechanism to work, allowing the sodium to get out of your gut and _into your blood_ many times faster.
Neither glucose nor sodium directly help with rehydration; on the contrary, glucose and sodium in your gut decrease osmotic pressure and reduce rehydration. However, kidneys tightly regulate the osmotic pressure, and in particular the sodium content, of your blood. If you take in water without taking in sodium, your kidneys will work to excrete the water without the sodium, producing hypotonic urine. If you overwhelm this mechanism with too much water, or if your kidneys are damaged, you can go into hyponatremia, which can kill you.
So, even though sodium interferes with rehydration in the sense of "absorbing water", it is necessary for rehydration in the sense of retaining water.
This is where the glucose comes in. In addition to simple diffusion of sodium out of your intestines, it was discovered in 1968 that the small intestine has a much faster active sodium-glucose cotransport mechanism, which allows you to absorb sodium about ten times as fast. It transports a single ion of sodium together with a single molecule of glucose across your intestinal wall. Until this discovery, as explained in the UNICEF page linked from the article, diarrhea was the leading cause of death among children. Oral rehydration solution diminished that problem enormously, as the article points out, and now respiratory infections are the leading cause of death among children.
(In a stunning example of the failure of diffusion of knowledge, it turns out that enteric sodium-glucose cotransport had been discovered by Crane in 1960, but the discovery wasn't applied to save lives on a large scale for some 11 years. You can read more about the mechanism at https://en.wikipedia.org/wiki/Sodium-glucose_transport_prote... or PubMed.)
The article claims that this cotransport mechanism is important in absorption of sodium from the blood by all the cells in the human body, not just in kidneys and intestines. As far as I know, this is a novel medical claim, and should be treated as alternative medicine. I am not aware of any evidence that adding glucose to an IV drip speeds recovery from dehydration.
However, the article's recommendation that dehydration should be treated with oral rehydration solution when possible, rather than intravenous fluids, is sound, already an official recommendation of the WHO, and should be more widely practiced.
(Originally posted at https://news.ycombinator.com/item?id=16440265)