LR has a sodium content of 130mEq/L, so huge volumes of it will eventually decrease serum sodium concentrations. It can also transiently decrease serum osmolality.
In majorly swollen strokes or mass lesions that I'm treating with osmotherapy and trying to get their Na and Osm way up, then it isn't my first choice. 0.9% NaCl is the standard.
Once they are on their way out of the woods, and they have a whopping hyperchloremic metabolic acidosis from all the saline you've given them, then LR is a great way to hydrate and give them a soft landing.
If someone has symptomatic hypernatremia, then LR probably won't bring it down fast enough to be a useful agent. It's not like I'd turn to LR for a DI patient with a sodium of 180. A couple references are below...
J Neurosurg. 1995 Dec;83(6):1060-6.
Anesth Analg. 1999 May;88(5):999-1003.