Well, the context matters greatly here. If dehydration is severe enough to lower blood pressure (a.k.a. hypovolemic shock) it can cause long term brain, liver, kidney, and heart damage. That is assuming you survived. It could also cause local ischemia ( loss of blood flow) requiring limb amputation.
If it is not bad enough to cause shock, the most probable long term sequelae would be kidney damage. Dehydration can precipitate ATN (acute tubular necrosis). In a kid this may appear to be transient. It would kill a certain percentage of your available nephrons. As a kid, you only need ~20% of your nephrons to assume full kidney function. This would mean that you would appear to recover but would likely go into kidney failure at an early age.
There are also psychological effects depending on severity and duration.
I love AOC, but this is just smoke and mirrors. The progressive reps always make a big deal when they know their “inquiries” will go nowhere because they don’t have the votes. It stirs up their base with no repercussions. This is just lip service at this point. Still glad it is being said though.