No it can't; you must use adult AED pads for an adult & child AED pads for a child.
early sign of hypovolemic shock
If the child is older than 8 or 55 pounds, it is OK to use adult pads. If not, do not use adult pads as the shock will be too much.
Child AED pads may not deliver enough energy, so they are not appropriate to use for an adult.
Shock
Not necessarily. Your body will try to compensate when it is in shock by raising the heartbeat (thereby increasing blood pressure). But sometimes the body can not compensate adequately. In this case, your blood pressure may not increase.
You can however the real question would be if it will be enough energy to resuscitate an adult. Chances are probably not. The AED should have both of the sizes of pads inside of it. If not then it needs to be serviced by the Manufacturer.
With adult grief it is expected that parents will die sooner or later before their children or, in some cases younger people have no reason to feel someone as young as a friend; sibling, etc., will die because of their youth. Although the grief is intense at any age when a parent loses a child it is a great shock because all parents go through life feeling they will die before their children and suddenly the shock of a child dying is more than most parents can bare as they have only had their child such a short time.
If the child is a pediatric patient, an adult size AED pad may be used. This is only an option when child sizes are not available.
In a healthy adult, this shouldn't be enough to cause any fatal dysrhythmias.
Yes
If a child or for that matter an adult vomits in the pool you should clear the pool clean out the material vomited into the pool by netting skimming and vacuuming. Shock the pool and leave overnight to be on the safe side.