Hi, Thanks for writing to Health Care Magic, I am Dr Asad Riaz, I have closely read your question and I understand your concerns, I will hereby guide you regarding your health related problem. Dehydration is also one major issue in child n old Bcs in old person is either reluctant to drink water / Dec activity /chair or bed bound these all conditions lead to dehydration.. dehydration lead to Dec CO result patient may feel dizziness , fatigue, tired .. to rehydrate in old patients need special care Bcs rapidly rehydration may lead to vol overload which result in heart prob most likely failure.. so in ur case need to calculate deficiet n then accordingly need to give..I advise u not to go out much specially in hot humid whethear n drink plenty of water... I will run some test to make sure u having normal S/E n n manage them as well.. in ur case rehydration can take 2-3 days or more depending upon how much u have fluid deficit n how much ur heart is functionally well to avoid overload.. I hope this answered your question, if you have more feel free to ask. Regards. Dr.Asad Riaz. General and Family Physician..