Thanks for posting your query at DoctorSpring.com.
I am Dr.R.K and I am pleased to assist you.
Loose stools can lead to dehydration and electrolyte imbalance. He needs to be rehydrated.
Decreased urine output and a dry tongue are indicators that you can look at to confirm dehydration.
Electrolyte solutions like equalyte would be helpful to keep him well hydrated.
Since he is having trouble even standing, I advice you to take him to ER for intravenous fluid infusion to correct his dehydration and electrolyte imbalance.
I hope that answers your question. Please let me know if I can assist you further.