Hello! thank you for your query. He may be experiencing dehydration/electrolyte imbalance secondary to Acute Gastroenteritis(sudden inflammation of lining of the stomach). He is losing too much fluid in the body due to vomiting and watery lose stools. When an elderly loses consciousness and is unable to drink or eat it is an emergency situation to point out the cause and treat it immediately. I suggest you bring him as soon as possible to the emergency department to be hydrated via an intravenous line since he is not able to take in much fluids because of vomiting. Fecalysis may also be suggested to Him and complete blood work up. Try to let him have frequent sips of water and bring him to ER immediately for further evaluation and work up. Hope this helps, and a feedback is greatly appreciated. Thank you!