70 Yr Male. 6.5 Ft/185kg Rotavirus X4 Days Low K+

Brief Answer:
Proper hydration with maintaing vitals.

Detailed Answer:
Hello and thanks for choosing "Ask a doctor" service for your query,
Have gone through your details and I appreciate your concern,
As you are sure it's Rotavirus only then I would not discuss about any possible bacterial or protozoal infection.
Rotavirus like all virus has a definite life cycle of around 5 to 7 days.As like any other virus treatment of patient is conservative i.e all we need to do is to shift patient on a soft or liquid diet.BRAT diet is usually given(Banana-Rich in potassium,Rice for simple carbohydrate ,Apple (again potassium and sodium rich)sauce and Toast again easy to digest carbohydrate source).
Now in old patients maintaing vitals as well as serum electrolyte is very important.
Pulse and blood pressure should be monitored every 3 to 6 hours.Pulse more then 110/ min and systolic blood pressure less then 90mm of hg is a dangerous sign and patient should be taken to ED for i.v resuscitation of fluids.
Creatine is on higher side very likely as a result of dehydration so please look for signs of dehydration.If possible plenty of Electral or oral rehydration solution/coconut water should be given this would also help in bringing back potassium levels to normal.Hower potassium supplement POTLOR can be given 5ml three times a day with daily potassium monitoring to keep it's level at some what near 4-4.5 mg/dl.
For low magnesium i.v shot of magnesium can be given as in old age and due to decreased intestinal absorption by inflammed intestines taking orally may not be helpful.
As patient would get rehydrated his creatine levels would come down to normal.
As per your query answer is -
Maintaining vitals blood pressure,pulse,saturation and regular monitoring of electrolytes is the treatment of Rotavirus infection.
Main aim is to shift patient from parental (i.v) therapy to oral fluids as early as possible.
Probiotics like VSl#3 or any sachromyces strain should be given to improve gut Flora.
In case of loose motions to prevent fluid loss Imodium 2-4 mg can be used thrice till loose stools stop.
Lots of oral fluid like oral rehydration solution and coconut water should be given.

A stool test should be done- routine and microscopy to rule out overlapping bacterial or protozoal infection.
Fecal calprotectin can be done to rule out the level of inflammation along gut.

Rest unless vitals are unstable or gross sodium potassium or chloride ion disbalance is there or patient is dehydrated there in no need to worry.

Virus would complete it's life cycle and symptoms would go off.
Hope I was helpful.
Feel free to follow up.
please do inform if you are managing the patient at home or in hospital.
Thanks you.

---