Travelled out of state for spouse's necessary medical treatment. Drove , using a rental car. Can I claim the rental car fees as medical travel expense and how much?

yes from IRS PUB 502

Car expenses. You can include out-of-pocket expenses,
such as the cost of gas and oil, when you use a car for
medical reasons. You can't include depreciation, insurance, general repair, or maintenance expenses.
If you don't want to use your actual expenses for 2022,
you can use the standard medical mileage rate. For 2022,
the standard medical mileage rate allowed is 18 cents a
mile from January 1, 2022, through June 30, 2022, and 22
cents a mile from July 1, 2022, through December 31,
2022.
You can also include parking fees and tolls. You can
add these fees and tolls to your medical expenses
whether you use actual expenses or the standard mileage
rate

Yes, you can, if it was necessary that you rent the car to be with your spouse for their medical care.  You can deduct the expense amount related to the medical care.

Be sure to include gas expenses, tolls, parking and anything else reasonably related to your travel for medical reasons.

Please see Transportation in the IRS' Publication 502 (2022), Medical and Dental Expenses and the TurboTax Help article What kinds of medical expenses are deductible? for information.