Final answer:
The nurse should report the serum potassium level of 6.5 mEq/L to the health care provider immediately as this high level can be life-threatening.
Step-by-step explanation:
The nurse should report the serum potassium level of 6.5 mEq/L to the health care provider immediately. This value is higher than the normal range, which is usually between 3.5 to 5.0 mEq/L. High serum potassium levels, also known as hyperkalemia, can be life-threatening and can cause cardiac arrhythmias. The burn injury may have caused tissue damage and release of potassium into the bloodstream.