Final answer:
The nurse should monitor for numbness and tingling of the extremities.
Step-by-step explanation:
A low potassium level or hypokalemia can cause various clinical manifestations. For a potassium level of 3 mEq/L, the nurse should monitor for numbness and tingling of the extremities. This is because low potassium levels can impair the function of skeletal muscles and the nervous system. Numbness and tingling in the extremities can be a sign of nerve and muscle dysfunction.