Final answer:
Position the patient supine with the legs elevated to improve blood flow to the brain and address orthostatic hypotension. Therefore, the correct option is C.
Step-by-step explanation:
When a patient complains of being lightheaded and exhibits pale, clammy skin with a blood pressure of mm Hg, it is likely that the patient is experiencing orthostatic hypotension. Orthostatic hypotension occurs when blood pressure drops below the normal range upon standing up.
To address this, the nurse should position the patient supine with the legs elevated to promote blood flow to the brain and improve blood pressure. This helps to counteract the effect of gravity, preventing more blood from pooling in the legs and increasing blood flow to the brain. Additionally, the nurse should closely monitor the patient's condition and inform the practitioner of the situation for further evaluation and possible interventions.