Final answer:
Magnesium sulfate is administered to patients with severe preeclampsia primarily to prevent seizures (eclampsia), while also aiding in blood pressure control and protection against heart failure.
Step-by-step explanation:
The primary indication for the administration of magnesium sulfate to a patient with severe preeclampsia is to prevent the development of seizures, which is a condition known as eclampsia. The use of magnesium sulfate acts to lower blood pressure and protect against complications such as heart failure and prevent the onset of convulsions. Due to its role in regulating muscle and nerve function, magnesium sulfate is effective in managing high blood pressure during hypertensive crises commonly associated with preeclampsia.