Can lorazepam help lower blood pressure?

Yes: Not a treatment for high blood pressure, but it can help if you are hypertensive due to anxiety

Lorazepam: One of the side effects of lorazepam is lowered blood pressure, called hypotension. But given this, it’s not a treatment for hypertension. Anxiety itself doesn't raise blood pressure very much, so treating anxiety won't amount to a substantial change in one's blood pressure, in particular if one suffers with hypertension. Please see primary care for treatment of high BP.