In this single-center, open-label, uncontrolled, pilot clinical study, the investigators hypothesize that clevidipine low-rate infusion will decrease sonographically-detected moderate cerebral vasospasm after aneurysmal SAH. The dose of the drug in this exploratory study is 2.5 to 5 times lower than the dose used previously to control BP. The effect of the drug will be evaluated in 20 patients by TCD monitoring during 3 periods: 1-hour pre-infusion, 4-hour infusion and 4-hour post infusion. The cerebral blood flow velocities, which are a surrogate marker of vasospasm, will be compared between the 3 periods. The primary efficacy end-point will be the percentage of measurements with at least a 10% or more decrease of the velocities during the infusion period. Potential long-term effects after discontinuation of the drug will be also evaluated in the post-infusion 4-hour period and beyond, until the last follow up. The major safety issue is hypotension induced by the drug during a period when vasospasm is present. For that reason, two measures will be taken. First, only patients with moderate vasospasm will be evaluated. Second, vasopressors will be used as needed during the infusion period to counteract the systemic circulatory effect of the drug and maintain a stable systemic Mean Arterial Pressure (MAP) within 10% range compared to pre-infusion. Potential effect of cerebral vasodilation on intracranial pressure (ICP) will be also evaluated during the infusion and post-infusion periods and any elevation > 10 mm Hg will be reported.