This study is a non-randomized, Phase 2 clinical trial designed to assess optical cerebral blood flow (CBF) response to bolus normal saline. Subjects will have had an ischemic stroke within 96 hours of enrollment. The study intervention will be a one hour monitoring session. There will be a 15 minute baseline measurement period, followed by intravenous administration of 500cc of 0.9% NaCl over 30 minutes, and finally 15 minutes of monitoring post-bolus. All study measurements will cease after 1 hour. Subjects will be followed during their hospitalization for 7 days or until discharge, whichever is sooner, to monitor for adverse events and to collect clinical information.