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.

Inclusion Criteria:

• Age ≥ 18 years
• Acute ischemic stroke in the territory of the anterior, middle, or posterior cerebral artery territory on either side of the brain
• Study intervention can be initiated within 96 hours of symptom onset
• Willingness and ability to sign informed consent by patient or legally acceptable surrogate decision-maker

Exclusion Criteria:

• Infarct limited to the brainstem and/or cerebellum with no involvement of the cerebral hemispheres
• Bi-hemispheric infarction or acute infarct in the contra-lateral hemisphere within the past 30 days
• Symptoms of active congestive heart failure (dyspnea, orthopnea, increased oxygen requirement)
• Exacerbation of congestive heart failure, requiring hospitalization, within the past 30 days or severe systolic dysfunction with a known ejection fraction <20%
• End stage renal disease requiring hemodialysis or a creatinine clearance <20 ml/min/1.73 m2
• Hemicraniectomy or other skull defect that would interfere with monitoring
• Pregnant women are excluded. Women of child-bearing age must have a negative pregnancy test prior to enrollment
• Participation in another clinical trial
• Any other illness or condition that the investigator feels would pose a hazard to the subject from participation in the study

81 subjects enrolled. A technical advancement in DCS fiber optic probe design increased signal-to-noise ratio occurred after the first 8 subjects; these subjects were excluded because their data was not comparable to later subjects. 5 subjects who failed to complete the monitoring session and 11 subjects were excluded due to poor data quality.