Trial patients will be examined daily with TCD (DWL, Germany) using a 2-MHz probe mounted on a purposed head frame for two weeks since SAH ictus. The systolic, diastolic, and mean FV will be recorded (trans-temporal) by a single user (MT). Vasospasm will be defined as mean FV > 120 cm/sec and Lindegaard ratio >3 [Lindegaard 1988]. The regression index (Mx) between mean FV and spontaneous changes in ABP will be calculated. Two carotid compressions lasting 5 seconds will be performed. The criteria for an acceptable THRT includes a sudden decrease in middle cerebral artery FV at the onset of compression, a stable TCD signal during compression, and a minimum of 30% decrease in FV with no blood pressure instability [Smielewski 1997]. The THRT ratio (THRR) is calculated using the formula: THRR = FVs (hyperaemia) / FVs(baseline), where FVs denotes systolic FV (Figure 1). THRR is classified as normal (≥l.10) or impaired (<1.10), and will be repeated 2 minutes later. The average value of the two tests will be recorded. Quality issues concerning the THRT response have been extensively evaluated in this laboratory [Smielewski 1997].