Biphasic cerebral blood flow velocity profile in patients with aneurysmal subarachnoid hemorrhage

Introduction: Increases in cerebral blood flow velocity (CBFV) as measured by transcranial Doppler (TCD) sonography are reflective of cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage (SAH). In serial TCD measurements, some patients exhibit CBFV temporal profiles with two peaks (biphasic). The significance of this finding remains unclear. This retrospective case-control study was conducted to investigate the characteristics and possible predictors of biphasic CBFV profiles. Methods: Biphasic CBFV profiles were identified in serial TCD examinations (every 1-2 days) of 182 consecutive patients admitted for aneurysmal SAH based on CBFV profiles of the middle cerebral artery on the side of higher maximum velocity. Patients undergoing angioplasty were excluded. Patients meeting these criteria (study patients) were compared to control patients matched for age and Hunt and Hess grade. Results: Eighteen patients (9.9%) demonstrated biphasic CBFV profiles. The first CBFV (134 ± 11 cm/second) peak occurred on post-SAH day 6 ± 1, and the second peak (148 ± 12 cm/second) on day 13 ± 1. Study patients more often exhibited focal (p < 0.05) symptoms at the time of the first peak. No patient deteriorated neurologically at the time of the second peak. No correlation was observed between CBVF and mean arterial pressure or central venous pressure trends. Conclusion: Serial TCD assessment identifies patients with SAH and a biphasic CBFV temporal profile. Although the second peak usually is not associated with a worsening of symptoms, these patients were more likely to exhibit clinical symptoms during the first CBFV peak.