The Сerebrovascular Time Constant in Patients with Head Injury and Posttraumatic Cerebral Vasospasm

The aim of the study was to assess the time constant of cerebral arterial bed in TBI patients with cerebral vasospasm (CVS) with and without intracranial hematomas (ICH).We examined 84 patients with severe TBI (mean 35 ± 15 years, 53 men and 31 women). The first group included 41 patients without ICH and the second group included 43 patients with epidural (7) and subdural (36) hematomas.Perfusion computed tomography (PCT) was performed in 1-12 days after TBI in the first group and in 2-8 days after craniotomy in the second group. Arteriovenous amplitude of regional cerebral blood volume oscillation was calculated as the difference of arterial and venous blood volume in the "region of interest." Mean arterial pressure was measured and the flow rate of middle cerebral artery was recorded with Transcranial Doppler after PCT. Time constant was calculated by the formula modificated by M. Kasprowicz. Results and Conclusion: The τ was shorter (p < 0.005) in both first and second group in comparison with normal values. The τ in the second group on ipsilateral side former hematoma with CVS was shorter than in the first group and in the second group on contralateral side former hematoma without CVS (р = 0.024).