title: Cerebrovascular Time Constant in Patients with Head Injury.
abstract: The cerebrovascular time constant (τ) theoretically estimates how fast the cerebral arterial bed is filled by blood volume after a sudden change in arterial blood pressure during one cardiac cycle. The aim of this study was to assess the time constant of the cerebral arterial bed in patients with traumatic brain injury (TBI) with and without intracranial hematomas (IH). We examined 116 patients with severe TBI (mean 35 ± 15 years, 61 men, 55 women). The first group included 58 patients without IH and the second group included 58 patients with epidural (7), subdural (48), and multiple (3) hematomas. Perfusion computed tomography (PCT) was performed 1-12 days after TBI in the first group and 2-8 days after surgical evacuation of the hematoma in the second group. Arteriovenous amplitude of regional cerebral blood volume oscillation was calculated as the difference between arterial and venous blood volume in the "region of interest" of 1 cm(2). Mean arterial pressure was measured and the flow rate of the middle cerebral artery was recorded with transcranial Doppler ultrasound after PCT. The time constant was calculated by the formula modified by Kasprowicz. The τ was shorter (p = 0.05) in both groups 1 and 2 in comparison with normal data. The time constant in group 2 was shorter than in group 1, both on the side of the former hematoma (р = 0.012) and on the contralateral side (р = 0.044). The results indicate failure of autoregulation of cerebral capillary blood flow in severe TBI, which increases in patients with polytrauma and traumatic IH.
authors.affiliation: Department of Polytrauma and Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhny Novgorod, 603126, Russian Federation. xtro7@mail.ru.|Department of Neurosurgery, Nizhniy Novgorod State Medical Academy, Nizhniy Novgorod, Russian Federation. xtro7@mail.ru.
authors.forename: Alex
authors.initials: A
authors.lastname: Trofimov
authors.affiliation: Department of Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhniy Novgorod, Russian Federation.
authors.forename: George
authors.initials: G
authors.lastname: Kalentiev
authors.affiliation: Department of Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhniy Novgorod, Russian Federation.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gribkov
authors.affiliation: Department of Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhniy Novgorod, Russian Federation.
authors.forename: Oleg
authors.initials: O
authors.lastname: Voennov
authors.affiliation: Department of Neurosurgery, Nizhniy Novgorod State Medical Academy, Nizhniy Novgorod, Russian Federation.
authors.forename: Vera
authors.initials: V
authors.lastname: Grigoryeva
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D062186:Arterial Pressure; D002560:Cerebrovascular Circulation; D005260:Female; D006407:Hematoma, Epidural, Cranial / Q000000981:diagnostic imaging* / Q000503:physiopathology; D046648:Hematoma, Subdural, Intracranial / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D020300:Intracranial Hemorrhages / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D055420:Perfusion Imaging; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D017585:Ultrasonography, Doppler, Transcranial; D014655:Vascular Resistance; D055815:Young Adult
keywords: Cerebral microcirculation; Cerebrovascular time constant; Head injury