The Cerebrovascular Resistance in Combined Traumatic Brain Injury with Intracranial Hematomas.

OBJECTIVE: The aim was to evaluate changes in cerebrovascular resistance (CVR) in combined traumatic brain injury (CTBI) in groups with and without intracranial hematomas (IH). MATERIALS AND METHODS: Treatment outcomes in 70 patients with CTBI (42 males and 28 females) were studied. Mean age was 35.5 ± 14.8 years (range, 15-73). The patients were divided into two groups: group 1 included 34 CTBI patients without hematomas; group 2 comprised 36 patients with CTBI and IH. The severity according to the Glasgow Coma Scale averaged 10.4 ± 2.6 in group 1, and 10.6 ± 2.8 in group 2. All patients underwent perfusion computed tomography (CT) and transcranial Doppler of both middle cerebral arteries. Cerebral perfusion pressure and CVR were calculated. RESULTS: The mean CVR values in each group (both with and without hematomas) appeared to be statistically significantly higher than the mean normal value. Intergroup comparison of CVR values showed statistically significant increase in the CVR level in group 2 on the side of the removed hematoma (р = 0.037). CVR in the perifocal zone of the removed hematoma remained significantly higher compared with the symmetrical zone in the contralateral hemisphere (p = 0.0009). CONCLUSION: CVR in patients with CTBI is significantly increased compared to the normal value and remains elevated after evacuation of hematoma in the perifocal zone compared to the symmetrical zone in the contralateral hemisphere. This is indicative of certain correlation between the mechanisms of cerebral blood flow autoregulation and maintaining CVR.

Comparison of Cerebral Oxygen Saturation and Cerebral Perfusion Computed Tomography in Cerebral Blood Flow in Patients with Brain Injury.

The purpose of this study was to determine the relationship between cerebral tissue oxygen saturation and cerebral blood volume in patients with traumatic brain injury. Perfusion computed tomography of the brain was performed in 25 patients with traumatic brain injury together with simultaneous SctO2 level measurement using cerebral near-infrared oxymetry. The mean age of the injured persons was 34.5±15.6 years (range 15-65); 14 men, 11 women. The Injury Severity Score (ISS) values were 44.4±9.7 (range 25-81). The Glasgow Coma Score (GCS) mean value before the study was 10.6±2.1 (range 5-13). SctO2 ranged from 51 to 89%, mean 62±8.2%. Cerebral blood volume (CBV) values were 2.1±0.67 ml/100 g (min 1.1; max 4.3 ml/100 g). Cerebral blood flow (CBF) was 31.99±13.6 ml/100 g×min. Mean transit time (MTT) values were 5.7±4.5 s (min 2.8; max 34.3 s). The time to peak (TTP) was 22.2±3.1 s. A statistically significant correlation was found between SctO2 level and cerebral blood volume (CBV) level (R=0.9; p<0.000001). No other significant correlations were found between brain tissue oxygenation and other parameters of brain perfusion.

Comparison of Two Algorithms for Analysis of Perfusion Computed Tomography Data for Evaluation of Cerebral Microcirculation in Chronic Subdural Hematoma.

The aim of this work was comparison of two algorithms of perfusion computed tomography (PCT) data analysis for evaluation of cerebral microcirculation in the perifocal zone of chronic subdural hematoma (CSDH). Twenty patients with CSDH after polytrauma were included in the study. The same PCT data were assessed quantitatively in cortical brain region beneath the CSDH (zone 1), and in the corresponding contralateral brain hemisphere (zone 2) without and with the use of perfusion calculation mode excluding vascular pixel 'Remote Vessels' (RV); 1st and 2nd analysis method, respectively. Comparison with normal values for perfusion indices in the zone 1 in the 1st analysis method showed a significant (p < 0.01) increase in CBV and CBF, and no significant increase in MTT and TTP. Use of the RV mode (2nd analysis method) showed no statistically reliable change of perfusion parameters in the microcirculatory blood flow of the 2nd zone. Maintenance of microcirculatory blood flow perfusion reflects the preservation of cerebral blood flow autoregulation in patients with CSDH.

Cerebrovascular Time Constant in Patients with Head Injury.

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.