Cerebral blood flow as a predictor of outcome following traumatic brain injury

Abstract

As part of a prospective study of the cerebrovascular effects of head injury, 54 moderate and severely injured patients underwent 184 133Xe-cerebral blood flow (CBF) studies to determine the relationship between the period of maximum blood flow and outcome. The lowest blood flows were observed on the day of injury (Day 0) and the highest CBFs were documented on postinjury Days 1 to 5. Patients were divided into three groups based on CBF values obtained during this period of maximum flow: Group 1 (seven patients), CBF less than 33 ml/100 g/minute on all determinations; Group 2 (13 patients), CBF both less than and greater than or equal to 33 ml/100 g/minute; and Group 3 (34 patients), CBF greater than or equal to 33 ml/100 g/minute on all measurements. For Groups 1, 2, and 3, mean CBF during Days 1 to 5 postinjury was 25.7 ± 4, 36.5 ± 4.2, and 49.4 ± 9.3 ml/100 g/minute, respectively, and PaCO2 at the time of the CBF study was 31.4 ± 6, 32.7 ± 2.9, and 33.4 ± 4.7 mm Hg, respectively. There were significant differences across Groups 1, 2, and 3 regarding mean age, percentage of individuals younger than 35 years of age (42.9%, 23.1%, and 76.5%, respectively), incidence of patients requiring evacuation of intradural hematomas (57.1%, 38.5%, and 17.6%, respectively) and incidence of abnormal pupils (57.1%, 61.5%, and 32.4%, respectively). Favorable neurological outcome at 6 months postinjury in Groups 1, 2, and 3 was 0%, 46.2%, and 58.8%, respectively (p < 0.05). Further analysis of patients in Group 3 revealed that of 14 with poor outcomes, six had one or more episodes of hyperemia-associated intracranial hypertension (simultaneous CBF > 55 ml/100 g/minute and ICP > 20 mm Hg). These six patients were unique in having the highest CBFs for postinjury Days 1 to 5 (mean 59.8 ml/100 g/minute) and the most severe degree of intracranial hypertension and reduced cerebral perfusion pressure (p < 0.0001). These results indicate that a phasic elevation in CBF acutely after head injury is a necessary condition for achieving functional recovery. It is postulated that for the majority of patients, this rise in blood flow results from an increase in metabolic demands in the setting of intact vasoreactivity. In a minority of individuals, however, the constellation of supranormal CBF, severe intracranial hypertension, and poor outcome indicates a state of grossly impaired vasoreactivity with uncoupling between blood flow and metabolism.

Cerebral Blood Volume Alterations in the Perilesional Areas in the Rat Brain after Traumatic Brain Injury—Comparison with Behavioral Outcome

“…Marked decrease in CBV and CBF has been found 3 to 4 h after injury in the rat model of closed head injury (Prat et al, 1997;Thomale et al, 2002). Local CBF has been found to decrease 15 mins after injury and remain decreased up to 4 h in lateral fluid percussion rat models (Ginsberg et al, 1997) and similar patter of CBF has been found in humans Kelly et al, 1996Kelly et al, , 1997. Interestingly, in experimental models transient hypoperfusion has also been detected in the contralateral hemisphere (Pasco et al, 2007).…”

Alterations in Cerebral Oxygen Metabolism after Traumatic Brain Injury in Children

“…9 Rodent and human studies have found that the CBF is decreased in the first 24 hours after TBI, 10,11 followed by a period of increased CBF. 12,13 The subacute phase is less studied, but CBF is reportedly decreased. 14 Relatively few studies have been performed in children with TBI.…”

MRI Characterization of Progressive Brain Alterations After Experimental Traumatic Brain Injury: Region Specific Tissue Damage, Hemodynamic Changes and Axonal Injury

“…increased perfusion in the tissue capillary bed and vasculature during the next 3 days), and vasospasm that invokes a fall in the CBF that lasts for the next two weeks. Particularly, decreased CBF acutely after impact has been documented (Kelly et al, 1996;Kelly et al, 1997;Martin et al, 1997). Long term deviations from the normal CBF level have been depicted, and even patients with symptomatic mild traumatic brain injury but without any other abnormal MRI findings have shown persistent regional hypoperfusion (Bonne et al, 2003).…”