Key result
Patients with severe acquired brain injury and orthostatic intolerance demonstrated impaired cerebral autoregulation during head-up tilt, indicated by a significant increase in mean flow index.
Why the study?
Does head-up tilt reveal impaired cerebral autoregulation in patients with severe acquired brain injury compared to healthy volunteers?
Observational (n=29)
No
Does head-up tilt reveal impaired cerebral autoregulation in patients with severe acquired brain injury compared to healthy volunteers?
Absolute Event Rate: 0.5% vs 0.28%
p-value: p=<0.001
Patients with severe acquired brain injury exhibit impaired cerebral autoregulation and baroreflex dysfunction during head-up tilt, which may explain orthostatic intolerance during early mobilization.
May link autoregulation impairment to orthostatic intolerance in brain injury; hypothesis-generating and should not yet change practice.
Early mobilization is of importance for improving long-term outcome for patients after severe acquired brain injury. A limiting factor for early mobilization by head-up tilt is orthostatic intolerance. The purpose of the present study was to examine cerebral autoregulation in patients with severe acquired brain injury and a low level of consciousness. Fourteen patients with severe acquired brain injury and orthostatic intolerance and fifteen healthy volunteers were enrolled. Blood pressure was evaluated by pulse contour analysis, heart rate and RR-intervals were determined by electrocardiography, middle cerebral artery velocity was evaluated by transcranial Doppler, and near-infrared spectroscopy determined frontal lobe oxygenation in the supine position and during head-up tilt. Cerebral autoregulation was evaluated as the mean flow index calculated as the ratio between middle cerebral artery mean velocity and estimated cerebral perfusion pressure. Patients with acquired brain injury presented an increase in mean flow index during head-up tilt indicating impaired autoregulation (P < 0.001). Spectral analysis of heart rate variability in the frequency domain revealed lower magnitudes of ~0.1 Hz spectral power in patients compared to healthy controls suggesting baroreflex dysfunction. In conclusion, patients with severe acquired brain injury and orthostatic intolerance during head-up tilt have impaired cerebral autoregulation more than one month after brain injury.
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Riberholt et al. (2016) conducted an observational in Severe acquired brain injury with orthostatic intolerance (n=29). Head-up tilt vs. Healthy volunteers was evaluated on Mean flow index (Mxc) during head-up tilt (p=<0.001). Patients with severe acquired brain injury and orthostatic intolerance demonstrated impaired cerebral autoregulation during head-up tilt, indicated by a significant increase in mean flow index.
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