Acta neurochirurgica. Supplement
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Acta Neurochir. Suppl. · Jan 2012
Assessment of cerebral autoregulation from respiratory oscillations in ventilated patients after traumatic brain injury.
Phase shift (PS) between oscillations in arterial blood pressure (ABP) and transcranial Doppler (TCD) cerebral blood flow velocity (CBFV) is thought to describe cerebral autoregulation. Ventilated patients show high amplitude and regular respiratory oscillations in ABP and CBFV, allowing reliable PS measurement. We analysed recordings of ABP, CBFV and intracranial pressure (ICP) from 187 TBI patients treated at Addenbrooke's Hospital, Cambridge, UK, from 1993 to 1998. ⋯ PS was significant (p < 0.05) for PSm only. Respiratory PS responds to changes in CPP and RR and correlates weakly with CA. Respiratory PS may have some prognostic value for patients with TBI.
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Acta Neurochir. Suppl. · Jan 2012
Realization of a comprehensive non-invasive detection of intracranial pressure analyzer based upon FVEP and TCD.
Up to now, several methods, such as flash visual evoked potential (FVEP) and transcranial Doppler (TCD), have been studied with regard to assessing intracranial pressure (ICP) non-invasively. However, there are still no instruments that are readily available for non-invasive measurement of ICP in clinical practice. Based on the advantages of FVEP and TCD for ICP assessment, the two methods are synthesized to develop a specific instrument to non-invasively measure ICP more reliably and applicably, as the integration of FVEP and TCD overcomes the shortcomings of a single method of ICP measurement.
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Acta Neurochir. Suppl. · Jan 2012
Pulse amplitude and Lempel-Ziv complexity of the cerebrospinal fluid pressure signal.
The complexity of the intracranial pressure (ICP) signal decreases with intracranial hypertension in children with acute brain injury as well as during infusion studies in adults with hydrocephalus. In this study we have analysed the pressure signal obtained in the lumbar subarachnoid space during infusion testing. The pulse amplitude rises when the ICP is increased by additional external volume. Our objective was to determine the relative influence of the pressure range and pulse amplitude on the loss of complexity observed during infusion-related intracranial hypertension. ⋯ The pulse amplitude of the CSFP signal seems to be a major determinant of the waveform complexity.
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Acta Neurochir. Suppl. · Jan 2012
Comparing brain tissue oxygen measurements and derived autoregulation parameters from different probes (Licox vs. Raumedic).
We investigated two commercially available probes for measurement of the partial pressure of brain tissue oxygen (PbrO2) and calculation of the index of brain tissue oxygen pressure reactivity (ORx) in 7 patients after aneurysmal subarachnoid hemorrhage (SAH). Simultaneous monitoring of PbrO2 using the Licox(®) probe and the multiparameter Raumedic probe (Neurovent PTO(®)), measuring PbrO2, intracranial pressure (ICP) and brain temperature (Neurovent PTO) was performed for a median of 9 days (range 7-17 days). Both probes provided stable monitoring throughout the desired period. ⋯ There was a difference in the measurement of PbrO2 of -2.73 ± 10.1 mmHg (Licox - Raumedic). The difference in the two values for the calculated ORx was far smaller (0.03 ± 0.31; Licox - Raumedic) and the correlation coefficient higher than for both values of PbrO2 (0.76 for ORx vs. 0.56 for PbrO2). The calculation of the autoregulation parameter ORx seemed more independent of the measurement process than the measurement of PbrO2 itself and signifies the potential clinical importance of this parameter.
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Acta Neurochir. Suppl. · Jan 2012
Non-invasively estimated ICP pulse amplitude strongly correlates with outcome after TBI.
An existing monitoring database of brain signal recordings in patients with head injury has been re-evaluated with regard to the accuracy of estimation of non-invasive ICP (nICP) and its components, with a particular interest in the implications for outcome after head injury. ⋯ When compared between patients who died and who survived mean nAmp showed the greatest difference, suggesting its potential to predict mortality after TBI.