Comparing Brain Tissue Oxygen Measurements and Derived Autoregulation Parameters from Different Probes (Licox vs. Raumed
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 (
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Abstract 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. Mean PbrO2 from Licox and Neurovent PTO was 16.1 ± 9.0 mmHg and 17.5 ± 11.9 mmHg respectively. Mean ORx was 0.35 ± 0.44 and 0.31 ± 0.43 respectively. 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. Keywords Aneurysmal subarachnoid hemorrhage • Brain tissue oxygen • Cerebrovascular autoregulation • Neuromonitoring
Introduction Advanced neuromonitoring of patients suffering from traumatic brain injury (TBI) and aneurysmal subarachnoid hemorrhage (SAH) has significantly improved our understanding of intracranial disease processes and is increasingly used to guide intensive care therapy [5–7]. Apart from measuring intracranial pressure (ICP) and cerebral perfusion pressure (CPP), continuous monitoring of the partial pressure of brain tissue oxygen (PbrO2) has emerged as a promising clinical tool [7]. PbrO2, a surrogate marker of cerebral blood flow, also allows calculation of the index of brain tissue oxygen pressure reactivity (ORx), which provides a bedside assessment of cerebrovascular autoregulation [6], a crucial factor to secondary brain damage in traumatic brain injury and delayed infarction after subarachnoid hemorrhage [4–6]. Probes from different manufacturers are commercially available for monitoring of PbrO2. They have been extensively tested in vitro by manufacturers and independent investigators [8]. However, only one report compared probes in vivo, mainly in patients after TBI [3]. We aimed to investigate simultaneous in vivo measurements using the Licox and Raumedic system in patients after SAH, and the effects on the ORx derived. Both probes differ from each other as they use different measurement processes (electro-chemical vs physical) for PbrO2 [3].
Materials and Methods
M. Dengl (), C. Renner, and J. Meixensberger Department of Neurosurgery, University of Leipzig, Liebigstrasse 20, 04103 Leipzig, Germany e-mail: [email protected] M. Jaeger Department of Neurosurgery, Liverpool Hospital, University of New South Wales, Liverpool, NSW, Australia
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