Continuous Assessment of the Cerebral Vasomotor Reactivity in Head Injury

Czosnyka, Marek; Smielewski, Peter; Kirkpatrick, Peter J.; Laing, Rodney; Menon, David; Pickard, John D.

doi:10.1097/00006123-199707000-00005

Cited by 732 publications

(620 citation statements)

References 22 publications

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“…2). The Mx index has previously been validated by comparison to the static rate of autoregulation [15], the transient hyperemic response test [16], the leg-cuff test of cerebral autoregulation [14], the autoregulation index ARI [17], the pressure-reactivity index PRx [18], the phase shift between slow waves of FV and ABP [19], and the CO 2 reactivity test [20]. Using the same principle, a moving correlation coefficient between 10 s averages of ABP and TOI signals (Tox) was calculated.…”

Section: Methodsmentioning

confidence: 99%

Near-Infrared Spectroscopy can Monitor Dynamic Cerebral Autoregulation in Adults

et al. 2008

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Objective To study the correlation between a dynamic index of cerebral autoregulation assessed with blood flow velocity (FV) using transcranial Doppler, and a tissue oxygenation index (TOI) recorded with near-infrared spectroscopy (NIRS). Methods Twenty-three patients with sepsis, severe sepsis, or septic shock were monitored daily on up to four consecutive days. FV, TOI, and mean arterial blood pressure (ABP) were recorded for 60 min every day. An index of autoregulation (Mx) was calculated as the moving correlation coefficient between 10-s averaged values of FV and ABP over moving 5 min time-windows. The index Tox was evaluated as the correlation coefficient between TOI and ABP in the same way. The indices Mx and Tox, ABP and arterial partial pressure of CO 2 were averaged for each patient. Results Synchronized slow waves, presenting with periods from 20 s to 2 min, were seen in the TOI and FV of most patients, with a reasonable coherence between the signals in this bandwidth (coherence >0.5). The indices, Mx and Tox, demonstrated good correlation with each other (R = 0.81; P < 0.0001) in the whole group of patients. Both indices showed a significant (P < 0.05) tendency to indicate weaker autoregulation in the state of vasodilatation associated with greater values of arterial partial pressure of CO 2 or lower values of ABP. Conclusion NIRS shows promise for the continuous assessment of cerebral autoregulation in adults.

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Section: Methodsmentioning

confidence: 99%

Near-Infrared Spectroscopy can Monitor Dynamic Cerebral Autoregulation in Adults

et al. 2008

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“…Cerebral autoregulation was tested using the pressurereactivity index (PRx) of Czosnyka et al [10], which is a calculation of the correlation coefficient between MAP and ICP. Only patients with intact autoregulation reflected by a negative value of PRx were included in our study.…”

Section: Patient Populationmentioning

confidence: 99%

“…Thus, inappropriate volume loading or periods of spontaneous or induced hypertension may aggravate brain edema. However, awareness of autoregulation as an important protective mechanism for patients with SAH and traumatic brain injury increases [10,11,25,46,47].…”

Section: Head Elevation and Cerebral Hemodynamicsmentioning

confidence: 99%

“…The higher the FV, the more impaired the cerebral autoregulation [46]. The pressure reactivity index (PRx), described by Czosnyka et al [10], measures the correlation between ABP and ICP waves and may reflect cerebral autoregulation in response to blood pressure changes. A negative PRx reflects intact cerebrovascular response, whereas a positive PRx reflects a passive nonreactive behavior of the vascular bed.…”

Section: Head Elevation and Cerebral Hemodynamicsmentioning

confidence: 99%

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Intracranial pressure pulse amplitude during changes in head elevation: a new parameter for determining optimum cerebral perfusion pressure?

2009

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Objective During short-term postural changes, the factors determining the amplitude of intracranial pulse pressure (ICPPA) remain constant, except for cerebrovascular resistance (CVR). Therefore, it may be possible to draw conclusions from the ICPPA onto the cerebrovascular resistance (CVR) and thus the relative change in cerebral perfusion pressure (CPP). Methods Age, sex, disease, Glasgow Coma Scale score, placement of ventricular drain, blood gas analysis, and parameters of airway management were prospectively recorded in 40 patients. The changes in intracranial pressure (ICP), CPP, mean arterial pressure (MAP), and ICPPA at head elevations of 0°, 30°, and 60°were measured and analyzed online. Status of cerebrovascular autoregulation was checked using the pressure-reactivity index (PRx). Results Altogether 36 subjects fulfilled the study conditions. Three patients had positive PRx indicating disturbed autoregulation and were excluded. Thus, 33 were left for analysis (18 females and 15 males). All of them were sedated and mechanically ventilated with Glasgow Coma scores ranging from 3-8. During change in head elevation from 0°to 60°, we found a significant (p<0.05) improvement of the ICP, an increase of the ICCPA, a reduction of the MAP, and a decrease in the CPP. Increasing ICPPA was linked to decreasing CPP (0°to 60°, r=−0.42, p<0.05).Conclusions Head elevation is an important part of the ICP and CPP therapy in neurointensive care. When searching for the patient-specific optimum upper body position, ICPPA may provide additional information. Providing that the cerebral autoregulation is intact, the lowest ICPPA of a patient corresponds to the individual upper body position with the highest CPP.

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“…Continuous cerebrovascular autoregulation has been measured in the neurointensive care unit as correlation coefficients between arterial blood pressure and ICP, or the transcranial Doppler systolic flow velocity and ICP. 8,9) The correlation between extracellular glutamate and CPP values was evaluated with the microdialysis method. Autoregulatory index, the correlation coefficient calculated by comparing glutamate concentration with CPP using Pearson's correlation, may be a good indicator for impaired or preserved autoregulation.…”

Section: Discussionmentioning

confidence: 99%

Lower Extracellular Glucose Level Prolonged in Elderly Patients With Severe Traumatic Brain Injury: A Microdialysis Study

Yokobori

Watanabe

Matsumoto

et al. 2011

Neurol. Med. Chir.(Tokyo)

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Age may be an independent predictor of outcomes in traumatic brain injury (TBI), but the causes of the poor outcomes in elderly patients remain unclear. To clarify the differences between elderly and young patients with TBI, brain metabolism parameters were monitored with the microdialysis method in 30 patients with severe TBI (Glasgow Coma Scale scores 3-8). The microdialysis probe was inserted in the penumbra area of the brain and extracellular levels of glucose, glutamate, glycerol, lactate, and pyruvate were measured hourly for the initial 168 hours (7 days) after operation. The lactate/pyruvate ratio, which is considered to be a good indicator of neuronal ischemia, was also calculated. The patients were divided into the elderly group aged 65 years or older and the young group aged less than 65 years, and the biochemical markers were compared daily between these two groups. The value of extracellular glucose concentration was significantly lower in the elderly group than in the young group, and continued until the 7th day after injury. Moreover, the lactate/pyruvate ratio peaked on the 5th day after injury in the elderly group, later than in the young group. We concluded that neural vulnerability persisted longer in elderly patients than in young patients with TBI, and this should be considered to prevent the occurrence of additional secondary brain injury.

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Continuous Assessment of the Cerebral Vasomotor Reactivity in Head Injury

Abstract: Computer analysis of slow waves in ABP and ICP is able to provide a continuous index of cerebrovascular reactivity to changes in arterial pressure, which is of prognostic significance.

Cited by 732 publications

References 22 publications

Near-Infrared Spectroscopy can Monitor Dynamic Cerebral Autoregulation in Adults

Near-Infrared Spectroscopy can Monitor Dynamic Cerebral Autoregulation in Adults

Intracranial pressure pulse amplitude during changes in head elevation: a new parameter for determining optimum cerebral perfusion pressure?

Lower Extracellular Glucose Level Prolonged in Elderly Patients With Severe Traumatic Brain Injury: A Microdialysis Study

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