A computing system for the clinical and experimental investigation of cerebrovascular reactivity

Smielewski, Peter; Czosnyka, Marek; Zabołotny, W.; Kirkpatrick, Peter J.; Richards, Hugh K.; Pickard, John D.

doi:10.1007/bf03356593

Cited by 24 publications

(23 citation statements)

References 36 publications

(50 reference statements)

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“…Recently, the variability of the NIRS CO # reactivity test was evaluated in only a small group of patients with carotid artery disease [10] ; reproducibility of NIRS and TCD parameters was higher than in our study. This discrepancy might be due to the lower CO # reactivity values measured in patients with carotid artery stenosis compared with healthy volunteers [1,28,35]. We excluded a systematic bias between measurements ; thus the observed variability is attributable to the physiological individual responses.…”

Section: Discussionmentioning

confidence: 80%

“…The contamination of the extracranial circulation was carefully investigated [7,10,[36][37][38]. The relative contribution of the extracranial tissues decreased as the interoptode distance increased ; for an interoptode distance greater than 4.5 cm, the extracranial contribution was negligible [7,35]. The contribution of the scalp might be minimized by applying moderate pressure on the optodes [36].…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of potential factors affecting the measurement of cerebrovascular reactivity by near-infrared spectroscopy

TOTARO¹,

BARATTELLI²,

Quaresima³

et al. 1998

Clinical Science

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1.Near-infrared (IR) spectroscopy is based on the relative transparency of skin, skull and brain to the light in the near-IR region (700-1100 nm) and on the oxygen-dependent tissue absorption changes of haemoglobin.2. We evaluated the most relevant factors (reproducibility, venous return, age and sex) that might affect reliability of near-IR spectroscopy to test CO2 cerebrovascular reactivity.3.Thirty-four healthy volunteers were enrolled in the study. The protocol consisted of a 3-min baseline, a 3-min hypercapnia (5% CO2 in air) and a 2-min recovery. Transcranial Doppler sonography measurements were simultaneously performed. The CO2 reactivity test was repeated on 27 subjects after 1 h to assess reproducibility. CO2 reactivity was also evaluated at different body positions (supine, 35 degrees Trendelenburg and 35 degrees reverse Trendelenburg), and over a gradual increase of the inspired CO2.4. Changes in near-IR spectroscopy and transcranial Doppler sonography parameters were significantly correlated with variations of end-tidal CO2 (P<0.005). A significant correlation between the reactivity indexes of near-IR spectroscopy parameters and flow velocity was also found (P<0.01). A high reproducibility was also found for deoxyhaemoglobin (rI=0.76), oxyhaemoglobin (rI=0.68) and flow velocity (rI=0.60) reactivity indexes. No significant differences between the reactivity indexes of different body positions were found (P>0.05). The reactivity index of oxyhaemoglobin and deoxyhaemoglobin decreased (P<0.05) and increased (P<0.01) with age respectively.5. We found that near-IR spectroscopy is a reliable and reproducible method for the evaluation of cerebrovascular reactivity and might be considered, after appropriate validation, for the assessment of patients with cerebrovascular disease.

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Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Evaluation of potential factors affecting the measurement of cerebrovascular reactivity by near-infrared spectroscopy

TOTARO¹,

BARATTELLI²,

Quaresima³

et al. 1998

Clinical Science

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“…28,29 Maximum physiological stability is generally observed at the time of application of clamps rather than removal; therefore, data from this period were used for analysis. Values of mean arterial pressure, laser Doppler flowmetry, FV and TOI were averaged at baseline (before clamping but after completion of dissection) and over a 2-minute period immediately after ECA and ICA clamping.…”

Section: Data Processing and Analysismentioning

confidence: 99%

Tissue Oxygen Index

Al-Rawi

Kirkpatrick

2006

Stroke

149

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Background and Purpose-To date, the clinical application of near infrared spectroscopy in the adult brain has been limited. The NIRO 300 (Hamamatsu Photonics) provides a continuous measurement of tissue oxygen index (TOI) using spatially resolved spectroscopy. Although TOI reflects cerebral oxygenation to a high degree of sensitivity and specificity, to become a useful clinical tool, thresholds for cerebral ischemia need to be defined. This study has attempted to identify a quantifiable TOI threshold for ischemia in the adult brain. Methods-One hundred sixty-seven patients undergoing carotid endarterectomy were studied. The NIRO 300 was incorporated into an established multimodal monitoring system enabling observations of cerebral hemodynamic changes under highly controlled conditions. Changes in TOI (%⌬TOI) on clamping the internal carotid artery were compared with intracranial blood flow (middle cerebral artery flow velocity) and cerebral function monitoring to identify and quantify periods of cerebral ischemia. Results-Significant correlation was seen between changes in middle cerebral artery flow velocity and ⌬TOI on clamping (rϭ0.74, Pϭ0.0001). Thirty-one patients showed cerebral ischemia on internal carotid artery clamping as defined by a sustained fall in cerebral function monitoring. A threshold for %⌬TOI of Ϫ13 was identified, above which no patients showed any evidence of ischemia on clamping. This threshold provided 100% sensitivity and 93.2% specificity for patients satisfying the preset criteria for cerebral ischemia. Conclusions-These data demonstrate the potential to identify TOI-quantified thresholds for cerebral ischemia in the adult brain and thus improve the clinical use of near infrared spectroscopy. Our observations have defined a drop in TOI (13%) that can be adopted as a threshold for severe cerebral ischemia with high sensitivity and specificity. Key Words: carotid endarterectomy Ⅲ cerebral ischemia Ⅲ near infrared spectroscopy Ⅲ spatially resolved spectroscopy Ⅲ tissue oxygen index O ptical methods based on near-infrared spectroscopy (NIRS) can be used to monitor hemodynamic variables in the clinical setting. 1 Applications include monitors of fetal physiology, 2-4 during cardiac surgery, 5,6 muscle function, 7-10 and neonatal, 11 pediatric, 12 and adult brain. [13][14][15][16][17][18][19] A number of NIRS instruments are now available that detect changes in optical attenuation from several wavelengths of light, and although a variety of algorithms have been applied to attempt quantification, accuracy of these instruments remains a concern.The NIRO 300 (Hamamatsu Photonics) provides a continuous online measurement of tissue oxygen index (TOI) using spatially resolved spectroscopy. 20,21 We have previously determined that TOI reflects cerebral oxygenation to a high degree of sensitivity and specificity during carotid surgery, 20 an indication that NIRS can show clinically relevant estimations of cerebral hemodynamic and oxygen changes in the adult head (Figure 1). However, there are no da...

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“…34,35 Maximum physiological stability is generally observed at the time of application of clamps rather than removal, and therefore data from this period were used for analysis. For purposes of comparison, multivariable linear regression was used to calculate the correlation coefficient between (1) ⌬TOI and ⌬FV and (2) ⌬TOI and ⌬LDF.…”

Section: Data Processing and Analysismentioning

confidence: 99%

Evaluation of a Near-Infrared Spectrometer (NIRO 300) for the Detection of Intracranial Oxygenation Changes in the Adult Head

Al-Rawi¹,

Smielewski²,

Kirkpatrick³

2001

Stroke

245

159

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Background and Purpose-The clinical application of intracranial near-infrared spectroscopy in adults has been hampered by concerns over contamination from extracranial tissues. The NIRO 300 (Hamamatsu Photonics) provides continuous online measurements of hemoglobin and cytochrome oxidase concentrations and a calculated tissue oxygen index (TOI). The present study seeks confirmation of the anatomic source of TOI in the adult cranium. Methods-Sixty patients undergoing carotid endarterectomy were studied. The NIRO 300 was incorporated into an established multimodal monitoring system. TOI, oxyhemoglobin, and deoxyhemoglobin changes were assessed and compared with (1) frontal cutaneous laser-Doppler flowmetry and (2) transcranial Doppler measurement of the ipsilateral middle cerebral artery flow velocity. Results-Changes in TOI were seen during cross-clamping of the carotid vessels in 49 patients (mean ⌬TOIϭϪ9.4%, SDϭ7.1). Significant correlation was seen between TOI and flow velocity (rϭ0.56) but not with laser-Doppler flowmetry (rϭ0.13). In 31 patients, oxyhemoglobin and deoxyhemoglobin concentrations were recorded, showing significant changes during both external carotid artery and internal carotid artery clamping. A change in TOI was predominantly associated with internal carotid artery clamping (nϭ41). When TOI changed during external carotid artery clamping (nϭ8), significant blood pressure changes occurred, or extracranial-to-intracranial anastomosis was evident. In the absence of such variables, the sensitivity of TOI to intracranial and extracranial changes was 87.5% and 0%, respectively, and specificity was 100% and 0%, respectively. Conclusions-The NIRO 300 reflects changes in cerebral tissue oxygenation when TOI is calculated, with a high degree of sensitivity and specificity. (Stroke. 2001;32:2492-2500.)

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A computing system for the clinical and experimental investigation of cerebrovascular reactivity

Cited by 24 publications

References 36 publications

Evaluation of potential factors affecting the measurement of cerebrovascular reactivity by near-infrared spectroscopy

Evaluation of potential factors affecting the measurement of cerebrovascular reactivity by near-infrared spectroscopy

Tissue Oxygen Index

Evaluation of a Near-Infrared Spectrometer (NIRO 300) for the Detection of Intracranial Oxygenation Changes in the Adult Head

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