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This is a prospective observational study, consisting of 3 substudies carried out during elective neurosurgery under general anaesthesia. Each participant will take part in all 3 substudies. First, the capability of Near Infra Red Spectroscopy (NIRS) to measure the brain oxygenation is examined. A NIRS-electrode is placed on forehead skin, on the skull, and on dura. Secondly, a small dose of Phenylephrine is given, and the brain oxygenation is measured by a Clark-electrode and a NIRS-electrode, to see how Phenylephrine affects these measurements. In the third substudy, the brain oxygenations' (NIRS and Licox) response to an inspired oxygen fraction of 0.30 vs. 0.80 is investigated.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| One strategy for all enrolled patients: | Other | All patients will participate in three substudies, in which they also act as controls, with exposure to the same three interventions: 1) NIRS-measurement on skin, skull and dura, 2) Phenylephrine 0.1 mg iv., and 3) inspired oxygen fraction of 0.3 vs. 0.8 |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| NIRS measurements on skin, skull and dura | Device | During a neurosurgical procedure, we will measure the brain oxygenation with a NIRS-electrode, first on forehead skin, then on the skull and finally directly on dura. |
| Measure | Description | Time Frame |
|---|---|---|
| ScO2 (NIRS-measured cerebral oxygen saturation) | Difference in ScO2 between dura and skin (Primary analysis for substudy 1) | During surgical procedure |
| Measure | Description | Time Frame |
|---|---|---|
| PBrO2 (Partial pressure of brain tissue oxygen) | Cerebral oxygenation, measured by a Clark-electrode (Licox (R)) (Primary outcome measure for substudy 2) | During surgical procedure |
| PBrO2 (Partial pressure of brain tissue oxygen) |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Rigshospitalet | Copenhagen | 2100 | Denmark |
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| Phenylephrine's effect on brain oxygenation | Drug | With a Clark-electrode (Licox(R)) in the white matter and a NIRS-electrode on the forehead skin, we will give a small dose (0.1 mg iv.) Phenylephrine. |
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| Normal vs. high inspired oxygen | Drug | By the end of the neurosurgical procedure, still with a Clark-electrode in the white matter and a NIRS-electrode on forehead skin, we will change the inspired oxygen fraction from 0.3 to 0.8. |
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Cerebral oxygenation during inspired oxygen fraction 0.80 vs. 0.30 (Primary outcome for substudy 3)
| 'Normoxia' is induced with FiO2 = 0.30 for 5 minutes, and then changed to 'Hyperoxia' with FiO2 = 0.80 for the subsequent 5 minutes, while registering the Licox-signal. |
| ScO2 (NIRS-measured cerebral oxygen saturation) | Difference in ScO2 between dura and skull, and between skull and skin (this will be the secondary analyses of substudy 1) | Measurements will be performed as the surgeon exposes the skull. |
| ScO2 (NIRS-measured cerebral oxygenation) | NIRS-signal during Phenylephrine intervention (this will be the secondary outcome of substudy 2) | NIRS signal is obtained continuously during the Phenylephrine intervention |