Neuro-Ox 2018: Assessment of Cerebral Oxygenation Under Three Clinically Relevant Conditions

Study Overview
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Brief Summary
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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.

Official Title
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Neuro-Ox 2018: Assessment of Cerebral Oxygenation Under Three Clinically Relevant Conditions

Conditions
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Neurosurgery, Elective Craniotomy, General Anaesthesia

Intervention / Treatment
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* Device: NIRS measurements on skin, skull and dura
* Drug: Phenylephrine's effect on brain oxygenation
* Drug: Normal vs. high inspired oxygen


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adult (>18 years) patients Elective craniotomy Exclusion Criteria: Repeat craniotomy Preoperative hypotension (defined as systolic blood pressure below 110 mmHg) Preoperative hypoxia (defined as peripheral oxygen saturation (SpO2) < 90% without oxygen supplementation before surgery) No negative pregnancy test for women <50 years.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: One strategy for all enrolled patients:<br>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 | Device: NIRS measurements on skin, skull and dura<br>* 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.<br>Drug: Phenylephrine's effect on brain oxygenation<br>* 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.<br>Drug: Normal vs. high inspired oxygen<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | 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 | 

Secondary Outcome Measures

| Outcome Measure | 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) | 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 |