Correlating Brain Tissue Oxygen and Regional Cerebral Oximetry
| Status: | Recruiting |
|---|---|
| Conditions: | Neurology |
| Therapuetic Areas: | Neurology |
| Healthy: | No |
| Age Range: | 18 - Any |
| Updated: | 11/8/2018 |
| Start Date: | June 29, 2017 |
| End Date: | December 21, 2019 |
| Contact: | Paul Picton, MB ChB |
| Email: | ppicton@med.umich.edu |
| Phone: | 734 615 9864 |
Correlating Brain Tissue Oxygen Tension (PbrO2) and Regional Cerebral Oximetry (rSO2) in Normal Human Brain Under the Conditions of Changing Ventilation Strategy
Controversy surrounds the use of regional cerebral oximetry (rSO2) as a measure of true
cerebral oxygenation because of extracranial signal contamination and unmeasured confounding
of cerebral a:v ratio. The measurement of brain tissue oxygen (PbrO2) has been used in
routine neurosurgery and has been shown to reliably demonstrate cerebral hypoxia following
severe head injury. It is the most direct measure of cerebral oxygenation. Here, we test the
hypothesis that there is a correlation between PbrO2 and rSO2 under conditions of varying
inspired oxygen fraction and the varying partial pressure of carbon dioxide in arterial blood
in uninjured, normal human brain.
Patients who are scheduled for elective removal of secondary cerebral metastases under
general anesthesia will be recruited following written informed consent obtained by a study
team member during their preoperative evaluation. BIS and rSO2 optodes will be applied,
before induction of anesthesia, by a single researcher on both sides of the patient's
forehead, as recommended by the manufacturer. General anesthesia will be maintained by total
intravenous anesthesia (TIVA) with a combination of propofol (80-150 mcg/kg/min) and
remifentanil (0.05-0.1 mcg/kg/min) targeted to a Bispectral Index range 40-60 (BIS; Covidien,
Boulder, CO). Following craniotomy, the LICOX probe will be placed under direct vision into
an area of normal brain within the tumor excision canal by the attending neurosurgeon. During
a pause in surgery FIO2 and minute ventilation will be sequentially adjusted to achieve the
following pairs of ventilation set points: 1) FIO2 0.3 and paCO2 30mmHg, 2) FIO2 1.0 and
paCO2 40mmHg. After ≥5 minutes at each set point FIO2, PaCO2, rSO2 and PbrO2 will be recorded
as a "snap-shot".
A sample size of 15 achieves an 80% power with a one-sided type I error of 5% to detect a
positive correlation of 0.6 (from the null hypothesis of no correlation) between changes in
PbrO2 and changes in rSO2 subsequent on alterations made in ventilation strategy. Correlation
will be measured using Pearson's Correlation. P values < 0.05 will be considered
statistically significant.
cerebral oxygenation because of extracranial signal contamination and unmeasured confounding
of cerebral a:v ratio. The measurement of brain tissue oxygen (PbrO2) has been used in
routine neurosurgery and has been shown to reliably demonstrate cerebral hypoxia following
severe head injury. It is the most direct measure of cerebral oxygenation. Here, we test the
hypothesis that there is a correlation between PbrO2 and rSO2 under conditions of varying
inspired oxygen fraction and the varying partial pressure of carbon dioxide in arterial blood
in uninjured, normal human brain.
Patients who are scheduled for elective removal of secondary cerebral metastases under
general anesthesia will be recruited following written informed consent obtained by a study
team member during their preoperative evaluation. BIS and rSO2 optodes will be applied,
before induction of anesthesia, by a single researcher on both sides of the patient's
forehead, as recommended by the manufacturer. General anesthesia will be maintained by total
intravenous anesthesia (TIVA) with a combination of propofol (80-150 mcg/kg/min) and
remifentanil (0.05-0.1 mcg/kg/min) targeted to a Bispectral Index range 40-60 (BIS; Covidien,
Boulder, CO). Following craniotomy, the LICOX probe will be placed under direct vision into
an area of normal brain within the tumor excision canal by the attending neurosurgeon. During
a pause in surgery FIO2 and minute ventilation will be sequentially adjusted to achieve the
following pairs of ventilation set points: 1) FIO2 0.3 and paCO2 30mmHg, 2) FIO2 1.0 and
paCO2 40mmHg. After ≥5 minutes at each set point FIO2, PaCO2, rSO2 and PbrO2 will be recorded
as a "snap-shot".
A sample size of 15 achieves an 80% power with a one-sided type I error of 5% to detect a
positive correlation of 0.6 (from the null hypothesis of no correlation) between changes in
PbrO2 and changes in rSO2 subsequent on alterations made in ventilation strategy. Correlation
will be measured using Pearson's Correlation. P values < 0.05 will be considered
statistically significant.
Inclusion Criteria:
- Patients who are scheduled for elective removal of secondary cerebral metastases under
general anesthesia.
Exclusion Criteria:
- Patients will be excluded if they refuse to give consent, have evidence of elevated
intracranial pressure on preoperative CT scan, have coagulopathy, are taking
therapeutic agents known to increase bleeding risk, have a history of cardiovascular
disease, cerebrovascular disease, suffer from respiratory failure, or are not fluent
English speakers.
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