Correlating Brain Tissue Oxygen and Regional Cerebral Oximetry

Summary

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.

Conditions

• Stroke

Interventions

DEVICE

IVOS cerebral oximeter

Measuring percutaneous cerebral oxygenation secondary to changing end tidal carbon dioxide and inspired oxygen fraction.

DEVICE

Licox cerebral oxygenation monitor

Measuring tissue cerebral oxygenation secondary to changing end tidal carbon dioxide and inspired oxygen fraction.

OTHER

Cerebral oxygenation

Measuring cerebral oxygenation with varying ventilation strategy

Sponsors & Collaborators

• University of Michigan

  lead OTHER

Principal Investigators

• Paul Picton, MB ChB · University of Michigan

Study Design

Allocation

NA

Purpose

DIAGNOSTIC

Masking

NONE

Model

SEQUENTIAL

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2017-06-29

Primary Completion

2021-06-22

Completion

2021-06-22

FDA Device

Yes

Countries

• United States

Study Locations