Measuring the Cerebral Oxygen Saturation With NIRS Sensor Placed on the Forehead of Patients in the Prone Position. How Does the External Pressure Affect the Measurement.

Measuring the Effect of External Pressure on the Regional Cerebral Oxygen Saturation Monitored by Near-infrared Spectroscopy(NIRS) Technology


Lead sponsor: Glostrup University Hospital, Copenhagen

Source Glostrup University Hospital, Copenhagen
Brief Summary

During general anaesthesia, to ensure sufficient oxygen supply to the brain, the NIRS technology can be used. It consist of two sensors placed on the forehead, and measures the oxygen saturation of the tissue underneath the sensor. For patients undergoing back surgery placed in the prone position, the NIRS measurement will be affected, because the weight of the head will produce a pressure on the sensors. We wish to investigate how much the measurement is affected. Furthermore we plan to lift the head to remove the pressure, and record the time needed for the measurements to return to baseline.

Detailed Description

When placed in the prone position an external pressure is applied to the NIRS sensor. This pressure changes the amount of blood in the underlying tissue and thereby has an influence on the regional cerebral oxygen saturation measured. We wish to investigate to which extend this value is affected by the external pressure. Furthermore by lifting the head we want to investigate how long takes for the measurements to return to baseline (no pressure in the supine position).

Patients will receive written and oral information about the study, when seen by an anaesthesiologist prior to surgery. Before the anaesthesia one NIRS sensors is placed on the right side of the forehead, avoiding til frontal sinus, and one NIRA sensor is placed on the left musculus deltoideus. The patient is placed in the prone position with the head in af prone-view face mask. Measurements will start after 30 minutes with no change in infusion rate of anaesthetic and no inotropics administered. Registration of NIRS measurements will be done every 15 seconds, first five minutes without intervention, then five minutes with headlift, and last five minutes without interventions. Blood pressure, pulse, saturation, end-tidal carbon dioxide and temperature, will be recorded. Registration wil be om case report forms.

Overall Status Completed
Start Date November 2013
Completion Date May 2014
Primary Completion Date May 2014
Study Type Observational
Primary Outcome
Measure Time Frame
Change in the regional cerebral oxygen saturation 15 seconds
Secondary Outcome
Measure Time Frame
The duration before the steady state in the regional cerebral oxygen saturation is obtained after changing the head position. 15 seconds
Enrollment 60

Sampling method: Non-Probability Sample


Inclusion Criteria:

- Surgery in the lumbar spine, in the prone position, with the head in a proneview facemask

- Free and painless movement of the neck

Exclusion Criteria:

- Known cervical spine pathology.

Gender: All

Minimum age: 18 Years

Maximum age: N/A

Healthy volunteers: No

Overall Official
University of Copenhagen, Glostrup Hospital
Location Countries


Verification Date

July 2014

Responsible Party

Responsible party type: Principal Investigator

Investigator affiliation: Glostrup University Hospital, Copenhagen

Investigator full name: Johnny Andersen

Investigator title: M.D.

Has Expanded Access No
Arm Group

Arm group label: Lumbar spine surgical patients

Description: Patients undergoing lumbar spine surgery in the prone position

Study Design Info

Observational model: Case-Only

Time perspective: Prospective