Isoflurane During Cardiopulmonary Bypass

June 18, 2021 updated by: University of Edinburgh

The Depth of Anaesthesia Associated With the Use of 2.5% Isoflurane During Cardiopulmonary Bypass

There is no clinical way of assessing the depth of anaesthesia while patients are on the heart-lung machine. A new method of measuring the depth of anaesthesia using brainwaves called the Bispectral index (BIS) has been developed and its use in cardiac surgery is now widespread. However BIS is also altered by patients body temperature. As cooling is common during heart surgery the use of BIS to measure the depth of anaesthesia during heart-lung bypass remains controversial. This study aims to find out what depth of anaesthesia is produced according to BIS during heart lung bypass using a standard anaesthetic technique that utilises the anaesthetic isoflurane.

Study Overview

Detailed Description

There is no clinical way of assessing patients' depth of anaesthesia on the heart-lung machine. For this reason, the amount of volatile anaesthetic agent like isoflurane, that is administered has traditionally been determined by anaesthetists' clinical experience. Recently, a device that assesses depth of anaesthesia by analysing the electrical brain waves called the Bispectral index (BIS) has been introduced. The study aims to determine whether the level of anaesthesia produced by isoflurane using the traditional approach is more than required simply to maintain unconsciousness according to BIS. In addition, the study will determine whether the concentration of isoflurane in exhaust gases from the heart-lung machine can be used as an estimate arterial blood concentration and so, depth of anaesthesia.

The study will recruit patients who are scheduled for heart surgery using a heart-lung machine. Patients will be anaesthetised using a long established balanced technique including the administration of isoflurane 2.5% whilst supported on the heart-lung machine. Measurements of exhaust gas concentration of isoflurane from the heart-lung machine and level of BIS will be recorded at three time points. Simultaneously, three arterial blood samples will be taken and the isoflurane concentration measured in these samples. The BIS levels will be averaged and the proportion of patients with a BIS below 40 (lower limit of normal) will be calculated. Concentrations of isoflurane in the exhaust gas of the heart-lung machine will be compared with blood concentrations of isoflurane and the both concentrations will be compared with the level of BIS to establish whether they can be used to assess depth of anaesthesia.

If this study finds that a large proportion of patients have more than adequate levels of anaesthesia, then future studies could explore whether administering lower concentrations of isoflurane improves outcome whilst maintaining anaesthesia.

Study Type

Observational

Enrollment (Actual)

22

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

    • Scotland
      • Edinburgh, Scotland, United Kingdom, EH16 4SA
        • Royal Infirmary of Edinburgh

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Those patients scheduled for elective heart surgery over the age of 18 requiring cardiopulmonary bypass

Description

Inclusion Criteria:

  • Participants over the age of 18
  • Scheduled for elective cardiac surgery under the care of trial anaesthetists
  • Patient has provided informed consent to participate

Exclusion Criteria:

  • Patients presenting for emergency cardiac surgery
  • Patients who will have cardiac surgery that does not require cardiopulmonary bypass
  • Unwilling/unable to provide informed consent
  • Patients under the age of 18
  • Anaesthesia undertaken by anaesthetists not involved in trial

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Elective Cardiac surgery
Those patients scheduled for elective heart surgery requiring cardiopulmonary bypass who will be given 2.5% isoflurane while on bypass.
Anaesthesia maintained during cardiopulmonary bypass with 2.5% isoflurane administered via the oxygenator of the bypass circuit.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Depth of anesthesia according to BIS
Time Frame: Intraoperative
BIS reading will be recorded at three time points during cardiopulmonary bypass
Intraoperative

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Comparison of exhaust gas and blood concentration of isoflurane
Time Frame: Intraoperative
Exhaust gas and blood concentrations of isoflurane will be recorded at three time points during the operation. These values will be compared to see if their values are are related.
Intraoperative
Comparison of blood isoflurane concentration and BIS score
Time Frame: Intraoperative
Blood isoflurane concentration and BIS will be recorded at three time points and compared to see if they are related
Intraoperative
Comparison of exhaust isoflurane Concentration and BIS score
Time Frame: Intraoperative
Exhaust isoflurane and BIS will be recorded at three time points and compared to see they are related.
Intraoperative

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Investigators

  • Principal Investigator: Peter Alston, MBChB, University of Edinburgh

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

April 1, 2015

Primary Completion (Actual)

January 1, 2019

Study Completion (Actual)

January 1, 2019

Study Registration Dates

First Submitted

June 1, 2015

First Submitted That Met QC Criteria

June 10, 2015

First Posted (Estimate)

June 15, 2015

Study Record Updates

Last Update Posted (Actual)

June 21, 2021

Last Update Submitted That Met QC Criteria

June 18, 2021

Last Verified

June 1, 2021

More Information

Terms related to this study

Other Study ID Numbers

  • 15 LO 0366
  • 2015/0199 (Other Identifier: NHS Lothian)

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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