An observational study in Cardiopulmonary Bypass, Consciousness Monitors and Isoflurane, sponsored by University of Edinburgh. Completed at 1 site in United Kingdom. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2021-06-21.
Sponsored by University of Edinburgh · Observational
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.
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.
University of Edinburgh is the lead sponsor of 393 studies on the registry; 64 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Those patients scheduled for elective heart surgery over the age of 18 requiring cardiopulmonary bypass
Exclusion Criteria:
Those patients scheduled for elective heart surgery requiring cardiopulmonary bypass who will be given 2.5% isoflurane while on bypass.
Procedure: 2.5 % Isoflurane administration
Anaesthesia maintained during cardiopulmonary bypass with 2.5% isoflurane administered via the oxygenator of the bypass circuit.
Depth of anesthesia according to BIS
BIS reading will be recorded at three time points during cardiopulmonary bypass
Time frame: Intraoperative
Comparison of exhaust gas and blood concentration of isoflurane
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.
Time frame: Intraoperative
Comparison of blood isoflurane concentration and BIS score
Blood isoflurane concentration and BIS will be recorded at three time points and compared to see if they are related
Time frame: Intraoperative
Comparison of exhaust isoflurane Concentration and BIS score
Exhaust isoflurane and BIS will be recorded at three time points and compared to see they are related.
Time frame: Intraoperative
This study is completed, as verified in Jun 2021. You cannot join it, but the record below documents what was studied.
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University of Edinburgh