Isoflurane anaesthesia during cardiopulmonary bypass
Research type
Research Study
Full title
What depth of anaesthesia is associated with administering 2.5% isoflurane during cardiopulmonary bypass?
IRAS ID
169723
Contact name
R Peter Alston
Contact email
Duration of Study in the UK
0 years, 3 months, 11 days
Research summary
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 as measured by BIS, in patients whilst on the heart-lung machine when administrating isoflurane using the traditional approach is more than required simply to maintain unconsciousness. 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.
REC name
London - City & East Research Ethics Committee
REC reference
15/LO/0366
Date of REC Opinion
16 Mar 2015
REC opinion
Further Information Favourable Opinion