The depth of anaesthesia associated with the administration of isoflurane 2.5% during cardiopulmonary bypass

Abstract

Background: Administering isoflurane 2.5% into the oxygenator during cardiopulmonary bypass results in no patient movement. However, doing so may result in an excessive depth of anaesthesia particularly, when hypothermia is induced. Bispectral index and arterial blood and oxygenator exhaust concentrations of volatile anaesthetics should be related to depth of anaesthesia. The primary aim of this study was to measure the depth of anaesthesia using bispectral index, resulting from administering isoflurane 2.5% into the oxygenator during cardiopulmonary bypass, and secondary aims were to examine the relationships between blood and oxygenator exhaust isoflurane concentrations and bispectral index. Methods: Arterial and mixed-venous blood samples were aspirated at three time points during cardiopulmonary bypass and measured for isoflurane concentration using mass spectrometry. Simultaneously, oxygenator exhaust isoflurane concentration, nasopharyngeal temperature and bispectral index were recorded. Results: When averaged across the three time points, all patients had a bispectral index score below 40 (binomial test, p < 0.001). There were no significant correlations between bispectral index score and arterial or mixed-venous blood isoflurane concentrations (r = –0.082, p = 0.715; r = –0.036, p = 0.874) and oxygenator exhaust gas concentration of isoflurane (r = –0.369, p = 0.091). Conclusion: When 2.5% isoflurane was administered into the sweep gas supply to the oxygenator during cardiopulmonary bypass, all patients experienced a bispectral index score less than 40 and no significant relationship was found between either arterial or mixed-venous blood or oxygenator exhaust concentrations of isoflurane and bispectral index.

The effect of hypothermia during cardiopulmonary bypass on three electro-encephalographic indices assessing analgesia and hypnosis during anesthesia: consciousness index, nociception index, and bispectral index

“…The weak correlation of the BIS with the temperature, observed also in other CPB studies, 7,8 might indicate a lower sensitivity of this index with respect to the other two indices, qNOX and qCON, which tracked the induced EEG changes corresponding with the experiment design, corroborating the existence of a significant effect of the hypothermia on the EEG activity.…”

“…Recently, a nociception index (qNOX) measures the probability of the patient to respond to external noxious stimuli, and thus, providing an objective measurement of the patient’s nociception or analgesia state. 5,6 At present, many studies have focused on qCON or BIS, and similar indices monitoring for hypnotic depths, in particular for CPB, 7–9 but only a few studies have focused on monitoring for analgesic depth, 10 in particular from EEG-derived monitoring, such as the qNOX. The study hypothesized that qNOX, in combination with the qCON or BIS, can effectively reflect the analgesia and hypnosis levels, particularly, in the CPB cardiac surgery.…”

Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) as an Alternative to Gas Chromatography/Mass Spectrometry (GC/MS) for the Analysis of Cyclohexanone and Cyclohexanol in Plasma

“…Current gold standard targeted analytical methods for simultaneous analysis of small molecules and their metabolites, such as steroids, use mass spectrometry coupled to liquid or gas chromatography . The detection of volatile substances such as ethanol and isoflurane in blood is enabled by headspace-gas chromatography/mass spectrometry (HS-GC/MS), and this approach can be applied to the measurement of volatile cyclohexanone and its metabolite cyclohexanol. However, HS-GC/MS analysis is costly and time consuming.…”