EEG alpha power and delirium in the postanaesthesia care unit in older adults: the AlphaMax trial part 1 - effect of desflurane and fentanyl titration during maintenance.

BACKGROUND

Frontal EEG alpha oscillations might reflect an ideal state of general anaesthesia with adequate antinociception. Low alpha power has been associated with a vulnerable brain phenotype at greater risk of postoperative delirium. This arm of the AlphaMax randomised trial aimed to determine if alpha oscillations could be maximised by EEG-guided titration of anaesthesia, and if this might reduce delirium in the postanaesthesia care unit (PACU).

METHODS

Male and female patients, aged ≥60 yr, were randomised to EEG-guided dose titration (targeting oscillatory alpha power) or routine care. Both groups received a standardised desflurane-fentanyl-based anaesthetic technique avoiding burst suppression. PACU delirium was assessed by blinded observers.

RESULTS

For feasibility reasons, we reduced the sample size and were underpowered for PACU delirium. A total of 200 patients aged 73 (SD 7) yr were included. The titration group received more fentanyl (median [interquartile range] 650 [500-850] μg vs 500 [350-600] μg, P<0.0001) and less desflurane (maintenance end-tidal concentration mean [SD] 3.9 [0.7] vol% vs 4.4 [0.8%], vol% P<0.0001) than the control group. Oscillatory alpha power was greater in the titration group early after surgical incision (+0.8 dB, P=0.008), but this effect was not sustained as surgery progressed. Titration resulted in absent desflurane-alpha correlation in the intervention group (r=-0.020, 95% confidence interval -0.155 to 0.115) and a negative association in the control group (r=-0.228, 95% confidence interval -0.396 to -0.059). The incidence of PACU delirium was similar between groups (37% vs 33%, P=0.553).

CONCLUSIONS

EEG-guided titration of fentanyl and desflurane anaesthesia had a limited enhancing effect on oscillatory alpha power with no appreciable difference in clinical outcomes.

CLINICAL TRIAL REGISTRATION: Australian and New Zealand Clinical Trial Registry (ID: 12617001354370).