Isolated Forearm Technique: a Meta-Analysis of Connected Consciousness During Different General Anaesthesia Regimens

Linassi F, Zanatta P, Tellaroli P et al.

British Journal of Anaesthesia. 2018;121(1):198-209. doi: 10.1016/j.bja.2018.02.019

Aim of Study

Determine the overall incidence of connected consciousness during general anaesthesia (GA) as demonstrated by a positive isolated forearm technique (IFT) result

Measure the effect of two different factors; route of anaesthetic and the use of anaesthetic brain monitoring (ABM), on the incidence of connected consciousness during GA

Methodology

Meta analysis of research published in English between 1977-2017

Excludes all paediatric studies and studies measuring connected consciousness by alternative methods to IFT

A total of 22 papers met the inclusion criteria

Results

Total positive IFT – 31.2% (total explicit recall 6.2%)

Positive IFT by GA method:

  • Inhaled – 47.3% total (25.5% during maintenance)
  • IV – 50.5% total (45.3% during maintenance)

Positive IFT by ABM monitoring

  • ABM guided – 64% total (57% during maintenance)
  • Non-ABM guided – 48% total (19% during maintenance)

Discussion

Similar incidence of total IFT responses at any time during GA in all four domains

Patients more likely to experience connected consciousness during IV GA, or GA guided by ABM

ABM has been shown in other research to have marked limitations. Possible that ABM falsely reassures clinicians of the depth of their patient’s levels of sedation.

These trends in positive IFT responses were closely correlated when compared to the incidence of explicit recall

Limitations

High heterogeneity between studies, exposing inconsistencies in data collection and interpretation

Paired with a small amount of literature, this led to wide ranging confidence intervals

Confounding factors such as age and weight impacted results and were not controlled for

Conclusion

IV GA and ABM monitored patients are more likely to maintain connected consciousness during anaesthesia

Still a challenge to actively monitor depth of anaesthesia

Further research is required to optimise treatment and reduce the potential psychological sequelae associated with connective consciousness whilst minimising the toxic effects of GA

Summary by Dr T Leahy. Journal Club Meeting 26 September 2019.

Image from http://www.nationalauditprojects.co.uk

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