Supraclavicular regional anaesthesia affecting bispectral index as level of consciousness monitor (SUPRABLOC): a pilot randomised controlled trial

Abstract

Background: Renewed interest in regional anaesthesia during the recent COVID-19 pandemic has inspired application of neuraxial anaesthesia for previously unconventional indications, such as awake abdominal surgeries. These patients needed little sedation, since studies demonstrate that neuraxial anaesthesia causes sedation as measured by the bispectral index (BIS). In contrast, no published study has investigated the possible sedative effects of non-neuraxial regional anaesthesia. This pilot randomised controlled trial (RCT) was designed as a template for, and to test the feasibility of, performing a definitive RCT to establish if nonneuraxial regional anaesthesia has any sedative effect.
Methods: Forty participants presenting for forearm surgery were randomly allocated to two treatment groups (supraclavicular block and control). Their level of sedation was monitored with BIS prior to surgery for 60 minutes. Specific feasibility outcomes were planned and data were collected according to CONSORT 2010 recommendations.
Results: Out of 48 patients screened, 41 (85.42%) were invited to participate. Forty patients (97.56%) consented and 100% of these completed the study. In four participants (10%), BIS electrodes needed replacement, while inadequate contact was shown in three participants (7.50%). Data collection and form completion were deemed “easy” and block success rate was 100%. Differences in mean BIS between groups were < 5 and a difference of 10% between groups in incidence of BIS < 80 (85% block group, 75% control group) was shown.
Conclusion: We propose that progression to formal RCT is feasible only with specific modifications to the study design. The decrease in BIS value from baseline should be measured per patient and a clinically significant decrease should be estimated; emergency patients should be excluded; the sample size should be 500 patients; and multiple trial sites should be used. Further consideration should be given to whether such a trial would provide clinically useful information, and would justify the risks, patient discomfort and the considerable financial cost.