The effect of supraclavicular brachial plexus blockade on Bispectral index (BIS): a pilot study

[摘要] Background: Many studies have demonstrated that neuraxial (spinal and epidural) anesthesia decreases level of consciousness.1-3 Plausible causal theories relate to afferent spinothalamic tracts suppression, rostral neuraxial spread of local anaesthetics, and systemic local anaesthetic effects.1-3No study has thus far interrogated the effect of non-neuraxial loco-regional anesthesia on level of consciousness.Methods: Un-premedicated ASA 1 patients undergoing elective hand surgery (n=20) were administered ultrasound-guided supraclavicular brachial plexus blocks using 2mg/kg of 0.5% bupivacaine. A pre-block numeric pain visual analogue score was performed. No sedation was administered. Bispectral index (BIS) control readings were obtained before brachial block. For an hour after the block, the lowest BIS readings, within each subsequent 10minute interval was documented. Over the 60minute observation period, a decrease in BIS reading was considered as being any change of BIS≤80.Results: In the hour post-block, BIS values ≤80 occurred in 65% (CI95% 40.4 to 83.6%) of patients when compared to their pre-block (control) BIS values. This result did not correlate to age, gender or the nature of the illness requiring surgery (traumatic versus pre-existing, chronic illness). There was no difference in the mean pre-block pain scores between the patients who experienced a drop in BIS≤80 and BIS>80 with mean values of 2.45 (IQR; CI95) and 2.44 (IQR; CI95) respectively (two-sample Wilcoxon rank-sum test, p = 0.9022).Conclusion: Brachial plexus blockade itself, in the absence of sedative drugs, reduced BIS. This is consistent with light to moderate sedation.

[发布机构] Stellenbosch University