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

Date
2016-12
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
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.1-3 No 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.
Agtergrond: Verskeie studies het gepostuleer en bewys dat neuraksiale (spinaal en epidurale) narkose die sentrale bewussynsvlak verlaag.1-3Die mees waarskynlike verklaring vir hierdie verskynsel is die onderdrukking van die afferente spinotalamiese neurlogiese bane, hoewel die rostrale verspreiding so wel as die sistemiese effekte van die lokale verdowingsmiddel, ook ‘n beduidende rol mag speel.1-3 ‘n Oorsig van die literatuur het geen spesifieke studies opgelewer wat die moontlike verwantskap tussen non-neuraksiale regionale narkose tegnieke en sentrale bewussynsonderdrukking evalueer nie. Metodiek: Twintig (N=20) ASA 1 pasiente wat presenteer het vir elektiewe handchirurgie, het non-neuraksiale regionale narkose in die vorm van ‘n ultraklank begeleide supraklavikulere bragiaalpleksus senuweeblok ontvang. Geen premedikasie of enige ander vorm van orale of parenterale analgesie of sedasie is voor of tydens die prosedure toegedien nie. Die pasiente se sentrale bewussynsvlak is moniteer deur gebruik te maak van die BIS (Bispectral Index) monitering sisteem.‘n Basislyn lesing vir elke pasient is noteer voor die aanvang van die regionale senuweeblok, en die laagste BIS waarde vir opeenvolgende 10 minuut intervalle tot en met ‘n total van 60 minute is gedokumenteer. Resultate: In 65% van ons steekproef van 20 pasiente is BIS waardes noteer wat beduidend is van ‘n geringe tot matige vlak van sentrale bewussyn onderdrukking (BIS <80) (CI95= 40.4-83.6%). Geen korrelasie tussen ouderdom, geslag of die aard van die presenterende siektetoestand (akuut versus chronies) is demonstreer nie. Slotsom: Ons studie het getoon dat non-neuraksiale regionale narkose (in die afwesigheid van enige ander vorm van analgesie of sedasie), ‘n gering tot matige onderdrukking van die sentrale bewussyn kan induseer. Alhoewel hierdie loodsstudie nie aangedrewe was om ‘n statisties betekenisvolle gevolgtrekking te lewer nie, beklemtoon dit wel die behoefte en potensiaal vir toekomstige studies om hierdie interessante verwantskap verder te ondersoek en te evalueer.
Description
Thesis (MMed)--Stellenbosch University, 2016.
Keywords
Spinal anesthesia, Brachial plexus -- Surgery, Local anesthesia, Loss of consciousness, Peridural anesthesia
Citation