title: Effect of interscalene anaesthesia on cerebral oxygen saturation.
abstract: Interscalene blockade (ISB) is commonly associated with Horner's syndrome, indicating spread of injectate to the cervical sympathetic chain. Cervical sympathetic nerve activity (SNA) is believed to influence cerebral autoregulation, and a decrease in sympathetic tone may alter cerebral blood flow (CBF). This study investigated whether ISB influenced CBF in patients undergoing shoulder surgery. Patients (n=30) scheduled for elective shoulder arthroscopy were recruited. Cerebral oxygen saturation (ScO(2)) of the left and right frontal cortices was continuously measured during ISB administration, sedation and anaesthetic induction. Baseline ScO(2) was similar in blocked and unblocked sides (74 ± 5% and 73 ± 5% respectively, P=0.70). ScO(2) decreased with sedation (-3 ± 3% and -4 ± 3%, P=0.93), and increased with pre-oxygenation and general anaesthesia (P <0.01). Following ISB there was no change in ScO(2) between blocked and unblocked sides (P=0.18), or any difference between right- or left-sided ISB. ISB is not associated with an increase in CBF as indicated by ScO(2), despite the presence of Horner's syndrome.
authors.affiliation: Visiting Anaesthetist, Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, and Associate Professor, Department of Pharmacology, University of Melbourne, Melbourne, Victoria.
authors.forename: P F
authors.initials: PF
authors.lastname: Soeding
authors.affiliation: Fellow, Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, Melbourne, Victoria.
authors.forename: D A
authors.initials: DA
authors.lastname: Currigan
authors.affiliation: Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Victoria.
authors.forename: Y
authors.initials: Y
authors.lastname: Mamo
authors.affiliation: Specialist Surgeon, Melbourne Orthopaedic Group, Windsor, Victoria.
authors.forename: G
authors.initials: G
authors.lastname: Hoy
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General / Q000379:methods*; D001182:Arthroscopy / Q000379:methods*; D002560:Cerebrovascular Circulation; D005260:Female; D006732:Horner Syndrome / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D010100:Oxygen / Q000378:metabolism*; D011446:Prospective Studies; D012785:Shoulder Joint / Q000601:surgery; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: anaesthesia; cerebral blood flow; cerebral oximetry; interscalene block