SummaryThis study investigates the incidence of clinically relevant asymmetry in bispectral index readings from different sides of the skull (using two monitors) during ear-nose-throat surgery in 42 adults and 46 children. A unilateral increase or decrease > 10% from baseline was defined as an 'asymmetry'. Asymmetry followed by movement after stimulation was defined as a 'clinically relevant asymmetry'. Asymmetry occurred in 39 out of 42 adults (93%) and in 20 out of 46 children (44%) during surgery and in 24 out of 42 adults (57%) and in 17 out of 46 children (37%) during recovery. Clinically relevant asymmetry was observed in 5 out of 42 adults (12%) and 6 out of 46 children (13%). The incidence of asymmetry was higher in adults during surgery (p = 0.0002). In conclusion, clinically relevant bispectral index asymmetry has been observed in > 10% of paediatric and adult anaesthesia and may have clinical implications.

BackgroundIschemic or volatile anesthetic preconditioning is defined as tissue protection from impending ischemic cell damage by repetitive short periods of tissue exposure to ischemia or volatile anesthetics. Objective of this study was to elucidate, if ischemic preconditioning and pharmacological preconditioning with sevoflurane have effects on muscle tissue oxygen saturation in patients undergoing surgical revascularization of the lower limb.MethodsIn this prospective randomized pilot study ischemic and pharmacological (sevoflurane) preconditioning was performed in 40 patients with lower limb arterial occlusive disease undergoing surgical revascularization. Sevoflurane preconditioning was performed in one group (N = 20) by repetitive application of sevoflurane for six minutes interspersed by six minutes of washout. Thereafter, ischemic preconditioning was performed in all patients (N = 40) by repetitive clamping of the femoral artery for six minutes interspersed by six minutes of reperfusion. The effect of both procedures on leg muscle tissue oxygen saturation (rSO2) was measured by near-infrared spectroscopy during both procedures and during surgery and reperfusion (INVOS® 5100C Oxymeter with Small Adult SomaSensor® SAFB-SM, Somanetics, Troy, Michigan, USA).ResultsRepetitive clamping and reperfusion of the femoral artery resulted in significant cyclic decrease and increase of muscle rSO2 (p < 0.0001). Pharmacological preconditioning with sevoflurane resulted in a faster and higher increase of rSO2 during postoperative reperfusion (Maximal 111% baseline ± 20 versus 103% baseline ± 14, p = 0.008) consistent with an additional effect of pharmacological preconditioning on leg perfusion.ConclusionsIschemic preconditioning of lower limb muscle tissue and pharmacological preconditioning with sevoflurane have an effect on tissue oxygenation in patients with lower limb occlusive arterial disease.Trial registrationThe trial has been registrated at http://www.ClinicalTrial.gov, Trial Number: NCT02038062 at 14 January 2014.

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