BIS Readings Of Aspect A 2000 Monitor Are Not Contaminated By Transmitted Oscillations Induced By Jet Ventilation

The tubeless high-frequency jet ventilation during surgery of the upper respiratory tract is usually performed with total intravenous anesthesia (TIVA). Because TIVA is associated with an increased incidence of awareness, the bispectral index (BIS) is considered useful to monitor the depth of anesthesia. However, BIS values can be influenced by physiological, pharmacological and technical factors. Specific technical devices are described to compromise BIS-readings during anasthesia by transmitted oscillations. Jet ventilation causes rhythmic pulsations that are conducted to frontal structures. We studied whether oscillations caused by tubeless jet ventilation affect BIS readings of an Aspect 2000 BIS monitor. Nineteen patients (13 male, 6 female; ASA status 1 3; mean age 46.9 ± 15.7 years; range 21 70) undergoing ear, nose and throat (ENT) procedures were enrolled. TIVA was standardized (propofol 8 10 mg/kg/h; remifentanil 0.2 0.5 μg/kg/min) and paralysis obtained with rocuronium (0.5 mg/kg). BIS was recorded with an Aspect A2000 BIS monitor before induction and during anesthesia (M1 = spontaneous breathing; M2 = superimposed high-frequency jet ventilation, pulsating frequency 600/min; M3 = high-frequency jet ventilation, pulsating frequency 60/min). The median BIS recordings (range of mean BIS values 31 35) during anesthesia did not show significant changes (p < 0.05) during jet ventilation (M2, M3) in comparison to spontaneous breathing (M1). In conclusion, oscillations of tubeless jet ventilation do not appear to contaminate BIS readings obtained during anesthesia in adults.