Changes in auditory evoked potential index, bispectral index and 95% spectral edge frequency during induction of anesthesia with nitrous oxide / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the feasibility of using auditory evoked potential index(AAI) to monitor the depth of nitrous oxide anesthesia. Methods Sixteen ASAⅠ-Ⅱpatients aged 23-64 years, weighing 51-86 kg scheduled for elective surgery under general anesthesia were studied. Patients with psychoneural diseases and hearing disturbances were excluded. The patients were premedicated with phenobarbital sodium 0.1g and atropine 0.5mg. AAI, BIS, 95% SEF, BP, HR, SpO2 monitoring were started before induction of anesthesia. The patients were preoxygenated for 5 min using a close-fitting face mask and 100% O2 at l0L?min-1 . Inhalation of nitrous oxide was then started. Nitrous oxide concentration was gradually increased in increments of 10% from 0% to 70% . AAI, BIS and 95%SEF were recorded and observer's assessment of alertness/sedation (OAA/S) scores were measured at each 10% increment of end-tidal nitrous oxide concentration which was maintained for 5 min. The correlation between AAI, BIS, 95% SEF and OAA/S scores was analyzed. Results OAA/S scores and AAI decreased as the nitrous oxide concentration increased. AAI correlated closely with OAA/S scores and end-tidal nitrous oxide concentration (the coefficients of Spearman' s rank correlation ? = - 0.739, 0.837, P