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Seung Ah Chung, Seran Jang, Koung Hoon Kook, Jong Bok Lee; Prediction of eye position during general anesthesia using bispectral index monitoring. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2560.
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The position of the eyes in general anesthesia is generally considered one of slight divergence and elevation, yet it has not been well characterized to date. We aimed to quantify eye position related to the depth of anesthesia using bispectral index (BIS), a derived electroencephalograph parameter.
In this prospective blinded study, we investigated the relationship between BIS, hemodynamic parameters during anesthesia and eye positions in 32 healthy children, mean age 5.4 years, who were undergoing surgical correction for epiblepharon using a standardized anesthetic technique with sevoflurane. BIS and hemodynamic parameters were continuously recorded throughout the procedure: from induction to awakening. Eye positions were video-recorded during surgery and analyzed after surgery at one-minute intervals by the examiner blinded to results of BIS.
There was significant negative correlation between BIS and end-tidal sevoflurane concentrations (p<0.001), and positive correlation between BIS and elevation of the eyes (eye position=0.014xBIS+0.699, p=0.011). Elevation of the eyes (83%) mostly occurred when BIS values reached over 65, while down-shoot eye movement (2%) was seen at BIS values less than 35.
A shallower level of anesthesia, indicated by a higher BIS values was associated with a higher position of the eyes, suggesting that BIS monitoring may be beneficial in predicting eye position. In ophthalmic surgery with particular attention to eye position, the anesthesia depth is recommended to be maintained by monitoring BIS values in range of 35-65.
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