Use of the Bispectral Index to Predict Eye Position of Children during General Anesthesia

Abstract

Purpose: To assess the relationship between eye position and anesthesia depth using the bispectral index (BIS) value, a parameter derived from electroencephalography data.

Methods: We investigated the relationship between BIS value and eye position in 32 children who underwent surgery for epiblepharon under general anesthesia. BIS values were recorded continuously throughout the procedure (from induction to awakening). Eye positions were video-recorded and analyzed after surgery. The vertical position of each eye was scored according to its height in relation to the medial canthus. An eye position in which the upper eyelid covered one-third of the cornea was defined as a significant ocular elevation.

Results: The BIS value correlated inversely with the end-tidal concentration of each anesthetic agent, whereas it correlated positively with the eye elevation score (eye position = 0.014 × BIS + 0.699, p = 0.011). The mean eye position score was significantly greater in patients whose BIS values were over 65. Eleven patients (34.4%) had significant ocular elevation; their mean concurrent BIS value was 61.6. Two of these patients had elevation during surgery and 9 had elevation during emergence from anesthesia.

Conclusions: We found that high BIS values were correlated with low levels of anesthetic concentration and high eye position, suggesting that BIS monitoring may be useful for predicting eye position during anesthesia. Particular attention must be given to eye position during ophthalmic surgery. Anesthesia depth can be maintained by assuring that the BIS value remains below 65.

Keywords: Bispectral index; Depth of anesthesia; Electrophysiology; Eye position; General anesthesia.

Conflict of interest statement

No potential conflict of interest relevant to this article was reported.

© 2018 The Korean Ophthalmological Society.

Figures

Fig. 1. Method used to score eye position (height) in relation to the medial canthus indicated with a yellow arrow. (A) A positive value indicates a superior position and a negative value indicates an inferior position. (B) A higher eye position in relation to the medial canthus is assigned a higher eye position score. A 15-mm circular tape was used as a reference to score eye position in this analysis.

Fig. 2. Linear regression analysis of eye position and bispectral index (BIS) value (eye position = 0.014 × BIS + 0.699, r = 0.181, p = 0.011).

Fig. 3. Boxplot of eye position scores in the 5 different bispectral index (BIS) groups. Central bars indicate medians, boxes indicate interquartile ranges, and whiskers indicate highest and lowest values. *p < 0.05 based on post-hoc analysis using one-way analysis of variance.