Key result
During general anaesthesia in elderly patients, BIS(XP) and Response Entropy values were within the recommended range of 40-60 for only 45% and 32% of the total time, respectively.
Why the study?
How do Bispectral Index (BIS(XP)) and Entropy values perform and correlate during general anaesthesia in elderly patients undergoing hip fracture repair?
Observational (n=16)
Blinded to monitoring values
How do Bispectral Index (BIS(XP)) and Entropy values perform and correlate during general anaesthesia in elderly patients undergoing hip fracture repair?
In elderly patients undergoing hip fracture repair, BIS and Entropy values frequently indicated deeper than recommended levels of anaesthesia and showed significant discrepancies in a subset of patients.
Suggests frequent excessive depth with standard targets in elderly patients; leaves optimal BIS/Entropy ranges open for prospective validation.
The interaction of many poorly defined, physiological, pharmacological, and pathological factors make titration of general anaesthesia in the elderly difficult. There may be a potential clinical benefit using the processed electroencephalogram (EEG) to monitor hypnotic level in this population. We prospectively studied 16 patients aged over 65 years having hip fractures repaired under general anaesthesia by experienced anaesthetists blinded to Bispectral Index (BIS(XP)) and Entropy values. Pre-induction EEG indices did not correlate with age or mini-mental state examination (MMSE). During maintenance of anaesthesia, BIS(XP) and Response Entropy (RE) values were within the recommended range of 40-60, 45% and 32% of the total time, respectively. BIS(XP) and Response Entropy (RE) values were above 60 for 11% and 13% of the total time, respectively, and below 40 for 44% and 55% of the total time, respectively. BIS(XP) correlated well with RE in 12 patients, but in the other four patients there was a difference of more than 20 points between BIS(XP) and RE.
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Arnold et al. (2007) conducted an observational in Hip fractures requiring repair under general anaesthesia (n=16). Bispectral Index (BIS(XP)) and Response Entropy (RE) monitoring was evaluated on Percentage of total time values were within the recommended range of 40-60. During general anaesthesia in elderly patients, BIS(XP) and Response Entropy values were within the recommended range of 40-60 for only 45% and 32% of the total time, respectively.
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