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BIS monitoring in ICU: advantages of the new XP generation


Bispectral Index (BIS) has been used to measure the level of sedation in critically ill patients [1]. The biggest problems were the artefacts raising from facial muscle or eye movements, and the wide variability of analysed clinical conditions [2]. BIS-XP is a new available device (Aspect, USA), with one more frontal electrode, that should minimise the movement related artefacts. The aim of our study was to compare the new and the old BIS measurement on the same patient in ICU.

Materials and methods

Thirty critically ill patients, admitted to our intensive care unit, were studied. Head-trauma patients were excluded. SAPS II and Ramsay Sedation Scale (RSS) were used to assess physiological impairment and sedation depth. Sedative agents were administered at the following maintenance doses: Propofol (1-3 mg/kg/hour) and Midazolam (0.025-0.033 mg/kg/hour), to achieve a sedation level of 3-4. Sufentanil was administrated (0.01-0.02 µg/kg/min), as needed, to ensure analgesia. Every patient was simultaneously monitored with both the BIS and the BIS-XP, along a period of 3-6 hours. BIS values were continuously recorded and their variations after painful stimuli were relieved.


Both systems well correlated with the level of sedation in every single patient. The BIS-XP was able to eliminate anecdotal rise in BIS value unrelated with depth modifications. Higher variability in BIS monitoring made the range wider than in BIS-XP (coefficient of variation 72% vs 55%). After painful stimuli, BIS-XP was shown to record variations with a mean advance of 42 s (30-67 s), compare to BIS (both BIS and BIS XP have been set with the same smoothing rate). Progress in electrode fixation on the skin were observed with BIS-XP, avoiding repeated installation and allowing long-term monitoring. Sedation level oscillations, undetected by BIS, were revealed by BIS-XP value variations.


The BIS-XP showed sedation monitoring improvement. The added electrode in BIS-XP was likely to improve the number validity, by eliminating patient related artefacts, though the higher sensitivity makes the BIS-XP trend less stable than the BIS one. Moreover the advance in relieving depth variations could be an useful improvement in guiding the administration of sedative-hypnotic agents to titrate adequate sedation.


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  2. Walder B, et al: Intensive Care Med. 2001, 27: 107-114. 10.1007/s001340000761.

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Coluzzi, F., Di Filippo, C., Rossetti, E. et al. BIS monitoring in ICU: advantages of the new XP generation. Crit Care 6 (Suppl 1), P68 (2002).

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