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The effects of midazolam on the EEG during sedation of critically ill patients
Author(s) -
VESELIS R. A.,
REINSEL R.,
MARINO P.,
SOMMER S.,
CARLON G. C.
Publication year - 1993
Publication title -
anaesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.839
H-Index - 117
eISSN - 1365-2044
pISSN - 0003-2409
DOI - 10.1111/j.1365-2044.1993.tb07063.x
Subject(s) - sedation , midazolam , medicine , anesthesia , mechanical ventilation , critically ill , sedative , electroencephalography , hypnotic , intensive care medicine , psychiatry
Summary Patients who require mechanical ventilation are often sedated with midazolam. As clinical signs of sedation are often confusing or nonexistent, and there are few adverse side effects when large doses are infused over a period of days, substantial drug accumulation can result in these critically ill patients, despite the short half‐life of midazolam. An objective monitor of sedation would help maintain sedation at a constant level despite changing pharmacokinetic values in patients. We undertook this study to describe the electroencephalographic changes which occur with intravenous midazolam in critically ill patients, and to determine if a relationship exists between these changes and the depth of sedation as measured using a clinical scoring method. A series of 31 critically ill patients who required intravenous midazolam during mechanical ventilation were studied. Four different levels of sedation were defined ranging from execution of verbal commands to no response to suctioning through the tracheal tube or sternal rub. Electroencephalographic recordings were obtained in patients on a daily basis and a concurrent sedation level was determined. High frequency electroencephalogram activity decreased as sedation level increased. This was reflected in decreases in the spectral edge (17.61 to 10.56 Hz (p = 0.0024)), the median frequency (4.27 to 2.56 Hz (p = 0.0278)), and the logarithm of the absolute power in the beta, (p = 0.0012), and beta 2 (p < 0.0001) bands. An incidental finding of asymmetry in power between right and left frontal electrodes was observed, with right‐sided power being 9–18% greater (p < 0.001). This form of monitoring of midazolam sedation in critically ill patients, which may allow better discrimination of different sedation levels than clinical examination alone, may be useful in guiding administration of midazolam to produce a constant sedative effect. Changes in electroencephalogram power, a useful sign of cerebral ischaemia, may be affected by the use of midazolam, which appears to cause asymmetry in power.