Midazolam hydrochloride, a water-soluble benzodiazepine for intravenous injection, is frequently used to provide sedation to mechanically ventilated patients in the critical-care unit. Although the effects of midazolam on the electroencephalograms (EEGs) of healthy volunteers have been reported previously, to our knowledge such effects in ill patients have not been documented. Herein we describe the effects of intravenously administered midazolam on the EEGs of eight seriously ill patients (age range, 49 to 80 years; mean, 69 years). The EEGs showed drug-induced relatively fast (alpha or beta) frequency activity superimposed on delta slowing in six patients and mild to moderate voltage attenuation in three patients. An alpha frequency coma pattern, a transient burst-suppression pattern, and a spindle coma pattern were also seen. Thus, the effects of intravenously administered midazolam on the EEGs of seriously ill patients are similar to those noted after the administration of other benzodiazepines. These potential effects should be considered when their EEG tracings are interpreted.
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