Effects of midazolam and flumazenilon autonomic nervous activities

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The effect of midazolam and flumazenil on depression of autonomic nervous activities were studied using power spectral analysis of fluctuations in heart rate, cutaneous blood flow and tonometry blood pressure.Healthy young male volunteers participated in two different sessions ; Group M received 0.07 mg/kg of midazolam only, and in Group MFmz, flumazenil 0.3 mg was administered 18 min after the injection of the same dose of midazolam. RR interval was recorded with SRR-5 (GMS Co.), and blood flow at the dorsum manus was measured with a laser doppler flowmeter AFL2 (Advance Co.). The successive analogue data were inputted via an A/D converter into a computer PC-9801BA2 (NEC Co.), and data were divided into subseries of 60 sec. Tonometry blood pressure were recorded with Jentow 7700 (Nihon-Khorin Co.) and analyzed by Autonomic Nervous System Package (Nihon-Khorin Co.). Analysis was carried out by the maximum entropy method (MEM) using MemCalc system (Suwa Trust Co.). Power spectrum densities were separated into four components (0.04-0.4Hz) in RR intervals and tonometry blood pressure, and into six (0.04-2.2Hz) in blood flow.The powers of 0.04-0.4Hz in RR intervals decreased to 27-50% (mean) of the basline value at 5 min in both groups. In Group MFmz, the decreased powers increased to 127-150% at 20 min. As to blood flow, powers of 0.1-0.20Hz decreased to 26-77% of the basline value at 5 min in both groups. In Group MFmz both values increased at 20 min. The same trend was obsewrved in tonometry blood pressure.It is indicated that midazolam depresses mainly the powers of low frequency, which means it depresses sympathetic nervous activity more than parasympathetic activity, and flumazenil antagonizes the depression.