Midazolam effectively suppresses sympathetic activation during mental arithmetic task

OBJECTIVES: Dental treatments are frequently accompanied with anxiety, which cause systemic complications related with autonomic nervous disturbances. Intravenous (IV) sedation is useful to mitigate dental stresses. There was no study which compared the anxiolytic or stress mitigating effects during midazolam and propofol sedation. This study was designed to examine whether midazolam or propofol sedation affects autonomic nervous activities during psychological stress and whether these results are accompanied with subjective feelings.

METHODS: Seven healthy volunteers were included in a randomized crossover manner. The subjects rested in a sitting position and heart rate (HR), HR variability (HRV), arterial oxygen saturation (SpO2) and bispectral index (BIS) value were continuously monitored. They were required to perform first mental arithmetic (MA) task for seven minutes as psychological stressor (Test-1). Second MA task was challenged under midazolam (M) or propofol (P) sedation (Test-2). We aimed for OAA/S score 4 and BIS value of 75–85 as sedation level for both groups. HRV was assessed by means of the power spectral analysis (low-frequency (LF), high-frequency (HF) components and LF/HF ratio). Face Anxiety Scale (FAS) was used to grade their feelings as subjective index.

RESULTS: During Test-2, there were no differences in BIS values, SpO2, the number of the answers and the rate of the correct answers between the two groups. HR, LF/HF and normalized unit LF (nuLF) increased, whereas normalized unit HF (nuHF) decreased in both groups. However, the changes in LF/HF, nuLF and nuHF were smaller in the M group and FAS score during Test-2 was also lower in the M group.

CONCLUSIONS: These results suggest that midazolam more effectively suppresses sympathetic activities and anxious feelings for psychological stresses than propofol because of its anxiolytic effect. It is concluded that midazolam may be more appropriate to be used for patients with stronger anxiety against dental treatments.