Objective: The aim of this study was to determine the anesthesia-promoting effects of hydroxyzine on electroencephalograms during sevoflurane anesthesia and during propofol anesthesia.
Methods: We analyzed 40 patients scheduled for elective surgery under sevoflurane anesthesia (n = 20) or propofol anesthesia (n = 20). Anesthesia was adjusted at a bispectral index value of 50-60, and then 0.5 mg/kg of hydroxyzine was administered intravenously. We analyzed frontal electroencephalograms before and after hydroxyzine injection with power spectral and bicoherence analyses, which are suitable for assessing the anesthetic depth induced by γ-aminobutyric acid (GABA)ergic anesthetics.
Results: Hydroxyzine increased the α bicoherence peaks in both sevoflurane anesthesia (mean difference, 11.2%; 95% confidence interval (CI), 7.6 to 14.8; P < 0.001) and propofol anesthesia (mean difference, 5.6%; 95% CI, 1.7 to 9.4; P = 0.008). Hydroxyzine increased the averaged δ bicoherence values in both sevoflurane anesthesia (mean difference, 5.5%; 95% CI, 2.1 to 8.8; P = 0.003) and propofol anesthesia (mean difference, 3.9%; 95% CI, 1.0 to 6.8; P = 0.011).
Conclusions: Hydroxyzine enhances both sevoflurane anesthesia and propofol anesthesia probably by facilitation of GABAergic neural circuit mechanisms.
Significance: The findings provide a new insight into the role of histaminergic neurons during general anesthesia in humans.
Keywords: Bicoherence; Electroencephalogram; Hydroxyzine; Propofol; Sevoflurane.
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