9 research outputs found

    Propofol EC50 for inducing loss of consciousness in patients under combined epidural-general anesthesia or general anesthesia alone: a randomized double-blind study

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    BackgroundCombined epidural-general anesthesia (GA + EA) has been recommended as a preferred technique for both thoracic and abdominal surgery. The epidural anesthesia on the general anesthetic (GA) requirements has not been well investigated. Therefore, we conducted the present study to explore the predicted effect-site concentration of propofol (Ceprop) required for achieving the loss of consciousness (LOC) in 50% of patients (EC50) with or without epidural anesthesia.MethodsSixty patients scheduled for gastrectomy were randomized into the GA + EA group or GA alone group to receive general anesthesia alone. Ropivacaine 0.375% was used for epidural anesthesia to achieve a sensory level of T4 or above prior to the induction of general anesthesia. The EC50 of predicted Ceprop for LOC was determined by the up–down sequential method. The consumption of anesthetics, emergence time from anesthesia, and postoperative outcomes were also recorded and compared.ResultsThe EC50 of predicted Ceprop for LOC was lower in the GA + EA group than in the GA alone group [2.97 (95% CI: 2.63–3.31) vs. 3.36 (95% CI: 3.19–3.53) μg mL−1, (p = 0.036)]. The consumption of anesthetics was lower in the GA + EA group than in the GA alone group (propofol: 0.11 ± 0.02 vs. 0.13 ± 0.02 mg kg−1 min−1, p = 0.014; remifentanil: 0.08 ± 0.03 vs. 0.14 ± 0.04 μg kg−1 min−1, p < 0.001). The emergence time was shorter in the GA + EA group than in the GA alone group (16.0 vs. 20.5 min, p = 0.013).ConclusionConcomitant epidural anesthesia reduced by 15% the EC50 of predicted Ceprop for LOC, decreased the consumptions of propofol and remifentanil during maintenance of anesthesia, and fastened recovery from anesthesia.Clinical trial registrationClinicalTrials.gov, identifier: NCT05124704

    Detrital zircon provenance record of the Oligocene Zhuhai Formation in the Pearl River Mouth Basin, northern South China Sea

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    The Oligocene Zhuhai Formation has been proven to be one of the main reservoirs in the Pearl River Mouth Basin in the northern South China Sea but its sedimentary provenance remains uncertain and controversial. Here we conducted a systematic study by U-Pb analysis of detrital zircon of the Zhuhai Formation in order to identify the source terrane, investigate the sedimentary source, and establish the framework for the provenance variation during the Oligocene. The study suggests that the detrital zircon in the different structural units reveal marked spatial differences in their age compositions that correlate with the changing sources. The western and eastern parts of the basin have a significantly different provenance manifested by the age compositions of the detrital sediments. The western basin generally has a relatively complex age spectrum and is characterized by a multi-peak distribution, suggesting that the main source was derived from the southern margin of the South China Block. In contrast, the eastern basin displays a dominant population ranging from 131 to 142 Ma, which implies that the sediments were mainly eroded from a nearby source. Our data demonstrate that the Cathaysia Block hinterland and the intrabasinal sources provided dominant provenance contributions to the Pearl River Mouth Basin during the Oligocene. Additionally, Hainan Island and Central Vietnam (eastern Indochina Block) do not appear to have been important sources, whereas Luzon Island and northern Palawan probably provided negligible contributions to the basin during the same time period
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