Propofol EC(50) for inducing loss of consciousness in patients under combined epidural-general anesthesia or general anesthesia alone: a randomized double-blind study

BACKGROUND: Combined 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 (Ce(prop)) required for achieving the loss of consciousness (LOC) in 50% of patients (EC(50)) with or without epidural anesthesia. METHODS: Sixty 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 EC(50) of predicted Ce(prop) 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. RESULTS: The EC(50) of predicted Ce(prop) 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). CONCLUSION: Concomitant epidural anesthesia reduced by 15% the EC(50) of predicted Ce(prop) for LOC, decreased the consumptions of propofol and remifentanil during maintenance of anesthesia, and fastened recovery from anesthesia. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT05124704.