Before beginning, the study was approved by the Institutional Review Board of Kaohsiung Chang Gung Memorial Hospital (IRB number: 201800207B0). Informed consent was waived because of the retrospective nature of the study. All methods were performed in accordance with the relevant guidelines and regulations. We retrieved anesthesia records from May 1st, 2017 to Aug 31st, 2017, from the hospital’s database, and a total of 13,027 general anesthesia records were collected. Exclusion criteria included ambulatory surgeries, sedated endoscopy, pediatric surgeries, a limited number of uncommon procedures (case numbers less than 50), and any record with missing data. Recruited patients received either sevoflurane or desflurane as their primary general anesthetic. The general anesthesia was carried out in semiclosed circuit with fresh gas flow of 1 L/min. The anesthesia machines automatically record the consumption of volatile anesthetics at the conclusion of anesthesia. Hourly consumption was calculated depending on the volatile anesthetics consumption and the total anesthesia time. Postoperative daily visit was performed by the well-trained nurse anesthetists and the postoperative events within 72 h including intraoperative awareness, headache or dizziness, postoperative nausea and vomiting, respiratory event, cerebrovascular event, and patients’ satisfaction were recorded.
We divided patients into two major groups as the BIS-guided anesthesia group and the standard anesthesia practice group, and these two groups formed the basis for comparing the consumption of volatile anesthetics in different patients. To elucidate the effect of anesthesia time in these two major groups, we allocated patients according to anesthesia time, namely 2-h, 4-h, 6-h, 8-h, and 10-h. To elucidate the effect of age on the consumption of volatile anesthetics in these two major groups, we stratified patients into four age groups, 21–40 years, 41–60 years, 61–80 years, and over 80 years for comparison.
As a standard practice in our hospital, general anesthesia was induced with propofol (1 to 2 mg/kg). The use of rocuronium (1 mg/kg) or cis-atracurium (0.2 mg/kg), fentanyl (1 mcg/kg) or alfentanil (10 mcg/kg), desflurane (1 to 1.3 MAC) or sevoflurane (1 to 1.3 MAC) depends on the anesthesiologists’ preferences. Nitrous oxide, midazolam or other amnestic drugs except propofol was not used in induction and maintenance of general anesthesia in our study. The patient decided whether or not to utilize BIS-guided anesthesia. In the BIS-guided group, the BIS score was kept in the range of 40 to 60 during anesthesia. In the standard anesthesia practice group, volatile anesthetics were titrated against blood pressure and heart rate changes during anesthesia to maintain stable blood pressure and heart rate within 20% of the patient’s normal range. A fresh gas flow of 50% oxygen with air was kept to 1 L/min. Maintenance of neuromuscular blocking agents or opioids depended on surgical stimulus, anesthesiologists’ preferences, and objective vital signs (more than 20% increase in heart rate, systolic blood pressure and mean arterial pressure). The total consumption of volatile anesthetics was automatically recorded by the anesthesia machine Avance (GE Datex-Ohmeda, Madison, WI), S/5 ADU(GE Datex-Ohmeda, Madison, WI), Carestation 620 (GE Datex-Ohmeda, Madison, WI), or Primus (Drägerwerk, AG, Lübeck, Germany).
We divided patients into two major groups as the BIS-guided anesthesia group and the standard anesthesia practice group, and these two groups formed the basis for comparing the consumption of volatile anesthetics in different patients. To elucidate the effect of anesthesia time in these two major groups, we allocated patients according to anesthesia time, namely 2-h, 4-h, 6-h, 8-h, and 10-h. To elucidate the effect of age on the consumption of volatile anesthetics in these two major groups, we stratified patients into four age groups, 21–40 years, 41–60 years, 61–80 years, and over 80 years for comparison.
As a standard practice in our hospital, general anesthesia was induced with propofol (1 to 2 mg/kg). The use of rocuronium (1 mg/kg) or cis-atracurium (0.2 mg/kg), fentanyl (1 mcg/kg) or alfentanil (10 mcg/kg), desflurane (1 to 1.3 MAC) or sevoflurane (1 to 1.3 MAC) depends on the anesthesiologists’ preferences. Nitrous oxide, midazolam or other amnestic drugs except propofol was not used in induction and maintenance of general anesthesia in our study. The patient decided whether or not to utilize BIS-guided anesthesia. In the BIS-guided group, the BIS score was kept in the range of 40 to 60 during anesthesia. In the standard anesthesia practice group, volatile anesthetics were titrated against blood pressure and heart rate changes during anesthesia to maintain stable blood pressure and heart rate within 20% of the patient’s normal range. A fresh gas flow of 50% oxygen with air was kept to 1 L/min. Maintenance of neuromuscular blocking agents or opioids depended on surgical stimulus, anesthesiologists’ preferences, and objective vital signs (more than 20% increase in heart rate, systolic blood pressure and mean arterial pressure). The total consumption of volatile anesthetics was automatically recorded by the anesthesia machine Avance (GE Datex-Ohmeda, Madison, WI), S/5 ADU(GE Datex-Ohmeda, Madison, WI), Carestation 620 (GE Datex-Ohmeda, Madison, WI), or Primus (Drägerwerk, AG, Lübeck, Germany).
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