Kaki Abdullah M, Almarakbi Waleed A
Department of Anesthesia, Faculty of Medicine, King Abdulaziz University Hospital, PO Box 2907, Jeddah 21461, Saudi Arabia.
Anesth Analg. 2009 Dec;109(6):1843-6. doi: 10.1213/ANE.0b013e3181bce58d.
Bispectral index (BIS) was developed to monitor patients' level of consciousness under general anesthesia. Several factors have been found to alter BIS readings without affecting the depth of anesthesia. We conducted a study to assess the impact of changing patients' position on BIS readings.
General anesthesia was administered to 40 patients undergoing minor surgeries. Patients were kept in neutral position (supine) for 15 min and BIS readings, mean arterial blood pressure, heart rate, end-tidal carbon dioxide, and end-tidal isoflurane were recorded. Patients were then shifted to head-down position (30 degrees), neutral position, and lastly head-up position (30 degrees) each of 15-min duration and the data were recorded.
There was a significant increase in BIS values in head-down position (median 47 vs 40) compared with neutral position, whereas head-up position significantly decreased BIS (39 vs 41) compared with neutral position (P < 0.05).
Changing a patient's position significantly affects the BIS values, which might affect the interpretation of anesthetic depth.
双谱指数（BIS）用于监测全身麻醉下患者的意识水平。已发现多种因素可改变BIS读数，而不影响麻醉深度。我们开展了一项研究，以评估改变患者体位对BIS读数的影响。
对40例行小手术的患者实施全身麻醉。患者保持中立位（仰卧位）15分钟，记录BIS读数、平均动脉压、心率、呼气末二氧化碳分压和呼气末异氟醚浓度。然后将患者依次转为头低位（30度）、中立位，最后转为头高位（30度），每个体位持续15分钟，并记录数据。
与中立位相比，头低位时BIS值显著升高（中位数47对40），而与中立位相比，头高位时BIS值显著降低（39对41）（P<0.05）。
改变患者体位会显著影响BIS值，这可能会影响对麻醉深度的判断。
