Objective:To evaluate the effect of small-dose furosemide on tissue edema after shoulder arthroscopy.Methods:A total of 368 patients of either sex, aged 18-65 yr, of American Society of Anesthesiology physical status Ⅰ orⅡ, were divided into 2 groups ( n=184 each) by a random number table method: control group (group C) and small-dose furosemide group (group F). A posterior approach to interscalene brachial plexus block was selected, tracheal intubation was performed under general anesthesia, and all the patients were placed in the lateral position.At 20-30 min before the end of surgery, patients in group F received intravenous injection of furosemide 2 mg (diluted to 2 ml in normal saline) and patients in group C received intravenous injection of normal saline 2 ml.The tissue thickness from the surface of the second rib of the middle clavicular line to the skin (CR2) was measured by ultrasound immediately after nerve block (T 0), immediately after tracheal intubation (T 1), immediately after the end of operation (T 2), and at 30 min and 1, 4 and 8 h after operation (T 3-6). Arterial blood gas analysis was performed at T 1-3, Hct and blood glucose concentration were measured simultaneously, and relative blood volume was calculated.Tube malposition at T 2 and hypoxemia within 30 min after operation were recorded. Results:Compared with the baseline at T 0, CR2 on the affected side was significantly increased at T 2-5 in group F, and CR2 on the affected side was significantly increased at T 2-6 in group C ( P<0.05). CR2 at T 2-5 was significantly higher on the affected side than on the healthy side ( P<0.05). Compared with group C, intraoperative urine volume was significantly increased, CR2 was decreased at T 2-5, the incidence of tube malposition and hypoxemia was decreased ( P<0.05), and no significant changes were found in pH value, PaO 2, PaCO 2, Na + , K + , Ca 2+ , Cl -, blood glucose concentration or relative blood volume at each time point in group F ( P>0.05). Conclusion:Small-dose furosemide can reduce tissue edema after shoulder arthroscopy and decrease the occurrence of postoperative tube malposition and hypoxemia, without causing disturbances in the internal environment.