Background: Norepinephrine infusion has been suggested as an effective method for preventing hypotension during spinal anaesthesia for Caesarean delivery. However, optimal dosing regimens for norepinephrine have not been well established. This study aimed to determine the doseeresponse characteristics of a weight-adjusted fixed-rate infusion of norepinephrine to prevent hypotension during neuraxial anaesthesia for Caesarean delivery. Methods: In a double-blind, randomised controlled trial, 80 parturients having elective Caesarean delivery received a prophylactic norepinephrine infusion at 0.025 mg kg À1 min À1 (Group N1), 0.05 mg kg À1 min À1 (Group N2), 0.075 mg kg À1 min À1 (Group N3), or 0.10 mg kg À1 min À1 (Group N4), starting immediately after induction of combined spinaleepidural anaesthesia.The primary outcome was non-occurrence of hypotension, defined as a decrease in systolic arterial pressure !20% below baseline value or to 90 mm Hg, before delivery. Values for 50% effective dose (ED 50 ) and ED 90 were calculated using probit regression. Results: The incidence of hypotension was 11/20 (55%), 6/20 (30%), 2/20 (10%), and 1/20 (5%) in Groups N1, N2, N3, and N4, respectively (P<0.0001). The ED 50 and ED 90 (95% confidence interval) of norepinephrine infusions for preventing hypotension were 0.029 (e0.002 to 0.043) and 0.080 (0.065e0.116) mg kg À1 min À1 , respectively. The incidence of reactive hypertension increased with increasing norepinephrine dose (P¼0.002). Other adverse effects were similar among groups.Conclusions: Under the conditions of this study, an infusion of norepinephrine 0.08 mg kg À1 min À1 was effective for preventing hypotension in 90% of patients. This information should provide a guide for initiating norepinephrine infusions. Clinical trial registration: ChiCTR1900022322 at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/enindex.aspx).

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Dexmedetomidine (Dex), a highly selective α2 receptor agonist can inhibit excessive inflammatory reaction and. In this study, we will investigate the effects of Dex can protect against intestinal mucosal barrier injury in patients via inhibiting intestinal inflammatory responses. This is a double-blinded randomized placebo-controlled trial. Ninety-four patients with acute intestinal obstruction, aged 33-81 years of age, weighing 48-80 kg, and having American Society of Anesthesiology physical status II or III, were divided into 2 groups using a random number table method (Con versus Dex). Patients in Dex were intravenously injected with in a loading dose of 0.5 μg/kg at 15 min before the induction of general anesthesia followed an infusion at 0.3 μg/kg/h until 30 min before the end of the operation. Before infusing the loading dose of Dex at 1, 3, and 7 d after surgery, peripheral venous blood samples were collected to measure the concentrations of diamine oxidase (DAO), D-lactic acid (D-Lac), bacterial endotoxin (BT), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The occurrence of postoperative complications, anal exhaust time and average length of hospital stay were recorded. Compared with those in Con, the levels of DAO, D-Lac, BT, TNF-α and IL-6 in Dex were significantly decreased at 1 and 3 days after surgery (P<0.05), and anal exhaust time and total incidence of complications were decreased in Dex (P<0.05). General anesthesia combined with Dex can improve hypoxic intestinal mucosal injury, possibly by inhibiting inflammatory response.