Dexamethasone on postoperative gastrointestinal motility: A placebo-controlled, double-blinded, randomized controlled trial.

BACKGROUND AND AIM: Following abdominal surgery, patients usually experience a transient episode of impaired gastrointestinal motility. This study aimed to determine whether a single preoperative dose of dexamethasone can promote the recovery of gastrointestinal function in patients following elective gastrointestinal surgery. METHODS: In this single-center, two-arm, parallel, randomized controlled trial, we studied 126 patients (aged 18-80 years) who underwent elective open or laparoscopic bowel surgery for malignant or benign pathology. At the induction of anesthesia, a treatment group (n = 64) received a single dose of 8-mg intravenous dexamethasone, and a control group (n = 62) received normal saline. RESULTS: Intravenous administration of 8-mg dexamethasone significantly decreased the time to return of flatus by an average of approximately 8 h (P < 0.05). Abdominal distension was significantly reduced on the third day after surgery in the dexamethasone group (P < 0.05), and the time to tolerance of a liquid diet was shorter in the dexamethasone group (P < 0.01). There were no significant differences in other secondary outcomes, including postoperative pain, complication rates, length of hospital stay, or time to first defecation, between the two groups. CONCLUSIONS: A single intravenous dose of 8-mg dexamethasone at induction of anesthesia significantly decreases the time to return of flatus, improves abdominal distension at 72 h, and promotes tolerance of a liquid diet. Although further studies are required to confirm our results, we recommend that dexamethasone should be used more widely in gastrointestinal surgery.

Distributed Dynamic Event-Triggered Consensus Protocol for General Linear Multiagent Systems Without Accurate System Information.

This study focuses on distributed event-triggered consensus control under the scenario where only inaccurate agent model information is available. By designing a novel triggering error, a distributed dynamic event-triggered consensus (DETC) protocol is proposed for multiagent systems (MASs) with general linear dynamics over digraphs, without accurate a priori information of agent models. To improve the efficiency of the dynamic triggering law, a mixed triggering threshold is designed with a resilient function integrated to further enlarge interevent intervals. Within the proposed DETC protocol, the computational cost is significantly reduced especially for MASs with nonsparse and high-dimensional agent system matrices. In addition, for each individual agent, the states of neighboring agents used for triggering detections or controller updates are required in an on-demand (instead of continuous) way, which preserves communication resources and facilitates practical implementation. The feasibility of the designed DETC protocol is corroborated by rigorous theoretical analysis on consensus convergence and Zeno behavior exclusion. Finally, simulations are shown to demonstrate the effectiveness of the studied theory.

Nonsingular fixed-time attitude coordinated tracking control for multiple rigid spacecraft.

This paper investigates the problem of fixed-time attitude coordinated control for multi-spacecraft systems with unknown external disturbance. Firstly, a distributed fixed-time observer is introduced to estimate the states of the virtual leader. The observer can track the leader completely in a fixed time without dependence on the initial conditions of the leader and observer. Then, we propose a novel nonsingular fixed-time sliding mode tracking controller to address the fixed-time attitude tracking problem. It is noteworthy that the requirement on initial conditions of spacecraft is removed in the proposed nonsingular sliding mode controller. Due to the robustness of sliding mode control, the influence of external disturbance can be eliminated, such that each spacecraft can track desired attitude trajectories precisely in a fixed time. Hence, the fixed-time attitude coordination for multiple spacecraft can be achieved. Finally, numerical simulation results and comparisons reveal the effectiveness of the proposed algorithms.