OBJECTIVE:The optimal strategy for fluid management during gastrointestinal surgery remains unclear. Minimizing the variation in arterial pulse pressure, which is induced by mechanical ventilation, is a potential strategy to improve postoperative outcomes. We tested this hypothesis in a prospective, randomized study with lactated Ringer's solution and 6% hydroxyethyl starch solution.METHOD:A total of 60 patients who were undergoing gastrointestinal surgery were randomized into a restrictive lactated Ringer's group (n = 20), a goal-directed lactated Ringer's group (n = 20) and a goal-directed hydroxyethyl starch group (n = 20). The goal-directed fluid treatment was guided by pulse pressure variation, which was recorded during surgery using a simple manual method with a Datex Ohmeda S/5 Monitor and minimized to 11% or less by volume loading with either lactated Ringer's solution or 6% hydroxyethyl starch solution (130/0.4). The postoperative flatus time, the length of hospital stay and the incidence of complications were recorded as endpoints.RESULTS:The goal-directed lactated Ringer's group received the greatest amount of total operative fluid compared with the two other groups. The flatus time and the length of hospital stay in the goal-directed hydroxyethyl starch group were shorter than those in the goal-directed lactated Ringer's group and the restrictive lactated Ringer's group. No significant differences were found in the postoperative complications among the three groups.CONCLUSION:Monitoring and minimizing pulse pressure variation by 6% hydroxyethyl starch solution (130/0.4) loading during gastrointestinal surgery improves postoperative outcomes and decreases the discharge time of patients who are graded American Society of Anesthesiologists physical status I/II.

In patients undergoing supratentorial tumor resection, goal-directed HES therapy was not superior to goal-directed LR therapy for brain relaxation or cerebral metabolism, although less fluid was needed to maintain the target SVV in the HES-based group than in the LR-based group.

UAVs-SfM (unmanned aerial vehicles-structure-from-motion) systems can generate high-resolution three-dimensional (3D) topographic models of aeolian landforms. To explore the optimization of UAVs-SfM for use in aeolian landform morphodynamics, this study tested flight parameters for two contrasting aeolian landform areas (free dune and blowout) to assess the 3D reconstruction accuracy of the UAV survey compared with field point measurements using differential RTK-GPS (real-time kinematic-global positioning system). The results reveal the optimum UAVs-SfM flight setup at the free-dune site was: flying height ¼ 74m, camera tilt angle ¼ À90°, photograph overlap ratio ¼ 85%/70% (heading/sideways). The horizontal/vertical location error was around 0.028-0.055m and 0.053-0.069m, respectively, and a point cloud density of 463/m 3 was found to generate a clear texture using these flying parameters. For the < 20m deep blowout the optimum setup with highest accuracy and the lowest cliff texture distortion was: flying height ¼ 74m combined camera tilt angle ¼ À90°and À60°, photograph overlap ratio ¼ 85%/70% (heading/ sideways), and an evenly distributed GCPs (ground control points) density of 42/km 2 using these flying parameters. When the depth of the blowouts exceeded 40m, the optimum flight/survey parameters changed slightly to account for more challenging cliff texture generation: flying height ¼ 80m (with À90°and À60°combined camera tilt angle), GCPs density ¼ 63/km 2 to generate horizontal and vertical location error of 0.024m and 0.050m, respectively, and point cloud density of 2597.11/m 3. The main external factors that affect the successful 3D reconstruction of aeolian landforms using UAVs-SfM are the weather conditions, manipulation errors, and instrument system errors. The UAVs-SfM topographic monitoring results demonstrate that UAVs provide a viable and robust means for aeolian landform morphodynamics monitoring. Importantly, the rapid and high precision 3D reconstruction processes were significantly advanced using the optimal flight parameters reported here.

No abstract