Extra-corporeal membrane oxygenation for refractory cardiogenic shock after adult cardiac surgery:a systematic review and meta-analysis

Background - Postcardiotomy cardiogenic shock (PCCS) refractory to inotropic support and intra-aortic balloon pump (IABP) occurs rarely but is almost universally fatal without mechanical circulatory support. In this systematic review and meta-analysis we looked at the evidence behind the use of veno-arterial extra-corporeal membrane oxygenation (VA ECMO) in refractory PCCS from a patient survival rate and determinants of outcome viewpoint. Methods - A systematic review was performed in January 2017 using PubMed (with no defined time period) using the keywords “postcardiotomy”, “cardiogenic shock”, “extracorporeal membrane oxygenation” and “cardiac surgery”. We excluded papers pertaining to ECMO following paediatric cardiac surgery, medical causes of cardiogenic shock, as well as case reports, review articles, expert opinions, and letters to the editor. Once the studies were collated, a meta-analysis was performed on the proportion of survivors in those papers that met the inclusion criteria. Meta-regression was performed for the most commonly reported adverse prognostic indicators (API). Results - We identified 24 studies and a cumulative pool of 1926 patients from 1992 to 2016. We tabulated the demographic data, including the strengths and weaknesses for each of the studies, outcomes of VA ECMO for refractory PCCS, complications, and APIs. All the studies were retrospective cohort studies. Meta-analysis of the moderately heterogeneous data (95% CI 0.29 to 0.34, p 70 years, 95% CI −0.057 to 0.001, P = 0.058), and long ECMO support (95% CI −0.068 to 0.166, P = 0.412). Postoperative renal failure, high EuroSCORE (>20%), diabetes mellitus, obesity, rising lactate whilst on ECMO, gastrointestinal complications had also been reported. Conclusion - Haemodynamic support with VA ECMO provides a survival benefit with reasonable intermediate and long-term outcomes. Many studies had reported advanced age, renal failure and prolonged VA ECMO support as the most likely APIs for VA ECMO in PCCS. EuroSCORE can be utilized to anticipate the need for prophylactic perioperative VA ECMO in the high-risk category. APIs can be used to aid decision-making regarding both the institution and weaning of ECMO for refractory PCCS

The effect of nozzle geometry on the behavior of saline effluent discharged in an inclined submerged form with an angle of 60 ͦ

In recent decades, the increase in desalination plant construction along coastlines due to climate change and fresh water resource depletion has been a major concern. The discharge of concentrated wastewater directly into the sea has been shown to cause irreversible damage to the environment. Therefore, the use of appropriate dischargers is crucial in reducing the negative environmental effects of this waste. In this study, ANSYS-FLUENT software was used to simulate the behavior of condensed effluent discharged from circular, triangular, and diamond nozzles. To investigate the effect of nozzle geometry, diamond and triangle nozzles with different dimensions (triangle 1, triangle 2, diamond 1, and diamond 2) were modeled. The effluent was discharged obliquely at a discharge angle of 60 degrees to the horizon in both static and dynamic water environments. The K-ε turbulence model (RNG) was employed for modeling, and the results were validated by comparison with experimental data. The results showed that the height of the maximum jet ascent and the horizontal distance of the point of impact of the effluent with the ground decrease, while the dilution rate of the effluent increases as it leaves the nozzle in a sheet. Moreover, the results indicated that the spreading rate at the inner edge of the jet is lower than that at the outer edge of the jet due to the presence of the bed and the Coanda effect. However, the nozzle geometry was found to have no effect on the reduction of concentration in the center line of the jet. The use of diamond 2 and triangle 2 nozzles for the discharge of concentrated wastewater was found to reduce environmental damage. The findings of this study provide insight into the design of appropriate dischargers for desalination plants and highlight the importance of considering environmental impacts when discharging waste water

Effect of background turbulence on an axisymmetric turbulent jet

AbstractThe effect of different levels of background turbulence on the dynamics and mixing of an axisymmetric turbulent jet at different Reynolds numbers has been investigated. Approximately homogeneous and isotropic background turbulence was generated by a random jet array and had a negligible mean flow (${\langle {U}_{\alpha } \rangle }/ {u}_{\alpha \mathit{rms}} \ll 1$). Velocity measurements of a jet issuing into two different levels of background turbulence were conducted for three different jet Reynolds numbers. The results showed that the mean axial velocities decay faster with increasing level of background turbulence (compared with a jet in quiescent surroundings), while the mean radial velocities increase, especially close to the edges of the jet. Furthermore, the axial root-mean-square velocities of the jet increased in the presence of background turbulence, as did the jet’s width. However, the mass flow rate of the jet decreased, from which it can be inferred that the entrainment into the jet is reduced in a turbulent background. The effect of background turbulence on the entrainment mechanisms is discussed.</jats:p