Clinical outcome of intraoperative hemodialysis using a hemoconcentrator during cardiopulmonary bypass for dialysis-dependent patients.

OBJECTIVES: The basic materials and structure of a hemoconcentrator incorporated into cardiopulmonary bypass (CPB) circuits are similar to those of hemodialyzers. Gravity drainage hemodiafiltration (GHDF) is an easy-to-use intraoperative renal replacement therapy (RRT) that utilizes a hemoconcentrator. This study aimed to verify whether GHDF can correct electrolyte imbalance and remove uremic toxins in dialysis-dependent patients and to evaluate the clinical outcomes of GHDF by comparing it with a conventional method of dilutional ultrafiltration (DUF). METHODS: This study retrospectively compared perioperative clinical values of 41 dialysis-dependent patients (21 patients with GHDF and 20 patients with DUF) who underwent open-heart surgery. Changes in serum parameters before and after passing through the hemoconcentrator were also compared. RESULTS: Compared to DUF, GHDF significantly lowered potassium, blood urea nitrogen, and creatinine levels at the outflow of the hemoconcentrator. Less catecholamine was needed to wean CPB in GHDF than in DUF. The P/F ratio (arterial blood oxygen pressure/inhaled oxygen concentration) at the end of surgery was significantly higher in GHDF than in DUF (450.8 ± 149.7 vs. 279.3 ± 153.5; p < 0.001). Postoperative intubation time was shorter in GHDF than in DUF (8.3 ± 5.9 vs. 18.7 ± 16.1 h; p = 0.006). The major morbidity and mortality rates were comparable in both groups. CONCLUSIONS: GHDF removed both potassium and uremic toxins more efficiently than DUF in dialysis-dependent patients. Less catecholamine was needed to wean CPB using GHDF. It improved the immediate postoperative respiratory function and enabled earlier extubation. GHDF is a novel and effective option for intraoperative RRT in dialysis-dependent patients undergoing open-heart surgery.

Procedures Never Explained in Textbooks: How to Correctly Convert a Closed-Suction Drain to a Closed-Gravity Drain, and How to Correctly Remove a Closed-Suction Drain Off Suction.

Objective: To describe a novel method to convert a closed-system suction drain to a highly efficient closed-system gravity-dependent drain and demonstrate its efficacy in an ex-vivo model. Methods: We reviewed the 5 top-selling urology and surgery text/reference books for information on drainage systems. An ex-vivo model was designed with a reservoir of fluid connected to a Jackson-Pratt bulb drain. We measured the volume of fluid drained from the reservoir into the bulb while on-suction and off-suction. This was repeated using a novel modified bulb, where the bulb's outflow stopper was replaced with a one-way valve oriented to allow release of pressure from the bulb. Results: With the bulb on-suction, drainage was maintained regardless of the height of the drain relative to the reservoir. With the bulb off-suction, closed passive gravity-dependent drainage occurred only when the drain was below the fluid reservoir; drainage ceased at minimal volumes. With addition of a one-way valve and maintenance of the bulb below the level of the reservoir, drainage proceeded to completion. Conclusion: How surgical drains work is not described in the leading urology and general surgery textbooks/reference books. Closed-system suction drains cannot be used to achieve passive gravity-dependent drainage without allowing release of displaced air from the bulb-lumen. The novel modified drain we describe affords reversible closed-system suction and passive drainage.

Impact of influent deviations on polymer coagulant dose in warm lime softening of synthetic SAGD produced water.

Warm lime softening is commonly used to reduce hardness, silica, and a small fraction of organic matter from steam-assisted gravity drainage (SAGD) produced water through the addition of lime, soda ash, MgO, coagulant and flocculant. We report a systematic study on the impact of solution chemistry on the epichlorohydrin-dimethylamine coagulant demand for the treatment of synthetic SAGD produced water. Concentrations of magnesium, calcium, sodium bicarbonate, clay (mimicking suspended solids), sodium metasilicate (representing silica), and humic acid (mimicking dissolved organic matter) were varied to study their impact on coagulant demand. The impact of the concentration of lime, soda ash, and MgO on coagulant demand was also studied. Within the studied concentration range, the coagulant dose increased linearly with increasing concentration of humic acid (Ycoagulant = 29 + 0.703XHA) and silica (Ycoagulant = 52 + 0.537Xsilica), and increased slightly with increasing concentration of lime and soda ash, but remained almost unchanged with increasing concentration of dissolved hardness, clay, or MgO. The observations were correlated to the understanding of the electrokinetic properties of CaCO3 and Mg(OH)2 particles in lime softening. The findings provide insights for evaluating onsite coagulant dose and optimizing the process.

A steam injection distribution optimization method for SAGD oil field using LSTM and dynamic programming.

Steam injection distribution optimization refers to the process of distributing steam injection in steam assisted gravity drainage (SAGD) oil field to maximize the total oil production. A novel optimization method that integrates long short-term memory (LSTM) neural network and dynamic programming is presented in this paper to solve the steam injection distribution optimization problem for the first time. In the proposed method, LSTM is used to construct the prediction model to predict oil production of the wells. With the prediction result, dynamic programming optimizes steam injection distribution in the oil field to maximize total oil production. Convergence stability and computational complexity of the dynamic programming method have been analyzed and presented in this research. A web-based geographical information system called Petroleum Explorer is also developed based on the proposed method. Experiments on two pads of a real-world SAGD project demonstrate that LSTM model gives better prediction result than other five existing models and production improvement of the proposed method is highly related to parameter setting of the optimization process.

Bayesian biclustering by dynamics: Algorithm testing, comparison against random agglomeration, and calculation of application specific prior information.

Bayesian Biclustering by Dynamics (BBCD) is a new clustering algorithm for Steam-Assisted Gravity Drainage (SAGD) oil recovery time series data [1]. In this companion paper the BBCD algorithm is tested on synthetic data, demonstrating use of the algorithm, as well as its robustness, and performance accuracy against Random Agglomeration. Supplementary information includes formulae to calculate analytical steam and oil volume data used as background knowledge for the SAGD application. Advantages of the BBCD algorithm are listed below. •It includes background knowledge directly into the clustering process.•It finds similarity between series and over time.•It allows a user-specified definition for behaviour of interest, which relaxes dependency on series shape. This is important when similar behavioural events do not necessarily occur in the same temporal order.

The flow of thin liquid layers on circular cylinders.

The time evolution of a coating layer of liquid on an inclined circular cylindrical substrate is studied experimentally and theoretically. For small-diameter cylinders, the motion of Newtonian liquids, driven by the combined influences of surface tension and gravity, is analyzed using the long-wave or "lubrication" approximation. Computed time-dependent solutions of the lubrication model are in general agreement with our experimental observations. Starting from a slightly-perturbed uniform coating, the full family of evolving flows is shown to depend only on three dimensionless parameters: the inclination angle of the cylinder from the vertical direction, the Bond number representing the ratio of gravity to surface tension effects, and a nondimensional measure of the initial coating thickness. Typically flow is initiated by the well-known Rayleigh-Plateau instability followed by drainage, and also wave propagation if the cylinder is not horizontal. Steady propagation of ring-like structures can occur as well as eventual overtaking, merging and reformation of the rings. We demonstrate that volumetric transport is maximized if the cylinder axis is inclined to, rather than aligned with, the direction of gravity. Results are relevant to the understanding, and potential optimization, of small-scale liquid transport. Such problems arise in the natural and industrial worlds.

A multiple lines of evidence approach for the ecological risk assessment of an accidental bitumen release from a steam assisted gravity drainage (SAGD) well in the Athabasca oil sands region.

To assess the ecological impacts of two independent accidental bitumen releases from two steam assisted gravity drainage (SAGD) wells in the Athabasca oil sands region, a multiple lines of evidence (LOE) approach was developed. Following the release in 2010, action was taken to minimize environmental impact, including the selective removal of the most highly impacted vegetation and the use of oil socks to minimize possible runoff. An ecological risk assessment (ERA) was then conducted based on reported concentrations of bitumen related contaminants in soil, vegetation, and water. Results of biological assessments conducted at the site were also included in the risk characterization. Overall, the conclusion of the ERA was that the likelihood of long-term adverse health effects to ecological receptors in the area was negligible. To provide evidence for this conclusion, a small mammal sampling plan targeting Southern red-back voles (Myodes gapperi) was carried out at two sites and two relevant reference areas. Voles were readily collected at all locations and no statistically significant differences in morphometric measurements (i.e., body mass, length, foot length, and adjusted liver weight) were found between animals collected from impact zones of varying levels of coverage. Additionally, no trends corresponding with bitumen coverage were observed with respect to metal body burden in voles for metals that were previously identified in the source bitumen. Hepatic ethoxyresorufin-O-deethylase (EROD) activity was statistically significantly elevated in voles collected from the high impact zones of sites compared to those collected from the reference areas, a finding that is indicative of continued exposure to contaminants. However, this increase in EROD was not correlated with any observable adverse population-wide biological outcomes. Therefore the biological sampling program supported the conclusion of the initial ERA and supported the hypothesis of no significant long-term population-wide ecological impact of the accidental bitumen releases.