Investigation of the inhibition of bacteria and endotoxin influx by back filtration through dialyzer membranes.

We investigated the usefulness of assays using human neutrophils for radical production as well as endotoxin (ET) measurement and bacterial culture for endotoxin and bacterial influx by back filtration using dialyzers with different membrane pore diameters. Three types of dialyzers made of cellulose triacetate membrane material with different pore size FB-110EG eco, FB-110U eco, and FB-150UHß eco were used. A circuit to generate back filtration was created. Back filtrate generated by hydraulic head pressure operation was collected. ET and bacteria were examined. Human neutrophils were exposed to back filtrate (experiments using three different membranes) and contaminated solution, and free radical production was measured using LBP-953 (Berthold) to see if there were differences in production. No bacteria were detected and the concentration of endotoxin was below the detection limit in the back filtrate from the three types of membranes and purified water. Free radical production from neutrophils in the contaminated water was highest at 4,405,750 ± 61,244 cpm (counts per minute) (mean ± SD) (P < 0.01 vs FB-150UHß eco, FB-110U-eco, and FB-110EG eco) followed by that in back filtrate via FB-150UHß eco, FB-110U-eco, FB-110EG eco. Radical production from neutrophils was thereby higher in the back filtrate of dialyzers with larger pore-size membranes. No bacteria were observed and the concentration of ET was below the detection limit in back filtrate from any of the membranes. However, when the reverse filtrate was exposed to neutrophils, radical production increased along with pore size, suggesting the influx of small pyrogens and other pyrogenic substances.

Evaluation of Proteins and Cells that Adsorb to Dialysis Membranes Used in Continuous Hemodiafiltration: Comparison of AN69ST, Polymethylmethacrylate, and Polysulfone Membranes.

OBJECTIVE: In intensive care medicine, continuous renal replacement therapy (CRRT) is important for critically ill patients. Various types of dialysis membranes are currently used in clinical settings, each having unique structures and characteristics. This study aimed to perform a detailed analysis of the characteristics of polysulfone (PS), polymethylmethacrylate (PMMA), and polyacrylonitrile (AN69ST) membranes, and to determine differences in the adsorption of proteins and blood cells by membrane material. METHODS: Subjects were patients undergoing CRRT in the ICU of the Kokura Memorial Hospital. After use, membranes were collected and analyzed. Semi-quantitative analysis of the membrane surface was performed by scanning electron microscopy. We determined the identity of proteins adsorbed to the surface of membranes by TOF/MS analysis, and measured the amount of adsorbed chemical mediators. RESULTS: Electron microscopy revealed that, compared to PS and PMMA membranes, AN69ST membranes had a greater amount of adsorbed activated white blood cells (WBCs). A large amount of platelets was adsorbed to PMMA membranes. In terms of the amount of adsorbed protein, significantly more proteins adsorbed to AN69ST membranes compared to PS and PMMA membranes. Moreover, TOF/MS analysis revealed a difference in the types of adsorbed proteins by membrane. Chemokines were particularly prevalent among adsorbed proteins for all 3 membranes. CONCLUSION: Compared to PS and PMMA membranes, AN69ST membranes had a higher capacity to remove activated WBCs. Moreover, apparent differences were noted in the types of proteins that adsorbed to each type of membrane. These differences in membrane properties may impact clinical outcomes.

Performance comparison of a new automated cuff pressure controller with currently available devices in both basic research and clinical settings.

BACKGROUND: The management of tracheal tube cuff pressure in patients receiving mechanical ventilation is important for the prevention of ventilator-associated pneumonia. Currently, cuff pressure is intermittently monitored with a pressure gauge and adjusted when necessary in a routine practice. However, this method results in wide variations in pressure, and adequate management is difficult due to the spontaneous release of air from the cuff, which reduces cuff pressure. In order to continuously maintain a uniform cuff pressure, we developed a new automated cuff pressure controller and compared its properties with existing devices. METHODS: The effectiveness of the new device was assessed with a model trachea/lung and tracheal tube by measuring cuff pressure while on mechanical ventilation. An electrically powered automatic cuff controller or manual cuff pressure control was used for comparison purposes. The effectiveness of the new device was also examined in patients receiving mechanical ventilation by continuously measuring cuff pressure for a 24-h period. RESULTS: Cuff pressure was uniformly maintained with the new device. Moreover, in the clinical setting, variation in pressure from the set pressure was minimal with both the new device and existing device, relative to the intermittent monitoring method. This suggests that, as with the existing device, uniform cuff pressure management is possible with the new device. CONCLUSIONS: Our results demonstrate the ability of the new cuff pressure controller to manage cuff pressure without the need of a power source, highlighting its potential utility in clinical settings.