Blood flow distribution in a polymyxin coated fibrous bed for endotoxin removal. Effect of a new blood path design.

The analysis of flow distribution in cartridges designed for hemoperfusion is extremely important. Taking advantage of a new imaging technique, based on the analysis of a helical scanner-generated imaging sequence, we studied the blood flow distribution in a series of cartridges for extracorporeal removal of endotoxin. Cartridges with improved design were compared to cartridges with a standard design. The improved design consists in a different structure of the holes of the distributor of the flow within the adsorbent unit. Cartridges were studied in vitro with human blood from voluntary donors at blood flows of 100 and 250 ml/min. The progression of density in specific regions of interest (ROI) was analyzed to detect the distribution of the dye injected in the blood circuit. The study demonstrates that both at 100 ml/min and at 250 ml/min of blood flow, the progression of flow appears more homogeneous in the devices with improved design. In detail, the flow distribution measured by the incremental density values detected in the ROIs of the proximal comers (close to the arterial port) and in the ROIs of the central region of the device (close to the inner wall of the case) displays a significant difference between the standard and the improved device. The ROIs studied in the standard devices display a slower increase in density and significantly lower absolute values expressed in Hounsfield units. The experimental method utilized to analyze flow distribution seems to represent an important means to study the performance and design of this type of device.

Impact of spacing filaments external to hollow fibers on dialysate flow distribution and dialyzer performance.

A new type of dialyzer (PAN 650 SF Asahi) is analyzed in terms of hydraulic properties, solute clearances and dialysate flow distribution. The new type of dialyzer is a polyacrylonitrile hollow fiber filter, equipped with spacing filaments placed externally to the fibers to facilitate dialysate distribution and avoid channeling. The new filter is compared with a similar filter without spacing filaments. For this purpose, blood and dialysate side clearances have been measured in sequential dialysis session carried out randomly in the same patients. Furthermore, a last generation helical scanner (X-Press/HS1, Toshiba) has been utilized to analyze in vitro the flow distribution of dialysate inside the dialyzer. A contrast medium was injected and a sequence of images has been achieved on a longitudinal section of the dialyzer. This new method permits to avoid any bias due to the cylindrical shape of the dialyzer, since a 10 mm thick rectangular section is analyzed and not the entire body of the filter. The dialyzers equipped with spacing filaments displayed a significant improvement of the dialysate distribution as demonstrated by the radiological pattern. In detail, despite a channeling phenomenon in the peripherical region of the bundle is still present, this is remarkably reduced in comparison with the channelling phenomenon observed in the standard dialyzers. This improved distribution is confirmed by a significant improvement of the solute clearances.

Technical and clinical evaluation of a new asymmetric polysulfone membrane (Biosulfane).

First generation asymmetric polysulfone membranes had high hydraulic permeability (kf = 40 ml/h/mmHg/sqm) but a low diffusive permeability due to the hydrophobic nature and wall thickness of 75-100 microns. We have tested a new polysulfone membrane with a wall thickness of 40 microns in a series of in vitro and in vivo dialysis session experiments. The new "Biosulfane" membrane presented a Kf of 45.8 with constant performance up to 240 mins. The koA was 760 and the clearance value at 350 ml/min of Qb in hemodiafiltration was 255 ml/min for urea, 210 for creatinine, 225 for phosphate, 76 for inulin. In high flux dialysis the clearances were similar except for inulin which was 32% lower due to the lower convection amount. Beta-2 microglobulin clearance was 22 ml/min in high flux dialysis and 37 in hemodiafiltration. Solute sieving coefficients were close to 1 for the majority of the studied solutes in a wide range of molecular weights and slight variations were observed for charged solutes due to Donnan's effect. The sieving for Inulin was 0.96 while that for Beta-2 microglobulin was not measurable due to a large molecule adsorption on the inner structure of the fibres. The good performances of this membrane are probably due to reduced wall thickness and a consequent improvement in diffusive permeability to small size solutes.

Dynamic catheterography in the early diagnosis of peritoneal catheter malfunction.

The dynamic catheterography is an image technique that allows to study the peritoneal solution inflow and outflow phases in case of catheter malfunction. The examination is carried out in three subsequent steps: 1) direct examination without contrast media in order to define the position of the catheter inside the abdomen; 2) low speed catheterography by normal injection of 10 ml of hydrosoluble contrast medium to verify the patency of the cannula; 3) high speed catheterography by 30 ml hydrosoluble dye injected with an automateds high pressure system to study the inflow phase, the fluid distribution in the peritoneal cavity and the patency of the catheter holes. Different radiographic patterns can be found: dislocation of the catheter tip, KinKing, one way obstruction, inner lumen obstruction. The procedure is simple, safe and reliable for a correct diagnosis and for the choice of a successful therapeutic approach to peritoneal catheter malfunction.

Paired filtration dialysis: studies on efficiency, flow dynamics and hydraulic properties of the system.

Several strategies have been proposed to increase dialysis efficiency in order to reduce dialysis treatment time. Paired filtration dialysis (two-chamber technique) is a new technique combining the advantages of highly permeable membranes and convective transport with the high depurative efficacy of diffusion. The system operates with two units in series (hemofilter + dialyzer) with membranes of polysulfone and hemophan, respectively. A detailed analysis of the hydraulic properties of the system and its possible optimization in terms of depurative efficiency is reported in this paper. In vitro and in vivo tests provided data sufficient to draw some hypotheses on a new utilization of the system. The system appears to be adequate for operating under conditions of high blood flows, however, some limitations were evidenced during our evaluation: the convective component may be insufficient and further increases are impossible because of the limiting effect of the low surface area of the hemofilter; the configuration in which the weight loss is achieved in the hemofilter exposes to the risk of backfiltration in the dialyzer, reducing the benefits of a highly biocompatible system, and the use of acetate in the dialysate and/or lactate in the substitution fluid may interfere with a satisfactory correction of metabolic acidosis. On the basis of our evaluations, some changes can be proposed such as: (1) increased surface area of the hemofilter; (2) use of blood flows higher than 300 ml/min; (3) use of bicarbonate in the dialysate and in the replacement solution; (4) increased convective component with ultrafiltration rates of 50-60 ml/min and full replacement with substitution fluid in between the two filters, and (5) weight loss achieved in the dialyzer with a constantly positive transmembrane pressure. With such a modification of the operative conditions, paired filtration dialysis can be probably applied as a highly efficient dialysis technique in a large number of patients with a significant reduction of dialysis treatment time.

[Hydronephrosis surgically treated in the 1st year of life. Short- and long-term radiologic and functional evaluation]. / L'idronefrosi operata nel 1 anno di vita. Valutazione radiologico-funzionale a breve e lungo termine.

Hydronephrosis in infancy and childhood is a frequent urinary malformation and is almost always congenital. In over 80% of the cases it is due to ureteropelvic junction obstruction; much less frequently it is due to anomalous renal vessels, sometimes associated to ureteropelvic junction obstruction. In this paper the Authors analyze their experience in the surgical treatment of this urinary malformation. 234 hydronephrosis out of 222 patients were operated on from January 1972 to June 1985. 61 hydronephrosis were operated on in 55 infants under 1 year. Primary nephrectomy was carried out only in 9 of the 234 hydronephrosis operated on (3.9%) and in 3 of the 61 hydronephrosis operated on in infants less than 1 year old (4.9%). All the 55 infants but one showed a significant radiological improvement after pyeloplasty. 28 infants but one showed a significant radiological improvement after pyeloplasty. 28 infants for a total of 30 hydronephrosis had a glomerular filtration rate determination during sequential scan for individual kidney function assessment. 90% of the kidneys operated on showed a normal or slightly reduced glomerular filtration rate. Recent advances in prenatal echographic diagnosis and relationship between obstructive uropathy, renal development and pulmonary hypoplasia are discussed. The Authors stress out the importance of early diagnosis to improve surgical results.

[A combined method of sialography and CT scan of the parotid gland]. / Metodica combinata scialografia+TC per la parotide.

Computed tomography (CT) of parotid gland was performed on 40 patients, immediately following sialography. The results of the combined CT-sialography were compared with those of sialography alone and are presented here. We have come to the conclusion that the main indication for this method, in the study of the parotid gland, is the mass-pathology, particularly situated in deep-lobe and in the pharyngo-maxillary space.

[Value and limits of defecography in childhood]. / Valore e limiti della defecografia in età pediatrica.

The experience about 73 defecographic exams performed in pediatric age is reported. The casuistry is critically analyzed, taking into consideration the most recent non radiological diagnostic improvements. In the authors' opinion, defecography in pediatric age is advisable in the diagnosis and post-operative control of fecal incontinence. In the other cases radiology may be substituted by other less invasive and sometimes more precise methods.