Controlling the alien hand through the mirror box. A single case study of alien hand syndrome.

Disruption of motor control in the alien hand syndrome might result from a dissociation between intentions and sensory information. We hypothesized that voluntary motor control in this condition could improve by restoring the congruency between motor intentions and visual feedback. The present study shows that, in one patient with right alien hand syndrome, the use of a mirror box paradigm improved motor speed. We speculate that the visual feedback provided by the mirror increases the sense of congruence between intention and sensory feedback, leading to motor improvement.

Exploring motor and visual imagery in Amyotrophic Lateral Sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is a motor neuron disease characterized by the progressive atrophy of both the first and the second motor neurons. Although the cognitive profile of ALS patients has already been defined by the occurrence of language dysfunctions and frontal deficit symptoms, it is less clear whether the degeneration of upper and lower motor neurons affects motor imagery abilities. Here, we directly investigated motor imagery in ALS patients by means of an established task that allows to examine the presence of the effects of the biomechanical constraints. Twenty-three ALS patients and 23 neurologically unimpaired participants have been administered with the (1) hand laterality task (HLT) in which participants were asked to judge the laterality of a rotated hand and the (2) mirror letter discrimination task (MLD) in which participants were asked to judge whether a rotated alphanumeric character was in its canonical or mirror-reversed form (i.e. control task). Results show that patients present the same pattern of performance as unimpaired participants at the MLD, while at the HLT, they present only partially with the effects of biomechanical constraints. Taken together, our findings provide evidences that motor imagery abilities, related to the mental simulation of an action, are affected by this progressive disease.

PD and HD in combination.

Peritoneal dialysis (PD) and hemodialysis (HD) are the most used therapies for endstage renal disease (ESRD). Peritoneal dialysis offers the advantages of long, slow, continuous ultrafiltration and preserve residual renal function (RRF) one of the most important factors affecting outcomes in PD. In contrast, HD offers superior solute removal but with undesirable cardiovascular tolerance of high rates of sodium and water removal. Peritoneal dialysis (PD) represents an effective way to maintain residual renal function and should be the first choice dialysis technique. However, with the loss of RRF, some limitations of PD alone in controlling the uremic state appear. Combination of the two techniques therapies, PD + HD (also called bimodal dialysis BMD), is the simplest way to deal with these limitations. The general prescription for BMD should be 5-6 days of PD and 1 or 2 HD sessions weekly. One of the most important controversy is how to evaluate the adequacy of the combined treatment: some Authors adopted the equivalent renal clearance (EKR), first transforming the weekly PD adequacy index (Kt/V), and then evaluating total clearance from both modalities. However, the EKR may overestimate the dialysis dose. Thus to accurately track dialysis dose some use the total effluent (PD, RRF, and HD) sampling method to yield Kt/Vef and creatinine clearance (CCref).

[Health-related quality of life in patients with chronic kidney disease]. / Qualita' della vita nei nefropatici.

Assessment of quality of life in patients with different degrees of chronic kidney disease is an important issue because of its impact on clinical decisions and financial resource management in the health-care system. The aim of this study was to assess whether a generic instrument like the SF-36 questionnaire is able to discriminate three different populations of patients with different degrees of renal disease (pre-ESRD, ESRD, TxR). Five hundred sixty-three patients from 12 Italian nephrology units completed the SF-36 scales by themselves. The results from these samples were compared with those from the general population. Univariate analysis and multivariate regression were used. The generic SF-36 questionnaire proved to be a powerful instrument to discriminate populations with different degrees of chronic renal failure. The quality of life of patients on dialysis is significantly worse than that of the normal population and other patients with less severe renal function impairment.

Acid-base balance in peritoneal dialysis.

In patients without functioning kidneys, alkali replenishment is accomplished by the addition, via dialysis solution, of either HCO 3 - itself or a metabolic precursor of this anion, such as lactate. The body base balance in peritoneal dialysis (PD) patients is self-regulated by the feedback between plasma bicarbonate concentration and dialytic base gain. Dialytic base gain is the only source of buffer for PD patients and this gain should counteract the metabolic acid production. Dialytic base gain depends on peritoneal buffer fluxes (lactate reabsorption minus bicarbonate lost). The plasma bicarbonate level is determined by the dialytic base gain and the metabolic acid production. Bicarbonate buffered PD solution provides some advantages over the conventional lactate buffered PD solution.

The ''Ronco'' catheter for continuous flow peritoneal dialysis.

To perform CFPD, a two way access must be available in order to allow continuous inflow and outflow of the solution. This is most likely achieved with a double lumen peritoneal catheter. To design a double lumen catheter does not necessarily mean to increase the size of the tube or to increase the discomfort of the patient. However, the real challenge is to find a design in which minimal re-circulation is experienced. The two tips of the catheter must be positioned such that a maximal exposure of the peritoneal surface to the fluid is guaranteed during one single passage of the fluid from one lumen to another. Double lumen catheters with one short branch and another long of straight and of spiral shape were originally designed. Ash and coworkers have designed a catheter with a t-shape configuration in order to distantiate to the maximum the tips of the two lumens. Recently we have designed a novel catheter for CFPD equipped with a thin walled silicone diffuser used to gently diffuse the inflow dialysate into the peritoneum. The holes on the round tapered diffuser are positioned to allow dialysate to perpendicularly exit 360 degrees from the diffuser. The diffuser design and hole locations disperse the high-flow dialysate fluid at 360 degrees, reducing trauma to the peritoneal walls and allowing the dialysate to mix into the peritoneum. The dispersed fluid infused into the peritoneal cavity is then drained through the second lumen whose tip is placed into the lower Douglas cavity. The new catheter with diffuser is also equipped with a special removable hub that allows for easy creation of the subcutaneous tunnel without increasing the size of the skin exit site. The results so far achieved seems to offer advantages in terms of high flows, minimal pressure regimes and negligible recirculation.

The Vicenza ''Short'' peritoneal catheter: a twenty year experience.

Dislocation of peritoneal dialysis catheters is one of the major causes of technique failure. We evaluated 701 Vicenza catheters, implanted since 1985 in 365 males, mean age 53 +/- 16 yrs, range 24 - 87, and 336 females, mean age 51 +/- 17 yrs, range 21 - 82. The Vicenza catheter is defined "short" since it consists of a classic straight double cuff PD catheter having however an inner segment (the portion located in the peritoneal cavity) much shorter than any other type of catheter. It is implanted in the lower abdomen, just a few centimeters above the pubis. The analysis of our results obtained in a large PD population displayed good device survival at 2 and 5 years (94.3% and 91.5% respectively), a low dislocation rate (4%) and an exit-site infection rate similar to other double cuffed catheters. There was no selection of patients receiving this catheter since from 1985 we have used this catheter in every incident patient. Due to its lower implantation site this catheter demonstrates excellent wearability and good body image acceptance.

Practice pattern and treatment options for kidney patients in a single North Italian nephrology center.

The experience and the current practice of a single center located in northern Italy is reported. The center of Vicenza is a self-standing nephrologic unit serving a population of about 300,000 individuals. The overall province counts approximately 800,000 individuals and some of them are referred to our center from peripheral hospitals for renal transplantation and/or particular pathologic conditions. The center offers an integrated approach to the treatment of uremia including hemodialysis (HD), peritoneal dialysis (PD), and renal transplantation. In HD and PD, the most peculiar aspect is the treatment personalization that leads to numerous types of applied therapies and technologies. The policy of the center is based on the belief that the nephrology team has a substantial influence on the outcomes of dialysis patients. A large number of treatment options are available. Special care is placed on the delivery of an adequate amount of dialysis, but the fractional clearance of urea in relation to volume (Kt/V) is seen as a prerequisite and other factors are considered important. Reduction in mortality and morbidity is largely dependent on beginning therapy early in the course of renal treatment. The attainment of appropriate hemoglobin concentrations, good nutrition, good control of calcium and phosphorus metabolism, lipids, and blood pressure, is considered of great importance. Beyond all these factors the time spent by the physician with the patient is considered one of the major factors influencing quality of care. The particularly low mortality of the center (6%/yr) may also be ascribed to a lower incidence of diabetes and other comorbidities.

Preliminary technical and clinical evaluation of a new hollow fiber dialyzer with a 5 microns thick cuprophan membrane.

In vitro and in vivo studies were performed on 10 dialyzers with 5 microns thick cuprophan membrane to evaluate hydraulic properties and permeability to solutes. Inlet and outlet pressures of the filter were measured at different blood flows to assess the resistance of the device and the end-to-end pressure drop. Hysolated ultrafiltration was performed to evaluate the spontaneous filtration at increasing blood flows, the ultrafiltration rate at different transmembrane pressures and, finally, the sieving coefficients for solutes. Standard hemodialysis was also performed to study the clearances throughout a 4-h session. During hysolated ultrafiltration the UF rate was increased up to 37 ml/min showing a very high hydraulic permeability of the membrane. The spontaneous filtration rates related to blood flow were quite low. Since the end-to-end pressure drop in the filter was also relatively low at high blood flow we may conclude that the geometry of the device is able to dissociate the influence of blood flow on the hydrostatic pressure inside the filter. This results in a easy modulation of the membrane permeability to water. Sievings were surprisingly high and clearances were stable along the dialysis session (BUN = 196 ml/min, creatinine = 161 ml/min and phosphate = 163 ml/min).

Pathophysiology of ultrafiltration in peritoneal dialysis.

Pathophysiology of peritoneal ultrafiltration is analyzed in the present study. Peritoneal equilibration test is the easiest procedure to study in detail the possible causes of failure to control the ultrafiltration rate in patients undergoing peritoneal dialysis. Membrane failure, reduction in peritoneal blood flow, excessive lymphatic reabsorption catheter malposition, and fluid sequestration are the most common causes of ultrafiltration loss. Pharmacologic manipulation of peritoneal membrane, correction of mechanical inconvenients, reduction in peritonitis rate and in the level of immunostimulation of the mesothelial macrophages, together with a careful policy in terms of glucose concentration in the dialysate and dwell times may contribute not only to treat different forms of ultrafiltration loss but also to prevent their incidence.

Oxalate removal by differing dialysis techniques.

Secondary hyperoxalemia is a common feature in patients with chronic renal failure, but oxalate removal is not adequately accomplished by regular dialysis treatment. Oxalate removal in two groups of patients, 11 on continuous ambulatory peritoneal dialysis (CAPD) and 12 on hemodialysis (HD), was investigated. HD patients were studied during a regular bicarbonate dialysis and during hemodiafiltration (HDF) with a high convective component (UF = 66 mL/min) and AN69 filter (Hospal Filtral 12, 1.2 m2, Hospal Industrie, Meyzieu, France). All HD and HDF spent dialysate and all 24 hr CAPD effluents were collected; oxalate concentration was measured by high performance liquid chromatography (HPLC) using an ion exchange column. Both oxalate flux and total extraction were statistically higher during HDF treatments (HDF = 1.87 +/- 0.77 mg/min and 335.9 +/- 131.5 mg/session, respectively; HD = 0.99 +/- 0.74 mg/min, 226 +/- 153 mg/session, respectively; p < 0.02). The positive interaction of convective and diffusive fluxes probably played a major role in oxalate removal during treatment with a high convective component; solute-membrane interactions can occur by using either cellulosic or synthetic fibers. In CAPD patients, oxalate removal (76.42 +/- 50.85 mg/day) was lower than in patients on either HD or HDF, although weekly oxalate extraction was statistically no different between CAPD (535.46 +/- 356 mg/week) and HD (677.72 +/- 460.82 mg/week). It was concluded that HDF is more effective than HD or CAPD in oxalate removal. Long-term studies are needed to demonstrate whether these kinetic findings have clinical relevance.

Continuous flow peritoneal dialysis: a new double lumen catheter.

Continuous flow peritoneal dialysis (CFPD) is a therapy originally utilized in the sixties. It was then abandoned because of technical reasons, but, today, a new interest in this technique is emerging, because of new technical solutions and new hardware capabilities. CFPD is a peritoneal dialysis technique in which a certain amount of fluid is maintained in the peritoneal cavity, while a continuous inflow and outflow is provided via twin catheters or through a double lumen catheter. In this paper a new double lumen catheter is presented. The catheter is characterized by the presence of a diffuser in the inflow lumen, while a standard coiled shape characterizes the outflow lumen. The diffuser allows the use of high dialysate flows without peritoneal damage and with an excellent distribution of the fluid. The other feature of the catheter is the removable hub which allows for an easy subcutaneous tunneling of the catheter with a subsequent connection to the y segment. The special shape also guarantees a minimum recirculation during treatment. Data obtained in the first implanted catheter showed a progressive increase in small solute clearances in relation to an increase of the flow and the tidal volume in the peritoneal cavity. In particular, urea clearances up to 48 ml/min and creatinine clearances up to 39 ml/min were obtained. No major complications were observed after one year of use of the catheter.

Solute and water transport during continuous arteriovenous hemofiltration (CAVH).

The transport mechanisms governing solvent and solute removal during CAVH were elucidated on the basis of in vitro and in vivo observations. Using a typical hemofilter (Diafilter D-20, AMICON), filtration rate rose with inlet blood flow rate until an asymptote was reached at blood flows of approximately 150 ml/min. The onset of the asymptote coincided with transition from a regime controlled by oncotic pressure (filtration pressure equilibrium), to one governed by simple Darcy's law filtration behaviour. Subsequent measurements showed that under clinical conditions, CAVH is generally in the pre-asymptotic regime and operates at filtration pressure equilibrium. These observations offer the theoretical bases for a new design for CAVH hemofilters. As a possible corollary, middle-molecule sieving coefficients were found to be stable with time during CAVH in vivo, whereas in chronic mechanical hemofiltration they declined significantly during clinical treatment. The sieving coefficients, however, were lower in mechanical hemofiltration from the beginning of the session. These observations suggest that the measured sieving coefficient for a membrane is not necessarily a constant directly and solely related to the membrane standard reflection coefficient for a given solute. Concentration polarization and the ultrafiltration rate per unit of surface area may in fact have a major effect on the final concentration of solutes in the ultrafiltrate.

Technical and clinical evaluation of a new polyamide hollow fiber hemofilter for CAVH.

We carried out an in-vivo and in-vitro evaluation of a new polyamide hollow fiber hemofilter especially designed to operate under conditions of low pressure and low blood flow, such as in continuous arteriovenous hemofiltration (CAVH). The results obtained suggest that this filter is a prototype of a new generation of hemofilters especially designed for CAVH. Its low resistance permits its use even in patients with severe hypotension. The high blood flows achieved at a given pressure reduce the risk of clotting and increase the ultrafiltration rate. When an average ultrafiltration of 20-25 ml/min is achieved in 24 hours CAVH becomes very efficient, and alternative techniques to increase its efficiency are no longer required.

Comparison of four different short dialysis techniques.

The goal of shortening dialysis treatment time has stimulated the development of new, highly efficient dialytic strategies. In this study the Authors compared four different short dialysis treatments in terms of efficiency, clinical tolerance, technological investment and costs: 1) Rapid bicarbonate dialysis with 1.5 sq.m. cuprophane membrane; 2) High flux biofiltration with 1.2 sq.m. AN69S hollow fiber membrane; 3) Hemodiafiltration with 1.2-1.9. sq.m. polysulphonic hollow fiber hemodiafilters, and 4) High flux hemodiafiltration with two serial hemodiafilters with AN69s membrane (total 2.4 sq.m.). Hydraulic properties and solute clearances at different blood flows (300-500 ml/min) were tested for each technique. Once the optimal operative level was established three patients were treated with each technique for at least six months. Since BUN clearance averaged 310 ml/min, the treatment duration varied from 120 to 180 min/session with KT/V always higher than 1. The average protein catabolic rate was 0.9 g/kg/24h. Clinical tolerance was generally good, slightly better in treatments with a high convective component. Despite the greater efficiency of treatment No. 4, the technological requirements and costs are such that the others are currently more feasible and acceptable in clinical routine. The study demonstrates that reduction of dialysis treatment time is possible in all centres in a selected population with adequate blood access. Treatment No. 1 can even be performed with standard equipment and cuprophan membranes, while bicarbonate in the dialysate is mandatory. The real limit to shortening treatment time seems to be related to the maximal rate of ultrafiltration achievable in the patient during dialysis.

Buffer kinetics in biofiltration.

A condition of metabolic alkalosis has been generally observed in patients undergoing regular biofiltration (BF). The aim of this study was to assess buffer kinetics during a dialysis session in five patients regularly treated by BF for 10 months (dialyzer Biospal 3000S, Qb 301; Qd 545; UF 36.76 ml/min; dialysate CH3 COO 38 mEq/L; replacement fluid 1000 ml/h with HCO3 100 mEq/L solution). As usually happens using dialyzers with high surface area and permeability, large HCO3 losses (756 +/- 112 mEq) and CH3COO uptakes (677 +/- 152 mEq) were observed. Acetate plasma levels rose to 10.4 mEq/L, a value potentially dangerous to the cardiovascular system. The dialytic buffer gain (acetate uptake + HCO3 administered - HCO3 loss) was high (230 +/- 137 mEq/dialysis) and excessive for patients' needs. It is therefore very important to reduce either the acetate concentration in dialysate or the amount of reinfused bicarbonate. In view of the plasma acetate levels it is preferable to use a dialysis solution containing less acetate.

A new blood module for continuous renal replacement therapies.

A new blood module for continuous renal replacement therapies has been utilized to perform CVVH in critically ill patients. The features of the new module named (HP300 and manufactured by Medica srl (Medolla, Modena) are the easy installation and transportability to the bedside, the simple and safe management and the continuous measurement of the pre and post filter pressure with automatic calculation of the end-to-end pressure drop inside the filter. The last feature permits to detect early malfunctions of the filter due to fibers clotting or due to the internal coating of the hollow fibers by plasma proteins. In both cases the efficiency of the treatment can be reduced because of a significant reduction of the ultrafiltration rates or a remarkable decay of the membrane permeability and solute sieving coefficients. In many cases this reduction is only detected when important effects on solute removal have already occurred. In our experience, the new module permitted the substitution of the filters when early malfunctions were detected and maximal treatment efficiency was therefore guaranteed over extended periods of time.

On line filtration of dialysate: structural and functional features of an asymmetric polysulfone hollow fiber ultrafilter (Diaclean).

The endotoxin transfer across dialysis membranes has been investigated using specific in vitro circuits. Backdiffusion and backfiltration have been analyzed and most dialysis membranes have shown to be permeable to LAL positive substances. Synthetic membranes however display the better capacity of retention of these products despite their higher porosity and permeability. For such reason synthetic polysulfone ultrafilters are used as pyrogen filters to obtain ultrapure dialysate. We have investigated the characteristics of a polysulfone ultrafilter named Diaclean and manufactured by Amicon Ireland. The capacity of endotoxin retention has been investigated both in filtration and backfiltration modes on new and used ultrafilters. The capacity of endotoxin adsorption was investigated as well. Used ultrafilters appeared to maintain the retention capacity and the adsorption capacity up to 4 months of use. Only slight differences were noted from the baseline values (p = n.s.). The best adsorption capacity is always displayed by the outer layer of the membrane suggesting its best utilization in back filtration mode with tangential flow. No morphological changes were observed in the used membrane analyzed by scanning electron microscopy.

Acid base correction in bicarbonate CAPD patients.

Bicarbonate has been proposed as buffer in CAPD solutions in recent years instead of lactate and acetate. The present study is designed to evaluate peritoneal bicarbonate kinetics using bicarbonate solutions. Seventy kinetic studies have been performed in 7 patients treated with 2 CAPD solutions containing 35 mmol/l (A) and 27 mmol/l (B) of bicarbonate. The changes in dialysate bicarbonate concentration at different dwell times were correlated with bicarbonate blood levels. Furthermore after 2 hours of dwell time and at subsequent observations, no differences in dialysate bicarbonate concentration were found between A and B solutions at the same bicarbonatemia. Thus a feedback between bicarbonate absorption and bicarbonate blood concentration was observed. If the amount of bicarbonate transferred to the patient is over the metabolic acid production, bicarbonatemia will rise: consequently bicarbonate dialysate absorption will decrease. After a few days, an equilibrium point will be reached. In this condition the bicarbonate absorption is equal to metabolic acid production and, in stable clinical conditions, a stable acid base status will be maintained by the patient. Our studies empirically demonstrated that the equilibrium is reached when a difference of 5 mmols between blood and inlet dialysate bicarbonate concentration is observed. Consequently to achieve 25 mmol/l of bicarbonatemia, the bicarbonate concentration of CAPD solution should be about 30 mmol/l.