Fungal Peritonitis in Peritoneal Dialysis: Our Experience and Review of Treatments

From January 1975 to April 1982, 10 of our patients undergoing chronic peritoneal dialysis developed fungal peritonitis. Of six treated without removing the catheter two survived after intraperitoneal (IP) administration of imidazole derivatives, and four died despite combined IP and intravenous (IV) therapy. Of four patients treated by catheter removal, all survived, two without any additional therapy and two after IV antifungal treatment. Three of the deaths followed cardiac or cerebral accidents, while one was related to Candida sepsis.

Bacterial peritonitis is a frequent complication of peritoneal dialysis (FD). In addition fungal peritonitis has been reported with increasing frequency with the growing diffusion of FD, the subsequent increase in infectious episodes, the antibiotic treatment, which such complications require and the improvement in technique for mycological diagnosis.

This paper describes our experience with the clinical manifestations of fungal peritonitis and its treatment in 10 patients undergoing intennittent peritoneal dialysis (IFD) or continuous ambulatory peritoneal dialysis (CAFD).

Different Buffers for Hemodiafiltration: A Controlled Study

Hemodiafiltration (HDF) is usually performed using a dialytic solution (D) containing acetate (A) or bicarbonate (B) and a replacement fluid (RF) containing lactate (L).

To clarify the role of buffers in HDF, 11 patients underwent different study periods, each three months long: bicarbonate hemodialysis (BHD = Baseline period); HDF with (A) in D and (L) in RF (first period of HDF); HDF with (A) in D and (B) in RF (second HDF); HDF with (B) in D and (L) in RF (third HDF); HDF with (B) in D and (B) in RF (fourth HDF = BHDF).

HDF achieved: 1) an increase in dialytic efficiency (kt/V, 1.28), reducing the time-session (197 min); 2) an improvement in acid-base status (pre-dialytic values in BHDF: pH 7.36; pCO2 39.8 mmHg; HCO−3 21.8 mM/L); 3) better “dry weight” gain (reached in 92.8% of HDF and in 81% of BHD sessions); 4) a significant decrease, in dialytic side-effects (mainly during the third and fourth periods).

On the whole, BHDF (HDF done using only bicarbonate buffer) represents an easy and safe technique, leading to better cardiovascular stability than BHD and HDF without bicarbonate buffer.

Anatomical Bases of Peritoneal Permeability: A Reappraisal. Anatomy of Peritoneum

The peritoneal membrane consists of flat mesothelial cells linked together with digitations and containing vesiculae with pinocytic capacity, of endothelial cells (containing Weibel-Palade's bodies and vesiculae) and of an interstitial tissue consisting of a network of watery channels.

The cellular structures of mesothelium and endothelium are characterized by tight and gap junctions or perhaps by macular junctions. The visceral peritoneum shows a prevalence of gap junctions, the pericytic veins contain only tight junctions while both types can be found in the arterioles.

Two different ways for solute transport are theoretically possible: the vesicles of plasmalemma (via pinocytosis) and the junctions (via size-sieving effect). Studies with tracers did not furnish unequivocal data on this problem and did not clarify if these structures could be the equivalent of the pores of the Landis-Pappenheimer's theory. The studies of Karnowsky and Simionescu, using tracers, have in fact given opposite results.

The role of Neurotransmitters in the Genesis of Uremic Encephalopathy

To classify the influence of neurotransmitters in the genesis of uremic encephalopathy we studied cerebrospinal fluid (CSF) and plasma (P) amino acid (AA) concentration, in patients undergoing various dialytic treatments (hemodialysis = HD, intermittent and continuous peritoneal dialysis = IPD and CAPD).

HD causes a significant decrease in CSF/P ratios of branched chain AA (BCAA) and a significant increase in CSF Glycine/Valine ratio, suggesting an augmented brain uptake of Glycine at detriment of Valine. In IPD the general trend of Aromatic AA/BCAA ratio suggests a preferentilal transport of Aromatic AA through the blood brain barrier. The differences between IPD and HD are confirmed by data concerning metabolites of Serotonin and Dopamine: CSF concentrations of 5-Hydroxyndoleacetic acid and Homovanillic acid are low in HD but high in IPD.

So, a reduced (in HD) and an increased (in IPD) activity of monoamine systems could be at the basis of some neurological disturbances appearing in uremia.

Hyperprolactinemia as a Marker of Neurotransmitter Imbalance in Uremic Population

Serum prolactin (PRL) levels are elevated in patients with chronic renal failure (CRF) but the mechanisms responsible for these abnormalities are not fully understood. PRL secretion is undoubtedly influenced by many substances, which can be variously altered in uremia: monoamines, endogenous opiates and PTH. Our data suggest that in early renal failure PRL levels are already significantly high and the 24-h pattern of PRL secretion is significantly different from that in controls.

PRL derangements could be due in mild renal failure, to unknown factors (GABA?); in severe CRF, to a major change in dopaminergic activity; in hemodialysis (HD), to a low turnover of monoamines, and in peritoneal dialysis (PD) to increased activity of sero-toninergic and dopaminergic systems.

[A new instrument to evaluate the quality of life on patients treated by hemodialysis (IPPE): first exploratory analysis of psychometric properties]

INTRODUCTION

The article presents a new instrument for the evaluation the Quality of Life, concerning patients on haemodialysis; IPPE tool has been created to be brief, multidimensional and also capable to considering, into the evaluation of patient Quality of Life, both familiar that hospital relational aspects. The purpose of this report is to explore the factor structure and the internal validity of the IPPE questionnaire.

METHODS

The research involved three ASL on the territory of Salerno (57%), Verona (20.3%), Cuneo (22.7%). IPPE has been administered to 256 patients on Haemodialysis.

RESULTS

As well as describing the IPPE's psychometric properties, the report offers a description of the normal distribution of the subjects in regard with risk and protection factors' (distinguishing the population by "age" and "gender"). The Exploratory Factor Analysis (EFA) of the definitive questionnaire (20 items) singles out six subscales ("perceived thirst", "body misperception", "dissatisfaction of therapeutic aspects", "perceived family support", "social daily life", "illness acceptance") that have an internal validity index alpha between .72 and .91. The Schmid-Leiman's solution confirms the existence of two macro-factors underlying as "risk factors" and "protection factors", reciprocally linked by a negative correlation (r = -.216, p < .001). SEM Analysis verifies the model "goodness of fit" and relations between risk and protection factors.

CONCLUSION

The data show that when the factors of protection increase, the perception of the risk factors decreases, and vice versa. The IPPE questionnaire considers the interactions between risk and protection factors' (bio-psycho-social model), operationalizing the QoL in a new way. Based on the results observed on the literature and on this work it is possible to hypothesize that the bio-psycho-social model of QoL could be considered as a process of psycho-social adaptation.

Significance of plasma B-type natriuretic peptide in hemodialysis patients: blood sample timing and comorbidity burden

Plasma B-type natriuretic peptide (BNP) concentration was evaluated in end-stage renal disease patients to verify if measurements before or after the session could furnish different information. BNP levels in plasma from 52 hemodialysis (HD) patients were measured both before and after the first session of the week. Echocardiographic studies were also performed and patients were followed over a period of 28 months. BNP removal from plasma was influenced by equilibrated Kt/V and patient characteristics. Initial plasma BNP concentration was correlated both with cardiac systolic function (LVEF) and mortality rate, independent of blood sample timing (before or after HD). A relative risk of death of 2.67 was found for plasma BNP levels above 335 pg/mL or 232 pg/mL, before and after HD, respectively. Higher BNP levels were observed in patients with higher burden of comorbidity, as measured by the Charlson Comorbidity Index; however, statistical significance was obtained only for BNP measured before HD. In conclusion, measurement of plasma BNP could give a valuable risk stratification of HD patients while cutting costs, by confining echocardiographic studies only to cases with BNP levels above the established cutoff values.

PON1 activity and genotype in patients with arterial ischemic stroke and in healthy individuals

OBJECTIVE

Paraoxonase-1 (PON1) is an esterase with antioxidant properties. Low PON1 enzyme activity or specific allelic polymorphisms seem to be associated with the risk of developing coronary artery disease or acute ischemic stroke (AIS). Our objective was to determine the distribution of both PON1 enzyme activity and its genotype in a group of patients with AIS.

MATERIALS AND METHODS

PON1 activity and the relative Q192R and L55M polymorphisms in the PON1 gene were assessed on 126 survivors of a first AIS and in 92 healthy subjects.

RESULTS

The genotype distribution for PON1 Q192R and L55M polymorphisms was similar in AIS patients and healthy subjects, but patients carrying the QRLL or RRLL genotype combination had lower PON1 enzyme activity compared with healthy subjects with the same genotype.

CONCLUSION

We postulate that lower than expected PON1 enzyme activity within specific genotypes might explain the reported association between R and L alleles and the risk of developing AIS.

Paraoxonase activity and paraoxonase 1 gene polymorphism in patients with uremia

Patients on hemodialysis (HD) show an increased risk for developing atherothrombotic events. The oxidative modification of low density lipoproteins (LDL) play an important role in the pathogenesis of atherosclerosis. In patients with uremia (chronic renal failure and HD), the increased oxidative stress induces oxidative modification of LDL. High density lipoproteins (HDL) exhibit a double antiatherogenic role, removing both lipid peroxides from LDL and cholesterol from tissues or vascular wall. Paraoxonase 1 (PON1) is one of three enzymes shown to prevent the formation of oxidized LDL. PON1 activity is modulated by its genetic polymorphism and by non-genetic factors, such as diet, smoking, acute phase reactants, and hormones. PON1 activity has been found to be significantly decreased in uremia. The present study aimed to verify the possibility that this reduced activity could be caused by a different PON1 gene polymorphism between patients on HD and healthy subjects, but this was not the case. The main cause may be identified in the different distribution of HDL subspecies, rather than in the different PON1 allele distribution between healthy subjects and patients with uremia.

HDL3-related decreased serum paraoxonase (PON) activity in uremic patients: comparison with the PON1 allele polymorphism

BACKGROUND

Patients with chronic renal failure on maintenance haemodialysis (HD) are at high risk of atherothrombotic events; an enhanced oxidant stress might have a major role. The decrease of human paraoxonase (PON1), an anti-oxidant high-density lipoprotein (HDL)-linked enzyme, is a possible mechanism for developing cardiovascular disease. To ascertain the causes of low PON1 in such patients, we investigated the contribution of both PON1 gene polymorphism and individual pattern of HDL.

METHODS

On 74 HD patients (47 M and 27 F) and on 92 healthy individuals (HS, 48 M and 44 F), we studied PON1 activity, PON1 genotype (55 and 192 PON1 allelic polymorphisms) and the lipid profile, including the HDL subfractions.

RESULTS

We observed in HD patients the following significant differences: (1) decreased median PON1 activity (73.5 vs. 110 U/l); (2) decreased mean HDL concentration (1.05 +/- 0.18 vs. 1.55 +/- 0.41 mmol/l); (3) decreased mean HDL3 concentration (0.79 +/- 0.21 vs. 1.28 +/- 0.24 mmol/l). Total HDL retained about 70% of serum activity, almost completely carried (95%) by the HDL3. Finally, PON1 activity remained significantly low in HD vs. HS after matching for the allelic polymorphism.

CONCLUSIONS

The reduction of the HDL3, not the genetic PON1 polymorphism, seems the most important determinant of PON1 activity reduction in HD.

Do different dialytic techniques have different atherosclerotic and antioxidant activities?

To compare the chronic effect of several dialytic techniques (bicarbonate dialysis, BHD; acetate free biofiltration, AFB; hemodiafiltration, HDF; paired filtration dialysis, PFD) on atherosclerosis and antioxidant activity, three different indices were created. The first (atherosclerotic index = AI) is formed using the sum of three plasma substances: MDA, Hcy, and Cys (malondialdehyde, homocysteine, cysteine). The second (antioxidant activity index = AOAI) is the sum of five erythrocyte (E) parameters: E-GSH, GPx, CAT, SOD, GR (E-glutathione, E-glutathione peroxidase, E-catalase, E-superoxide dismutase, E-glutathione reductase). The third (defense index = DI) is derived from the previous two: (AOAI - AI). The indices were so expressed as AI in mmol/L, AOAI in U/g hemoglobin (Hb), and DI in arbitrary units. These indices were calculated in 20 controls and 51 chronic HD patients (26 female, 25 male) before, during, and after the first session of the week. HD patients were divided according to their dialytic technique: BHD, n = 35; AFB, n = 5 patients; HDF, n = 7 patients; or PFD = 4 patients. All patients had been treated with a given technique for at least 12 months, before entering the study. As expected, HD patients had AI values higher than controls, both before and after the session, with a mean value of 541 (before) and 331 (after), whereas controls had a mean value of 205. The AOAI was lower than controls, both before and after the session, the mean value being 1,122 (before) and 1,582 (after), that of controls being 2,424. In all cases, PFD gave the best "acute" results; at the end of a PFD session, near normal values of AI, AOAI, and DI (defensive index = AOAI - AI) were obtained.

Homocysteine as a cardiovascular risk factor

Hyperhomocysteinemia (HH), a known risk factor for vascular diseases, is a frequent condition in hemodialysis (HD) patients. HH induces an oxidant stress to the vascular endothelium, causing a failure of vasodilation and an impairment of the antithrombotic properties. Vitamins B(6), B(12) and folic acid are important cofactors for the enzymes in the catabolism of homocysteine (Hcy). Failure of Hcy catabolism forces the cell to export Hcy into the plasma. The kidney is an important metabolic site for removal (up to 70%) of plasma Hcy (P-Hcy). HD lowers the P-Hcy concentration by 29 and 41% with cellulosic and noncellulosic membranes, respectively, yet values return to normal in only a few patients. Clearly, we must decrease the dangerous high levels of Hcy in different ways. Vitamin Supplementation: Vitamins B(6), B(12) and folic acid decreased the basal level of Hcy by about 40%, starting from the sixth month. Membranes: Some membranes performed better than the others.

TECHNIQUES

On the chronic basis, in our 1-year experience, paired filtration dialyis led to the best results, when compared to bicarbonate dialysis and acetate-free biofiltration. Finally, as in HD patients no one type of treatment can normalize the P-Hcy concentration, we should try other, different strategies such as absorption, the use of liposomes and new types of supplementation.

Role of cellulosic and noncellulosic membranes in hyperhomocysteinemia and oxidative stress

Hyperhomocysteinemia is an independent risk factor for cardiovascular morbidity and mortality in end-stage renal disease (ESRD) with an increased relative risk (RR) of 1% per micromol/L in total homocysteine concentration. In ESRD patients who undergo hemodialysis (HD), the antioxidant system is largely inadequate in correcting the imbalance between generation and scavenging of reactive oxygen species (ROS). To clarify the role of several cellulosic (CMs) and noncellulosic of synthetic membranes (NCMs) upon hyperhomocysteinemia and the oxidative stress, we measured plasma (P) homocysteine (t-HCY), plasma lipid peroxidation (LPO), and erythrocyte (E) concentration of several antioxidant enzymes in 20 normal subjects, in 35 HD patients treated with CMs, and in 29 patients treated with NCMs. Before, during, and after the first session of the week (at times 0', 120', end, 30' after HD end), blood samples were drawn. Plasma (P) homocysteine (t-HCY), cysteine (CYS), malondialdehyde (MDA), erythrocyte (E)-glutathione (GSH), glucose-6-phosphodehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), and superoxide-dismutase (SOD) were determined. The dialytic procedure significantly decreased the three plasma parameters, but none normalized (as a mean). The E-enzymes scavenging ROS (lower than normal before session) increased throughout the session, but the normal range of activity was never reached. Different membranes have shown different effects. When these effects on P and E spaces were pooled, we were able to classify the membranes as follows. In a general sense, cellulosic membranes are less effective than synthetic membranes both on lipoperoxides (LPO) and antioxidant activity (AOA). Among synthetic membranes, PMMA is the best membrane both for plasma values and lesser enzymatic derangement during the session. A practical system for classifying the anti-atherosclerotic action and antioxidant activity of dialytic membranes is proposed.

An overview of haemodialysis and oxidant stress

Today's patient population is increasingly older. Patients with chronic renal failure therefore start extracorporeal substitutive treatment having congestive heart failure, chronic liver disease, diabetes and so forth. In these patients, however, long-term haemodialytic treatment may add further aggravation on their pre-existing pathological conditions. Oxidative stress and alterations in lipid metabolism are caused by haemodialysis mainly due to (1) bioincompatibility type of reactions such as production of reactive oxygen species by inflammatory cells due to complement-mediated or -independent pathways, and (2) the imbalance between oxidants and antioxidants due to the diffusive loss of hydrophilic vitamins such as ascorbic acid. The events related to the oxidant stress may sustain a state of chronic inflammation. Recent advances suggest that atherosclerosis and proliferation of the smooth muscle are initiated and sustained by inflammatory mechanisms. Therefore, attempts to counterbalance the prooxidant effect of haemodialysis and to reduce the chronic inflammatory state will be presented.

Dialysis kinetics of homocysteine and reactive oxygen species

In patients with chronic renal failure who undergo hemodialysis (HD), the antioxidant system is inadequate to correct the imbalance between the generation and scavenging of reactive oxygen species. To clarify the role of six different membranes on oxidative stress, the authors measured plasma lipid peroxidation and erythrocyte (E) concentrations of several antioxidant enzymes in 30 HD patients: 20 on bicarbonate HD, 4 on paired filtration dialysis, 3 on acetate free biofiltration, and 3 on hemodiafiltration. Before, during, and after the first session of the week (at times 0, 30, 60, and 120 min, end, and 30 min after end of HD), several blood samples were drawn. Plasma (P) homocysteine (HCY), cysteine (CYS), malondialdehyde (MDA), E-glutathione (GSH), glucose-6-phosphodehydrogenase, glutathione reductase (GR), glutathione peroxidase (GP), catalase (CAT), and superoxide dismutase (SOD) were determined. All six membranes (Hemophan [HEMO]; cellulose diacetate [DIAC]; acrylonitrile-69 [AN69]; polymethylmethacrylate [PMMA]; cuprammonium rayon [CURAY]; polysulfone plus hemophan [PS + HEMO]) induced a significant decrease in plasma lipid peroxidation (p < 0.001) and an increase in E-GSH, GR, GR + flavinadenine dinucleotide, GP, and SOD (p < 0.001). Some membranes, however, showed some peculiar effects on reactive oxygen species: HEMO is better than DIAC, as far as P-MDA and P-HCY are concerned; PMMA induces higher changes in E-GR and P-CYS than does HEMO; and patients chronically using PMMA and PS + HEMO membranes show the lowest P-HCY levels both before and after dialytic sessions. Based on these changes, implications as to the effects on vascular disorders could be derived.

Free radicals and oxidative stress challenge dialysis patients: effects of two different membranes

Patients with end-stage renal disease (ESRD) who undergo hemodialysis manifest pronounced oxidative stress (OS), for the antioxidant system is inadequate to correct the imbalance between generation and scavenging of reactive oxygen species (ROS). To clarify the role of two different membranes on the OS, we measured plasma lipid peroxidation (LPO) and erythrocyte concentration of several antioxidant enzymes on 20 controls and 6 patients on bicarbonate dialysis (BHD). At 7 days intervals, 2 BHD sessions were done on the same 6 hemodialysis patients: the two BHD sessions were similar, except for the membrane used (cuprophan, first study; regenerated cellulose = Bioflux, second study, 7 days later). Before, during, and after each session (0', 30', 60', 120', end, 30' after BHD end), several blood samples were drawn. Lipid peroxidation and erythrocyte glutathione (GSH), superoxide dismutase (SOD), and catalase were spectrophotometrically determined (Bioxytech, France), but for erythrocyte glutathione peroxidase (Gpx) and G-6-PD, Gunzler's and Beutler's methods were used, respectively. Both membranes induce a significant decrease in LPO (p < 0.01) and an increase in erythrocyte SOD (p < 0.05). Bioflux shows some peculiar effects: a significant increase in erythrocyte GSH (p < 0.05) and erythrocyte catalase (p < 0.01) with a gradual increase of erythrocyte SOD and catalase/SOD ratio. Cuprophan, on the contrary, causes a sudden increase in erythrocyte SOD, while erythrocyte catalase decreases. These data support the view that Bioflux induces an OS lower than cuprophan because with the former, increased H2O2 production leads (thanks to catalase and GPx action) to water generation. With cuprophan, instead the reduced SOD/catalase ratio causes a greater H2O2 generation and a lower conversion to water.

The role of erythrocytes in the deperoxidative processes in people on hemodialysis

The defenses against the production of free radicals and reactive oxygen species (ROS) are to be found in plasma (ascorbate, urate, alpha tocopherol) and in erythrocytes (superoxide dismutase or SOD; catalase or CAT; glutathione peroxidase or GPx). In chronic renal failure, an increased lipid peroxidation and a reduced antioxidant activity seem to be present, but previous reports are conflicting. To clarify the peroxidative status and the defense mechanisms taking place in patients on dialysis, in 30 patients on dialysis (15 men, 15 women) and in 20 control subjects (10 men, 10 women), the following parameters were measured: plasma 4-hydroxinonenal (4-HNE) and erythrocyte reduced glutathione (GSH), SOD, GPx, and glucose-6-phosphate dehydrogenase (G-6-PD). Patients on dialysis, in comparison with control subjects, had 1) increased levels of 4-HNE (p < 0.001); 2) a significant increase in erythrocyte-GSH (p < 0.05); and 3) significant decreases in erythrocyte-SOD (p < 0.001), erythrocyte-G-6-PD (p < 0.005), and the erythrocyte-SOD/GPx ratio (p < 0.001). The dialysis procedure induced a certain reduction in plasma 4-HNE, an increase in erythrocyte-SOD activity, and an important consumption of erythrocyte-GSH, while the erythrocyte-SOD/GPx ratio changed. The current study supports the view that 1) erythrocytes act as small detoxifying packets; 2) in chronic renal failure, the antioxidant system is largely inadequate; and 3) in patients on dialysis, the antioxidant mechanism of erythrocytes in scavenging ROS is effectively exerted during dialysis but remains largely inadequate, as signs of lipid peroxidation persist with time.

Serum paraoxonase activity is decreased in uremic patients

Paraoxonase is a high-density lipoprotein (HDL)-associated enzyme capable of hydrolysing lipid peroxides. We measured the activity of serum paraoxonase together with serum concentrations of a variety of lipid constituents--total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL), cholesterol, triglycerides, apolipoproteins A-I and B--in 60 hemodialyzed (HD) patients. We found that the paraoxonase activity was significantly reduced in HD patients compared with 64 healthy controls (mean median and interquartile values: 93, 63, 87 IU/l in HD patients and 151, 120 and 135 IU/l in controls). In patients, the trimodal frequency of distribution of paraoxonase activity showed a shift toward lower levels. The effect of NaCl on enzyme activation was more pronounced in the patient group, as compared with controls, suggesting a higher frequency of the B allozyme (more responsive to NaCl) in this population. We suggest that altered HDL subfraction, present in HD patients, may be the main cause of the widespread depression of paraoxonase. Furthermore, the higher frequency of allozyme B among HD patients might increase the risk of coronary artery disease. In conclusion, paraoxonase activity may be an adjunctive index of altered lipoprotein metabolism with important repercussions on atherosclerosis.

The plasma glutathione peroxidase enzyme in hemodialyzed subjects

The kidney is probably the major site of production of the plasma enzyme glutathione peroxidase (GSHPx-P). For this study, GSHPx-P activity was determined in 40 healthy people, in 34 patients with differing degrees of renal impairment, and in hemodialysis patients from whom blood samples were withdrawn either before or after each session (18 patients) or throughout the dialysis session (27 patients). Hemodialysis patients were treated by means of different techniques (bicarbonate hemodialysis, hemodiafiltration, and acetate free biofiltration), and different membranes (cuprophane, polyacrylonitrite, and polymethylmethacrylate). The following results were obtained: 1) GSHPx-P activity was significantly decreased in renal impairment patients; 2) GSHPx-P activity negatively correlated with serum creatinine values in renal impairment patients (r = -0.55; p < 0.001); and 3) the enzyme activity slightly increased after the session in hemodialysis patients. The following conclusions can be drawn: GSHPx-P activity could be new index of renal function, because it was decreased in patients with renal failure; the decrease in GSHPx-P activity paralleled the severity of renal impairment, and was maximal in hemodialysis patients; GSHPx-P activity was slightly raised at the end of the hemodialysis session, concomitant with other enzyme activities (aspartate transaminase, alanine transaminase, and alkaline phosphatase) and total protein concentration. This seems to be attributable to the process of water loss rather than other hypothetical mechanisms, such as A) enzyme activation by either peroxide generation during blood-membrane contact, or by the removal of a hypothetical inhibitor; and B) de novo synthesis in the residual renal mass or in other sites of production.

Plasma glutathione peroxidase activity as an index of renal function

The kidney is a major source of the plasma enzyme glutathione peroxidase. We measured plasma glutathione peroxidase activity in 130 patients affected with different renal diseases at various stages, and compared it with the following indices of kidney function: serum creatinine, creatinine clearance, and urinary excretion of alpha 1-microglobulin, beta 2-microglobulin, albumin and N-acetyl-beta-D-glucosaminidase. Plasma glutathione peroxidase activity appeared significantly reduced in most of the renal diseases considered, and showed a significant correlation with most of the renal function indices. Linear discriminant analysis showed that the set of indices composed of plasma glutathione peroxidase activity, serum creatinine and creatinine clearance allowed the best classification of renal diseases. During treatment with the nephrotoxic aminoglycoside, tobramycin, plasma glutathione peroxidase activity showed an early and progressive decrease. We suggest the measurement of plasma glutathione peroxidase activity as an adjunctive index for the assessment of kidney alterations.

[The diabetic patient in extracorporeal dialysis]

The authors describe the main problems observed in diabetics undergoing dialytic therapy. A series of therapeutic approaches are illustrated that are apt to facilitate the dialytic and pharmacologic management of these difficult patients.

[Metabolic aspects of intestinal urinary diversion. Comparison with ileo-cecal bladder substitution and ileal conduct]

The aim of this study was the metabolic evaluation of 10 patients with 2 different types of urinary diversions, after cystectomy for infiltrating carcinoma. The patients were divided into two groups, homogeneous for age and follow up, according to the type of urinary diversion: group A (5 patients with ileo-cecal bladder) and group B (5 patients with ileal conduit). The follow up duration was 16.8 +/- 7.3 months in group A and 25.4 +/- 7.8 months, in group B. Even though the glomerular filtration rate (GFR) in both groups was within the normal limits, however - on closer evaluation - patients of A group revealed a slight functional damage, shown by reduced creatinine secretion, lower bicarbonatemia and lower urinary acid secretion when compared with ileal conduit patients. According to this study, the ileal conduit seems to be associated with a fairly good metabolic status while the ileo-cecal bladder could require closer clinical-metabolic follow up and bicarbonate supplementation.

Effect of aging on the body composition of dialyzed subjects. Comparison with normal subjects

A bioimpedance analyzer (BIA-CHIP; Akern RJL System) was applied to 366 normal subjects (171 men and 195 women). Each gender group was divided into eight groups, according to age: 20-29 years; 30-39 years; 40-49 years; 50-59 years; 60-69 years; 70-79 years; 80-89 years; and 90-95 years. The same was done with 44 hemodialysis patients (22 men, 22 women), each being evaluated 15 times over a period of 5 years: these were divided into seven groups (seven, because no patient was older than 89) using the same criteria. For each subject, 23 parameters were determined: 5 directly measured (height, weight, resistance, reactance, phase angle) and the others (fat and lean mass, body water, body cell mass, extra and intracellular water, etc.) from appropriate equations. Twenty-four thousand data points were collected and served to form a data bank. Men and women on hemodialysis showed different effects of aging: women normalized their BC at an age > 70 years, whereas men continued to have a muscle mass lower than that of normal subjects until the age of 80. A computerized program (Nutritio) permits fast and reliable evaluation of the nutritional status of hemodialysis patients, each subject being compared with both the similarly aged population (dialyzed or not) or with his or her own data, obtained over time.

New compartmental model approach to dialysis

Compartmental models are used for solving the problem of the control of dialysis therapy. The inadequacy of the existing monocompartmental model is faced, first with a careful analysis of the physiology of the system, then with a method focused on the construction of a new multicompartmental model. Moreover, impedance techniques allow us to solve the problem of measuring the total body water for each patient.

Metabolic complications of the urinary intestinal diversion: ileo-caecal bladder compared with ileal conduit

Five patients with an ileal conduit and 5 with an ileo-caecal bladder substitute have been studied metabolically. All had undergone cystectomy for infiltrating carcinoma and they formed 2 homogeneous groups in terms of age and follow-up. Function in both groups was within normal limits but closer examination of patients with an ileo-caecal bladder revealed mild functional damage as shown by reduced creatinine secretion, a lower level of bicarbonate and lower urinary acid valency secretion. It was concluded that the ileal conduit is more satisfactory from a metabolic point of view than the ileo-caecal bladder, which requires closer follow-up and treatment with bicarbonates if necessary.

Intermittent venovenous hemofiltration as a chronic treatment for refractory and intractable heart failure

Chronic heart failure (HF) is considered to be refractory when persisting despite an intensive drug regimen, or intractable when requiring "artificial" supports. Among them, hemofiltration (HE) has been used frequently, but only on an "acute" basis, to induce fast and safe water removal. Since 1985 the authors have treated refractory and intractable HF first by means of acute CAVH (continuous arteriovenous HE: 11 patients) and then (1988-1992) with IVVH (intermittent venovenous HE), initially done on an "acute" basis (13 patients) and then an a chronic basis (CIVVH): 8 subjects (6M, 2F; mean age, 60.8 years), 3 with RCHF and 5 with ICHF. This report deals with our experience in CIVVH. All patients were in severe failure. During a follow-up period of 63 months (range, 1-17/patient), 82 IVVH treatments (10.2/patient) were carried out, using this schedule: permanent Tesio catheter in superior vena cava, 0.6 m2 filter, double blood pump (blood flow = 80-250 ml/min); transmembrane pressure = 50-150 mmHg; mean ultrafiltration = 19 ml/min; replacement fluid = 8.6 ml/min; and session time = 340 +/- 88 min, according to individual dry weight (bioimpedance system). Six patients died (1-13 months after IVVH began); four of six had ICHF and two of six had RCHF; five of eight patients showed a significant amelioration of functional state, changing from fourth to third, to second and first degree failure, but this was after heart transplantation. In all cases a marked reduction in the drug regimen and in hospitalization was the rule.

[Is it possible to improve the nutritional status of dialysis patients?]

It is well known that hemodialyzed patients show a protein-calorie malnutrition (PCM) due to several factors: dialytic and/or biologic age, diet, hormonal status, amino acid loss. The nutritional status of 44 HD patients was quarterly evaluated from september '87 to may '90 (32 months) and ten of them (5 M, 5 F) were treated by means of L-carnitine (6 g/ev/week) from september '88 to may '90. In the 5 treated males a net gain (+ 80 g/month) of the muscle mass was observed while the 5 treated females showed a low increase of fats. This trend was different (even though not significantly different) from that observed in the untreated group, in which a muscle mass loss and a fat increase was the rule.

Effect of dialysate and substitution fluid buffer on buffer flux in hemodiafiltration

The effect of differing dialysate and substitution fluid buffer types and concentrations on acid-base balance have not been assessed in patients treated with hemodiafiltration for ESRD. To determine bicarbonate, acetate, lactate and total buffer flux, mass balance studies were performed in patients treated with hemodiafiltration using four different combinations of dialysate and substitution fluids. Driving force for bicarbonate flux was assessed in all treatments. Bicarbonate flux depended on bicarbonate driving force and ultrafiltration rate. Bicarbonate flux was negative in all treatment combinations, even when the driving force was positive. Acetate flux was positive in all treatment combinations, but the net magnitude was small. Lactate flux, when lactate containing substitution fluid was used, varied with dialysate buffer employed during treatment. Overall buffer flux depended on the bicarbonate driving force, ultrafiltration rate, and varied with the type of substitution and dialysate buffer employed. The types and concentrations of buffer used in dialysate and substitution fluid have important effects on the acid-base balance of patients treated with hemodiafiltration. The long-term implications of different therapeutical choices in these patients is unknown.

[Bioelectric impedance in the study of body composition in healthy and dialyzed individuals]

The bioelectrical impedance can correctly evaluate the body composition both in normal subjects and those uremia. Thus, due to its reliability and simplicity, it could be largely used not only in normal subjects but also in all the pathologies concerning bodywater and malnutrition.

[Clinical evaluation of 2 years of hemodiafiltration using bicarbonate]

At the end of a previous study concerning the use of different buffers for hemodiafiltration (BHDF) in both the re-infusate (40 mM/L) and dialysate (26 mM/L). Retrospective data analysis and showed BHDF to permit good acid/base balance, good clinical tolerability and satisfactory and persistent sense of well-being. From the point of view of kinetics, it is essential to evaluate carefully the acute and/or chronic effect of an alkaline blood pH during or after dial lysis, especially since the volume distribution of bicarbonate is not known.

Cardiovascular stability during the haemodialysis session: relationship between modelling and impedance parameters

The percentage of body water, if calculated from impedance, was found to be significantly different from the classic 58%. This supports the view that the evaluation of the dialytic efficiency should be, in the near future, carried out on the basis of a 'two-pool' model instead of the old 'one-pool'. The serial collection of data during a dialytic session supported the hypothesis that, 90 min after the start or, in general, after a body-water loss of about 5%-6%, some fundamental changes in measured indexes (phase angle, systolic pressure, body volumes, correlation matrix) usually appear. Large-scale research, based on an RS 232 interface connected to a computerised program, will probably help in clarifying whether some major intra-dialytic phenomena could in the near future be easily and automatically predicted.

Different buffers for hemodiafiltration: a controlled study

Hemodiafiltration (HDF) is usually performed using a dialytic solution (D) containing acetate (A) or bicarbonate (B) and a replacement fluid (RF) containing lactate (L). To clarify the role of buffers in HDF, 11 patients underwent different study periods, each three months long: bicarbonate hemodialysis (BHD = Baseline period); HDF with (A) in D and (L) in RF (first period of HDF); HDF with (A) in D and (B) in RF (second HDF); HDF with (B) in D and (L) in RF (third HDF); HDF with (B) in D and (B) in RF (fourth HDF = BHDF). HDF achieved: 1) an increase in dialytic efficiency (kt/V, 1.28), reducing the time-session (197 min); 2) an improvement in acid-base status (pre-dialytic values in BHDF: pH 7.36; pCO2 39.8 mmHg; HCO3- 21.8 mM/L); 3) better "dry weight" gain (reached in 92.8% of HDF and in 81% of BHD sessions); 4) a significant decrease, in dialytic side-effects (mainly during the third and fourth periods). On the whole, BHDF (HDF done using only bicarbonate buffer) represents an easy and safe technique, leading to better cardiovascular stability than BHD and HDF without bicarbonate buffer.

Chronobiological variations of prolactin (PRL) in chronic renal failure (CRF)

During a 24-hour period, the serum levels of prolactin (PRL) were determined in 89 subjects, including 24 controls and 65 with chronic renal failure (CRF), divided into groups according to sex, age and serum creatinine. In mild CRF, both in males and females, PRL level proved to be higher than controls while its circadian rhythm of secretion disappeared. The MANOVA analysis (multivariate analysis of variance) showed that all 3 considered factors (sex, age, creatinine) have a systematic effect on PRL values, that of creatinine being the most prominent. With the progression of renal failure, the physiological PRL oscillations tended to diminish. In general, increasing creatinine levels progressively shifted the acrophase (that is the time-distance between a given hour and the maximum peak of the function) to the morning, with hemodialysis patients showing acrophases between 12 p.m. and 1 a.m. It is possible that in CRF the PRL feedback system could no longer function.

High-flux haemodialysis with 1.5 m2 modified cuprammonium rayon membrane: technical and clinical evaluation

The feasibility and reliability of a short dialysis technique performed with standard dialysis equipment and a modified cuprammonium rayon hollow-fibre filter has been studied. The hydraulic response of the filter and membrane to high blood flows and transmembrane pressures were tested in vitro and the maximal clearances of different solutes achievable during high-flux bicarbonate dialysis were studied in vivo. Clinical studies were undertaken to evaluate the long-term effects of the short, highly efficient dialysis therapy. Six patients were treated for more than a year with single-pass bicarbonate dialysis with a blood flow of 500 ml/min, dialysate flow of 700 ml/min, and average duration of 150 min/session three times weekly. The treatment showed an adequate efficiency with an average KT/V greater than 1. All patients obtained an average blood urea nitrogen during the study of less than 80 mg/dl and an average protein catabolic rate of 0.9 g/kg per 24 h. The treatment was well tolerated by all patients and, on echocardiography, no significant changes in myocardial function were detected after one year of therapy. The treatment is efficient, well tolerated, simple to monitor and does not require the use of synthetic membranes or machines with advanced technology. Thus the reduction of dialysis treatment time is feasible in all centres at a relatively low cost.

Hyperprolactinemia as a marker of neurotransmitter imbalance in uremic population

Serum prolactin (PRL) levels are elevated in patients with chronic renal failure (CRF) but the mechanisms responsible for these abnormalities are not fully understood. PRL secretion is undoubtedly influenced by many substances, which can be variously altered in uremia: monoamines, endogenous opiates and PTH. Our data suggest that in early renal failure PRL levels are already significantly high and the 24-h pattern of PRL secretion is significantly different from that in controls. PRL derangements could be due in mild renal failure, to unknown factors (GABA?); in severe CRF, to a major change in dopaminergic activity; in hemodialysis (HD), to a low turnover of monoamines, and in peritoneal dialysis (PD) to increased activity of serotoninergic and dopaminergic systems.

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.

Uremic encephalopathy: an updating

Uremic encephalopathy (UE) is a clinical syndrome, closely linked to the progression of renal failure. Many approaches can be utilized to diagnose it: EEG changes, somatosensory evoked potentials, choice reaction time test, cerebrospinal fluid (CSF) studies, brain computerized tomography, plasma and CSF amino acid concentration. On the basis of the data available at present, it is possible to postulate that UE could be caused by amino acid derangements (mainly glutamine, glycine, aromatic and branched-chain amino acids) and by the subsequent imbalance of neurotransmitters (mainly GABA, dopamine, serotonin). Disturbances of mental, neurologic, motor and hormonal functions could derive.