Automated peritoneal dialysis with 'on-line'-prepared bicarbonate-buffered dialysate: technique and first clinical experiences

BACKGROUND: Automated peritoneal dialysis (APD) has the possibility of increasing the dialysis efficacy by using higher fill volumes, frequent dialysate exchanges, and tidal techniques. It is then possible to treat patients adequately without residual renal function. The drawbacks of the required high amounts of dialysis solution of up to 30 litres per session are the high costs of lactate-based dialysate bags and difficulties for the patients in handling these bags. So far, bicarbonate-based peritoneal dialysate, which may be more biocompatible, is only available for CAPD in double-chamber bags. In APD this could be overcome by 'on-line' preparation of bicarbonate-buffered dialysate using advanced technologies originally designed for on-line preparation of substitution fluid for haemofiltration. METHODS: Four patients without residual renal function were treated with APD five times weekly in a crossover study design. Patients received standard lactate-based (35 mmol/l) treatment (25 litres per session each) in weeks 1 and 3. In week 2 on-line-produced bicarbonate-buffered (37 mmol/l) dialysate was used. This dialysate was prepared by an AK 100 Ultra haemodialysis machine. The machine was modified for adding glucose from a 50% concentrate to the desired concentration of 1.7%. Electrolytes, pH, pCO2, and dialysis efficacy parameters were measured. Microbiological testing was carefully performed. RESULTS: Creatinine clearances, Kt/V, and pCO2 did not vary between the different treatment phases, whereas the pH showed a distinct increase during the bicarbonate phase. Repeated determinations of endotoxins and culturing showed no contamination of the dialysate. The composition of the produced dialysate was reproducible with respect to pH, pCO2, sodium, calcium and bicarbonate, whereas the glucose concentration varied by +/- 20%. CONCLUSIONS: On-line preparation of PD fluid with the AK 100 Ultra is easy and safe to handle. APD with dialysate containing 37 mmol/l bicarbonate provides improved acid base balance and possibly improved biocompatibility, and may lead to a significant cost reduction. Further development in order to provide smaller machines and more precise ways of achieving a desired dialysate glucose concentration is necessary.     

Absence of bacteremia and endotoxemia despite contaminated dialyzate

Fevers associated with hemodialysis have been attributed to the transfer of relatively large endotoxin molecules and/or bacteria from contaminated dialyzate across the dialyzing membrane. We evaluated 27 patients during hollow-fiber dialysis when, due to a malfunction, dialysis fluids contained bacteria and endotoxin at levels previously reported to be associated with pyrogenic reactions. Neither endotoxin nor bacteria was detected in 54 venous and arterial blood specimens collected at the termination of hemodialysis. Temperature elevations did not occur during or within 1/2 hr after dialysis. In an extended study, 20 dialyzers were collected after single patient use and the dialyzate compartment was filled with highly contaminated dialyzate, while the blood compartment was filled with sterile pyrogen-free saline. Following 5 to 7 days incubation, bacteria were present in the blood compartments of 4 of 20 dialyzers, probably due to contamination during dialyzer handling. However, the much smaller endotoxin molecule could not be detected in the absence of bacterial contamination. These results indicate that the intact cellophane membrane is an effective barrier to endotoxin and bacteria under clinical conditions.     

POEMS syndrome in a patient with diabetic ketoacidosis: case report and review

This article summarise the main data in the literature on the role of bacteriological contamination of the dialysate fluid in inflammatory reactions in hemodialysis. Pyrogenic substances of small molecular weight from Gram-negative bacteria grown in dialysate can pass across intact dialyzer membrane to stimulate cytokine production by peripheral blood mononuclear cells. Cellulosic hemodialysis membranes are more permeable to endotoxins than synthetic membranes. Polysulfone membranes and polyamide membranes are able to adsorb bacterial toxins on the dialysate side. The diffusive transfer of bacterial products across dialysis membrane from dialysate fluid was demonstrated. Transmembrane passage of cytokine-inducing bacterial products across reprocessed dialyzers is greater than across new dialyzers. Bacteriological contamination of the dialysate fluid is a problem which must be considered with much more care by nephrologists, especially as LAL test is unable to detect all the bacterial products which can contaminate the dialysate fluid.     

Interleukin-10, interferon gamma, interleukin-2, and soluble interleukin-2 receptor alpha detected during peritonitis in the dialysate and serum of patients on continuous ambulatory peritoneal dialysis

OBJECTIVE: To analyze interleukin (IL)-10, interferon gamma (IFN-gamma), IL-2, and soluble IL-2 receptor alpha (sIL-2R alpha) in the dialysate and serum of patients on continuous ambulatory peritoneal dialysis (CAPD). DESIGN AND PATIENTS: Samples from dialysate bags were collected during the initial month of dialysis. During peritonitis, samples were collected from the first three bags on the day of admittance to the hospital and from the night bags on days 3 and 10. Serum samples were drawn on days 1 and 10. RESULTS: IL-10 was detected in all dialysate samples except one on the first day of infection, with a peak median level of 50 pg/mL and a slow decrease thereafter. In serum the median levels never exceeded detectable levels. Patients infected with Escherichia coli or Staphylococcus aureus had higher IL-10 levels in dialysate on day 3 as compared to the remaining patients (p < 0.05). If the catheter had to be drawn, because of persistent cloudy dialysate, the IL-10 levels remained elevated for a longer time (p < 0.05). IFN-gamma and IL-2 were detected only in the dialysate of patients infected with either S. aureus or S. epidermidis. Only one serum sample showed increased IFN-gamma. SIL-2R alpha was found in all the serum and dialysis samples from the first day of infection. Contrary to the analyzed cytokines, the receptor showed severalfold higher levels in serum as compared to the dialysate. During the infection the receptor levels in the dialysate increased, while they remained stationary in the serum, indicating a local production. CONCLUSION: This is the first time IL-10 has been demonstrated in the dialysate during peritonitis in CAPD patients. In view of its role as a suppressor of the immune and inflammatory responses, it is a potentially important observation, which might have clinical implications in the future.     

Long-term experience with an ultrapure individual dialysis fluid with a batch type machine

BACKGROUND: This paper discusses long-term experience with a specific type of dialysis equipment which has been used more than 15 years without variation. The system was designed to allow easy individualization of dialysis fluid composition and to deliver dialysate of the highest hygienic quality. METHODS: Data from 399 patients covering the period from 1971 onwards were analysed retrospectively. Survival probabilities were estimated by the Kaplan-Meier method and the median number of days in hospital was calculated. Additional data collected from patient subgroups included serum albumin level, erythropoietin requirement and antihypertensive treatments. Kt/V and PCR from one subgroup were computed using the formulae of Daugirdas and Depner. RESULTS: The estimated survival probability after 5 years for all patients was 59.1% (95% CI: 52.6-65.6%). The main risk factors from the available covariables were age and IDDM. The cumulative incidence of carpal tunnel syndrome after 10 years of dialysis was estimated as 7% (95% CI: 0-14%). Data from the subgroups revealed that 82% of the patients had serum albumin levels >4.0 g/dl, 65% of the patients received no antihypertensive drugs and 39% received erythropoietin (37 +/- 28 units/kg bw/week) to correct dialysis anaemia (haemoglobin level = 98 +/- 8 g/l). Average Kt/V was 1.21 +/- 0.17, PCR was 1.10 +/- 0.22 g/kg/day. CONCLUSIONS: The setup described permits individualized therapy of high quality. The high serum albumin values and our very low incidence of carpal tunnel syndrome underline the importance of water and dialysate quality.     

Relationship between fluctuations in the cerebral hemoglobin oxygenation state and neuronal activity under resting conditions in man

This study gives the results in terms of precision and repeatability of a new on-line urea monitoring system (Ureascan P2 Hospal) capable of measuring the urea concentrations in the spent dialysate. The Ureascan P2 Hospal (UP2H), fitted on single-pass dialysis machines (Integra-Hospal), functions by the presence of a disposable mini-reactor containing urease. The passage through the reactor of a minimum quantity of spent dialysate from the filter diluted with a pH 7 buffer solution (1 ml/min) increases its ionic strength, which is detected by a differential measurement of conductivity in proportion to the urea concentration in the dialysis liquid. We studied 13 dialysis sessions, with bicarbonate buffer, in 8 anuric patients. From 4 to 7 dialysate samples were taken during each treatment to determine the urea and 65 samples were analysed overall. Urea values from the UP2H were compared with those measured on the Dimension Du Pont analyser. Simple linear regression analysis showed an excellent correlation between the 2 measuring methods (r=0.987; p<0.001). The Bland-Altman test gave an average difference between the urea values measured with the UP2H and in the laboratory of 1.3+/-1.2 mg/dl. The agreement limits between 2 SD were -1.2 mg/dl and +3.8 mg/dl respectively. In conclusion, the UP2H we have developed has proved to be a reliable and very useful instrument for adapting, through the urea kinetic mathematical models, the dialysis dose for individual patients.     

Conformational change of human lens insoluble alpha-crystallin

BACKGROUND: It is useful to measure the luminal concentration of drugs which act in the gut. Dialysis of the rectum has not previously been used or validated for this purpose. AIM: To determine the precision of rectal dialysis for measuring rectal drug concentrations. METHODS: To establish the duration of dialysis required to approach equilibrium, the rate of methotrexate diffusion into dialysis bags was first determined in vitro. The precision of rectal dialysis for sampling the methotrexate concentration of colonic lumen extracellular fluid was determined in seven subjects who underwent two consecutive dialysis procedures. Subjects treated with subcutaneous methotrexate for refractory inflammatory bowel disease were studied. RESULTS: Methotrexate crossed the dialysis membrane by a first-order process, and after a 2 h in vitro dialysis, equilibration was 74 +/- 2% (mean +/- s.d.) complete. Rectal dialysis was well tolerated by all subjects. The mean +/- s.e. methotrexate concentration of 3.6 +/- 1.1 nmol/L in the first dialysate was not significantly different from 3.6 +/- 0.9 nmol/L in the second dialysate. P = 0.99 (paired two-tailed t-test). Similar precision was obtained for an endogenous molecule, potassium, secreted by the rectal mucosa. CONCLUSIONS: Dialysis of the rectum is a well tolerated and precise technique for sampling the colonic lumen extracellular fluid for quantitative analyses of exogenous and endogenous substances.     

The synaptic process in Locusta migratoria spermatocytes by synaptonemal complex analysis

BACKGROUND: Bacterial contamination of treated water and dialysate comprises an important problem for patients undergoing haemodialysis. Both the progressive reduction of the thickness of cellulose membranes and the expanding use of high-flux membranes probably enhance the risk of pyrogenic reactions, therefore increasing the need for atoxic water and non-pyrogenic dialysis fluid. METHODS: Samples of tap water, treated water, and effluent dialysate in all 85 haemodialysis centres in Greece were examined for total heterotrophic bacteria counts employing the pour plate method, total and faecal coliforms, faecal streptococci and pseudomonas spp. using the membrane filter technique, and sulphite-reducing clostridia applying the most probable number method. Overall 255 paired samples were tested from January to March 1997. RESULTS: For total heterotrophic bacteria, the overall compliance of treated water and dialysate to the American Association of Medical Instrumentation standards (<200 c.f.u./ml for water and <2000 c.f.u./ml for dialysate) was 92.6 and 63.7% respectively, whereas the compliance of tap water samples to our national standards (total heterotrophic bacteria < 10 c.f.u./ml and absence of the other indicator bacteria) was 80.7%. The most commonly isolated bacteria were pseudomonas spp., found in 22.2% of treated water and 59.5% of dialysate samples, whereas the respective frequencies were 12.3 and 36.2% for total coliforms, 8.6 and 30.0% for faecal coliforms, 14.8 and 28.7% for faecal streptococci, and sulphite-reducing clostridia were isolated in 5.8% of dialysate samples only. Haemodialysis centres equipped with storage tanks for treated water experienced lower levels of total heterotrophic bacteria, but higher counts of total and faecal coliforms, faecal streptococci, and pseudomonas spp., although the difference was statistically significant only for faecal streptococci counts, (P<0.05). Sixty-seven haemodialysis centres were equipped with bacterial filters, but mean values of all the examined microorganisms were not statistically different from those of the other centres. Faecal streptococci counts in treated water samples were positively correlated with ageing of both haemodialysis centres (P<0.005) and purification system (P<0.05), whereas pseudomonas counts were significantly correlated with ageing of the purification system (P<0.05).     

Transmembrane passage of cytokine-inducing bacterial products across new and reprocessed polysulfone dialyzers

The widespread use of bicarbonate dialysate and reprocessed high-efficiency and "high-flux" dialyzers has raised concerns about the increased risk of reverse-transfer of dialysate contaminants into the blood compartment. To evaluate this concern, the reverse-transfer of bacterial products from contaminated bicarbonate dialysate into the blood compartment was compared during in vitro dialysis with new or reprocessed high-flux polysulfone dialyzers. In vitro dialysis was carried out at 37 degrees C by use of a counter-current recirculating loop dialysis circuit with either new high-flux polysulfone dialyzers or dialyzers reprocessed once or 20 times with formaldehyde (0.75%) and bleach (< 1%) with an automated system. Heparinized whole blood from healthy volunteers was circulated through the blood compartment, and bicarbonate dialysate was circulated in the dialysate compartment. The dialysate was challenged sequentially by 1:1000 and 1:100 dilutions of a sterile Pseudomonas aeruginosa culture supernatant (bacterial challenge). Samples were drawn from the blood and dialysate compartments 1 h after each challenge. Peripheral blood mononuclear cells (PBMC) were harvested by Ficoll-Hypaque separation from whole blood in the blood compartment and a 5 x 10(6) PBMC/mL cell suspension was prepared. Likewise, dialysate samples (0.5 mL) were added to 0.5 mL suspension of 5 x 10(6) PBMC/mL drawn at baseline. All PBMC suspensions were incubated upright in a humidified atmosphere at 37 degrees C with 5% CO2 for 24 h, and total interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF alpha) cytokine production (cell-associated and secreted) was measured by radioimmunoassay. Eight experiments were performed for each arm of the study with the same donor for each arm. One hour after contaminating the dialysate with a 1:1000 dilution of the bacterial challenge, IL-1 alpha production by PBMC harvested from the blood compartment was 160 +/- 0, 171 +/- 11, and 270 +/- 35 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.004). One hour after challenging the dialysate with 1:100 dilution, IL-1 alpha production by PBMC harvested from the blood compartment was 188 +/- 20, 228 +/- 35, and 427 +/- 67 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.006). IL-1 alpha production by PBMC from dialyzers reprocessed 20 times was significantly greater than both new and dialyzers reprocessed once. However, there were no significant differences between new dialyzers and dialyzers reprocessed once. Similarly, after the 1:1000 challenge, TNF alpha production by PBMC harvested from the blood compartment was 160 +/- 0, 160 +/- 0, and 213 +/- 22 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.008). After the 1:100 challenge, TNF alpha production was 168 +/- 8, 188 +/- 20, and 225 +/- 32 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.20). These results demonstrate that reprocessing of high-flux polysulfone dialyzers with bleach increases the risk of reverse-transfer of bacterial products from contaminated dialysate, and this risk appears to increase with the number of reuses. Consequently, units that reprocess membranes with bleach and have suboptimal water quality might subject their patients to a higher risk of cytokine-related morbidity.     

Peritonitis in continuous ambulatory peritoneal dialysis. Culture of peritoneal dialysate fluid

Conventional aerobic and anaerobic culture of peritoneal dialysate effluent from patients in continuous peritoneal dialysis (CAPD) was compared to culture in a semiautomated blood culture system. During a two-year period 78 of 79 consecutive episodes of peritonitis among 45 Danish CAPD patients were cultured and the etiology of the infection found in 73 (94%). The sensitivity of the blood culture system was 88%, whereas the sensitivity of the conventional culture of the dialysate effluent was 81%. This difference is not significant (McNemar test; 0.5 > p > 0.3). The majority of isolates were Gram-positive bacteria dominated by coagulase-negative staphylococci (38%). In comparison, only 2% of the cultures of peritoneal dialysate effluent taken within the same period from patients without clinical signs of peritonitis were positive. All the Gram-positive aerobic bacteria were sensitive to vancomycin whereas 97% of the Gram-negative aerobic bacteria were sensitive to gentamicin. An initial empiric treatment of peritonitis with a combination of vancomycin and gentamicin is recommended.     

Spatial physiological heterogeneity in Pseudomonas aeruginosa biofilm is determined by oxygen availability

The role of oxygen availability in determining the local physiological activity of Pseudomonas aeruginosa growing in biofilms was investigated. Biofilms grown in an ambient-air environment expressed approximately 1/15th the alkaline phosphatase specific activity of planktonic bacteria subjected to the same phosphate limitation treatment. Biofilms grown in a gaseous environment of pure oxygen exhibited 1.9 times the amount of alkaline phosphatase specific activity of air-grown biofilms, whereas biofilms grown in an environment in which the air was replaced with pure nitrogen prior to the inducing treatment did not develop alkaline phosphatase activity. Frozen cross sections of biofilms stained for alkaline phosphatase activity with a fluorogenic stain demonstrated that alkaline phosphatase activity was concentrated in distinct bands adjacent to the gaseous interfaces. These bands were approximately 30 micron thick with biofilms grown in air, 2 micron thick with biofilms grown in pure nitrogen, and 46 micron thick with biofilms grown in pure oxygen. Overall biofilm thickness ranged from approximately 117 to approximately 151 micron. Measurements with an oxygen microelectrode indicated that oxygen was depleted locally within the biofilm and that the oxygen-replete zone was of a dimension similar to that of the biologically active zone, as indicated by alkaline phosphatase induction. These experiments revealed marked spatial physiological heterogeneity within P. aeruginosa biofilms in which active protein synthesis was restricted by oxygen availability to the upper 30 micron of the biofilm. Such physiological heterogeneity has implications for microbial ecology and for understanding the reduced susceptibilities of biofilms to antimicrobial agents.     

Aluminum kinetics using bicarbonate dialysate with the sorbent system

In the REDY system a sorbent cartridge is used to regenerate the spent hemodialysate so that only six liters of dialysate are required for a treatment. The manufacturer claims that the cartridge can be used to remove aluminum from the dialysate and that it does not add aluminum to the dialysate. This claim for acetate dialysate is supported by the literature, but there are few data available relative to bicarbonate dialysate. The present study evaluates the use of bicarbonate dialysate and the REDY system in regard to aluminum kinetics both in vitro and in vivo. In vitro, the sorbent cartridge removed aluminum from dialysate prepared from water containing as much as 470 micrograms/liter of aluminum, giving a dialysate containing less than 10 micrograms/liter. The first 500 ml of effluent contained 13 micrograms/liter of aluminum but after filtration decreased to below 10 micrograms/liter. Thus, it is unnecessary, as recommended, to discard the first effluent since this unfilterable aluminum will not pass through a dialysis membrane. In vivo, in a crossover study comparing the REDY with single pass, there were no significant differences between the pre- and post-plasma aluminum concentrations, and the dialysate aluminum remained below 4 micrograms/liter during the dialysis. In a second in vivo study the effect of dialysate from tap water on plasma aluminum using the predialysis purification procedure was evaluated. There was no differences between the pre- and post-plasma aluminum concentration. The aluminum levels were comparable to those of the crossover study. The dialysate remained below 4 micrograms/liter during the dialysis.     

Substitution of acetic acid for hydrochloric acid in the bicarbonate buffered dialysate

In a multicenter study including 5 dialysis units, blood acetate changes during 4 h dialysis sessions in 141 patients treated with a 4 mM acetate-containing bicarbonate dialysate (ABD) were evaluated and compared to the values of 114 patients using an acetate-free bicarbonate dialysate (AFD). Acetate-free bicarbonate dialysate was delivered by a dialysis machine from the mixing with water for dialysis of a 1/26.2 bicarbonate concentrate, and a 1/35 acid-concentrate in which acetic acid was substituted for hydrochloric acid (Soludia, Fourquevaux, France). This new type of dialysate was routinely in use for 3 years on average (range, from 2 to 5 years). All patients fasted before and during dialysis. Blood samples were withdrawn at the start and at the end of dialysis sessions. The acetate plasma concentration was determined using the acetyl-CoA synthetase enzymatic method (Boehringer, Manheim, Germany). In patients treated with ABD whose predialysis blood acetate levels were in the physiologic range of < or = 100 microM (n = 113), the acetate plasma concentration increased from a predialysis mean value of 22+/-3 microM to a postdialysis mean value of 222+/-11 microM in 88 patients (78% of patients) whereas the acetate plasma concentration changes remained in the range of physiologic values from 21+/-6 to 58+/-7 microM in the other 25 patients. In contrast, patients treated with AFD whose predialysis blood acetate levels were in the physiologic range (n = 108), acetate plasma concentration increased from a predialysis mean value of 49+/-6 microM to 160+/-19 microM in only 13 patients (12% of patients) whereas acetate plasma concentration changes remained in the range of physiologic values of 23+/-2 to 41+/-3 microM in most of the patients of this group. In this study, a significant number of patients, whether receiving standard or acetate-free bicarbonate dialysates, exhibited an extremely high acetate plasma concentration at the start of the dialysis session. Hyperacetatemia was controlled with AFD in patients whose predialysis acetate plasma concentration of 316+/-82 decreased to 55 +/-23 microM (n = 6) at the end of the dialysis session whereas the acetate plasma concentration remained high when the predialysis concentration was 580+/-76 microM, with a postdialysis concentration of 233+/-39 microM (n = 28). It is concluded that in patients whose predialysis blood acetate levels were in the physiologic range, acetate-containing bicarbonate dialysate induces hyperacetatemia whereas postdialysis blood acetate remains in the normal range in such dialysis patients treated with acetate-free dialysate. Chronic hyperacetatemia, which could be found in dialysis patients, is well controlled by dialysis using an acetate-free dialysate.     

Imprecision of the hemodialysis dose when measured directly from urea removal. Hemodialysis Study Group

BACKGROUND: The postdialysis blood urea nitrogen (BUN; Ct) is a pivotal parameter for assessing hemodialysis adequacy by conventional blood-side methods, but Ct is relatively unstable because of hemodialysis-induced disequilibrium. The uncertainty associated with this method is potentially reduced or eliminated by measuring urea removed on the dialysate side, a more direct approach that can determine adequacy from the fraction of urea removed and by substituting an estimate of the equilibrated postdialysis BUN (Ceq) for Ct. For a patient with a known urea volume (V), Ceq, the equilibrated Kt/V (eKt/V), and the solute removal index (SRI) can be calculated from the predialysis BUN (C0), total urea nitrogen removed (A), and V from simple mass balance calculations (dialysate/volume method). However, a theoretical error analysis showed that relatively small errors in A, C0, or V are magnified when SRI or eKt/V is calculated using this method, especially at higher eKt/V values (for example, if eKt/V = 1.4 per dialysis, a 7% dialysate collection error causes a 20% error in eKt/V). METHODS: During three to four baseline dialyses in each of 39 patients enrolled in the pilot phase of the HEMO Study, "A" was measured using an instrument that sampled dialysate frequently (Biostat), and V was calculated from A, C0, and Ceq (median CV for V = 5.6%). The mean V was then applied to the dialysate/volume method to estimate eKt/V and SRI during two to five subsequent dialyses per patient (comparison dialyses). The accuracy and precision of these estimates were assessed by comparing them with eKt/V and SRI derived from a direct measurement of Ceq drawn 30 minutes after dialysis (reference method), from mathematical curve-fitting of sequential dialysate urea concentrations (dialysate curve-fit method), and from another blood-side method that estimates eKt/V from single pool Kt/V and the fractional rate of solute removal (rate method): eKt/V = spKt/V - 0.6.K/V + 0.03. RESULTS: During 128 comparison dialyses, median absolute errors for calculated eKt/V compared with the reference method were 0.169, 0.061, and 0.071 for the dialysate/volume method, the rate method, and the dialysate curve-fitting method, respectively. The corresponding correlation coefficients were 0.47, 0.88, and 0.81. For SRI, median absolute errors were 0.044, 0.018, and 0.027, and the correlation coefficients were 0.54, 0.85, and 0.74 for the three methods. CONCLUSIONS: The precision of eKt/V and SRI measurements was significantly lower for the dialysate/volume method compared with the blood-side methods. Inclusion of the dialysate curve analysis provided by the Biostat restored precision to the dialysate method to a level comparable to that of the blood-side methods. New techniques employing dialysate urea analysis should include a concentration profile to avoid these inherent methodological errors and assure the accuracy of eKt/V and SRI.     

Acid-base balance in chronic peritoneal dialysis patients

Endogenous acid production has never been measured directly in dialysis patients and an empiric formula is used to estimate acid production from their protein catabolic rate. We have studied acid-base balance in 19 stable CAPD patients attending the peritoneal dialysis clinic of Mount Sinai Hospital. They obtained a 24 hour collection of peritoneal dialysis fluid and urine while consuming their usual diet and performing their usual activities. Total alkali gain was calculated from net GI alkali absorption plus urinary net acid excretion plus alkali gain from dialysate, while total acid production was measured directly from the urinary and dialysate excretions of sulfate and organic anions. Net GI alkali absorption was estimated from the difference between cations (Na + K+Ca + Mg) and anions (Cl + 1.8P) in the 24 hour dialysate and urine collections minus the daily total amount of lactate infused. All of our patients had a normal or high serum bicarbonate concentration, which was stable with time. Total alkali gain was virtually identical to total acid production (54.2 vs. 52.4 mEq/day) which suggests that these patients were in neutral acid-base balance. Net GI alkali absorption (22.7 mEq/day) was one of the same range as that of chronic renal failure patients not on dialysis and represented almost one half of the total daily alkali gain. The daily acid production of 52.4 mEq/day was numerically equal to 84% of the protein catabolic rate expressed as g/day, which is similar to the predicted value of 77% of PCR reported in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lactogenic hormone signal transduction

Dialyzers are reused in approximately three quarters of the dialysis units in the United States, but the effect of reprocessing on dialyzer performance has not been extensively evaluated. In a crossover study of six chronic hemodialysis patients, we determined urea, creatinine, phosphate, and beta2-microglobulin clearances and dialysate protein loss for two types of low-flux and two types of high-flux dialyzers during use numbers 1, 2, 5, and 15. Dialyzers were reprocessed by an automated machine using Renalin (Renal Systems, Plymouth, MN) as the germicide. Dialyzer arterial and venous blood and dialysate outflow samples were obtained at 5 and 180 minutes of each dialysis session to evaluate solute clearances. Urea, creatinine, and phosphate clearances were calculated using dialysate concentrations, whereas beta2-microglobulin clearance was calculated using plasma concentrations to include its removal by adsorption to the dialysis membrane. There was a trend for urea, creatinine, and phosphate clearances to decrease with reuse for both low-flux and high-flux dialyzers, but these differences were not statistically significant. The clearance of beta2-microglobulin and dialysate total protein concentration was small for low-flux dialyzers; these values were not dependent on reuse. There was a trend for beta2-microglobulin clearance and dialysate total protein concentration to decrease during a dialysis treatment using high-flux dialyzers. More significantly, beta2-microglobulin clearance and dialysate total protein concentration decreased substantially with the reuse of high-flux dialyzers. These observations show that the maintenance of small solute clearances during reuse of high-flux dialyzers does not ensure the maintenance of large solute clearances.     

Effects of different procedures of disinfection on the bacteriologic quality of hemodialysis monitors of the Cobe CS3 and AK 100 type

]n recent years, hemodialysis treatment for chronic renal failure has been increasing. Although the technical evolutions have improved the therapy, the problem of microbial, toxic and chemical contamination of the dialysis fluid is now re-emerging. Most of all, because of increasing use of high-flux dialysis and its potential for transmembrane transport of bacteria into patients, one should be aware that dialysis fluid pathways may be colonised with bacteria. On the bacterial point of view, the French legislation proposed 100 CFU/mL as a maximum for total count of aerobic bacteria in the bi-osmosed water used for dilution of the dialysis concentrate. This study took place during 8 weeks in the children-hospital dialysis unit in Nancy (France). Our laboratory have succeeded in validating an aseptic bacteriological sampling procedure within fluid pathways of haemodialysis monitors Cobe CS3 and AK 100. It has also be shown that 6 to 12 hours of dialysis monitoring doesn't affect the quantitative and qualitative bacterial contamination of the biosmosed water (mean: 5 CFU/100 mL) drained through the 5 years' old internal pipes of the 2 monitors. So it has whatever the 4 different disinfection procedures applied and on the monitors (Formol or Formol + Citric acid + Chlorine or Heat or Heat + dehydrated Citric acid).     

Lymphatic drainage of hypertonic solution from peritoneal cavity of anesthetized and conscious sheep

Lymphatic drainage of the peritoneal cavity may reduce ultrafiltration in continuous ambulatory peritoneal dialysis. We assessed lymphatic drainage of the peritoneal cavity in sheep under dialysis conditions by cannulation of the relevant lymphatic vessels and compared lymphatic drainage in anesthetized and conscious animals. Lymph was collected from the caudal mediastinal lymph node and the thoracic duct, both of which are involved in the lymphatic drainage of the ovine peritoneal cavity. Volumes of a hypertonic dialysis solution (50 ml/kg 4.25% Dianeal) containing 25 microCi 125I-human serum albumin were instilled into the peritoneal cavity, and lymph flows and the appearance of labeled protein in the lymphatic and vascular compartments were monitored for 6 h. Intraperitoneal pressures increased 4-5 cmH2O above resting levels after infusion of dialysate. On the basis of the appearance of tracer in the lymph, drainage of peritoneal fluid into the caudal lymphatic was calculated to be 3.09 +/- 0.69 and 14.14 +/- 2.86 ml/h in anesthetized and conscious sheep, respectively. Drainage of peritoneal fluid into the thoracic duct preparations was calculated to be 1.32 +/- 0.33 and 14.69 +/- 5.73 ml/h in anesthetized and conscious sheep, respectively. Significant radioactivity was found in the bloodstream, and at least a portion of this was likely contributed by the right lymph duct, which was not cannulated in our experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

An assay to measure antibiotic efficacy against Staphylococcus epidermidis biofilms on implant surfaces

Infection is a major limitation of implantable devices. Optimal antibiotic therapeutic regimes have not yet been defined. Implant-associated infections have a number of differentiating characteristics, which include the predominance of Staphylococcus epidermidis and other skin bacteria of normally low pathogenicity as the causative agents, together with a relative resistance to host defenses and to antibiotic therapy. These properties have been ascribed to the ability of the bacteria to exist on implant surfaces in the biofilm phase, which is protective. An assay of antibiotic activity using a standardized bacterial biofilm preparation of S. epidermidis is described. The assay is used to evaluate the relative efficacy of antibiotics to sterilize the biofilm, when they are used singly, or in double or triple combinations. The modulating effects of changing antibiotic concentrations and modifying the environment with CAPD variables (fresh and spent dialysis fluid, common PD solution additives) are also measured and the data summarized. It is hoped that, by using this and similar assays, individualized optimal therapeutic regimes of implant-associated infections may be logically planned.