Determination of peritoneal membrane transport characteristics with dialysis adequacy and transport test in Thai patients.

OBJECTIVE: The characteristics of peritoneal membrane transport are useful for the determination of dialysis treatment prescription. The peritoneal equilibration test (PET) is accepted as a gold standard tool for identification of these characteristics. Unfortunately, the process of PET is troublesome and unsuitable for clinical practice. Dialysis adequacy and transport test (DATT), which is easier and more convenient method, is proposed as an alternative test. The aim of the present study was to evaluate the accuracy of the DATT in determination of membrane characteristics in Thai patients. MATERIAL AND METHOD: Fifteen patients underwent both DATT and PET on the same day. The second DATT was performed. The 24-hour dialysate-to-plasma ratio of creatinine (D/Pcr) from each DATT was compared with the adjusted 4-hour D/Pcr from the corresponding PET. The types of membrane solute transport were classified using the PET proposed by Twardowski and the DATT suggested by Rocco into high, high average, low average, and low transporter RESULTS: The mean age was 48.1 +/- 16.4 years. The mean value of D/Pcr derived from DATT was higher than PET (0.80 +/- 0.10 vs. 0.74 +/- 0.14). The results of both D/Pcr were correlated (r = 0.78, p = 0.001). However, determinations of characteristics of membrane transport were discordant (kappa coefficient = 0.25). The results of the repeated D/Pcr were not different and the classification of membrane transport properties were concordant (kappa coefficient = 0.68). CONCLUSION: The results of D/Pcr derived from both tests were correlated. However determinations of characteristics of membrane transport were discordant.

Correction formula for creatinine concentration with glucose in dialysate.

OBJECTIVE: Previous studies showed that high glucose in dialysate could interfere with creatinine measurement. This error might produce some mistakes in peritoneal dialysis (PD) treatment. The correction of creatinine is essentially needed. MATERIAL AND METHOD: Creatinine powder diluted in 0.1 N HCl was used as the standard reference. Different creatinine measurements obtained from unused dialysate solutions in various glucose concentrations were performed. Creatinine correction was performed by Twardowski's formula which was recommended by Nephrology Society of Thailand and by Tam's formula which utilized unused dialysate creatinine and glucose ratio. Comparison of the results in determination of membrane transport characteristics was based on the criteria proposed by Twardowski et al in used dialysate solutions derived from 17 CAPD patients with different approaches. RESULTS: The mean creatinine concentrations obtained from the standard creatinine solution and the above two correction methods were different. The mean creatinine derived from Twardowski's formula was the lowest. The correlation coefficients between glucose and creatinine interference obtained by direct measurement and by Twardowski's formula were high (r = 0.80-0.98) at all creatinine levels. However, the correlation between glucose and creatinine interference were significant only at creatinine concentrations of 2.9 and 17.5 mg%. Classification of membrane transport was discordant when different correction formulae were used. CONCLUSION: Creatinine correction in dialysate was crucial. Creatinine correction with fresh dialysate creatinine and glucose ratio might be suitable in clinical practice.

Bedside renal assessment: a comparison of various prediction equations in Thai healthy adults.

OBJECTIVES: To compare the performance of various prediction equations for creatinine clearance (CrCl) and glomerular filtration rate (GFR) estimation in healthy Thai adults. MATERIAL AND METHOD: 60 healthy adults had urine analysis, serum creatinine and 24-hour urinary creatinine assessment. The author compared Cockcroft-Gault (CG), MDRD, and Rule equations, and that using urine-CrCl for estimation of GFR. RESULTS: The urine-CrCl was 105.3 +/- 39.3 ml/min/1.73 m2. The CrCl/GFR using CG and MDRD equations were significantly lower than urine-CrCl. There was considerable difference between the stratification of renal function with the various formulae. According to both equations, the incidence of subjects with CrCl/GFR of < 90 ml/min/1.73 m2 was about 60%. R2 reflecting the degree of correlation between estimated CrCl/GFR and the urine-CrCl was weak. CONCLUSION: The performance of the CG and MDRD equations were suboptimal for renal function assessment in Thai healthy adults. Further research is required to develop more reliable methods for estimating GFR across different ethic groups.

Body fluid volume determination via body composition spectroscopy in health and disease.

The assessment of extra-, intracellular and total body water (ECW, ICW, TBW) is important in many clinical situations. Bioimpedance spectroscopy (BIS) has advantages over dilution methods in terms of usability and reproducibility, but a careful analysis reveals systematic deviations in extremes of body composition and morbid states. Recent publications stress the need to set up and validate BIS equations in a wide variety of healthy subjects and patients with fluid imbalance. This paper presents two new equations for determination of ECW and ICW (referred to as body composition spectroscopy, BCS) based on Hanai mixture theory but corrected for body mass index (BMI). The equations were set up by means of cross validation using data of 152 subjects (120 healthy subjects, 32 dialysis patients) from three different centers. Validation was performed against bromide/deuterium dilution (NaBr, D2O) for ECW/TBW and total body potassium (TBK) for ICW. Agreement between BCS and the references (all subjects) was -0.4 +/- 1.4 L (mean +/- SD) for ECW, 0.2 +/- 2.0 L for ICW and -0.2 +/- 2.3 L for TBW. The ECW agreement between three independent reference methods (NaBr versus D2O-TBK) was -0.1 +/- 1.8 L for 74 subjects from two centers. Comparing the new BCS equations with the standard Hanai approach revealed an improvement in SEE for ICW and TBW by 0.6 L (24%) for all subjects, and by 1.2 L (48%) for 24 subjects with extreme BMIs (<20 and >30). BCS may be an appropriate method for body fluid volume determination over a wide range of body compositions in different states of health and disease.

Estimation of total-body and limb muscle mass in hemodialysis patients by using multifrequency bioimpedance spectroscopy.

BACKGROUND: Skeletal muscle mass can be measured noninvasively with magnetic resonance imaging (MRI), but this is time-consuming and expensive. OBJECTIVE: We evaluated the use of multifrequency bioimpedance spectroscopy (BIS) measurements of intracellular volume (ICV) to model total-body skeletal muscle mass (TBMM) and limb skeletal muscle mass in hemodialysis patients. DESIGN: TBMM was measured by MRI in 20 male and 18 female hemodialysis patients with a median (range) age of 54 y (33-73 y), weight of 78.9 kg (43.2-120 kg), and body mass index (BMI; in kg/m2) of 27.3 (19.4-46.6). We measured total body water (TBW) by using D2O dilution, extracellular volume (ECV) as bromide space, and ICV as TBW minus bromide space. Total body potassium (TBK) measured as 40K was used as an independent model of TBMM. BIS was used to measure whole-body TBW (ankle to wrist) and TBW in the arms and legs. BIS-estimated ICV was used to construct models to calculate limb muscle mass and TBMM. The latter was compared with models derived from isotopic methods. RESULTS: BIS yielded a model for TBMM [TBMM = 9.52 + 0.331 x ICV + 2.77 (male) + 0.180 x weight (kg) - 0.133 x age] (R2 = 0.937, P < 0.0001) as precise as TBK-measured TBMM [TBMM = 1.29 + 0.00453 x TBK (mEq) + 1.46 (male) + 0.144 x weight (kg) - 0.0565 x age] (R2 = 0.930, P < 0.0001) or isotopic methods. BIS models were also developed for measuring leg and arm muscle mass. CONCLUSION: BIS provides an estimate of TBMM that correlates well with isotopic methods in approximating values obtained by MRI and can be used to estimate limb muscle mass.

Nitric oxide and hemodialysis.

Nitric oxide (NO), previously thought of as a noxious gas, is now recognized as an important mediator of vascular responsiveness. Soon after its discovery, it was realized that the actions of NO are similar to the previously described endothelium-derived relaxing factor (EDRF). It is synthesized in the vascular endothelium utilizing the enzyme nitric oxide synthase (NOS) and diffuses in the adjacent vascular media, where it has a vasodilatory action. Opposing actions of NO and vasoconstrictor agents (such as endothelin-1, angiotensin IotaIota, and others) maintain the vascular tone of the renal arteries. The same balance at the level of the macula densa maintains glomerular filtration rate (GFR) during varying levels of salt excretion. Lack of NO can result in disruption of this fine balance, with resultant vasoconstriction and disease progression, hypertension, and accelerated atherosclerosis. In addition, hypertension may result from positive salt balance that occurs when macula densa NOS is inhibited. While most investigators report low levels of NO in uremic subjects, the levels in hemodialysis (HD) patients have not been characterized adequately. This is primarily because HD patients are exposed to both stimulatory and inhibitory factors for NO synthesis. Retention of inhibitors of NOS tends to decrease NO levels, whereas production of NO will be increased by cytokines generated during blood-dialyzer interaction. There is less disagreement, however, over the finding of elevated levels in those with dialyzer reactions and dialysis-induced hypotension. Recent developments in the isolation of inducible and constitutive forms of NOS makes understanding of its pathophysiologic effects more complete. Newer treatment directed at inhibiting only the inducible forms of NOS (sparing the constitutive forms) may soon be found useful for the treatment and prevention of hypotension and dialyzer reactions in HD patients.

Methods and reproducibility of measurement of resistivity in the calf using regional bioimpedance analysis.

UNLABELLED: The usefulness of regional bioimpedance analysis (RBIA) in determining the dry weight in dialysis patients is currently being investigated. The aim of this study was to evaluate the reproducibility of measurement of resistivity in the calf. METHODS: Twenty-five normal subjects and 10 patients undergoing regular hemodialysis were studied. Four electrodes inserted into a blood pressure cuff were placed on the calf. Bioimpedance was continuously measured over 3- to 5-min periods (Xitron Hydra). After a resting period of 1 min, cuff pressure was increased to above the systolic blood pressure (SBP) for a few seconds to expel excess ECF fluid and then deflated. The effect on recordings of moving the electrodes 2 cm higher and then 2 cm lower than the normal position was studied in 8 normal subjects. In a second study of reproducibility, post-dialysis measurements were made twice in 10 patients who maintained the same post-dialysis target weight throughout the study period. RESULTS: The mean resting resistivity rho(0) in normal subjects was 532.6 +/- 95 omega.cm rising to 583.9 +/- 99.7 omega.cm when cuff pressure was applied rho(p). The average values of rho(0) and rho(p) in patients post-dialysis were 489 +/- 74 and 537 +/- 77 respectively showing that there were no significant differences in rho(0) and rho(p) between normal subjects and patients post-dialysis. The mean values of change in resistivity when the electrodes were shifted between the lowest and highest positions on the calf were -3.66 +/- 4.45 and -1.44 +/- 3.82%, respectively. Repeat measurement of resistivity in patients post-dialysis varied by 2.04 +/- 2.29% while post-dialysis body weight varied by 0.17 +/- 0.47%. CONCLUSION: In this study, resistivity measurement by RBIA at the calf showed similar levels of fluid loading in patients post-dialysis as in normal subjects. This study also showed that change in electrode position resulted in a mean change in resistivity of <5% and repeated measurements showed a change in resistivity <3% while body weight changes were <0.2%. This technique appears to have an acceptable level of reproducibility for its application to the assessment of patient hydration.

Candida parapsilosis peritonitis in patients on CAPD.

Twenty-four episodes of C. parapsilosis peritonitis in 23 patients on continuous ambulatory peritoneal dialysis (CAPD) over 6 years were reviewed. Clinical manifestations and laboratory findings were similar to those of other pathogens. All started treatment with intravenous amphotericin B. In six cases it was attempted to maintain a peritoneal catheter in situ, but removal became essential to relieve fungal peritonitis. Of the patients who developed peritonitis, 15 episodes (62.5%) continued the CAPD program. Nine cases could not resume CAPD because of death in 4, patient preference in 2, and abdominal adhesion in 3. Antifungal treatment alone was ineffective in most cases. It was found that peritonitis developing after gram negative bacterial peritonitis and the use of fluconazole after catheter removal were associated with CAPD discontinuation. It was suggested that C. parapsilosis peritonitis in CAPD patients should be treated with rapid catheter removal, particularly those with fungal peritonitis who had prior gram negative peritonitis.