No increase in Kidney Injury Molecule-1 and Neutrophil Gelatinase-Associated Lipocalin excretion following intravenous contrast enhanced-CT.

OBJECTIVES: To analyze kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (N-GAL) excretion post-intravenous contrast enhanced-CT (CE-CT) in patients with chronic kidney disease (CKD). METHODS: Patients were enrolled in a trial on hydration regimes to prevent contrast-induced acute kidney injury (CI-AKI). Blood and urine samples were taken at baseline, 4 - 6, and 48 - 96 h post CE-CT. Urinary KIM-1 and N-GAL values were normalized for urinary creatinine levels, presented as medians with 2.5 - 97.5 percentiles. RESULTS: Of the enrolled 511 patients, 10 (2%) were lost to follow-up. CI-AKI occurred in 3.9% of patients (20/501). Median KIM-1 values were 1.2 (0.1 - 7.7) at baseline, 1.3 (0.1 - 8.6) at 4 - 6 h, and 1.3 ng/mg (0.1 - 8.1) at 48 - 96 h post CE-CT (P = 0.39). Median N-GAL values were 41.0 (4.4 - 3,174.4), 48.9 (5.7 - 3,406.1), and 37.8 µg/mg (3.5 - 3,200.4), respectively (P = 0.07). The amount of KIM-1 and N-GAL excretion in follow-up was similar for patients with and without CI-AKI (P-value KIM-1 0.08, P-value N-GAL 0.73). Neither patient characteristics at baseline including severe CKD, medication use, nor contrast dose were associated with increased excretion of KIM-1 or N-GAL during follow-up. CONCLUSION: KIM-1 and N-GAL excretion were unaffected by CE-CT both in patients with and without CI-AKI, suggesting that CI-AKI was not accompanied by tubular injury. KEY POINTS: • KIM-1 and N-GAL excretion were unaffected by intravenous contrast-enhanced CT (CE-CT). • Patient or procedure characteristics were not associated with increased KIM-1 or N-GAL excretion. • Performance of CE-CT in CKD patients is likely to be safe.

Abnormal surface EMG during clinically normal wrist movement in cervical dystonia.

We investigated whether patients with cervical dystonia (CD) have abnormal muscle activation in non-dystonic body parts. Eight healthy controls and eight CD patients performed a flexion-extension movement of the right wrist. Movement execution was recorded by surface electromyography (EMG) from forearm muscles. Although patients had no complaints concerning wrist movement and had no apparent difficulty in executing the task, they demonstrated lower mean EMG amplitude (flexor: 0.32 mV and extensor: 0.61 mV) than controls (flexor: 0.67 mV; P = 0.021 and extensor: 1.18 mV; P = 0.068; borderline significant). Mean extensor muscle contraction was prolonged in patients (1860 ms) compared with controls (1334 ms; P = 0.026). Variation in mean EMG amplitude over movements tended to be higher in patients (flexor: 43% and extensor: 35%) than controls (flexor: 34%; P = 0.072 and extensor: 26%; P = 0.073). These results suggest that CD patients also have abnormal muscle activation in non-dystonic body parts at a subclinical level. This would support the concept that in dystonia, non-dystonic limbs are in a 'pre-dystonic state'.

Body composition in adult growth hormone-deficient men, assessed by anthropometry and bioimpedance analysis.

Anthropometry and bioimpedance analysis (BIA) were used to assess body composition in 42 GH-deficient (GHD) adult males (mean age, 27.2 +/- 4.7 yr). During childhood, all patients had received GH treatment for a mean period of 8.4 +/- 3.8 yr. At the start of this study, GH therapy had been discontinued for a mean period of 7.5 +/- 4.5 yr. Eighteen patients had isolated GH deficiency (I-GHD). Twenty-four patients had multiple pituitary hormone deficiencies (M-PHD), substituted adequately. Compared to age- and sex-matched controls, the sum of skinfolds measured at 7 different sites was significantly higher in I-GHD and M-PHD patients [controls, 73.1 +/- 25.4 mm; I-GHD patients, 102.1 +/- 37.7 mm (P less than 0.001); M-PHD patients, 126.8 +/- 35.4 mm (P less than 0.001)]. The increase in sc fat deposition was most pronounced on the trunk, particularly in the breast and abdominal area. Total body muscle mass was significantly lower in GHD patients (P less than 0.001). In patients, body muscle mass and plasma somatomedin-C level were positively correlated (r = 0.43; P less than 0.005). Total body resistance measured by whole body BIA was significantly higher in the patient group and was negatively correlated with plasma somatomedin-C (r = -0.53; P less than 0.001). The high resistance values observed in GHD patients could only in part be explained by their lower lean body mass. The most important cause, however, was an increase in specific electrical resistance of the lean body mass (LBM), reflecting relative dehydration. We conclude that GH deficiency in adult males is associated with an increase in sc fat and a decrease in body muscle mass. In addition, there is a qualitative change in LBM. The BIA data indicate that in these patients, the hydration state of the LBM is lower than normal, due to a decrease in extracellular water.

Use of bioelectrical impedance analysis measurements in the clinical management of patients undergoing dialysis.

The use of bioelectrical impedance analysis (BIA) in patients with end-stage renal disease who are receiving dialysis provides researchers with two important applications: 1) a biological model in which the underlying assumptions of BIA can be tested, and 2) if valid, a tool that can be used to improve the clinical management of patients receiving dialysis. We review the rationale of and purpose for using BIA in the dialysis population, the physiologic changes that occur during dialysis that influence BIA measurements, and last, conclusions reached from the current scientific literature.

Adipose tissue fatty acid composition and its relations to diet and plasma lipid concentrations in hemodialysis patients.

Adipose tissue fatty acid composition, serum lipid profile, and dietary intake of 37 patients on maintenance hemodialysis were studied. In August 1982, 1984, and 1986, analyses were carried out in 15 normotriglyceridemic (NTG) and 22 hypertriglyceridemic (HTG; type IV hyperlipidemia) patients. No correlations were found between dietary intake of polyunsaturated fatty acids (PUFAs), ratio of polyunsaturated to saturated fatty acids (P-S ratio), and carbohydrate content on the one hand and serum lipid concentrations on the other in the two groups. Adipose tissue linolenic acid correlated negatively with serum cholesterol in both groups. Strong correlations were found between dietary intake of PUFAs and adipose tissue linoleic acid content, between PUFAs and the double-bond index, between P-S ratio and adipose tissue linoleic acid content, and between P-S ratio and the double-bond index. No significant differences in dietary intake or adipose tissue fatty acid composition were observed between NTG and HTG patients. Thus, no evidence was found for exogenous dietary influences on serum lipid concentrations. The adipose tissue linoleic acid content did reflect the dietary intake of PUFAs.

Evaluation of electrical impedance tomography in the measurement of PEEP-induced changes in lung volume.

STUDY OBJECTIVES: A new noninvasive practical technique called electrical impedance tomography (EIT) was examined for the measurement of alveolar recruitment. DESIGN: Prospective clinical study. SETTING: ICU of a general hospital. PATIENTS: Acute respiratory failure (ARF) patients. MEASUREMENTS: The ventilation-induced impedance changes (VICs) of the nondependent and the dependent part of the lung were determined by EIT as a measure of tidal volume distribution. By the use of an impedance ratio (IR), defined as the VIC of the nondependent part of the lung divided by the VIC of the dependent part of the lung, the ventilation performances in both parts of the lung were compared to each other. RESULTS: Between patients, the VIC of the nondependent part of the lung was significantly lower in the patients with a level of positive end-expiratory pressure (PEEP) of > 10 cm H2O than in patients with a PEEP of < 5 cm H2O (p < 0.05). A significantly lower IR (-/+ SD) was found in the group with PEEP of > 10 cm H2O than in the group with PEEP between 0 and 5 cm H2O (1.28+/-0.58 vs 2.99+/-1.24, respectively; p < 0.01). In individual patients, the VIC of the whole lung increased when the PEEP level was increased. The VICs of the nondependent part of the lung and of the dependent part of the lung showed significant increases at a PEEP of 10 cm H2O compared to a PEEP of 0 cm H2O (p < 0.05). Also the IR decreased in individual patients when the PEEP was increased; a significant decrease was found at 10 cm H2O compared to 0 cm H2O (1.67+/-1.24 vs 2.23+/-1.47, respectively; p < 0.05). CONCLUSIONS: The decrease in IR indicates an increase in VIC in the dependent part of the lung above the nondependent part of the lung. The increase in VIC can be regarded as an increase in lung volume, implying alveolar recruitment in the dependent part of the lung. The same results also have been shown in earlier reports by CT scan. Since EIT is far more practical than CT scanning and also is a bedside method, EIT might help in the adjustment of ventilator settings in ARF patients.

The effect of right ventricular hypertrophy on left ventricular ejection fraction in pulmonary emphysema.

STUDY OBJECTIVE: The development of right ventricular (RV) hypertrophy in emphysema is accompanied by involvement of the left ventricle (LV) and its systolic function. Our objective was to study the relation between RV hypertrophy and LV ejection fraction in emphysema by means of MRI. PATIENTS: Ten emphysematous patients (FEV1, 0.99+/-0.32 L; FEV1/vital capacity (VC), 0.32+/-0.11 [mean+/-SD]) and 10 age-matched control subjects were included. Exclusion criteria were any history of systemic hypertension, ischemic or valvular heart disease, or episodes of right- and/or left-sided cardiac failure. MEASUREMENTS AND RESULTS: Rapid scout imaging was used to measure RV and LV wall mass, wall thickness, and end-diastolic volume. Stroke volume was derived from the main pulmonary artery flow. RV wall volume, RV wall thickness, and the ratio of RV to LV wall thickness were significantly larger in the patient group than in the control group (p<0.01). Furthermore, patients had significantly lower values of LV ejection fraction (p<0.01) than the control subjects. A flattening or leftward displacement of the ventricular septum during systole was observed. In addition, our study showed an increase of LV ejection fraction proportional with the RV wall thickness (r=0.78, p<0.01) in severely emphysematous patients. CONCLUSION: These data are in support of the hypothesis that flattening of the interventricular septum explains the relatively normal LV ejection fraction in emphysematous patients with severe RV hypertrophy.

Electrical impedance tomography in the assessment of extravascular lung water in noncardiogenic acute respiratory failure.

STUDY OBJECTIVES: To establish the value of electrical impedance tomography (EIT) in assessing pulmonary edema in noncardiogenic acute respiratory failure (ARF), as compared to the thermal dye double indicator dilution technique (TDD). DESIGN: Prospective clinical study. SETTING: ICU of a general hospital. PATIENTS: Fourteen ARF patients. INTERVENTIONS: In order to use the TDD to determine the amount of extravascular lung water (EVLW), a fiberoptic catheter was placed in the femoral artery. MEASUREMENTS AND MAIN RESULTS: Fourteen consecutive ARF patients receiving mechanical ventilation were measured by EIT and TDD. EIT visualizes the impedance changes caused by the ventilation in two-dimensional image planes. An impedance ratio (IR) of the ventilation-induced impedance changes of a posterior and an anterior part of the lungs was used to indicate the amount of EVLW. For the 29 measurements in 14 patients, a significant correlation between EIT and TDD (r = 0. 85; p < 0.001) was found. The EIT reproducibility was good. The diagnostic value of the method was tested by receiver operator characteristic analysis, with 10 mL/kg of EVLW considered as the upper limit of normal. At a cutoff level of the IR of 0.64, the IR had a sensitivity of 93%, a specificity of 87%, and a positive predictive value of 87% for a supranormal amount of EVLW. Follow-up measurements were performed in 11 patients. A significant correlation was found between the changes in EVLW measured with EIT and TDD (r = 0.85; p < 0.005). CONCLUSION: We conclude that EIT is a noninvasive technique for reasonably estimating the amount of EVLW in noncardiogenic ARF.

Noninvasive assessment of right ventricular diastolic function by electrical impedance tomography.

STUDY OBJECTIVES: Electrical impedance tomography (EIT) offers the possibility to study blood volume changes within the right atrium during the cardiac cycle. The aim of this study was to determine the applicability of EIT in the assessment of right ventricular diastolic function in COPD. DESIGN: By means of region of interest analysis, impedance changes within the right atrium during the cardiac cycle were plotted as a function of time. As a diastolic index of the right ventricle, the right atrium emptying volume (RAEV), defined as the ratio between the volume change during the rapid filling phase relative to the total ventricular filling volume, was calculated. In a first study, the validity of the EIT method was assessed by comparison of the RAEV measured by EIT and MRI in a group of eight patients with severe COPD and seven control subjects. A second study was undertaken to assess the relation between RAEV and pulmonary artery pressure in a group of 27 patients measured by right-sided heart catheterization. RESULTS: The correlation coefficient between RAEV measured with MRI and EIT was 0.78. The difference between RAEV measured by MRI and EIT was 8.3 +/- 15.7% (mean +/- SD) for the control subjects and 3.5 +/- 10.9% for the COPD patients. RAEV values measured by EIT and MRI were larger in the control group (47.1 +/- 7.6%) compared with the patient group (38.1 +/- 10.4%). There was a clear nonlinear relationship between RAEV and the pulmonary artery pressure (y = 315 x-0.64, r = 0.83, p < 0.001). CONCLUSION: Our results indicate that RAEV measured by EIT is a useful noninvasive and inexpensive method for assessing right ventricular diastolic function in COPD patients.

The influence of weight on stroke volume determination by means of impedance cardiography in cardiac surgery patients.

OBJECTIVES: Obesity is thought to be one of the conditions in which the impedance cardiographic method is less reliable for estimating stroke volume (SV). This led to the introduction of a weight correction factor, sigma, into the equation according to Sramek and Bernstein. However, no scientific evidence has been published to support the use of this factor. The objectives of the present study are to evaluate the influence of body weight on the accuracy of impedance cardiography and to validate Bernstein's weight correction factor by comparison with thermodilution in patients after coronary bypass surgery. DESIGN: Prospective clinical study. SETTING: A surgical intensive care unit in a university hospital. PATIENTS: 37 consecutive patients 24-36 h after coronary bypass surgery, sub-divided into a normal-weight group (n = 24), patients whose weight deviated less than 15% from their ideal weight, and an obese group (n = 13), patients whose weight deviated more than 15% from their ideal weight. MEASUREMENTS: Kubicek's impedance cardiographic method and Sramek and Bernstein's method to assess SV are applied and compared to thermodilution. In order to study the validity of sigma, the results are compared between 24 patients with normal weight and 13 obese patients. RESULTS: A significant correlation between miscalculation of SV by impedance cardiography and the degree of obesity for Sramek and Bernstein's method is found when sigma is not included in the equation (r = -0.55, p < 0.05). This relation, however, remained significant when sigma was included in the equation (r = -0.40, p < 0.05). Kubicek's method shows no significant correlation for this relation (r = -0.30). Besides this, Sramek and Bernstein's method underestimates SV significantly in the obese group, independent of the use of sigma in the equation. These results are explained as being intrinsic to the equation, according to Sramek and Bernstein. In the whole group the impedance-derived SV did not significantly differ from SV as measured by means of thermodilution, independent of the method used to calculate SV. However, a considerably better correlation and agreement (mean difference +/- 2 standard deviations is found when Kubicek's method is applied (r = 0.90, 0.5 +/- 17.1 ml vs 0.64, -4.9 +/- 31.8 ml for Sramek and Bernstein's method). CONCLUSIONS: Weight significantly influences Sramek and Bernstein's method of impedance cardiography, whereas Kubicek's method is not biased by this factor.

Impedance cardiography. Importance of the equation and the electrode configuration.

OBJECTIVE: Electrical impedance cardiography (EIC) has been suggested as a non-invasive method to measure cardiac output. In several studies it proved to be a reliable method, although there were some restrictions. In 1966 Kubicek et al. developed an impedance cardiac output system based upon electrodes and a specific stroke volume formula. In 1983 Sramek et al. developed a new electrode configuration, and a new equation to calculate stroke volume, an equation that was adjusted by Bernstein in 1986. Since then these two methods have been used in clinical medicine. The purpose of the present study was to compare both electrode configurations and both stroke volume calculation equations with each other. The cardiac output (CO) values obtained by means of EIC are compared with CO values obtained by means of thermodilution. DESIGN: Prospective study. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: 20 mechanically ventilated patients after cardiac surgery. MEASUREMENTS AND RESULTS: Simultaneous measurement of CO by means of electrical impedance cardiography (COEIC) and thermodilution (COTD) was performed. COEIC was obtained using the lateral spot electrode configuration (LS) and an adjusted circular electrode configuration (SC). The formulas of Sramek (S), Sramek-Bernstein (SB), Kubicek (K) and an adjusted Kubicek formula (aK) were employed. Using the LS electrode configuration, significant differences were found between COEIC and COTD with the S formula (p < 0.005), the K formula (p < 0.001), and the aK formula (p < 0.05). Using the SC electrode configuration, significant differences between COEIC and COTD were found with the K formula (p < 0.005), the S formula (p < 0.01), and the SB formula (p < 0.05). No significant differences was found between EIC and TD using the LS electrode configuration together with the SB formula or using the SC electrode configuration with the aK formula. In both cases a good correlation was found between COEIC and COTD (r = 0.86, p < 0.001 and r = 0.79, p < 0.001, respectively). The mean difference between EIC and TD was 0.15 +/- 0.96 1/min and 0.19 +/- 1.19 1/min, respectively.

Biochemical and neurophysiological parameters in hemodialyzed patients with chronic renal failure.

Serum concentrations of accumulated solutes, standard clinical biochemistry, and parameters of clinical neuropathy, were determined in hemodialyzed patients with chronic renal failure. Analyses by high-performance liquid chromatography included creatinine, pseudouridine, urate, p-hydroxyhippuric acid, hippuric acid, indoxylsulfate, tryptophan, tyrosine, 3-indoleacetic acid, and a number of as-yet unidentified solutes. Standard biochemical parameters were measured; aluminium, parathyroid hormone, serum electrolytes and enzymes, hemoglobin, bilirubin, phosphate and urea. Measures of clinical neuropathy were: maximal motor nerve conduction velocities, and Hoffmann reflex latency. Several solutes had higher concentrations when nerve function was impaired. Serum total LDH, and total calcium levels correlated positively with values of the Hoffmann reflex, as did serum hippuric acid concentrations. Concentrations of p-hydroxyhippuric acid and two fluorescent compounds correlated negatively with motor nerve conduction velocities. In principal component analysis a number of 'organic acid-like' substances, like hippuric acid and p-hydroxyhippuric acid, were shown to associate multivariately with the neurophysiological variables while urea, creatinine, urate and phosphate were not.

Prediction of peak oxygen uptake in men using pulmonary and hemodynamic variables during exercise.

PURPOSE: Many attempts have been made to predict peak VO2 from data obtained at rest or submaximal exercise. Predictive submaximal tests using the heart rate (HR) response have limited accuracy. Some tests incorporate submaximal gas exchange data, but a predictive test without gas exchange measurements would be of benefit. Addition of stroke volume and pulmonary function (PF) measurements might increase the predictability of a submaximal exercise test. METHODS: In this study, an incremental exercise test (10 W x min(-1)) was performed in 30 healthy men of various habitual activity levels. Step-wise multiple regression analysis was used to isolate the most important predictor variables of peak VO2 from a set of measurements of PF: lung volumes, diffusion capacity, airway resistance, and maximum inspiratory and expiratory pressures; gas exchange; minute ventilation (V(E)), tidal volume (V(T)), respiratory exchange ratio (RER = carbon dioxide output divided by VO2); and hemodynamics (HR, stroke index (SI) = stroke volume/body surface area, and mean arterial pressure). These measurements were made at rest and during submaximal exercise. RESULTS: Using the set of PF variables (expressed as percentages of predicted), FEV1 explained 30% of the variance of peak VO2. No other PF variables were predictive. After addition of resting hemodynamic data, SI was included in the prediction equation, raising the predictability to 40%. At the 60-W exercise level, 48% of the variance in peak VO2 could be explained by SI and FEV1. At 150 W, the prediction increased to 81%. At this level VCO2/O2 (RER) also entered the prediction equation of peak VO2: 6.44 x FEV1(%) + 13.0 x SI - 1921 x RER + 2380 (SE = 142 mL x min(-1) x m(-2), P < 0.0001). Leaving out the gas exchange variable RER, maximally 64% of the variance in peak VO2 could be explained. CONCLUSION: In conclusion, inclusion of pulmonary function and hemodynamic measurements could improve the prediction accuracy of a submaximal exercise test. The submaximal exercise test should be performed until a level of 150 W is reached. Noninvasive stroke volume measurements by means of EIC have additional value to measurement of HR alone. Finally, measurement of gas exchange significantly improves the predictability of peak VO2.

Four-site skinfold anthropometry (FSA) versus body impedance analysis (BIA) in assessing nutritional status of patients on maintenance hemodialysis: which method is to be preferred in routine patient care?

BACKGROUND: Both four-site skinfold anthropometry (FSA) and bioelectrical impedance analysis (BIA) claim to be useful in routine clinical practice of maintenance dialysis as easy methods to assess nutritional status. The purpose of this study was to investigate which of these two methods is to be preferred. METHODS: Both before and after dialysis nutritional and hydration status were evaluated by BIA in 20 stable hemodialysis patients. Variables of nutritional status as lean body mass (LBM) and body fat (BF) were assessed by four-site skinfold anthropometry (LBM-FSA and BF-FSA) and BIA (LBM-BIA and BF-BIA). Variables of hydration status were total body water (TBW), its distribution into intracellular and extracellular compartments (ICW and ECW, respectively) and ICW/ECW. RESULTS: Weight loss during dialysis correlated with a change of LBM-FSA (r = 0.75, p <0.005) and also with that of LBM-BIA (r = 0.69, p < 0.005). To promote reliability of follow-up measurements in intervention studies it is warranted to evaluate nutritional status in an unchanged hydration status. The highly significant correlation (r = 0.93, p < 0.005) between the two techniques and the comparability between means and SD indicate that both techniques were almost equivalent to each other, although, compared to LBM-BIA, LBM-FSA was less affected by changes in fluid status. The sam held true for BF-BIA and BF-FSA. BF-FSA correlated significantly with BF-BIA (r = 0.65, p <0.005), whereas no difference of mean +/- SD was found between BF-FSA and BF-BIA. CONCLUSION: FSA and BIA are almost comparable techniques to assess both LBM and BF, although FSA is less affected by changes in fluid status. However, assessing LBM in normohydration is mandatory. Compared with FSA, BIA is able to establish hydration status and lacks depency on operator interpretation. Therefore, in routine patient care the BIA technique is the one to be preferred.

Diameter of inferior caval vein (VCD) and bioelectrical impedance analysis (BIA) for the analysis of hydration status in patients on hemodialysis.

BACKGROUND: Vena cava diameter (VCD) measurement is an accepted method to evaluate hydration status in patients on hemodialysis. Bioelectrical impedance analysis (BIA) is a less laborious method to assess hydration variables and more suitable for routine patient care. However, BIA has not yet been validated in dialysis patients. We investigated whether BIA can replace VCD in patients on hemodialysis. METHODS: In 20 stable hemodialysis patients [age (+/-SD): 47+/-17 yrs, dialysis duration (+/-SD): 76+/-59 months] hydration status was evaluated by VCD. Impedance variables such as resistance, reactance and phase angle were provided by BIA. They were used to calculate intracellular water (ICW), extracellular water (ECW) and total body water (TBW). RESULTS: VCD did not correlate with TBW-BIA, but correlated with ECW/TBW (r = 0.46; p<0.025), ECW/m2 (r = 0.42; p<0.005) and ICW/ECW (r = -0.49; p<0.005). Hemodialysis decreased TBW with 2.7+/-1.91. The difference in ECW before and after dialysis (8.9+/-1.3 and 7.4+/-1.41, respectively) was significant (p = 0.001). The same did not hold true for ICW (13.3+/-1.4 and 13.1+/-1.41). Major underhydration (n = 9; VCD <6.5 mm/m2) revealed sharp limits for ICW/ECW (>1.80) and ECW/TBW (<0.35), whereas these BIA-variables were significantly (p<0.005) different from those in minor underhydration (n = 8; 6.6 < VCD <8.0 mm/m2), normohydration (n = 15; 8 11.5 mm/m2). CONCLUSION: BIA can replace VCD only in major underhydration (VCD < 6.5 mm/m2). Fluid loss during hemodialysis is caused by a decrease of ECW, compatible with the postulation that excess fluid volume is carried by the extracellular compartment.

Long-term use of magnesium hydroxide as a phosphate binder in patients on hemodialysis.

The long-term use of magnesium hydroxide [Mg(OH)2] as a phosphate binder was investigated in 18 patients on chronic hemodialysis. All patients received a basal treatment with oral calcium carbonate. Vitamin D supplements were not used. In period I each patient ingested aluminum hydroxide [Al(OH)3], in period II Mg(OH)2 and in period III Mg(OH)2 and Al(OH)3 together. During period II and III a dialysate devoid of Mg was used. Mg(OH)2 doses were adjusted to prevent severe hypermagnesemia and diarrhea. The mean dose of Mg(OH)2 in period II was 2.4 +/- 0.6 and in period III 2.6 +/- 1.2 g/day. Serum phosphate increased significantly in period II and fell again in period III. Despite a halving of the Al(OH)3 dose in period III, serum Al was similar in period I and period III (55.8 +/- 19.1 vs 57.1 +/- 27.3 microg/l). Parathyroid hormone (PTH) concentration fell in period II and decreased even further in period III. We conclude that oral Mg(OH)2 may reduce the required Al(OH)3 dose, however, without an effect on serum Al concentration. The observed suppression of parathyroid activity needs further study.

The recovery of the fluid balance after hemodialysis and hemofiltration.

Dialysis dysequilibrium syndrome is a frequent complication of renal replacement therapy and seems to be related to changes in fluid balance. From previous studies it is known that these changes are less pronounced during hemofiltration (HF), leading to a lower incidence of complaints compared to hemodialysis (HD). To assess the severity and duration of the dysequilibrium syndrome, intracellular (ICV) and extracellular fluid volumes (ECV) were measured during and after HD and HF by means of a non-invasive conductivity method. Blood volume changes were calculated from pre- and post-treatment erythrocyte counts. Seven HD and eight HF patients were studied. Ultrafiltration volume did not differ between both groups. Blood volume decrease was less during HF due to a significant decrease in ICV, the latter being in contrast to an ICV increment during HD. The significant decrease in ICV led to a less severe decrease in ECV (90 versus 85%). Overall, this resulted in a better vascular refill during HF. At the end of treatment ICV and ECV were not in equilibrium yet. During the recovery period ICV increased roughly 3% in the HF group. In the HD group some patients showed an increase while others showed a decrease in ICV. Overall, no change in ICV was noticed. During recovery ECV decreased further in both groups. The measured recovery period was significantly shorter after HF (245 +/- 68 min) than after HD (299 +/- 37), supporting the hypothesis that HF is a more physiological way of treatment compared to HD.

The inaccuracy of Kubicek's one-cylinder model in thoracic impedance cardiography.

The validity of a one- and a two-cylinder model, underlying thoracic impedance cardiography (TIC), was investigated by studying the length dependence of the impedance parameters Z0, (dZ/dt)min, and stroke volume (SV). It can be shown that, within a one-cylinder model, all parameters are directly proportional to the length, whereas, if the volume conduction of the thorax and the neck are modeled separately, Z0 and (dZ/dt)min are expected to be linear dependent and SV will be nonlinear upon the length. The expectations were compared to results from in vivo measurements. Two electrode arrays were studied, in which the caudal recording electrode position was varied; SV was calculated using Kubicek's equation. Except for small distances, the results showed a nearly linear relation between the parameters and the length. Regression analysis of the linear part revealed statistically significant intercepts (p < 0.05). Neither the intercept nor the nonlinear part can be explained by a one-cylinder model, whereas a model consisting of two cylinders serially connected describes the experimental results accurately. Thus SV estimation based on a one-cylinder model is biased due to the invalid one-cylinder model. Corrections for the Kubicek-equation need to be developed in future research using this two-cylinder model.

Survival of Ralstonia solanacearum Biovar 2, the Causative Agent of Potato Brown Rot, in Field and Microcosm Soils in Temperate Climates.

ABSTRACT After outbreaks of potato brown rot in three different fields in the Netherlands, the fate of the brown rot pathogen, Ralstonia solanacearum biovar 2, was monitored in soil by immunofluorescence colony staining (IFC) supported by R. solanacearum division-2 specific polymerase chain reaction. In selected areas of all fields, the R. solanacearum population densities were initially on the order 10(4) to 10(6) per g of topsoil. These population densities then declined progressively over time. In two fields, however, the pathogen persisted for periods of 10 to 12 months. The survival of a selected R. solanacearum biovar 2 isolate, strain 1609, in three soils, a loamy sand and two different silt loam soils, was further studied in soil microcosm experiments. The effects of temperature and soil moisture content were assessed. At 12 or 15 and 20 degrees C, a gradual decline of the population densities was observed in all three soils, from the established 10(5) to 10(6) CFU g(-1) of dry soil to significantly reduced levels, occasionally bordering the limit of detection (10(2) CFU g(-1)of dry soil), in periods of approximately 90 to 210 days. Soil type affected the rate of population decline at 20 degrees C, with the greatest decline occurring in loamy sand soil. In all three soils, the survival of IFC-detectable R. solanacearum 1609 cells at 4 degrees C was severely impaired, reflected in an accelerated decline of CFU counts, to undetectable numbers. Moreover, indications were found for the occurrence of viable but nonculturable strain 1609 cells in the loamy sand as well as in one silt loam soil under these conditions. In addition, a single freezing-thawing cycle caused a significant additional reduction of the culturable R. solanacearum 1609 populations in the three soils, though detectable populations remained. Moderate soil moisture fluctuations of approximately pF 2 did not affect the survival of R. solanacearum 1609 in soil. Severe drought, however, drastically reduced the populations of strain 1609 CFU in all three soils.

Sleep complaints and sleep disordered breathing in hemodialysis patients.

BACKGROUND: The objective of the study was to determine the prevalence of sleep complaints and of sleep disordered breathing (SDB) in hemodialysis patients not selected for sleep complaints and to determine the effect of hemodialysis on SDB. The feasibility of home recording of sleep related respiration in these patients was also studied. METHODS: The patients completed a questionnaire and parameters of SDB were examined in the home setting on nights following dialysis and nights following no dialysis with the Edentrace II Recording System. RESULTS: Six (46%) of 13 patients had sleep complaints. Symptoms suggestive for sleep apnea syndrome were found in four (31%) of these 13 patients. In three (75%) of these four patients SDB was found. Sleep related respiration was monitored in 15 patients. Registrations satisfactory for interpretation were obtained in all patients. SDB was observed in five (33%) of these 15 patients. There were no significant differences in parameters of SDB between nights following dialysis and nights following no dialysis. CONCLUSIONS: Home recording of sleep related respiration in hemodialysis patients is feasible. Sleep complaints and SDB are common in these patients. No clinically significant differences in SDB were found between nights following dialysis and nights following no dialysis.