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Biomedical subjects

P M De Vries

Publications and source records attributed to P M De Vries.

15 recordsLinked to original sources
PubMed2000

Determination of stroke volume by means of electrical impedance tomography.

ECG-gated electrical impedance tomography (EIT) is a non-invasive imaging technique, developed to monitor blood volume changes. This study is the first in comparing this non-invasive technique in measuring stroke volume with established techniques. The objective of this study was to validate EIT variables derived from the EIT images with paired obtained stroke volume measurements by thermodilution and MRI. After right cardiac catheterization, EIT measurements were performed in 25 patients. Regression analysis was used to analyse the relation between the EIT results and stroke volume determined by thermodilution. From the regression line an equation was derived to estimate stroke volume (in ml) by EIT. A strong correlation was found between EIT and stroke volume measured by the thermodilution method (r = 0.86). In a group of 11 healthy subjects this equation was validated to MRI. The mean and standard deviation of the difference between EIT and MRI was 0.7 ml and 5.4 ml respectively. These data indicate that EIT is a valid and reproducible method for the assessment of stroke volume.

Aged↗
PubMed2000

The impact of equations on calculation of lean body mass by bioelectrical impedance analysis in RDT patients.

Several equations are available to derive lean body mass (LBM) from bioelectrical impedance analysis (BIA). The purpose of this study was to investigate in dialysis patients the impact of the equation used on the outcome of LBM assessment. To avoid dyshydration as a confounder, vena cava diameter measurement was used to assess normohydration in the 21 patients studied. Five equations were compared. In a previously published study to assess total body water using antipyrine as a gold standard, Deurenberg's formula was advocated to be used in the estimation of LBM by BIA. Therefore, this formula was used as a basis for comparison with the other four equations. One equation gave results comparable to those obtained by Deurenberg's formula. Despite high correlations and agreement according to Bland and Altman analysis, the other three equations showed a significant difference with Deurenberg-derived LBM. Thus, the equation used has a major impact on the outcome of LBM estimations.

Adult↗
PubMed1997

Haemodynamic and biochemical responses to L-arginine and L-lysine infusions in normal subjects: L-arginine-induced vasodilatation cannot be explained by non-specific effects of cationic amino acids.

1. Pharmacological stimulation of the synthesis of nitric oxide (NO) may be important in the prevention or treatment of cardiovascular diseases. 2. There is much discussion as to whether the precursor of NO, L-arginine, is able to stimulate basal endothelial NO production. L-Arginine is known to have vasodilating effects. However, it is not clear whether L-arginine-induced vasodilatation is attributable to an increase in NO production or to other systemic effects of L-arginine. 3. To investigate further the mechanisms of the L-arginine-induced vasodilatation, we compared the responses to L-arginine with those to saline and L-lysine in healthy subjects. L-Lysine is not a substrate for NO synthesis, but shares many of L-arginine's other properties. 4. During L-arginine infusion, blood pressure decreased [systolic blood pressure from 120.2 (SD 8.8) to 117.3 (12.1) mmHg (P = 0.05); diastolic blood pressure from 65.3 (5.9) to 61.6 (7.9) mmHg (P < 0.01)], and heart rate and extracellular fluid volume increased. The total peripheral vascular resistance decreased during L-arginine infusion by 18.0 (11.4)% (P < or = 0.05 compared with baseline and compared with L-lysine infusion). These results indicate vasodilation. No changes were observed during L-lysine and saline infusion. 5. Plasma cyclic GMP (the second messenger for NO) increased during L-arginine but also during L-lysine infusion [from 5.7 (1.2) to 6.8 (1.7) nmol/l (P < 0.01), and from 5.8 (1.8) to 7.0 (2.9) nmol/l (P < 0.05) respectively]. Plasma L-citrulline (a by-product of NO synthesis from L-arginine) increased during L-arginine infusion from 30.6 (7.5) to 47.1 (9.9) mumol/l (P < 0.001), but also during L-lysine infusion from 32.7 (6.5) to 42.0 (8.3) mumol/l (P < 0.001). 6. Plasma electrolytes and atrial natriuretic peptide concentrations responded similarly to L-arginine and L-lysine infusion, indicating similar effects on osmolality, plasma volume expansion and potassium distribution. 7. In conclusion, although L-lysine infusion had effects that were similar to those of L-arginine infusion, no vasodilatation was observed. Therefore, these effects cannot account for the L-arginine-induced vasodilatation. This finding indirectly supports the hypothesis that the vasodilatation during L-arginine infusion might be mediated by an increase in NO synthesis. If so, our data suggest that the presumed markers for NO synthesis, plasma cyclic GMP and L-citrulline concentrations, do not accurately reflect this increase. Instead, the rise in plasma cyclic GMP may be related to the rise in ANP. The rise in L-citrulline may be related to competition with L-arginine for the same cell membrane transport mechanism and to stimulation of the urea cycle.

Adult↗
PubMed1997

Detection of hydration status by total body bioelectrical impedance analysis (BIA) in patients on hemodialysis.

The purpose of the present study was to investigate whether total body bioelectrical impedance analysis (BIA) could be appropriate to assess normohydration (i.e. dry weight) in hemodialysis patients. This study is warranted, because the simultaneous assessment of both hydration and nutritional status by BIA requires the presence of a situation of normohydration in order to guarantee valid conclusions about the nutritional analysis. Segmental bioelectrical impedance was performed to classify patients according to their hydration status. BIA measurements revealed significant differences in TBW, ECW and ICW/ECW between three hydration subgroups (under-, normo-, and overhydration), whereas ICW was similar. Therefore, TBW, ECW and ICW/ECW appear appropriate variables to assess hydration status in patients on hemodialysis. Hemodialysis diminished ECW significantly, whereas ICW did not change, suggesting that a decrease of ECW explains the fluid loss during hemodialysis.

Adult↗
PubMed1995

Bioelectrical impedance analysis: clinical tool in assessing total body water and thoracic fluid.

Bioelectrical impedance analysis forms a non-invasive tool for detection of body fluids. Total body measurement gives total body water (TBW) and, in case of multi-frequency analysis, of intra- and extracellular fluid volume. The thoracic approach measures thoracic fluid (TF). The set-up of both techniques is discussed. An overview is given of the clinical usefulness of the total body technique to monitor fluid changes and the process of refill during hemodialysis and to detect dry weight. The simultaneous measurement of TBW and TF was applied to obtain a more detailed picture of the body fluids. In a group of healthy subjects the age dependency of both variables was shown. During hemodialyss TBW and TF showed a major and comparable decrease. Fluid retention during cardiac surgery led to a slightly more pronounced increase of TF than of TBW. The combination of both impedance techniques offers clinicians a means to monitor alterations in fluid status in patients in more detail.

Aging↗
PubMed1994

Prevention of hypovolemia-induced hypotension during hemodialysis by means of an optical reflection method.

In this study protocol we evaluate the clinical value of the continuous monitoring of blood volume (BV) during hemodialysis (HD) by means of an optical reflection method. In the course of a dialysis session the ratio between the ultrafiltration (UF) rate and the patient's refill capacity determines the extent of decrease of BV. A steep fall of BV and, moreover, a remaining absolute BV too low, cause the greater part of hemodialysis-induced complaints. During 23 standard HD sessions BV was monitored by means of the optical method. Nine of the sessions were complicated by hypotension (group H). Comparison of the mean BV graphs of group H with the graphs of non-complicated sessions (non-H) produces several differences. Most important is the fact that BV is better preserved in group non-H, a difference which is already significant during the first ninety minutes of dialysis. By making use of the shape of the monitored BV graph and HD patient, in that way, might be recognized as hypotension-prone during the first third of a dialysis session. To prevent the occurrence of hypovolemia-induced hypotension two strategies can be followed. First, the decrease of BV of a patient prone to hypotension can be triggered to the mean BV decrease according to the BV graph of the non-H group. This can be achieved by interventional methods, e.g. temporary lowering of the UF rate. However, for this intervention the development of a closed-loop circuit is required. Another possibility is to measure a patient's maximal refill capacity each hour of hemodialysis by taking advantage of the displayed BV graph.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

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.

Adipose Tissue↗
PubMed1990

Ultraviolet-absorbing organic anions in uremic serum separated by capillary zone electrophoresis, and quantification of hippuric acid.

Organic anions accumulated in blood serum of patients with chronic renal failure were separated by a novel technique: closed-system capillary zone electrophoresis (CZE) in a pH6 carrier-electrolyte system. Hippuric acid (HA), p-hydroxyhippuric acid, and uric acid were identified by their co-elution with standards prepared in ultrafiltered normal serum and by comparison with the corresponding ultraviolet-detected peaks positively identified in the HPLC analyses. Analysis time for the entire profile is 8 min. Repeatabilities (CVs) of CZE migration times and peak areas of the three acids in serum samples were about 0.7% and 6%, respectively. We quantified HA in 10 ultrafiltered uremic serum samples and compared results with those by a previously described HPLC procedure. The very good agreement further supports the identification of hippuric acid. Accuracy and precision of the CZE method were similar to those for the HPLC gradient-elution method, but analysis time for HA (8 min) is much less than by HPLC (90 min). Our technique is very suitable for selective, rapid analysis for (ultraviolet-absorbing) anionic constituents in ultrafiltered uremic serum, without any sample pretreatment.

Anions↗
PubMed1989

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.

Calcium↗
PubMed1989

Interstitial correction of blood volume decrease during hemodialysis.

The etiology of hypotension during hemodialysis is multifactorial. Probably a decrease in blood volume caused by ultrafiltration, and acetate are both involved, while refilling from the interstitium acts as a compensatory mechanism. An osmotically induced transcellular fluid shift to intracellular might reduce the refilling capacity. This study investigated the effect of ultrafiltration on blood volume, blood pressure and refilling. The role of acetate and blood volume decrease in hypotension was established and intra- and extracellular fluid changes were calculated. Blood volume decrease depended on ultrafiltration: at high ultrafiltration rates refilling failed, apparently more so at high acetate plasma levels. An isolated blood volume decrease did not lower blood pressure. Concomitant high acetate levels caused hypotension and also seemed to reduce refilling. Nearly all refilling fluid came from the extracellular compartment. Only high dialysate sodium concentrations gave rise to an intracellular loss.

Acetates↗
PubMed1987

Comparison of biochemical and serological typing results and antimicrobial susceptibility patterns in the epidemiological investigation of Klebsiella spp.

An analysis of the serological and biochemical typing results of 925 clinical isolates of klebsiella revealed that biotyping and serotyping of klebsiella could replace each other for epidemiological purposes. The combination of both typing methods provided even more epidemiological information in analysing clusters of particular serotypes and biotypes in time. Clustering serotypes, mainly of neonatal origin, were nearly uniformly more resistant to the antibiotics in common use than other serotypes. Biotyping as well as serotyping of klebsiella isolates recovered from environmental surveys in the neonatal ward showed that epidemic and non-epidemic klebsiella isolates could occasionally be cultured from the environment and from the staff.

Cross Infection↗
PubMedDate not supplied

MRI evaluation of right ventricular pressure overload in chronic obstructive pulmonary disease.

In chronic obstructive pulmonary disease (COPD), the development of pulmonary hypertension is common. This study was performed to assess the signs of right ventricular (RV) pressure overload and RV failure in COPD. In 8 COPD patients without primary cardiac disease, RV wall thickness, mass, and end-diastolic volume were measured by cardiac-triggered cine MRI. MR phase-contrast velocity quantification was used to measure stroke volume and the patterns of flow into and out of the RV. Data of patients were tested versus those of a control group matched for age (n = 8). Results showed that the RV wall thickness was increased (.6 +/- 0.1 vs 0.4 +/- 0.1 cm, P < .001). RV mass was increased (67 +/- 11 vs 57 +/- 5 g, P < .005). RV stroke volume was decreased (57 +/- 13 vs 71 +/- 13 ml, P < .01), but RV ejection fraction was not different. In the main pulmonary artery flow, the quotient of acceleration time divided by ejection time was decreased (33 +/- 5% vs 38 +/- 4%, P < .05), which is indicative of pulmonary hypertension. In conclusion, this MRI protocol provides a tool to assess the effects of RV pressure overload in COPD before heart failure has become manifest.

Aged↗
PubMedDate not supplied

The adjustment of post dialytic dry weight based on non-invasive measurement of extracellular fluid and blood volumes.

One of the major problems in the clinical practice of hemodialysis is an incorrect estimation of post dialytic (PD) dry weight. Underestimation of dry weight leads to hypovolemia induced hypotension, and overestimation to hypertension, pulmonary edema, and left ventricular hypertrophy. Because of the insensitivity of clinical variables to estimate dry weight, a more accurate technique is warranted. For this purpose and for the continuous surveillance of changes in blood volume (BV) during hemodialysis, two non-invasive techniques were applied. Based on post dialytically obtained extracellular fluid volume (EFV) values, measured by means of a conductivity method, 30 stable hemodialysis patients were divided into three groups for further analysis: de- (n = 9), normo- (n = 15), and overhydrated (n = 6). Using an on-line optical reflection method, changes in BV were measured continuously during therapy. Mean BV decrease, corrected for UF, differed slightly between the three groups (0 = 1.84 +/- 2.06, N = 3.20 +/- 1.80, D = 4.20 +/- 1.60 %/L). However, eight hypotensive episodes occurred in group D versus none in groups N and O. These hypotensive episodes were characterized by a greater reduction of BV--corrected for ultrafiltration--from the start of treatment until the moment of hypotension (6.96 +/- 2.21 %/L), compared with the 22 non hypotensive controls (2.16 +/- 2.01 %/L, p < 0.001). Based on the PD EFV dry weight of the overhydrated and dehydrated patients was decreased and increased, respectively, by 500 g after each session, until PD EFV was within normal bounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗