| 1. |
- Metry, George, et al.
(författare)
-
Computed tomographic measurement of lung density changes in lung water with hemodialysis
- 1997
-
Ingår i: Nephron. - 0028-2766 .- 1423-0186. ; 75:4, s. 394-401
-
Tidskriftsartikel (refereegranskat)abstract
- In 10 hemodialysis patients, with an ultrafiltration volume ranging from 1 to 4.5 liters per session, the lung density was measured by computed tomography (CT) and the lung volumes by total body plethysmography. From the CT numbers (difference in X-ray attenuation between lung and water, measured in Hounsfield units, HU), and by using a special computer program, quantitative estimates of the densities of normally inflated (pixels between -1,000 and -500 HU), poorly inflated (pixels between -500 and -100 HU) and noninflated lung tissue (pixels between -100 and +100 HU) were obtained. The sizes of the normally and poorly inflated areas were also measured. The results showed that, after dialysis, the normally inflated area was decreased in density and increased in size, and conversely, the size of the poorly inflated area was diminished but without change in density. This finding implied introduction of more gas into the lung. The above observation was reflected by the results of pulmonary function measurements, in that the total lung capacity and functional residual capacity were significantly increased after dialysis. In conclusion, changes in lung fluid (both intra- and extravascular) with hemodialysis can be measured quantitatively by the changes in lung density as estimated by the CT densitometry technique.
|
|
| 2. |
- Metry, George, et al.
(författare)
-
Effect of normalization of hematocrit on brain circulation and metabolism in hemodialysis patients
- 1999
-
Ingår i: Journal of the American Society of Nephrology. - 1046-6673 .- 1533-3450. ; 10:4, s. 854-863
-
Tidskriftsartikel (refereegranskat)abstract
- Full correction of anemia with recombinant human erythropoietin (rhEPO) has been reported to reduce the risk of cardiovascular morbidity and mortality and improve the quality of life in hemodialysis (HD) patients. Effects of normalization of hematocrit on cerebral blood flow and oxygen metabolism were investigated by positron emission tomography. Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction ratio (rOER), and metabolic rate for oxygen (rCMRO2) were measured in seven HD patients before and after correction of anemia and compared with those in six healthy control subjects. In addition, blood rheology before and on rhEPO therapy was measured in HD patients, which included blood viscosity, plasma viscosity, erythrocyte fluidity, and erythrocyte aggregability. The results showed that plasma viscosity was high (1.51+/-0.19 mPa x s) and erythrocyte fluidity was low (85.8+/-4.8 Pa(-1) x s(-1)), while whole blood viscosity was within the normal range (3.72+/-0.38 mPa x s) before rhEPO therapy. After treatment, the hematocrit rose significantly from 29.3+/-3.3 to 42.4+/-2.2% (P<0.001), accompanied by a significant increase in the whole blood viscosity to 4.57+/-0.16 mPa x s, nonsignificant decrease in erythrocyte fluidity to 79.9+/-7.4 mPa(-1) x s(-1) and nonsignificant change in plasma viscosity (1.46+/-1.3 mPa x s). Positron emission tomography measurements revealed that by normalization of hematocrit, rCBF significantly decreased from 65+/-11 to 48+/-12 ml/min per 100 cm3 (P<0.05). However, arterial oxygen content (caO2) significantly increased from 5.7+/-0.7 to 8.0+/-0.4 mmol/L (P<0.0001), rOER of the hemispheres significantly increased from 44+/-3 to 51+/-6% (P<0.05) and became significantly higher than healthy control subjects (P<0.05). In addition, rCBV significantly increased from 3.5+/-0.5 to 4.6+/-0.6 ml/100 cc brain tissue. The results showed that oxygen supply to the brain tissue increased with normalization of hematocrit, but it was accompanied by increased oxygen extraction in the brain tissue. This may be assumed to be related to the decrease of erythrocyte velocity in the cerebral capillaries as a result of the decreased blood deformability and the increased plasma viscosity.
|
|
| 3. |
- Metry, George, et al.
(författare)
-
Fluid balance in patients with chronic renal failure assessed with N-terminal proatrial natriuretic peptide, atrial natriuretic peptide and ultrasonography
- 2001
-
Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 171:2, s. 117-122
-
Tidskriftsartikel (refereegranskat)abstract
- The N-terminal proatrial natriuretic peptide (proANP) has become an important parameter for assessing the prognosis of patients with cardiac disease. Its use for evaluating the hydration status in patients with chronic renal failure, however, is still under investigation. The present study comprised 12 haemodialysis (HD) and 17 pre-dialysis patients. In the HD patients, the inferior vena cava diameter during quiet expiration (IVCe) was estimated by ultrasonography and plasma concentrations of N-terminal proANP, atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) were measured before and 4 h after termination of HD. In the pre-dialysis patients venous blood samples were taken during rest to measure plasma N-terminal proANP and ANP and serum creatinine. Normal values for N-terminal proANP and ANP were obtained from 18 healthy volunteers. The plasma concentrations of N-terminal proANP and ANP in healthy volunteers were 328 +/- 92 and 11.4.0 +/- 3.1 pM L-1, respectively. In pre-dialysis patients, serum creatinine ranged from 110 to 447 microM L-1 and was significantly correlated to plasma N-terminal proANP (r = 0.60, P < 0.05) but not to ANP. This may indicate that N-terminal proANP is more dependent on renal function for its clearance than ANP, which is probably cleared by extrarenal mechanisms as well. In HD patients, IVCe was significantly correlated to the three hormones before HD, most strongly to N-terminal proANP. After dialysis, IVCe was significantly correlated to ANP and cGMP but was not correlated to N-terminal proANP. This may suggest that proANP takes a longer time than other hormones to reflect changes in intravascular volume. In conclusion, N-terminal proANP is a hormone closely related to degree of renal function. Furthermore, it is a sensitive marker reflecting the interdialytic hydration status in HD patients, as indicated by its high correlation to IVCe, a standard method which is used frequently nowadays to assess the body hydration. However N-terminal proANP could not reflect the acute changes in fluid volume induced by HD, probably because it is slowly metabolized.
|
|
| 4. |
- Metry, George, et al.
(författare)
-
Gender and age differences in thoracic bioimpedance
- 1997
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 161:2, s. 171-175
-
Tidskriftsartikel (refereegranskat)abstract
- Thoracic impedance consists of a constant baseline component Z0 and a time-variable component delta Z which represents the impedance change related to the cardiac cycle. The maximum part of delta Z [(dZ/dt)max] represents the peak of the ascending aortic blood flow. Measurements of basal thoracic impedance are affected by structural and anatomical differences in the thorax related to sex and ageing. This component is a variable in the denominator of Sramek's formula which is used for calculating stroke volume. The aim of this study was to elucidate the question as to whether the age- and sex-related variation in basal impedance may affect bioimpedance measurements of stroke volume. The study comprised 111 healthy subjects (55 males and 56 females) of ages between 20 and 69 years, divided according to age decades into five groups each of males and females. Stroke volume index (SI), Z0 and (dZ/dt)max were measured in every subject, using transthoracic bioimpedance cardiography. Z0 and (dZ/dt)max had significantly higher values in females than in males in every age group except the oldest one in the case of Z0 and the oldest two groups in the case of (dZ/dt)max. Stroke index showed no significant sex difference, although the higher Z0 in females may underestimate the values of stroke index. Elevation of (dZ/dt)max in females may therefore reflect a positive relation to Z0 rather than higher flow rates. Since Z0 and (dZ/dt)max are variants in opposite positions in Sramek's formula (denominator and numerator, respectively), this functional relationship may keep the bioimpedance measurements from being affected by the sex- and age-related changes in Z0.
|
|
| 5. |
|
|
| 6. |
- Metry, George, et al.
(författare)
-
Lung density for assessment of hydration status in hemodialysis patients using the computed tomographic densitometry technique
- 1997
-
Ingår i: Kidney International. - : Elsevier BV. - 0085-2538 .- 1523-1755. ; 52:6, s. 1635-1644
-
Tidskriftsartikel (refereegranskat)abstract
- The density of the lung reflects the total mass of fluid, air, and dry lung tissue per unit volume of the lung. Lung density can be measured by evaluation of attenuation of an electron beam with computed tomography (CT). This technique has been shown to be sufficiently reliable and sensitive to distinguish normal from abnormal lung water. The aim of this study was to find out whether lung density properly reflects the hydration status in hemodialysis patients in comparison with other standard methods. Fourteen hemodialysis patients, with an ultrafiltration ranging from 0.3 to 4.5 liters per session, underwent CT measurements of lung density, ultrasonographic measurements of the diameter of the inferior vena cava after quiet expiration (IVCe) and quiet inspiration (IVCi), and measurements of the hematocrit and plasma levels of the biochemical hydration markers cyclic guanosine monophosphate (cGMP) and atrial natriuretic peptide (ANP). These measurements were performed before and 3.5 to 4 hours after termination of dialysis. Quantitative estimates of lung density were obtained within pixels with CT numbers ranging between -1000 and -100 Hounsfield Units (HU), and compared with normal data from 18 normal controls. In normal controls, the lung density ranged from -800 to -730 HU. In hemodialysis patients, lung density was significantly higher than normal before dialysis (-678 +/- 96 HU, P < 0.01) and significantly decreased after dialysis (-706 +/- 92 HU, P < 0.05), indicating a decrease in fluid content of the lung. The density was normalized in 5 patients. A significant correlation was found between lung density and IVCe both before and after dialysis (r = 0.8, P < 0.01 for both). Change in density was significantly correlated to amount of ultrafiltration (r = 0.67, P < 0.01) and percent change in blood volume (r = 0.63, P < 0.05), indicating that lung density is greatly affected by changes in the extracellular fluid volume, mainly the intravascular volume. In conclusion, lung water reflects the hydration status in hemodialysis patients and can be monitored by measuring the lung density by CT. Accordingly, normalization of lung density can help to achieve a proper dry weight in these patients.
|
|
| 7. |
|
|
| 8. |
- Metry, George, et al.
(författare)
-
Proportional changes in body fluid with hemodialysis evaluated by dual-energy X-ray absorptiometry and transthoracic bioimpedance with particular emphasis on the thoracic region
- 1997
-
Ingår i: Artificial Organs. - 0160-564X .- 1525-1594. ; 21:9, s. 969-976
-
Tidskriftsartikel (refereegranskat)abstract
- Alterations in body composition during extracorporeal hemodialysis (HD) were investigated in 12 hemodialysis patients (9 males and 3 females, mean age 50 +/- 15 years) with a mean ultrafiltration of 2.6 +/- 1.0 L. Analysis was performed using a dual-energy x-ray absorptiometry technique (DXA), which measures 3 principal components of the body: fat mass (FM): lean body mass (LBM), i.e., all soft tissues excluding fat; and bone mineral content (BMC). These 3 components were calculated for the whole body and for different body regions (namely, the thorax, trunk, lower limbs, and upper limbs). The thoracic cage region could be defined manually, separately from the trunk, and its tissue composition was calculated. DXA analysis was performed concomitant with a measurement of the basal thoracic impedance (TFI) by bioimpedance cardiography prior to and 1 h after dialysis. We found a significant decrease in the total LBM, from 55.8 +/- 8.8 to 53.3 +/- 9.3 kg (p < 0.05), but no change in either the FM or BMC. Moreover, there was a disproportional reduction in the LBM in different regions, being significantly greater in the thorax (7.47 +/- 3.7%) than in the other body regions (trunk 4.3 +/- 2.0%, lower limbs 5.4 +/- 2.1%, and upper limbs 4.7 +/- 1.5%). Regarding bioimpedance, a stronger significant correlation was detected between the percentage changes in the TFI and the changes in thoracic fluid (r = 0.80, p < 0.01) than between the changes in the TFI and the changes in the total body fluid (r = 0.63, p < 0.01). The absolute values of the TFI were also significantly and negatively correlated to the thoracic lean mass to fat mass ratio, both before and after HD (r = 0.82, p < 0.001 and r = 0.86, p < 0.001, respectively). In conclusion, DXA is a very sensitive technique to detect fluid changes during HD in the thorax when the thoracic cavity is defined as a region of interest as well as for the whole body. The data also indicate an extracellular compartmental imbalance between different regions with a significantly greater change in the thoracic region. Transthoracic bioimpedance is a useful technique for evaluating the HD induced changes in the thoracic fluid, rather than total body fluid.
|
|
| 9. |
|
|
| 10. |
- Ronco, Claudio, et al.
(författare)
-
Blood flow distribution in sorbent beds : analysis of a new sorbent device for hemoperfusion
- 2000
-
Ingår i: International Journal of Artificial Organs. - 0391-3988 .- 1724-6040. ; 23:2, s. 125-130
-
Tidskriftsartikel (refereegranskat)abstract
- A new polymer-based sorbent cartridge has been recently developed for enhancing middle molecule removal during hemodialysis. The cartridge (Betasorb, Renaltech, New York, USA) has been designed to be placed in series with the dialyzer in the blood circuit. It is therefore important to evaluate the distribution of flow into the blood compartment of the device in order to assess if the surface of the sorbent is utilized to the best. For this purpose, a special imaging technique was utilized. Cartridges were analyzed during a simulated in vitro circulation at 250 and 350 ml/min of blood flow and 25% and 40% hematocrit. Cartridges were placed in vertical position and a cross longitudinal section 1 cm thick was analyzed in sequence by a helical scanner. Dye was injected into the arterial inlet and the progressive distribution was evaluated by sequential densitometrical measures carried out automatically by the machine. The sequential images analyzed by the scanner demonstrated excellent distribution of the flow in the blood compartment with minimal difference between the central and the peripheral regions of the compartment. In particular the following flow velocity pattern could be observed under the different experimental conditions tested. We may conclude that the cartridge design is adequate and no channelling effects could be detected in the blood compartment. The flow distribution is slightly affected by changes in flow rate and hematocrit showing an optimal utilization of the available surface for molecule adsorption.
|
|
