Helmut Pogglitsch

Essential trace elements in humans. Serum arsenic concentrations in hemodialysis patients in comparison to healthy controls.

Serum arsenic concentrations of persons suffering from renal failure and undergoing hemodialysis treatment (n=85) and of healthy controls (n=25) were determined by hydride-generation AAS technique after microwave digestion. The results were evaluated by comparing the values of both groups, considering physiological factors and individual data, as well as comorbid conditions of the hemodialysis (HD) patients. Serum arsenic levels were diminished in the patient group compared with controls (mean values 8.5±1.8 ng/mL vs 10.6±1.3 ng/mL). Furthermore, additional diseases within the hemodialysis group, particularly injuries of the central nervous system (CNS), vascular diseases, and cancer, were correlated to occasionally markedly decreased serum arsenic concentrations. It was concluded that arsenic homeostasis is disturbed by HD treatment and certain additional diseases. Desirable arsenic concentrations in the body seem to be reasonable. This consideration results in the conclusion that arsenic could play an essential role in human health. Thus, reference arsenic concentrations in different human tissues and body fluids should be established in order to recognize not only arsenic intoxication, but also arsenic deficiency. Perhaps arsenic deficiency contributes to the increased death risk of HD patients, and therefore, arsenic supplementations for patients with extremely low serum arsenic concentrations should be taken into account.

Determination of the glomerular filtration rate by identification of sinistrin kinetics.

A computer-based method of system identification and estimation of parameter variance for two-compartment models matched to dynamic sinistrin concentration profiles for the determination of glomerular filtration rate is described. Thereby a procedure for the judgment of the optimal sampling time horizon is presented. Since single-injection techniques are suspected of yielding systematic overestimation of the glomerular filtration rate, a method is demonstrated confirming that such a technique employing sinistrin kinetics can be used to correctly determine the glomerular filtration rate. The validation of the system parameters gained by the single-injection method is made through prediction of the concentration contour under a constant infusion regimen in the same subject on a different occasion. This was performed in healthy controls and in patients with various degrees of renal insufficiency. Upon consideration of the dependence of the clearance estimates and their variances on the protocol duration in test subjects examined from four to ten hours, an adaptive design of the protocol length is developed.

Relationship between generation and plasma concentration of anorganic phosphorus. In vivo studies on dialysis patients and in vitro studies on erythrocytes.

The plasma concentration of inorganic phosphorus (Pi) was determined before, during and after hemodialysis in 28 patients with chronic renal failure. Pi plasma concentration decreased rapidly when hemodialysis was started but did not fall below normal levels during continued dialysis. These changes of Pi concentration were fitted to a model of Pi kinetics in which Pi delivery to plasma is a nonlinear function of the extracellular Pi concentration. In separate in vitro studies, erythrocytes from six subjects with normal renal function and from 14 patients with chronic renal failure were incubated in homologous plasma with various amounts of Pi added. All other factors known to affect the Pi shift between intra - and extracellular fluid compartments (pH, calcium concentration) were kept constant. The relation between Pi concentration in plasma used for incubation and in red cells after 1h incubation suggested a mechanism in which a high plasma concentration results in movement of Pi into red cells where Pi is stored most probably in glucose esters. At low Pi plasma concentration Pi is delivered to plasma at a rate which cannot be explained solely by passive movement of intracellular Pi to plasma but requires additional generation from intracellular storage forms. The generation and delivery of Pi in patients and in their erythrocytes indicate a simple cell-mediated Pi homeostasis counter-acting abnormal fluctuations of plasma Pi.

Cerebral Hemodynamic Changes following Treatment with Erythropoietin

Adverse hemorheologic effects induced by erythropoietin (EPO) treatment of renal anemia may pose a cerebrovascular risk. We therefore investigated the changes in cerebral perfusion, cerebral blood flow velocity (BFV) and neuropsychologic performance in 11 patients (mean age 37 years) receiving EPO. In response to EPO there was a significant (p less than 0.01) increase in hematocrit (35%), hemoglobin (43%) and whole-blood viscosity (50% at high and 90% at low shear rate). The initially increased blood flow velocity dropped significantly (p less than 0.05) and returned toward normal values in the middle cerebral arteries and the basilar artery (22 and 19% decrease, respectively). Global cerebral blood flow (CBF) decreased by 10% (not significant). The score of the Wechsler Adult Intelligence Scale digit symbol test improved significantly (p less than 0.01) after EPO treatment. None of the patients developed cerebrovascular symptoms or side effects. We conclude that the hematologic and rheologic changes following EPO treatment cause CBF and BFV to return toward normal and improve neuropsychologic performance in patients with end-stage renal disease.

The Determination of Aluminium in Human Plasma

SummaryDetermination of aluminium in human plasma is of great interest in monitoring dialysis patients under oral aluminium therapy. Flameless atomic-absorption is chosen as the method because of the low normal levels of this non-essential trace element. A method avoiding the analytical problems of aluminium determination in human plasma is described. Normal values for healthy persons and levels for dialysis patients are given.ZusammenfassungDie Bestimmung von Aluminium im menschlichen Plasma ist von großem Interesse bei der Überwachung von Dialysepatienten, die unter oraler Aluminiumtherapie stehen. Die flammenlose Atomabsorption ist die Methode der Wahl, da die Normalwerte dieses nicht essentiellen Spurenelements sehr niedrig sind. Eine Methode, die die analytischen Probleme bei der Bestimmung von Aluminium im menschlichen Plasma vermeidet, wird beschrieben. Normalwerte gesunder Personen und solche von Dialysepatienten werden angegeben.

SERUM-ALUMINIUM AND DIALYSIS ENCEPHALOPATHY

Publisher Summary This chapter discusses a study to examine the serum-aluminium and dialysis encephalopathy. 64 patients with haemodialysis were investigated. The mean duration of the dialysis was 43 months. In all the patients serum aluminium levels, systolic blood pressure and the EEG were investigated. Psychologic testing was performed to assess the level of intelligence. In six patients, the diagnosis of dementia was made on the basis of psychologic testing and clinical observations. The patients with dementia showed significantly higher aluminium levels than the nondemented 58 patients, while the age of the patients, duration of dialysis, and blood pressure were the same in both groups. The EEG was abnormal in all six patients with dementia, in the 58 nondemented patients only in 23 cases. A significant correlation between serum aluminium levels and the EEG findings with regard to bilateral slow waves, focal slow waves, and epileptic potentials was found. The EEG and the age of the patients, the duration of dialysis, and the blood pressure showed no correlation. It can be concluded that in patients with dialysis, there is a correlation both between the appearance of dementia and EEG changes with serum aluminium levels.