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Biomedical subjects

H Mann

Publications and source records attributed to H Mann.

153 records · Page 9Linked to original sources
PubMedDate not supplied

Less symptomatic hypotension using blood volume controlled ultrafiltration.

Symptomatic hypotension due to ultrafiltration (UF) is one of the most frequent unwanted side effects of dialysis therapy. Using hemoglobinometry for continuous monitoring of blood volume (BV), ultrafiltration rate (UFR) can be adapted to actual changes in BV. A control system is shown in which UFR is set according to a predefined profile of BV. The conditions of control are: relative BV shall decrease steadily; BV shall decrease rapidly during the first 60 min of dialysis, thereafter decrease in BV should be less; UFR shall be as high as possible; and dry weight should be obtained within a given time. Application of this controlled UF method in 10 dialysis patients shows significantly fewer hypotensive periods and muscle cramps compared to conventionally constant UFR. It is concluded that BV controlled UF is an important step toward optimizing dialysis therapy.

Blood Flow Velocity↗
PubMedDate not supplied

Vasoactive hormones during hemodialysis with intermittent ultrafiltration.

The correlations between actual blood volume (BV), blood pressure (BP), heart rate, and plasma levels of renin activity (PRA), serum aldosterone (ALD), antidiuretic hormone (ADH), epinephrine (E), norepinephrine (NE), atrial natriuretic factor (ANF), cGMP, and cAMP were investigated in 10 stable patients during HD. HD consisted of four periods of about 60 min each. One half with an UF rate greater than 1,000 ml/h, followed by a time interval of 30 min without UF resulting in a "saw tooth" profile of BV. Decrease in BV was measured by continuous hemoglobinometry. Average total decrease in BV was 25%, while BP and HR did not change significantly. E, NE, ANF and ADH levels were directly related to actual changes in BV, suggesting that BP regulation in this special mode of HD is mainly supported by endogenous catecholamine and ADH secretion. The second messenger cGMP did not follow actual BV changes, but showed a significant decrease correlated with diminished BV. A significant change in PRA and ALD was missing. It is concluded that vascular stability in these patients is maintained by the response of catecholamins and ADH to decrease in blood volume, and not by the renin-aldosterone system.

Aldosterone↗
PubMedDate not supplied

A new method of continuous haemoglobinometric measurement of blood volume during haemodialysis.

Since the total amount of haemoglobin in blood is constant during haemodialysis, haemoglobin concentration reflects changes of blood volume caused by ultrafiltration and solute transport. Haemoglobin concentration therefore could serve as a control parameter for ultrafiltration. Blood is taken continuously from the arterial blood line at the very small rate of 0.1 ml/h and diluted at a constant ratio of 1/200 by a sterile solution 0.05 per cent NH3. By the diluting medium the erythrocytes are haemolysed and the haemoglobin is transformed into oxyhaemoglobin. The haemoglobin concentration is determined measuring the absorbance at 415 nm. The error in the measurement of the haemoglobin concentration is less than 3 per cent. The method was tested in vivo during 10 haemodialysis treatments of five patients. Haemoglobin concentration appeared to reflect the well-known effects of ultrafiltration, of food intake and changes of position (sitting, lying). If the body weight approached the suspected dry weight, haemoglobin concentration increased more rapidly. During high ultrafiltration rates (1.0 litre/h) and sudden changes of ultrafiltration rate haemoglobin concentration seemed to be unevenly distributed in the vascular space. If haemoglobin concentration indeed reflects changes in blood volume the method can be used to study the relationship between blood volume and blood pressure in haemodialysis therapy and to control ultrafiltration.

Blood Volume↗
PubMedDate not supplied

The Donnan effect in artificial kidney therapy.

The calculation of the effective sodium gradient in dialysis has to consider a membrane potential difference which is generally derived from the Donnan effect. Strictly this is allowed only under equilibrium conditions. This paper considered the effect of the deviation from equilibrium in haemodialysis and haemofiltration. The mathematical analysis is based on the integration of the local transport rate over the membrane area. The local transport rate is calculated from the Nernst-Planck equation using the constant field assumption. Deviation from equilibrium results in a diffusion potential across the membrane. Experimental evidence was presented for part of the theoretical results. The diffusion potential, both in haemodialysis and in haemofiltration, is too small to have any clinical significance. From the theory it follows that better tolerance of haemofiltration in comparison with haemodialysis cannot be explained by a difference in sodium transport. Calculation of the sodium transport in dialysis therapy based on the equilibrium Donnan effect is sufficiently accurate for kinetic considerations in the dialysis routine.

Acetates↗