Biomedical subjects

K Lindmark

Publications and source records attributed to K Lindmark.

5 recordsLinked to original sources

PubMed2002

Theoretical and experimental aspects of erythrocyte filterability testing; flow acceleration and systemic resistance.

Blood cell filterability is an established method in blood rheology. The dynamics at flow onset and its relevance to the data interpretation is, however, not fully known. This paper aims to investigate what controls the length and slope of flow acceleration as the medium accelerates to reach the steady state, and how this phenomenon may interfere with the data output. The acceleration time was not constant. With buffer the steady-state flow showed a logarithmic correlation (p<0.05) versus acceleration time and a linear correlation (p<0.001) versus acceleration slope. With 5% erythrocyte resuspension the steady-state flow instead demonstrated a linear relationship versus acceleration time (p<0.001) and no correlation versus acceleration slope. A cut-off timing of 0.6s is suggested to avoid artifacts associated with flow acceleration. The possible influence on data interpretation from the flow channel systemic resistance was also addressed, and found to significantly underestimate measurable changes in erythrocyte properties from unprocessed flow curves. This was despite the traditional correction for blank filtration flow. Both acceleration and effects from systemic resistance do probably have minor influence on the historic data interpretation but could perhaps be considered in the methodology to sharpen the data output.

Adult↗

PubMed2000

D-glucose additive protects against osmotic-induced decrease in erythrocyte filterability.

Glucose has long-term effects on erythrocyte filterability owing to sorbitol accumulation and glycosylation of intracellular proteins, but glucose effects prior to these long-term metabolic consequences have not been studied to the same extent. D-glucose is osmotically inert in erythrocytes because of facilitated diffusion. Erythrocyte volume regulation, hemolysis and filterability were studied with reference to effects of glucose derivatives dissolved in water. Control situations were water alone or buffer. Salt-stock dilution by water, D-glucose, or 3-O-M-glucose in water (both 570 mmol/L additives) created volume increases of 4.0 +/- 0.2%, 3.4 +/- 0.5% and 3.3 +/- 0.2%, respectively, whereas L-glucose resulted in a 2.2 +/- 0.4% volume decrease (all p < 0.001 versus baseline, mean values +/- SEM). D-glucose at a final concentration 30 mmol/L did not display any osmotic properties. Despite erythrocyte swelling, electrolyte-free glucose did not induce any significant changes in filterability with either 3-microm or 5-microm filters. 3-O-M-glucose gave a 7.8 +/- 1.4% decrease in 3-microm filterability (mean value +/- SEM, p < 0.001), but not to the same extent as by water alone at the corresponding dilution rate (31.7 +/- 3.5%, mean value +/- SEM, p < 0.001). L-glucose caused a 2.0 +/- 0.8% decrease in filterability across the 5-microm (mean value +/- SEM, p < 0.05), but not with the 3-microm filters. Stressing the glucose transport system further, to simulate the water-like properties of electrolyte-free glucose during intravenous infusion, we found that glucose becomes osmotically active and prevents hemolysis at these extreme concentrations (> 114 mmol/L). We conclude that an in vivo concentration range of D-glucose protects the erythrocytes from a decreased filterability induced by osmotic swelling but without having any osmotic properties.

Cell Separation↗

PubMed2000

Narrow-pore flow behavior of blood cells in cardioplegic suspension.

Cardioplegia alters the ionic composition of the myocardium and also the blood in a way that may influence the cellular capillary flow behavior. We measured changes in RBC volume and narrow-pore flow resistance of blood cardioplegia versus crystalloid medium. Potassium, magnesium and sodium as osmotic control caused an expected cell shrinkage and reduced the flow resistance through 3 microm pores; however, stressing the osmosis further resulted in increased resistance. No major effects were seen with the 5 microm filters. Twenty percent blood cells in the cardioplegic medium caused a 360% increase in 5 microm pore resistance. There were no obvious additional filterability effects of the cardioplegic additives other than their osmotic patterns. There may be a theoretical advantage in having a cell-free medium in terms of flow resistance. Using blood cardioplegia, a limited hypertonicity may be beneficial in reducing the capillary flow resistance of RBC.

Aged↗

PubMedDate not supplied

Analysis of flow acceleration during erythrocyte filtration: dependence of hematocrit and cell rigidity.

At flow onset the blood filtration rate accelerates to a steady state, this may affect the interpretation of red blood cell (RBC) filterability. We studied the acceleration of flow while the pressure is built up across the filter to analyse effects of various hematocrits and RBC rigidity by glutaraldehyde (GA) hardening. This was analysed by a new filtration system with high time resolution and unlimited filtration volume. The system uses a digital balance that samples the accumulated weight (e.g., filtration rate through 5 microns Nucleopore membranes) with on-line computer communication. The filtration is computer controlled via a pneumatic valve. White blood cells (WBC) were removed prior to filtration by a WBC-eliminating filter to avoid clogging artifacts. When flow is initiated a steady state is reached at 0.3-0.4 s. This timing was also tested and confirmed by a video monitoring technique of filtration flow into a horizontal pipette. The digital balance has a mathematical function to reduce the effects of vibration noise; when this function was activated the apparent acceleration was retarded to 1.2 s. With any of these techniques the steady state timing did not vary with the hematocrit, however, the volume of filtered suspension during acceleration varied with both the hematocrit and the GA hardening (p < 0.001). Extrapolation to yield the initial filtration rate from the relative flow curve (RBC suspension divided by buffer flow) varied depending on if the acceleration phase was included or not. In the most unfavourable situation, with GA-hardened RBC, this difference was 340% (p < 0.01). The slope to calculate clogging rate was affected in a similar way. Moreover, with the most GA-hardened RBC a delay in flow onset was observed with this technique. The acceleration phenomenon may cause artifacts in systems employing volume-derived filtration kinetics because of fixed volumes of filtrated medium.

Erythrocyte Aggregation↗

PubMedDate not supplied

Use of polyester leukocyte elimination filters in blood filterability research.

We tested a new routine to eliminate leukocytes for blood rheology measurements using commercial leukocyte absorbing filters (here PALL RC400). These filters were punched out and fitted in smaller chambers through which blood was filtered under controlled suction pressure (< 30 mm Hg). This technique resulted in a very effective leukocyte elimination to 0.0022% but also a platelet reduction to 0.2%. The process causes a small but significant hemolysis with free hemoglobin, of the order of 0.06% of the filtered erythrocytes. A small fraction of the erythrocytes were retained in the filter, versus plasma, to reduce the hematocrit on the order of 1.4%. The leukocyte filtration did not cause any detectable functional trauma to the erythrocytes, measured as micro-pore filterability of normal and glutaraldehyde (GA) hardened erythrocytes. However, when 10% of the erythrocytes were hardened with GA, which caused an increase in pore clogging slope (p < 0.05), the additional passage through the leukocyte elimination filter removed this measured change in clogging. This observation suggests that the leukocyte elimination filter may selectively remove, not only leukocytes and platelets, but also hardened erythrocytes. Reticulocyte counting did not reveal any selective removal of young erythrocytes. In general, we find the presented method reproducible, efficient and easy for eliminating leukocytes for blood rheology research although the risk of removing undeformable erythrocytes must be considered.

Adult↗