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Biomedical subjects

O Linderkamp

Publications and source records attributed to O Linderkamp.

At least 109 records · Page 6Linked to original sources
PubMed1993

Mechanical and geometrical properties of density-separated neonatal and adult erythrocytes.

Neonatal red blood cells (RBC) show large variations in size, density, and deformability, with a relatively high percentage of neonatal RBC being extremely dense, almost spherical, and poorly deformable. Previous reports suggest that loss of membrane and oxidation of fetal Hb might account for the generation of the dense, rigid RBC in neonates and the shortened life-span of neonatal RBC. To test whether the dense RBC population is particularly fragile and which mechanical properties are responsible for the rigidity of these cells, the following measurements were made for the top (least dense) and bottom (most dense) 3% fractions of density-separated neonatal and adult RBC: cellular deformability (rheoscope); RBC geometry (micropipette system); elasticity, fragility, and viscosity of RBC membrane (micropipette system); Hb solution viscosity (cone-plate viscometer); and selected biochemical parameters. Fetal Hb of neonatal RBC decreased with increasing cell density. When the bottom fractions were compared with the top fractions, neonatal RBC showed a greater reduction in glutamic oxalacetic transaminase activity (72% versus 53%), potassium (39% versus 19%), volume (32% versus 19%), and surface area (42% versus 21%), and a greater rise in density (3.5% versus 1.9%) and mean corpuscular Hb concentration (42% versus 23%) than adult RBC. Cellular deformability in the rheoscope (shear stress 5 Pa) decreased by 24% in adults and by 41% in neonates. Membrane extensional and bending elastic moduli (i.e. membrane deformability) and membrane fragility of neonatal and adult RBC did not significantly change with increasing cell density.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Haemorheological changes in uraemic children in response to erythropoietin treatment.

The increased risk of hypertension during treatment of uraemic patients with recombinant human erythropoietin (rHuEpo) has been related to increased blood viscosity. We therefore studied rheological parameters determining whole blood viscosity in seven haemodialysed uraemic children and adolescents during treatment with rHuEpo (initial dose 75 IU/kg per week). Before treatment the patients were anaemic and had reduced red blood cell (RBC) deformability at low shear stress of 0.7 Pa in the rheoscope compared with six healthy control children (0.14 +/- 0.03 versus 0.19 +/- 0.02). The RBC membrane rigidity (i.e. membrane elastic shear modulus) determined in a flow channel was increased (2.04 +/- 0.26 versus 1.36 +/- 0.05 x 10(-5) N/m). After two weeks of rHuEpo, RBC deformability improved and RBC membrane rigidity decreased significantly. With increasing doses of rHuEpo the haematocrit rose steadily. After 14 weeks of therapy RBC deformability reached control values, and after 30 weeks RBC membrane rigidity became normal. RBC aggregation and plasma viscosity were similar in patients and controls and did not change significantly in response to rHuEpo. The early improvement of RBC deformability may lead to an increase in tissue oxygenation by facilitating microcirculatory blood flow.

Adolescent↗
PubMed1992

Therapeutic use of surfactant in neonatal respiratory distress syndrome. Correlation between pulmonary X-ray changes and clinical data.

As part of a multicenter surfactant rescue study, the chest X-rays of 239 preterm and term infants were analyzed. To study the influence of surfactant administration on radiographic appearance, 130 patients with a clinical and radiological diagnosis of typical respiratory distress syndrome were selected, in whom adequate chest x-rays before and within 48 h after treatment were available. Median gestational age was 30 weeks (range 25-38 weeks), median birth weight was 1335 g (range 625-3450). The time of surfactant application ranged between 90 min and 24 h after birth (median 6 h). The most common finding after surfactant administration was uniform (n = 47) or disproportionate (n = 46) improvement of pulmonary aeration, which showed a significant correlation to posttreatment reduction of oxygen requirement (p less than 0.0001). Asymmetric clearance was more often localized on the right side and usually disappeared within two to five days. Only in 13 patients no change of ventilation was found. Development of interstitial emphysema (n = 24, including three patients with pneumothorax) after surfactant treatment was an unfavourable prognostic sign. 54% of these patients (13 of 24) died within the first month of life, compared to 8% (7 of 93) in the group of patients with initial improvement of ventilation.

Female↗
PubMed1992

Effect of lipid A on the deformability, membrane rigidity and geometry of human adult red blood cells.

Lipid A is responsible for the activities of endotoxin and may cause circulatory failure and haemolysis. This study evaluated the effects of different lipid A concentrations on red blood cell (RBC) deformation (rheoscope), the aspiration pressure required to aspirate RBC into 3.3 microns pipettes, the membrane shear elastic modulus (i.e. membrane rigidity) and cellular geometry (micropipette system) after 15 min of incubation. Lipid A concentrations of 10 and 100 micrograms ml-1 of RBCs decreased RBC deformability by 26% and 39%, respectively. The aspiration pressure for RBCs into a 3.3 microns micropipette increased by 235% at a lipid A concentration of 10 micrograms ml-1 and by 586% at a concentration of 100 micrograms ml-1. The elastic shear modulus almost doubled at a lipid A concentration of 10 micrograms ml-1 and tripled at 100 micrograms ml-1. At a lipid A concentration of 100 micrograms ml-1, 37% of RBCs showed spicules. These echinocytes were less deformable than discocytes. Mean corpuscular volume, RBC volume and surface area were not affected by lipid A. We conclude that lipid A causes marked reduction of RBC deformability due to increasing membrane rigidity.

Adult↗
PubMed1992

The effect of early and late cord-clamping on blood viscosity and other hemorheological parameters in full-term neonates.

This study was done to compare postnatal alterations in blood viscosity (capillary viscometer) and its determinants: hematocrit, plasma viscosity (capillary viscometer), red cell aggregation (Myrenne aggregometer) and red cell deformability (rheoscope) in the first five days of postnatal life in full-term neonates with early (< 10 s) and late (3 min) cord-clamping. The fetal blood volume of the placenta ("residual placental blood volume") decreased from 52 +/- 8 ml/kg of neonatal body weight after early cord-clamping to 15 +/- 4 ml/kg after later cord-clamping. Neonatal blood volume, calculated as the difference between an assumed total feto-placental blood volume of 115 ml/kg and the measured fetal blood volume of the placenta, was 50% higher in the late cord-clamped infants than in the early cord-clamped infants. Both groups showed similar viscosity, hematocrit and other rheological parameters in cord blood. In the infants with early cord-clamping, the hematocrit decreased from 0.48 +/- 0.04 l/l at birth to 0.43 +/- 0.6 l/l after 24 h (p < 0.05). Whole blood viscosity did not change significantly with age. After late cord-clamping, the hematocrit rose from 0.50 +/- 0.04% at birth to 0.63 +/- 0.05 l/l at 2 h of age (p < 0.005) and dropped to 0.59 +/- 0.5 l/l (p < 0.05) at 24 h. Blood viscosity increased by 40% (p < 0.001) within the first 2 h, but did not change significantly during the following five days. In both groups, plasma viscosity and red cell aggregation increased significantly (p < 0.05) on day 5 due to significant increases in total plasma protein and fibrinogen concentrations (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Proteins↗
PubMed1992

Mechanical fragility of erythrocyte membrane in neonates and adults.

The shortened life span of neonatal red blood cells (RBC) is associated with accelerated membrane loss. The present study was designed to measure the critical shear force that causes membrane failure and the rate of membrane failure for neonatal and adult RBC. A micropipette technique was used to determine the membrane extensional (shear) elastic modulus (i.e. resistance of the membrane to extensional elastic deformation), the rate of extensional membrane deformation (i.e. surface viscosity), and the tension for local membrane fragmentation. A flow channel system was used to determine the critical shear force of plastic membrane deformation (i.e. beginning of membrane tether formation), the rate of plastic deformation, and the plastic shear viscosity coefficient. The extensional elastic modulus of neonatal RBC was 18% smaller and the rate of elastic deformation was 25% longer compared with adult cells (p less than 0.05). Membrane surface viscosity was similar for both cell types. The tension for local membrane fragmentation in the micropipette was 23% lower in neonates than in adults. However, the strain (i.e. extent of membrane deformation calculated as ratio of the stress resultant and the elastic modulus) at which membrane rupture in the micropipette occurred was similar for neonatal and adult RBC. This indicates that the smaller critical tension for neonatal RBC membrane failure was due to increased membrane elastic deformability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Blood viscosity and optimal hematocrit in preterm and full-term neonates in 50- to 500-micrometer tubes.

Blood viscosity is an important determinant of blood flow resistance. Because a substantial part of flow resistance arises in small arteries and arterioles with diameters of 100 microns and less, rheologic properties of blood from preterm infants (24 to 36 wk of gestation), full-term neonates, and adults were measured in glass tubes with diameters of 50, 100, and 500 microns for a wide range of adjusted feed hematocrits (0.15-0.70). At each of the feed hematocrits, blood viscosity decreased when going from a 500-microns tube to a 50-microns tube. The viscosity reduction increased with increasing hematocrit. Moreover, the viscosity reduction was more pronounced in the neonates than in the adults. At a hematocrit of 0.70, the viscosity reduction averaged 56% in preterm infants, 50% in full-term neonates, and 39% in adults (p less than 0.005). However, the viscosity reductions at a hematocrit of 0.30 were only 35, 29, and 19%, respectively (p less than 0.05). In all four groups, blood viscosity increased exponentially with increasing hematocrit. The steepness of the hematocrit-viscosity curves decreased with decreasing tube diameter and with decreasing maturity of the infants. Erythrocyte transport efficiency (hematocrit/blood viscosity) was calculated to estimate the optimal hematocrit (i.e. hematocrit with maximum erythrocyte transport). In 500-microns tubes, the optimal hematocrit was about 0.40 in all of the groups. In 100-microns tubes, the optimal hematocrit was 0.44 +/- 0.05 in the adults and 0.52 +/- 0.04 in the neonates (p less than 0.05). In 50-microns tubes, the optimal hematocrit was 0.51 +/- 0.04 in adults and 0.60 +/- 0.05 in the neonates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[The critical hemoglobin value in newborn infants, infants and children].

The optimum and critical hemoglobin concentrations are determined by the oxygen demand of the tissues and several oxygen transport parameters (i.e., blood flow, arterial oxygen saturation, oxygen affinity of hemoglobin, and the critical venous oxygen pressure). Most of the oxygen transport parameters change markedly during the first weeks after birth. Oxygen consumption and cardiac output in neonates are three times those of adults on a body weight basis. Due to the high oxygen affinity of fetal hemoglobin, the oxygen unloading capacity of hemoglobin in neonates is about 50% less than in adults. From oxygen transport parameters and oxygen consumption we have calculated the optimum and the critical hemoglobin concentrations for preterm and full-term neonates during the first weeks after birth. A hemoglobin concentration of 15 g/dl appears optimal for preterm and full-term infants at birth as well as for adults. The calculated minimum acceptable hemoglobin concentration is 6 g/dl for children and adults, 12 g/dl for preterm infants and 11 g/dl for full-term neonates at birth. Due to the postnatal decrease in oxygen affinity, the minimum acceptable hemoglobin concentration decreases by approximately 1 g/dl/week for the first 5-6 weeks until the minimum value of 6 g/dl for children and adults is reached. The minimum hemoglobin concentration should be 2 g/dl higher in patients who require increased oxygen or suffer from other serious disorders. A minimum hemoglobin concentration of 10 g/dl is recommended in children with leukemia or other oncological disease. In infants and children with chronic hypoxemia (cyanotic congenital heart disease) the minimum hemoglobin concentration should be increased by the percentage of arterial oxygen desaturation.

Adolescent↗
PubMed1992

Increased aggregation with normal surface charge and deformability of red blood cells in children with nephrotic syndrome.

Hemorheological risk factors for thromboembolic disease were evaluated in 25 pediatric patients with idiopathic nephrotic syndrome (NS). In patients with increased proteinuria (greater than 100 mg/m2/24 h) red blood cell (RBC) aggregation and plasma viscosity were significantly increased when compared with patients in remission (less than 100 mg/m2/24 h) and with healthy controls. RBC surface charge was normal during increased proteinuria and remission. RBC aggregation correlated positively with plasma viscosity, fibrinogen, alpha 2-macroglobulin, immunoglobulin M, and the degree of proteinuria, and negatively with plasma albumin levels. RBC aggregation showed no correlation to RBC surface charge. Hematocrit and RBC deformability (rheoscope) were similar in both patient groups and in controls. Increased RBC aggregation and plasma viscosity may contribute to the increased risk of venous thromboembolism in NS.

Blood Viscosity↗
PubMed1991

Cardiac output by pulsed Doppler in neonates using the apical window.

In 18 healthy neonates, cardiac output was measured by range-gated Doppler echocardiography with simultaneous two-dimensional echocardiography, using the apical approach. Maximal and modal flow velocities were compared by using spectral analysis of the Doppler signal. Blood flow velocities were measured in the left ventricular outflow tract and in the ascending aorta. Cardiac index (cardiac output per kg body weight), with the sample volume placed in the left ventricular outflow, averaged 170 +/- 45 ml/min/kg in the maximal flow velocity mode and 133 +/- 39 ml/min/kg in the modal mode, respectively (p less than 0.05). Sampling in the ascending aorta gave cardiac index values of 198 +/- 73 ml/min/kg in the maximal velocity and 167 +/- 58 ml/min/kg in the modal velocity mode. Maximal flow velocities in the ascending aorta came closest to published data obtained by invasive and noninvasive methods.

Blood Flow Velocity↗
PubMed1991

High-dose intravenous gammaglobulin for neonatal alloimmune thrombocytopenia in twins.

We report the successful treatment of neonatal alloimmune thrombocytopenia with repeated infusions of high-dose immunoglobulin G (400 mg/kg/d for 5 days) in twins. Platelet counts increased within 3 days from less than 20 x 10(9)/l to more than 70 x 10(9)/l. The first twin survived without neurological or other sequelae. The second twin had probably developed intracranial hemorrhage (ICH) in utero. This infant developed long-term neurological sequelae with blindness, cerebral palsy and infantile spasms. Implications of the therapeutic approach and prevention of severe complications in pregnancies with known risk for neonatal alloimmune thrombocytopenia are discussed.

Autoimmune Diseases↗
PubMed1991

Periodic variations in skin perfusion in full-term and preterm neonates using laser Doppler technique.

In 37 full-term and preterm infants periodic oscillations of skin blood flux were studied by means of laser Doppler technique during the first week of life. The development of rhythmic oscillations of skin blood flux was similar in all infants. On the first postnatal day rhythmic oscillations were present in the heel skin of all full-term and preterm infants, but were rarely observed in the back and thigh skin. These flux motion patterns were not influenced by small changes in skin temperature. On day 4 rhythmic oscillations became predominant in all body regions. The oscillation frequencies of blood flux in the back, thigh and heel skin of full-term neonates reached the lower range of adult values at the end of the first postnatal week, whereas the oscillation frequencies in the preterm infants were still below the range of full-term neonates.

Back↗
PubMed1991

Postnatal changes in cardiac output and haemorrheology in normal neonates born at full term.

Circulatory adaptation was studied serially in 11 healthy term neonates on days 1, 3, and 5 by cross sectional and pulsed Doppler echocardiography. Changes in the determinants of blood viscosity (packed cell volume, plasma viscosity, red cell aggregation, and red cell deformability) were studied on day 1 and day 5. There was a 27% increase in the cardiac output as a result of increasing stroke volume, whereas heart rate did not change significantly. Mean blood pressure increased by nearly the same extent as cardiac output (21%), so that the overall resistance remained unchanged. Packed cell volume, red cell aggregation, and red cell deformability did not change significantly during the first five postnatal days. Plasma viscosity rose significantly (by 12%) so that whole blood viscosity increased during that period. As there was no change in overall systemic vascular resistance the vascular hindrance--calculated as the ratio of resistance: blood viscosity--decreased, thereby indicating vasodilation.

Aging↗
PubMed1991

Atrial natriuretic peptide and blood volume during red cell transfusion in preterm infants.

Because raised plasma concentrations of atrial natriuretic peptide indicate volume expansion, we studied the effect of red cell transfusion on plasma atrial natriuretic peptide concentration, packed cell volume, and intravascular volume in eight preterm infants. Red cell transfusion increased red cell mass, packed cell volume and erythrocyte count, but decreased plasma volume. Total blood volume, plasma atrial natriuretic peptide concentration, urine flow rate, and urinary sodium excretion did not change. We conclude that a slow transfusion of less than 10 ml red cells/kg body weight does not cause volume expansion with subsequent atrial natriuretic peptide release thereby affecting the cardiovascular system.

Anemia, Refractory↗
PubMed1991

Deformability and volume of neonatal and adult leukocytes.

Volume and deformability of blood cells are important determinants of the microcirculation. Leukocytes are larger and considerably less deformable than erythrocytes. In our study, volume and deformability of polymorphonuclear neutrophils (PMN), lymphocytes, and monocytes in adults and full-term neonates were studied by means of a micropipette system. Neonatal immature granulocytes were also investigated. Membrane cytoplasm tongues were aspirated into 2.5-microns (diameter) micropipettes over a period of 1 min. Adult and neonatal PMN were totally aspirated into 5-microns micropipettes. Tongue growth and final tongue length of PMN were about twice those of monocytes and lymphocytes. At a pressure of -2 cm H2O, tongue growth of lymphocytes and monocytes was similar. At a pressure of -4 cm H2O, however, tongue growth of monocytes was faster and the final tongue was longer than those of lymphocytes (p less than 0.05). Cellular volume and deformation behavior of the different leukocyte subpopulations (PMN, monocytes, and lymphocytes) were similar in neonates and adults. Compared to mature neonatal PMN, immature neonatal neutrophilic granulocytes were significantly less deformable (final tongue length of 5.4 +/- 1.52 versus 9.3 +/- 1.48 microns at -2 cm H2O) and larger (421 +/- 68 versus 360 +/- 38 fL). The entry time of PMN into 5-microns micropipettes was similar in neonates and adults at aspiration pressures of -2, -3, and -4 cm H2O. We conclude that the deformability of neonatal and adult leukocytes is not different despite functional differences and that immature granulocytes may contribute to impaired microcirculation in neonates with severe septicemia or hypoxemia.

Adult↗
PubMed1991

[Effect of regionalization of perinatal management on mortality and long-term sequelae of small premature infants].

In Germany and Switzerland only 20% of the high risk neonates are born in perinatal centers with a neonatal intensive care unit adjacent to the delivery rooms. Several studies have shown that both mortality and long term morbidity (i.e. brain damage, retinopathy and chronic lung disease) of very low birth weight (VLBW) infants (less than 1500 g) are by approximately 50% lower in inborns compared with outborns. The results of the Bavarian Neonatal Study and of the perinatal centers in Baden-Württemberg indicate that every year approximately 2000 VLBW infants die and 4000 survive with severe handicaps in the western states of the Federal Republic of Germany because they are not born in a perinatal center.

Brain Damage, Chronic↗
PubMed1991

[Retinopathy of prematurity: why are girls more frequently affected?].

In 226 prematures (birth weight less than or equal to 1500 g), who were examined prospectively between 1986 and 1988, retinopathy of prematurity occurred significantly more often in girls: 31.0% of the eyes of 134 girls and 22.3% of the eyes of 92 boys showed retinopathy of prematurity (p = 0.042). Different factors may influence the sex ratio of retinopathy of prematurity: (1) hormonal differences are already present shortly after birth; (2) there are different ventilation rates in girls and boys; (3) the mortality varies between girls and boys. The influence of mortality was demonstrated in the group of preterms examined: in this time period, 59 of 285 prematures died: 21 of 155 girls (13.5%) and 38 of 130 boys (29.2%). Significantly more boys than girls died (p = 0.001). For this reason the percentage of surviving girls at high risk of having retinopathy is high. The apparently greater prevalence in girls is the result.

Cross-Sectional Studies↗