Pyoderma gangraenosum, a rare, but potentially fatal complication in paediatric oncology patients.

Pyoderma gangraenosum (PG) is a serious chronic, ulcerative skin disorder afflicting both adults and children. As PG is often associated with systemic diseases (>50%) such as inflammatory bowel disease, rheumatoid arthritis or haematological disorders, it requires a multidisciplinary approach. This disorder is not commonly reported in paediatrics; therefore children with PG represent a particularly difficult diagnostic challenge. Clinical diagnosis is often delayed and PG is only considered after eliminating other causes of cutaneous ulcers. We report a 4-year-old boy with secondary myelodysplastic syndrome following treatment for acute lymphoblastic leukaemia who presented with a massive inflammatory, ulcerative proliferation of the lower lip which was diagnosed as PG. We have reviewed the literature with reference to diagnostic criteria and treatment options of this disorder that is particularly rare in childhood.

Impaired deformability of erythrocytes and neutrophils in children with newly diagnosed insulin-dependent diabetes mellitus.

AIMS/HYPOTHESIS: Abnormal rheological properties of erythrocytes, leucocytes and plasma may have a role in the development of diabetic microangiopathy. We hypothesized that changed haemorrheological variables may already be found in children with onset diabetes. METHODS: Erythrocyte deformation (rheoscope), neutrophil deformation (micropipette), erythrocyte aggregation, blood and plasma viscosity were measured in 15 children with insulin-dependent diabetes mellitus before initiation of insulin treatment and 4 to 6 weeks later, 15 diabetic children treated with insulin for 5 to 8 years, 15 healthy children and 15 healthy adults. RESULTS: At a low shear stress of 0.6 Pa, erythrocyte deformation was decreased in the diabetic children before (-28%), after 4 to 6 weeks (-22%) and after 5 to 8 years (-17%) of insulin treatment compared with healthy children. More active neutrophils were counted in the untreated diabetic children (9 +/- 6%) than in healthy children (3 +/- 2%). Deformability of passive neutrophils was greatly decreased in the children with onset diabetes and moderately reduced in the diabetic children who were treated with insulin. Neutrophil deformation (r = -0.52) and erythrocyte deformation at 0.6 Pa (r = -0.62) were inversely related to haemoglobin A1c. Haematocrit and blood viscosity were increased in the untreated children and in the children treated with insulin for 5 to 8 years. Plasma viscosity and erythrocyte aggregation were similar in the three groups of children. CONCLUSION/INTERPRETATION: Decreased erythrocyte deformation at low shear force, increased count of active neutrophils and impaired deformability of passive neutrophils may increase the risk for acute cerebro-vascular complications in children with uncontrolled insulin-dependent diabetes mellitus.

Clinical symptoms, biochemical studies and therapeutic approaches in a sibship with a new congenital tubulopathy.

UNLABELLED: We report on two siblings suffering from a new congenital tubulopathy. Following normal pregnancies not complicated by polyhydramnios, severe renal losses of potassium, chloride, sodium and magnesium occurred in the first weeks after birth. Calcium metabolism was not affected. The distal tubular chloride reabsorption was considerably decreased in the two siblings (0.25 and 0.28, respectively). Secondary hyperaldosteronism, activation of the kallikrein-kinin system and elevated urinary prostaglandin excretion were observed. The effects of indomethacin, spironolactone and captopril on symptoms, electrolyte wasting, activation of renin-angiotensin-aldosterone and kallikrein-kinin system and prostaglandin synthesis were studied. In spite of persisting elevation of prostaglandin synthesis, captopril decreased electrolyte wasting, polyuria and hyperaldosteronism most effectively. CONCLUSION: We delineate an apparently new disorder characterized by a postnatal onset, an extremely decreased chloride reabsorption with extensive hyperchloriduria and hypermagnesiuria in the presence of normal calcium metabolism. The disorder can be distinguished from other tubulopathies with hypokalaemic alkalosis.

Effects of high-frequency oscillatory ventilation on circulation in neonates with pulmonary interstitial emphysema or RDS.

OBJECTIVE: Mechanical ventilation may impair cardiovascular function if the transpulmonary pressure rises. Studies on the effects of high-frequency oscillatory ventilation (HFOV) on cardiovascular functions have yielded conflicting results. This study was done to compare alterations in left ventricular output and blood flow velocities in the anterior cerebral artery, internal carotid artery, and celiac artery using a Doppler ultrasound device before and 2 h after initiating HFOV in neonates with respiratory distress syndrome (RDS) or pulmonary interstitial emphysema (PIE). DESIGN: Prospective clinical study. SETTING: Neonatal intensive care unit in a perinatal center. PATIENTS: 18 critically ill infants (postnatal age 47 +/- 12 h; mean +/- SD) were studied before and during HFOV (piston oscillator). Indications for HFOV were severe respiratory failure due to PIE (n = 10) and severe surfactant deficiency (RDS, n = 8). In the RDS group, gestational age was 27 +/- 6 weeks (range 26-31 weeks) and birth-weight 1620 +/- 380 g (range 850-1970 g). In the PIE group, gestational age was 28 +/- 2 weeks (range 26-36 weeks) and birth-weight 1740 +/- 470 g (range 890-2760 g). MEASUREMENTS AND MAIN RESULTS: During HFOV, mean airway pressure was maintained at the same level as during intermittent mandatory ventilation in both groups (RDS, 12 +/- 2 cmH2O; PIE, 10 +/- 2 cmH2O). Compared to intermittent mandatory ventilation, several of the 12 parameters studied changed significantly (p < 0.004) during HFOV. In the RDS group, the partial pressure of oxygen in arterial blood/fractional inspired oxygen (PaO2/FIO2) ratio increased from 56 +/- 9 to 86 +/- 7 and partial pressure of carbon dioxide in arterial blood (PaCO2) decreased from 49 +/- 4 to 35 +/- 3 mmHg. In the PIE group, PaO2/FIO2 ratio increased from 63 +/- 8 to 72 +/- 7 and PaCO2 decreased from 63 +/- 7 to 40 +/- 5 mmHg. In the PIE group, heart rate decreased (135 +/- 15 before HFOV vs 115 +/- 14 min-1 during HFOV) and mean systolic blood pressure increased (before 43 +/- 4 vs 51 +/- 4 mmHg during HFOV) significantly, whereas these parameters did not change in the RDS group. Left ventricular output increased significantly in the PIE group (210 +/- 34 before vs 245 +/- 36 ml/kg per min during HFOV; p < 0.004), but not in the RDS group (225 +/- 46 before vs 248 +/- 47 ml/kg per min during HFOV; k < 0.05). Shortening fraction and systemic resistance did not change in either group. In the PIE group, mean blood flow velocities in the internal carotid artery (+59%), anterior cerebral artery (+65%) and celiac artery (+45%) increased significantly but did not change in the RDS group. CONCLUSIONS: The results show that HFOV as used in this study, improves oxygenation, CO2 elimination, and circulation in infants with RDS and PIE. However, systemic, cerebral, and intestinal circulation improved more in neonates with PIE than in those with RDS. This may be due to higher pulmonary compliance in infants with PIE when compared to those with RDS.

Alternative pathway activation of the complement system in preterm infants with early onset infection.

The increased incidence of infection in preterm neonates has been related in part to their relative deficiency of most complement components, because complement is known to participate in the defense against bacterial and viral infections. In a prospective study, complement activation products were determined in 52 preterm infants. Twenty preterm infants suffered from proven early onset infection, 11 infants were presumed to suffer from infection, which could not be confirmed. Twenty-one preterm infants without infection or perinatal asphyxia formed the control group. EDTA plasma was obtained within the first 6 h after birth, and follow-up examinations were done in 15 patients with proven infection during the next 24 h. The complement activation products C3a-desArg, C3bBbP, and sC5b-9 were measured with enzyme immunoassay systems. In preterm neonates with early onset infection, a significant elevation of C3a-desArg was found in the very early course of the disease. C3a-desArg generation resulted from alternative pathway activation as shown by a concurrent increase of C3bBbP concentration. In addition, significantly higher concentrations of sC5b-9 predicted infection in the first few hours after birth. Thus, despite very low levels of native complement proteins, preterm babies are able to generate remarkable amounts of activation products of the complement cascade. The elevation of these activation products preceded by hours significant changes of routine laboratory markers of infection, such as leukocyte count, differential blood count, and C-reactive protein. Thus they might help to identify preterm neonates with severe systemic infection earlier than other laboratory parameters.

[High frequency jet ventilation during tracheal resection in children and infants]. / Hochfrequenz-Jet-Beatmung während Trachearesektion bei Kindern und Säuglingen.

Between 1986 and 1996, 16 infants and children less than 11 years of age (m = 11, f = 5) underwent resections for acquired or congenital tracheobronchial stenoses. During this period, various techniques of total intravenous anaesthesia (TIVA) were employed (midazolam, fentanyl, pancuronium; propofol, fentanyl, pancuronium). During the phase of dividing the airways, high-frequency-jet ventilation (HFJV) into the trachea or the main bronchi by 8-12Fr catheter(s) was applied for 10-75 min with driving pressures between 0.3-1.8 bar, frequencies between 100-200/min, I:E ratio between 1:4-1:1, and FjetO2 1.0. Catheter position was controlled visually, gas exchange was monitored by pulse oximetry and blood gas analysis. There were two incidents of transient hypoxaemia (paO2 less than 60 mmHg), and 4 cases of hypercapnia (paCO2 more than 45 mmHg). No complications due to the HFJV-catheter technique, such as barotrauma or aspiration were seen. All children were kept postoperatively on a ventilator due to swelling of the airway anastomosis. In 5 children ventilator treatment exceeded 7 days, 3 children were discharged tracheostomised. These observations serve to confirm that HFJV is capable of maintaining gas exchange during tracheal resection in infants and children, if the following prerequisites are met: 1. Tracheobronchial pathology suitable for poststenotic placement of jet catheter. 2. No respiratory impairment by parenchymal pathology. 3. Monitoring by continuous visual control of respiratory mechanics, pulse oximetry and blood gas analysis. Cardiopulmonary bypass should be applied if airway pathology precludes safe placement of jet catheters, or in the presence of parenchymal respiratory failure.

[Bronchopulmonary dysplasia. Retrospective analysis of various forms of treatment and development of a staged therapeutic plan]. / Bronchopulmonale Dysplasie. Retrospektive Analyse verschiedener Behandlungsformen und Entwurf eines therapeutischen Stufenplans.

50 premature infants with bronchopulmonary dysplasia (BPD) were treated in the Perinatal Center of the University of Heidelberg from January 1990 to December 1992. Gestational age was 24-31 weeks and birthweight was 500 to 1430 grams. 27 infants received dexamethasone only and 14 were initially given dexamethasone followed by beclomethasone inhalation. Nine infants without assisted ventilation were only treated with inhaled beclomethasone. Infants with fluid intake > 150 ml/kg/d and < or = 150 ml/kg/d were analysed separately. Extubation in ventilated infants was possible 1 to 29 days after the beginning of dexamethasone treatment. Most infants who were not ventilated any more could be weaned from oxygen during the period of dexamethasone treatment. Inhaled beclomethasone allowed reduction in supplemental oxygen in all infants. Effects of treatment with dexamethasone and beclomethasone were similar in infants with fluid intake of < 150 ml/kg/d and > 150 ml/kg/d. Our data show that dexamethasone and inhaled beclomethasone improved the clinical course of BPD in premature infants. Fluid intake had no influence on clinical outcome. Based on our results, we suggest guidelines for the treatment of BPD.

[Rheologic changes in stored erythrocyte concentrates]. / Rheologische Veränderungen gelagerter Erythrozytenkonzentrate.

We studied the effect of two different preservation solutions on mean corpuscular volume (MCV), red cell deformability and flow in narrow tubes in red blood cell concentrates. Blood from 10 healthy blood donors was processed in parallel in SAG-M (S-RBC) as well as in PAGGS-M (P-RBC) in identical aliquots. Samples were studied at days 0, 7, 14, 28 and 42 of storage. MCV was determined using a Du Pont cell counter. Whole cell deformability was determined in a Myrenne Rheodyn. Viscosity reduction in narrow tubes was determined by means of capillary viscosimetry. P-RBC showed a constant MCV over the entire storage period. In contrast, MCV of S-RBC increased and MCHC decreased during storage. P-RBC showed similar deformability and viscosity reduction during storage, whereas deformability decreased and viscosity reduction became less pronounced for S-RBC. Our study shows superior rheological properties of P-RBC. Thus, PAGGS-M may provide better hemoglobin flux and oxygen transport to tissues than SAG-M.

Effect of Leboyer childbirth on cardiac output, cerebral and gastrointestinal blood flow velocities in full-term neonates.

The Leboyer birth method requires that the newly born infant is placed on the mother's abdomen and the cord is clamped when it stops pulsating. This investigation was done to study the effect of Leboyer childbirth on neonatal circulation during the first 5 days after birth. Hematocrit, blood viscosity, left and right ventricular output, and cerebral blood flow velocities in the arteria carotis interna, arteria cerebri anterior, and truncus coeliacus were studied in 15 full-term neonates with early (less than 10 seconds) cord clamping and 15 full-term neonates delivered according to Leboyer (cord clamping after 3 minutes) on day 1 (2 to 4 hours after birth) and day 5. The fetal placental blood volume decreased from 42 +/- 8 mL/kg (mean +/- SD) of neonatal body weight after early cord clamping to 19 +/- 7 mL/kg after Leboyer delivery. Neonatal blood volume, calculated from the fetal placental blood volume, was 32% higher in the Leboyer group compared with the early cord-clamped infants. In the infants with early cord clamping, hematocrit, and blood viscosity did not change significantly during the first 5 days. After Leboyer birth, the hematocrit rose from 0.51 +/- 0.05 in cord blood to 0.62 +/- 0.06 at 2 to 4 hours of age, thereby increasing blood viscosity by 32%. Stroke volume, heart rate, cardiac output, left-to-right shunt across the ductus arteriosus, and blood flow velocity in the truncus coeliacus were similar in both groups and did not change during the first 5 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of red cell transfusion on cardiac output and blood flow velocities in cerebral and gastrointestinal arteries in premature infants.

Anaemia may increase the risk of tissue hypoxia in preterm infants. The effect of transfusion on circulation was studied in 33 preterm infants with a mean (SD) gestational age of 29 (5) weeks (range 26-34), birth weight 1153 (390) g (range 520-1840), and postnatal age of 48 (21) days (range 19-100). Packed cell volume, blood viscosity (capillary viscometer), cardiac output, and cerebral blood flow velocities in the internal carotid artery, anterior cerebral artery, and coeliac trunk (Doppler ultrasound) were determined before and after transfusion of 10 ml/kg of packed red blood cells. Transfusion increased packed cell volume from a mean (SD) 0.27 (0.45) to 0.37 (0.48). Mean arterial blood pressure did not change while heart rate decreased significantly from 161 (14) l/min to 149 (12). Cardiac output decreased from 367 (93) ml/kg/min to 311 (74) due to decrease in stroke volume from 2.28 (0.57) ml/kg to 2.14 (0.46) and in heart rate. There was a significant increase in systemic red cell transport (cardiac output times packed cell volume) by 17%, systemic flow resistance (blood pressure to cardiac output ratio) by 23%, and blood viscosity by 33%. Vascular hindrance (flow resistance to blood viscosity ratio) did not change significantly, thereby suggesting that neither vasoconstriction nor vasodilation occurred with transfusion. After transfusion blood flow velocities decreased significantly in the anterior cerebral artery by 23%, in the internal carotid artery by 8%, and in the coeliac trunk by 12%. Red cell transport estimated as products of blood flow velocities times packed cell volume increased significantly by 25% in the internal carotid artery and by 21% in the coeliac trunk. These results indicate that red cell transfusion improved systemic oxygen transport as well as oxygen transport in the internal carotid artery and coeliac trunk.

Plasmapheresis in severe septic shock with disseminated intravascular coagulation.

An 18-year-old female with CNS relapse of acute lymphoblastic leukemia after previous complete remission of the disease underwent chemotherapy. Due to the therapy she suffered from profound suppression of bone marrow with consecutive thrombocytopenia and leukopenia. Despite prophylactic treatment, severe septicemia occurred with septic shock, hemolysis and disseminated intravascular coagulation (DIC). As the clinical course became uncontrollable by means of conventional therapy, including broad-spectrum antibiotics, substitution of fresh frozen plasma, antithrombin III and heparin therapy, plasma exchange was used as a rescue therapy. This method succeeded in effective replacement of clotting factors and normalization of coagulation, in removal of fibrinogen degradation products and probably of toxins and shock mediators. The patient recovered from shock.

Complement activation in newborn infants with early onset infection.

The complement system is an important element in host defense. Quantitative deficiencies of total hemolytic complement activity and decreased C3 levels were reported in sera from normal neonates. However, little is known about complement activation products in the newborn. In a prospective study, complement activation products were determined in 32 healthy term neonates, in 41 neonates with colonization of their mothers, in 15 colonized neonates, and in 10 neonates with early onset infection. In all newborns, EDTA plasma was obtained within the first 6 h of life. The anaphylatoxin C3a-desArg was determined with a novel ELISA using an MAb reacting with a neoepitope of C3a-desArg. C3bBbP (alternative pathway convertase) and C1rsC1-inactivator (activation product of classical pathway) were measured with double-sandwich ELISA. C3 was determined by radial immunodiffusion. Plasma concentrations of C3a-desArg were similar in healthy term neonates and healthy adults, whereas diminished C3 levels were observed in the newborn infants. There were no significant differences between healthy neonates, neonates with colonized mothers, and colonized neonates. In neonates with infection, a significant elevation of C3a-desArg was found at the onset of the disease, resulting from alternative pathway activation. In contrast, the C1rsC1-inactivator complex showed no significant differences among healthy, colonized, and infected neonates. The anaphylatoxin C3a mediates inflammatory reactions such as vasodilatation and an increase in microvascular permeability and might therefore play an important role in severe neonatal infection.

The effect of Leboyer delivery on blood viscosity and other hemorheologic parameters in term neonates.

OBJECTIVE: This study was done to compare postnatal alterations in blood viscosity, hematocrit value, plasma viscosity, red blood cell aggregation, and red blood cell deformability in term neonates undergoing both early umbilical cord clamping and delivery according to the Leboyer method. STUDY DESIGN: The umbilical cords of 15 healthy, term infants were clamped within 10 seconds of birth (early cord clamping), and 15 infants delivered according to the Leboyer method were placed on the mother's abdomen, and the umbilical cords were clamped 3 minutes after birth. Hemorheologic parameters were studied in umbilical cord blood at 2 hours, 24 hours, and 5 days from the time of delivery. RESULTS: The residual fetal placental blood volume decreased from 45 +/- 8 ml/kg (x +/- SD) after early cord clamping to 25 +/- 5 ml/kg after delivery by the Leboyer method. After Leboyer-method delivery, the hematocrit value rose from 48% +/- 5% at birth to 58% +/- 6% 2 hours after delivery, 56% +/- 7% at 24 hours, and 54% +/- 8% after 5 days. Blood viscosity in the Leboyer-method group increased by 32% within the first 2 hours but did not change significantly during the following 5 days. Plasma viscosity, red blood cell aggregation, and red blood cell deformability were not affected by the mode of cord clamping. CONCLUSIONS: Delivery by the Leboyer method leads to a significant increase in blood viscosity as a result of increasing hematocrit value, whereas other hemorheologic parameters are similar to those of infants with early cord clamping.

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 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)

[The critical hemoglobin value in newborn infants, infants and children]. / Kritische Hämoglobinwerte bei Neugeborenen, Säuglingen und Kindern.

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.

A European multicenter randomized controlled trial of single dose surfactant therapy for idiopathic respiratory distress syndrome.

We performed a multicenter prospective randomized controlled trial to determine the efficacy and safety of the surfactant preparation, Survanta (Abbott Laboratories, Chicago, USA), for 750-1750 g infants with idiopathic respiratory distress syndrome, (IRDS) receiving assisted ventilation with 40% or more oxygen. One hundred and six eligible infants from the eight participating centers were randomly assigned between March 1986 and June 1987 to receive either surfactant (100 mg phospholipid/kg, 4 ml/kg) or air (4 ml/kg) administered into the trachea within 8 h of birth (median time of treatment 6.2 h, range 3.2-9.1 h). The study was stopped before enrollment was completed at the request of the United States Food and Drug Administration when significant differences were observed in incidence of periventricular-intraventricular hemorrhage (PIH), between the surfactant treated and control infants. Surfactant treated infants had larger average increases in the arterial-alveolar oxygen ratio, (a/A ratio) (P less than 0.0001), and larger average decreases in FiO2 (P less than 0.0001) and mean airway pressure, (MAP) (P less than 0.017) than controls over the 48 h following treatment. The magnitude of the differences between the surfactant and control groups were 0.19 (SE = 0.03) for a/A ratio, -0.28 (SE = 0.04) for FiO2 and -1.7 cm H2O (SE = 0.70) for MAP. The clinical status on days 7 and 28 after treatment was classified using four predefined ordered categories: (1) no respiratory support; (2) supplemental O2 with or without continuous positive airway pressure (CPAP); (3) intermittent mandatory ventilation; and (4) death. There were no statistically significant differences in the status categories on days 7 or 28 between surfactant and control infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood viscosity and optimal hematocrit in narrow tubes.

Blood viscosity in normal adults was measured in glass tubes with diameters of 50, 100 and 500 microns for a wide range of adjusted feed hematocrits (15-70%). Blood viscosity decreased at each of the adjusted feed hematocrits when going from a 500-micron tube to a 50-micron tube. The viscosity reduction increased with increasing hematocrit. The steepness in the hematocrit-viscosity curves decreased with decreasing tube diameter. Erythrocyte transport efficiency (hematocrit/blood viscosity) was calculated to estimate the optimal hematocrit for oxygen transport. Optimal hematocrit averaged 38% in 500-micron tubes, 44% in 100-micron tubes and 51% in 50-micron tubes. Our results suggest that the strong Fåhraeus-Lindqvist effect at high hematocrits may help to maintain oxygen transport in polycythemic patients as long as the driving pressure is sufficient.

Viscosity reduction of red blood cells from preterm and full-term neonates and adults in narrow tubes (Fahraeus-Lindqvist effect).

In artificial tubes as well as in blood vessels with diameters less than 500 microns, blood viscosity decreases with decreasing diameter (Fahraeus-Lindqvist effect). Our study measured viscosity of red blood cells (RBC) from 10 preterm infants, 10 term neonates, and 10 adults by means of a capillary viscometer. RBC were suspended in buffer at hematocrits of 0.20, 0.40, and 0.60 1/1 (1.00 1/1 = 100%). Tubes with diameters of 50, 100, and 500 microns were perfused with these suspensions. Viscosity in the 500-microns tubes was not significantly different, at any hematocrit, among the three groups. Viscosity decreased at each of the adjusted hematocrits in the three groups when going from a 500-microns tube to a 50-microns tube. At a hematocrit of 0.60 1/1, viscosity reduction averaged 48 +/- 7% in the preterm infants, 42 +/- 8% in the full-term neonates, and 35 +/- 5% in the adults, whereas the reductions at a hematocrit of 0.20 1/1 were only 32 +/- 6, 27 +/- 4, and 24 +/- 6%, respectively. For the combined data from the neonates and adults, there was a significant inverse relationship of the viscosity in 50-microns tubes at a hematocrit of 0.60 1/1 to the mean corpuscular volume (r = 0.69). To evaluate whether increased membrane elasticity of neonatal RBC contributes to the stronger viscosity reduction of neonatal RBC in narrow tubes, heated neonatal and adult RBC were also studied. The resulting loss of membrane elasticity caused a marked decrease in the viscosity reduction in 50-microns tubes, particularly in the neonates.(ABSTRACT TRUNCATED AT 250 WORDS)