Follow-up studies of very low birth weight infants (1,250 grams or less) born and treated within a perinatal center

The growth and development of inborn very low birth weight infants was evaluated in 50 of 60 survivors from 132 babies weighing less than or equal to 1,250 gm born July 1974 to December 1977. Mean +/- SE birth weight and gestation was 1,066 +/- 19.3 gm and 29.5 +/- 0.3 weeks, respectively, with 13 infants small-for-gestational age. Of the survivors, 26% weighed less than or equal to 1,000 gm. Male to female ratio was 1:1.4. Apgar scores less than or equal to 5 at five minutes occurred in 16% of the infants. Respiratory distress syndrome occurred in 56%, but only 10% (5/50) required mechanical ventilation. At 1 year, 46% small for gestational age (SGA) and 8% appropriate for gestational age (AGA) infants were less than the third percentile for weight. Major neurologic abnormality occurred in three infants (6%), one of whom is also blind. Grade V retrolental fibroplasia occurred in two others. Severe developmental delay (development quotient < 80, Gesell) occurred in these five infants and two other neurologically normal babies. Of 15 infants weighing less than or equal to 1,000 gm, two had major handicaps. Eight percent of the AGA infants and 30% of the SGA infants had major handicaps. These data indicate that infants born and treated in a perinatal center have a decreased incidence of asphyxia and severe respiratory distress syndrome and that the incidence of major handicaps is reduced, especially in the appropriate for gestational age baby.

A simple test for detection of sickle hemoglobin in the neonatal period

The ease of denaturation by shaking of a solution of oxyhemoglobin S (oxy-Hb S) forms the basis for a simple and reliable test for confirmation or rapid detection of Hb S in children and adults. Comparison of results of this test with those from agar gel electrophoresis in capillary blood samples from 187 black neonates at 2 to 7 days of life showed no overlap of the amounts of hemoglobin precipitated between the group of neonates with Hb S (5.7--12.0%) and that without Hb S (0--4.7%). These results indicate that the shaking test, by virtue of being simple, reliable and inexpensive, may be used to detect and confirm Hb S in large numbers of neonates before their discharge from the nursery.

Pulmonary lavage in preterm lambs

Pulmonary function was studied before and after bilateral lung lavage with oxygenated FC-80 fluorocarbon liquid in seven perterm lambs, 134 days of gestation. Measurements of transpulmoary pressure, airflow, tidal volume, and functional residual capacity (FRC) enabled calculation of lung resistance and compliance, specific compliance, and work of breathing. Immediately postlavage, arterial oxygen tension (PaO2) decreased significantly (P less than 0.05) by 41% from control values. In addition, at 1 hr postlavage, lung compliance significantly decreased (P less than 0.01) by 43% from control levels. Lung resistance, FRC work of breathing arterial carbon dioxide tension, and pH postlavage were not significantly different from prelavage values. The mean volume of FC-80 remaining in the lungs at 1 hr postlavage was 32% of the instilled volume. These data indicate that lung lavage with a low surface tension liquid has a relatively small effect on lung mechanics of the premature lung.

Alterations in pulmonary function of premature lambs due to positive end-expiratory pressure

These studies compare lung mechanics and volumes of premature lambs delivered at 139 days of gestation by cesarean section and ventilated by either intermittent positive pressure (IPP) or positive end-expiratory pressure (PEEP). During the first few hours of life, sequential determinations of lung compliance, specific lung compliance; lung resistance, specific lung conductance and functional residual capacity were made at half-hour intervals. Measurements in 5 lambs ventilated with PEEP demonstrated that lung compliance (p less than 0.005), specific lung compliance (p less than 0.001) and specific lung conductance (p less than 0.005) decreased; while lung resistance (p less than 0.10) and functional residual capacity (p less than 0.02) increased as compared to 7 lambs ventilated with IPP.

Positive end expiratory pressure: effects on lung mechanics of premature lambs

Pulmonary mechanics were determined at 0, 3, 6, and 10 cm H2O positive and expiratory pressure (PEEP) in premature lambs at a mean gestational age of 134 days. Functional residual capacity increased (p less than 0.005) by 7% (1.6 ml/kg) per cm H2O PEEP. Dynamic lung compliance and specific compliance significantly decreased by 10% (0.11 ml/cm H2O/kg) and 9% (0.0051 l/cm H2O) per cm H2O PEEP, respectively, for PEEP above 3 cm H2O level. Inspiratory lung resistance increased significantly (p less than 0.05) only between 0 and 6 cm H2O PEEP while expiratory lung resistance increased (p less than 0.05) between 0 cm H2O PEEP and all higher levels. The data suggest that PEEP in excess of 3 cm H2O produces undesirable effects on lung mechanics in premature lambs. These results may be important in predicting contraindications and potential complications of positive pressure breathing in the newborn.

Pulmonary function in premature lambs during the first few hours of life

This study establishes the mean values, variations, and trend of pulmonary function during the first few hours of life in premature lambs. Measurements of intraesophaheal and tracheal pressure, air flow, tidal volume, and functional residual capacity enabled calculations of lung compliance, specific lung compliance, and inspiratory and expiratory resistance of the lungs. Arterial carbon dioxide tension and pH were maintained within a physiologic range. Mean arterial oxygen tension (PO2) at elevated inspired oxygen tension, varied in the individual animals from 51 to 185 mm Hg at an inspired oxygen concentration of 46 to 71%. It was found that the lungs of premature lambs delivered by cesarean section were mechanically unstable; the lambs were all ineffectual at breathing and required some form of mechanical ventilation. During the first 6 hours of postnatal life the lungs of premature lambs are characterized by a wide range of mechanical values and blood gas tensions.

The role of exchange transfusion in the management of low-birth-weight infants with and without severe respiratory distress syndrome. I. Initial observations

Exchange transfusions within the first 8 hours of life, as an adjunct to conventional therapy, were evaluated in two groups of infants: (1) infants with birth weights of less than 1,250 gm without severe respiratory distress and (2) infants of any birth weight with evidence of severe respiratory distress syndrome. A total of 63 infants were studied in Group 1. Infants who received an exchange transfusion had a survival rate of 86% as contrasted with a survival rate of 57% in the control group (p less than 0.01). A total of 82 infants were studied in Group 2. Infants who received an exchange transfusion had a 59% survival rate as compared with a 39% survival rate for the control group (p less than 0.04). The mechanism by which early exchange transfusion improves survival rate is unknown.

Gaseous exchange and acid-base balance in premature lambs during liquid ventilation since birth

Nine distressed premature lambs were studied before, during, and after ventilation with fluorocarbon liquid (FC-80). It was found that premature lambs, delivered by cesarean section, could be adequately ventilated with oxygenated liquid for period up to 3 hr. Using fluarocarbon liquid in conjunction with the described liquid breathing system, it was possible to maintain remarkably good pulmonary gas exchange and acid-base balance during normothermic conditions. In addition, peak intratracheal pressures measured during recovery from liquid ventilation were significanly reduced (P is less than 0.001) as compared with preliquid ventilation values. This improvement in lung function is in direct contrast to the deterioration in that of the adult animal following liquid ventilation as reported previously.

Effect of hyperoxia and androgen on red cell 2,3-diphosphoglycerate and oxygen affinity

Increased plasma erythropoietin (ESF) activity, a rise in RBC 2,3-DPG, and a 'right shift' of the oxygen hemoglobin equilibrium curve following androgen administration to mice in ambient or hyperoxic conditions, was demonstrated. If androgens had a direct effect on the RBC metabolism, increased 2,3-DPG would result in a facilitated release of oxygen to the tissue. This would have been accompanied by a decrease rather than an increase in the level of ESF. Hyperoxia has abolished detectable rising levels of plasma ESF and RBC 2,3-DPG following androgen administration. These levels were close to those seen in the ambient nontreated mice.

Oxygen affinity in red cells: changes induced in vivo by propranolol

Propranolol, a blocking agent for the beta adrenergic receptor, produces a redistribution of 2,3-diphosphoglycerate in the red cell. At concentrations of 3.3 x10(-5)M, 2,3-diphosphoglycerate in the red cell membrane becomes unbound in vitro. The administration of propranolol to hunmns produces similar changes and results in a decrease in the affinity of hemoglobin for oxygen.

The effects of deoxygenation of adult and fetal hemoglobin on the synthesis of red cell 2,3-diphosphoglycerate and its in vivo consequences

Patients over 1 month of age with arterial oxygen pressures of less than 60 mm Hg were found to have elevated red cell 2,3-diphosphoglycerate (2,3-DPG) levels and blood with a decreased affinity for oxygen. The increase in 2,3-DPG was proportional to the degree of hypoxemia. In patients under 1 month of age this relationship was not observed. Red cells from adults, but not newborns, showed rapid increases in 2,3-DPG when incubated under nitrogen. Adult, but not fetal, deoxyhemoglobin was shown to facilitate in vitro synthesis of 2,3-DPG by binding this organic phosphate and relieving the product inhibition of 2,3-DPG mutase. Throughout a wide range change in oxygen affinity as measured by the P(50) is linear with respect to the 2,3-DPG concentration; a change of 430 mmumoles of 2,3-DPG/ml of red blood corpuscles (RBC) resulting in a change of the P(50) of 1 mm Hg. It appears that the 2,3-DPG of the adult's red cells responds rapidly to metabolic and environmental influences and in turn effects metabolism and the cellular environment. Many of these effects are not shared by the red cells of the newborn.

Oxygen-hemoglobulin dissociation curves: effect of inherited enzyme defects of the red cell

The blood of a patient with a deficiency of hexokinase in the red cells and a decreased concentration of 2, 3-diphosphoglycerate in the red cells showed an increased affinity for oxygen, whereas a patient with a deficiency of pyruvate kinase and an elevated concentration of 2, 3-diphosphoglycerate in the red cells had blood with a decreased affinity for oxygen. Defects in red cell glycolysis may alter the oxygen affinity of blood by virtue of their effect on 2, 3-diphosphoglycerate concentrations in red cells.