Thomas R.C. Sisson

Retinal changes produced by phototherapy

This study was undertaken to assess the effect of blue fluorescent light on retinas of a pigmented, diurnal animal, the newborn piglet. The animals, having one eye shielded, were placed under a phototherapy unit as used for newborn infants. Three weeks after exposure, under light microscopy, the tissues of eyes exposed for 72 hours, and in one instance for slightly less than 12 hours, showed marked damage to the photoreceptors (rods and cones). Under electron microscopy, changes in the visual receptors were observed in the exposed eyes which were not observed in the shielded eyes. High-intensity blue fluorescent light was shown to damage the retinas of newborn piglets, developmentally similar to those of human infants. Therefore, utmost care would seem to be required to shield the eyes of infants exposed to bilirubin phototherapy units.

The blood volume of infants

Summary The subjects of this study were 126normal full-term infants on whom 223 plasma volume determinations were made using a T-1824 dye dilution technique. Of these infants, 2 observations were made on 47, and 3 or more serial observations were made on 20. Total blood and erythrocyte volumesand total circulating hemoglobin mass values were calculated from the plasma volume, venous hematocrit, and hemoglobin concentration. No reliable average blood volume could be observed in either the neonatal period or during the succeeding 11 months of life, owing to a wide range of values throughout the year. The average erythrocyte volume, circulating hemoglobin mass, and total hemoglobin iron values did not return to neonatal levels until 16 weeks after birth. Assessment of anemia in the infant from blood loss, iron deficiency, or other causes can be aided by the determination of the erythrocyte volume and hemoglobin mass. We believe that more reliance can be placed on these values than on those of the hemoglobin concentration and hematocrit because of the considerable number of infants who demonstrate hypo- or hypervolemia. In these states paradoxical values of hemoglobin concentration and hematocrit are frequently encountered which yield misleading information.

The blood volume of infants: III. Alterations in the first hours after birth

Summary We have concluded that a significant increase of the circulating plasma, erythrocyte, and total blood volumes takes place in the normal newborn infant during the first few hours of life. The average increments were: plasma volume 20.0 per cent, red blood cell mass 25.6 per cent, and total blood volume 22.5 per cent. There was no indication that a shift of fluid, particularly of plasma, from intravascular to extravascular spaces occurred in these normal infants. This does not imply that it cannot occur, especially in the case of a circulatory overload. Our understanding of the changes that take place in the adjustment from fetal to neonatal and then to adult circulatory and pulmonary patterns is incomplete. The results of this study indicate that caution should be used in producing an artificial expansion of the neonatal blood volume. Interference with these hemodynamic changes by effecting a transfusion of placental blood seems unwise; the hazards outweigh the rather uncertain benefits. We have postulated that the marked increase in blood volume (62 ml. average) of the infants studied was due to an initial temporary sequestration of blood in the viscera and caudal end of the body, and that this blood was then introduced into the general circulation as vascular and pulmonary patterns were stabilized.Summary The subjects of this study were 126normal full-term infants on whom 223 plasma volume determinations were made using a T-1824 dye dilution technique. Of these infants, 2 observations were made on 47, and 3 or more serial observations were made on 20. Total blood and erythrocyte volumesand total circulating hemoglobin mass values were calculated from the plasma volume, venous hematocrit, and hemoglobin concentration. No reliable average blood volume could be observed in either the neonatal period or during the succeeding 11 months of life, owing to a wide range of values throughout the year. The average erythrocyte volume, circulating hemoglobin mass, and total hemoglobin iron values did not return to neonatal levels until 16 weeks after birth. Assessment of anemia in the infant from blood loss, iron deficiency, or other causes can be aided by the determination of the erythrocyte volume and hemoglobin mass. We believe that more reliance can be placed on these values than on those of the hemoglobin concentration and hematocrit because of the considerable number of infants who demonstrate hypo- or hypervolemia. In these states paradoxical values of hemoglobin concentration and hematocrit are frequently encountered which yield misleading information.

The blood volume of infants: II. The premature infant during the first year of life

Summary One hundred and forty-five plasma volume determinations were performed on 51 healthy premature infants between birth and 1 year of age. Two or more serial observations were made on 38 of the infants. Plasma volumes were measured with the use of T-1824. Serum iron and iron-binding capacity determinations were also made. The average blood volume at birth was found to be 109 ml. per kilogram, a value slightly higher than in fullterm infants. In the first 2 1/2 months of life there was a tendency for the plasma volume to increase as the erythrocyte volume decreased. This had the effect of maintaining the total blood volume at a relatively high level. The erythrocyte volume at birth was 45.5 ml. per kilogram (about 5 ml. higher than in full-term infants) and was close to 20 ml. per kilogram between 12 and 52 weeks of age. There was no significant correlation between erythrocyte volume and growth gain, nor between erythrocyte volume and venous hematocrit. Normal growth increments far outdistanced the expansion of erythrocyte volume. The circulating hemoglobin mass was 36.5 Gm. in the first 2 days of life; it declined 33 per cent by 4 weeks of age. At 12 weeks it was again at the value recorded in the first 2 days. Further increments were more gradual. On the basis of body weight, an abrupt fall from 20.5 Gm. per kilogram at birth to 10 Gm. at 6 weeks occurred. The average value remained between 6.4 and 8.0 Gm. per kilogram for the rest of the year. There was poor correlation between the values for hemoglobin concentration and circulating hemoglobin mass in both the neonatal period and later. The total hemoglobin iron reached its lowest level between 3 and 6 weeks of life. By the tenth week, values recorded in the first week were regained. It was concluded that erythropoiesis became active between 3 and 7 weeks after birth and that the original iron stores were adequate for hemoglobin synthesis until only about 10 weeks after birth. This explains in part the development of iron depletion and iron deficiency at an earlier age in the premature infant than in the full-term one. The results of this investigation indicate the average values of total blood, plasma, and erythrocyte volumes and of circulating hemoglobin mass of premature infants from birth through 1 year of age. It was concluded that within the limitations of the techniques used, these values are representative of an urban clinic group. It was observed that considerable variation about the mean values was present throughout the year. The average values, therefore, indicate changes that may be expected in the first year of life but should be considered specific in only a restricted sense.