P. Herin

POSTNATAL DEVELOPMENT OF RENAL FUNCTION IN PRE-TERM AND FULL-TERM INFANTS

ABSTRACT. Aperia, A., Broberger, B., Klinder, G., Herin, P. and Zetterström, R. (Department of Paediatrics, Karolinska Institute, St. Görans Childrens Hospital, Stockholm and Huddinge Hospital, Huddinge, Sweden). Postnatal deveopment of renal function in preterm and full‐term infants. Acta Paediatr Scand, 70:183, 1981. –This study has been designed to examine the effect of gestational age (GA) on the postnatal development of renal function and has been performed in pre‐term (PT) infants (GA=30–34 weeks) and in full‐term (FT) infants (GA=39–41 weeks). Postnatal age has ranged from 1–35 days. From 8 hour urine samples collected after spontaneous voiding and a capillary blood sample, determinations have been made of the clearance of creatinine (CCr), the fractional excretion of β2‐microglobulin (FEβ2) and the fractional excretion of sodium (FENa). In some infants receiving fluid parenterally, simultaneous determinations were made of the clearance of creatinine and inulin. As judged from this study, CCr is a reliable indicator of the glomerular filtration rate (GFR). GFR was almost the same in newborn PT and FT, but from 0.3–1 week of age GFR increased significantly more rapidly in FT than in PT. From 1–5 weeks of age GFR increased at approximately the same rate in PT and FT infants. The absolute value for GFR in 3–5 weeks old infants was lower in PT than in FT. FEβ2 was higher in PT than in FT infants during the entire first month of life and FENa was higher in PT than in FT infants during the first week of life, suggesting a glomerular tubular imbalance at least at the level of the proximal tubule in PT infants. It is concluded that different stages of maturation will alter the preconditions for the renal adaptation to extrauterine life during at least the first month of life. Therefore special attention must be paid to the limited renal function in PT during their entire first month of life.

Kidney function in adults born with unilateral renal agenesis or nephrectomized in childhood

We have evaluated the long-term prognosis in an unselected group of adult patients either uni-nephrectomized in childhood because of hydronephrosis or born with unilateral renal agenesis. Thirty-six patients aged 7–47 years were followed for 7–40 years. In 23 control subjects aged 20–47 years the glomerular filtration rate (GFR) and thep-aminohippuric acid clearance (CPAH) did not change significantly with age. In patients with a single kidney the size of that kidney was larger and GFR and CPAH were higher than single kidney values in control subjects. However, in patients with a single kidney since childhood the GFR and the CPAH declined slowly but significantly during the follow-up period. Significant microalbuminuria occurred in 47% of the patients with a single kidney and was more frequent with a longer follow-up period. No patient had renal insufficiency or a marked increase in arterial blood pressure. We conclude that in patients with a single kidney since childhood the long-term prognosis is good, but the late decrease in GFR and increase in albumin excretion may indicate a moderate risk for premature renal damage.

SODIUM EXCRETION IN RELATION TO SODIUM INTAKE AND ALDOSTERONE EXCRETION IN NEWBORN PRE‐TERM AND FULL‐TERM INFANTS

Abstract. The importance of aldosterone for the control of salt balance has been examined in pre‐term infants (gestational age 28–34 weeks) and in full‐term infants. The post‐natal age has varied from 2–21 days. Eight‐hour urinary specimens have been analysed with regard to sodium, potassium and aldosterone. The daily sodium intake has been recorded following determination of milk intake and analyses of sodium in breast milk. Due to variations of sodium content of breast milk, the daily sodium intake in pre‐term infants was lower than in full‐term infants during the first 10 days of life. The sodium excretion was significantly higher in pre‐term infants than in full‐term infants during the fist six days of life. During the first week of life the sodium balance is negative in pre‐term infants and positive in full‐term infants. Aldosterone excretion is high during the first week of life and increases further from the 2nd to the 3rd week of life in both pre‐term and full‐term infants. The correlation between aldosterone excretion and urinary potassium/sodium quotient is 0.87 in full‐term infants, 0.57 in pre‐term infants aged 13–20 days and does not exist in pre‐term infants aged 2–10 days. It is suggested that the high sodium excretion in newborn pre‐term infants can in part be explained by an unresponsiveness to aldosterone at this developmental stage.

Postnatal Development of Renal Function in Very Low Birth weight Infants

ABSTRACT. The postnatal development of renal function was compared in infants with a gestational age of 25–30 weeks, mean 27.8 weeks (GA 28), and in infants with a gestational age of 31–34 weeks, mean 32.5 weeks (GA 32). The infants were comparable with regard to postnatal course, fluid, caloric and salt intake. Observations were made during the 1st, 2nd and 4th‐7th (mean 5th) postnatal weeks. From the 1st to the 5th postnatal week the creatinine clearance (CCr ml/min/1.73 m2), increased from 11 to 20 in GA 28 and from 15 to 30 in GA 32. At 2 weeks of age CCr was significantly lower in GA 28 than in GA 32. During the first week of life diuresis was lower in GA 28 than in GA 32 but thereafter was the same in both groups. We interpret this as a sign of dehydration in GA 28. Serum arginine vasopressin (S‐AVP) concentrations were high in both groups at all ages. Mean urine osmolality was low (<300) regardless of postnatal age and S‐AVP. Urinary sodium excretion was high at 1 week of age in both groups and decreased with increasing postnatal age. Na excretion was slightly higher in GA 28 than in GA 32 at 1 but not at 2 and 5 weeks. UK/UNa was below 1 in both groups during the first week of life and increased with postnatal age. Urinary aldosterone excretion was high in both GA 28 and GA 32 at all ages. Serum sodium levels were lower in GA 28 than in GA 32 at all ages. Hyponatremia was observed in 13/32 infants in GA 28 and in 1/45 infants in GA 32. We conclude that the postnatal development of renal function is retarded in all preterm infants and is slightly slower in infants with a GA below 31 weeks than in infants with a GA of 31–34 weeks. Extrarenal factors must contribute to the low serum Na values in infants with GA <31 weeks.

NEONATAL AORTIC THROMBOSIS: A Possible Clinical Manifestation of Cangenital Antithrombin III Deficiency

Abstract. Bjarke, B., Herin, P. and Blombäck, M. (Department of Pediatrics, Karolinska Institutet, S:t Görans Childrens Hospital and Department of Blood Coagulation, Karolinska Sjukhuset, Stockholm, Sweden). Neonatal aortic thrombosis. Acta Paediat Scand 63:297, 1974.–Two cases of neonatal aortic thrombosis are presented. Possible etiologies, as quoted in the literature, are discussed and the fact that the etiology seems to be unknown in at least half of the cases is stressed. The mothers of the two neonates presented had an antithrombin III (AT III) deficiency, which is associated with an increased tendency to thrombosis. One of the mothers had manifested such a tendency. The AT III deficiency as an ethiological factor for the thrombus formation in the two babies is discussed.

Renal function in sick, very low‐birth‐weight infants

Renal immaturity is pronounced in very low‐birth‐weight infants with a gestational age 30 weeks. We attempted to elucidate if conditions requiring mechanical ventilation, including patent ductus arteriosus, might further compromise renal function due to decreased renal perfusion. Forty infants studied between 4 and 28 days of age were divided into four groups: Control with no patent ductus or mechanical ventilation (n= 8); PDA + MV, with both patent ductus and mechanical ventilation (n=17); PDA, with patent ductus (n= 6); MV, with mechanical ventilation (n= 9). The groups PDA + MV and MV had significantly lower creatinine clearances and significantly higher fractional sodium excretions than controls. Mean arterial pressure was significantly lower in all groups compared to controls and correlated significantly with creatinine clearance (r = 0.47, p < 0.02). In conclusion, low renal function in these infants is further compromised by a patent ductus arteriosus and/or the use of mechanical ventilation.

Salt content in human breast milk during the three first weeks after delivery.

During a study of electrolyte balance in newborn infants, the concentration of sodium and potassium in breast milk was determined on different days after delivery. Material and Methods. Mothers who were delivered at term were studied on the first ( n = 5 ) , second (n=5) , third (n=17), fourth (n=14), fifth (n=19), sixth (n=6), seventh (n=5), eighth and ninth ( n = 5 ) , tenth and eleventh (n =5) , and twenty-second to twentysixth (n=12) days after delivery. In addition, 19 samples were obtained 1-11 days after delivery from mothers who were delivered during the 32nd-34th gestational week. A 1 ml sample of breast milk was obtained at the beginning and/or at the end of the feeding. The concentration of sodium and potassium in 1/50 diluted breast milk was determined with a flame photometer. Results and Comments. In 11 mothers delivered at term and studied 3-6 days after delivery, the concentration of sodium and potas-

Changes in Intracranial Arterial Blood Flow Velocities during Surgical Ligation of the Patent Ductus Arteriosus

ABSTRACT. A combined continuous and range‐gated Doppler instrument was used to assess intracranial arterial blood flow velocity changes in infants and neonates undergoing surgical ligation of the Ductus Arteriosus (DA). Continuous recordings during DA closure in six infants (3.5‐10 months old), showed an abrupt increase in diastolic blood flow velocity simultaneous with an increase in systolic and diastolic arterial blood pressure. In five infants, these changes were followed by a rapid fall in systolic and diastolic blood pressure without a concomitant change in blood flow velocity, which may be secondary to a rapid fall in intracranial vascular resistance. The mean blood flow velocity increase following DA closure was 27 % (8‐43 %) and the changes in diastolic and mean blood flow velocity were significant (p<0.01). In seven preterm neonates (24‐28 weeks) studied before and after surgery, a mean blood flow velocity increase of 50 % (14‐115 %) (p<0.01), mainly due to an increase in diastolic blood flow velocity (p<0.01), was recorded. These rapid intracranial hemodynamic changes during surgical DA closure should be taken into consideration when selecting techniques for DA closure.

POSTNATAL CONTROL OF WATER AND ELECTROLYTE HOMEOSTASIS IN PRE-TERM AND FULL-TERM INFANTS

Aperia, A., Broberger, O., Herin, P., Thodenius, K. and Zetterström, R. (Department of Paediatrics, Karolinska Institute, St. Görans Childrens Hospital, Stockholm, Sweden). Postnatal control of water and electrolyte homeostasis in pre‐term and full‐term infants. Acta Paediatr Scand, Suppl. 305: 61–65, 1983.—A review is given of the progress which has been made during the last decade within the field of renal control of water and sodium homeostasis in newborn infants of varying gestational age. Both preterm and full‐term infants have a low capacity for rapid excretion of a salt load. The natriuretic response improves gradually up to the age of 15 months. The capacity to excrete a load of sodium bicarbonate is higher than to excrete a load of sodium chloride. Under basal conditions preterm infants of a gestational age below 35 weeks have a higher renal sodium excretion than full‐term infants. They also appear to be unable to retain sodium when in negative balance. The capacity to concentrate the urine is low in newborn infants, the maximal osmolality being only slightly above that of plasma. The concentrating capacity increases relatively fast during the first 4–6 postnatal weeks in full‐term as well as in pre‐term infants but does not reach the adult level until the second year. Water loaded newborn infants are able to excrete a urine with a osmolality as low as 30–50 mOsm per kg. In full‐term infants free water clearance per unit filtered water is higher than in adults. Water‐loaded pre‐term infants with a gestational age of more than 30 weeks also have a supernormal diluting capacity.

Studies in renal response to various protein intakes in preterm infants.

ABSTRACT. The renal effects of two diets—breast‐milk and breast‐milk with extra human protein (7 g/l breast‐milk)—were compared in very low birth weight infants with a gestational age of 26 to 30 weeks. When the infants were given the high protein diet for one week the glomerular filtration rate (GFR) increased significantly more than when breast‐milk alone was given. Sodium clearance showed a similar increase in proportion to the GFR during the two diets. The high protein diet raised the urine osmolality moderately in all individuals, while the diuresis remained unchanged. The data in the present study indicate that the function of the immature kidney is influenced by the amount of protein in the diet. However, the long‐term renal effects in preterm infants maintained on a high protein intake remain unknown.