Infant mortality in the United States.

The infant mortality rate (IMR) of 6.0 per 1000 live births in the United States in 2013 is nearly the highest among developed countries. Moreover, the IMR among blacks is >twice that among whites-11.11 versus 5.06 deaths per 1000 live births.This higher IMR and racial disparity in IMR is due to a higher preterm birth rate (11.4% of live births in 2013) and higher IMR among term infants. The United States also ranks near the bottom for maternal mortality and life expectancy among the developed nations-despite ranking highest in the proportion of gross national product spent on health care. This suggests that factors other than health care contribute to the higher IMR and racial disparity in IMR. One factor is disadvantaged socioeconomic status. All of the actionable determinates that negatively impact health-personal behavior, social factors, heath-care access and quality and the environment-disproportionately affect the poor. Addressing disadvantaged socioeconomic status by improving access to quality health care and increasing social expenditures would have the greatest impact on the USA's IMR and racial disparity in IMR.

Renal function correlates of postnatal diuresis in preterm infants.

A characteristic pattern of fluid homeostasis occurs in the first week of life in many preterm infants. Initially, urine output is low independent of fluid intake, subsequently a diuresis occurs, and finally urine output begins to vary with intake. Renal clearance measurements were made during each of these three phases to elucidate the renal mechanisms involved. Periods during which the ratio of urine output to fluid intake was greater than or equal to 1 and urine output was greater than or equal to 3 mL/kg/h were defined as diuretic. Of 22 preterm infants studied from 12 to 120 hours of age, 17 had at least one period of diuresis. In these infants, urine output, fluid intake rate, output to intake ratio, glomerular filtration rate, and fractional sodium excretion were lowest at 12 to 24 hours of age. During diuresis, urine output tripled without a significant change in fluid intake so that output to intake increased to levels exceeding unity. Diuresis was associated with significant increases in glomerular filtration rate and fractional sodium excretion. By 108 to 120 hours of age, urine output decreased despite an increase in fluid intake. This was accompanied by a decrease in glomerular filtration rate. These results suggest that the initial antidiuretic phase is the result of a low fractional sodium excretion in the face of a low glomerular filtration rate. Subsequently, diuresis and natriuresis occur as a result of abrupt, nonmaturational increases in glomerular filtration rate and fractional sodium excretion. With cessation of diuresis, glomerular filtration rate and fractional sodium excretion decrease and water and electrolyte output begin to vary appropriately with intake.

Phases of fluid and electrolyte homeostasis in the extremely low birth weight infant.

OBJECTIVE: We had shown previously that preterm infants undergo three phases of fluid and electrolyte homeostasis; prediuretic, diuretic, and postdiuretic. The objectives of the present study were: (1) to determine whether infants even more immature and infants cared for under thermal environmental conditions different from those previously studied also undergo these three phases; and (2) to relate these phases to changes in renal function. METHODS: Consecutive, timed urine collections were made during the first 5 days of life in 32 infants with birth weights of 1000 g or less. Infants were cared for in radiant warmers for 24 hours and then transferred to nonhumidified incubators. Diuresis was defined as urine flow rate (V) of 3 mL or more/kg per hour and weight loss of 0.8 g or more/kg per hour. The physiologic relationships among water and sodium balance, insensible water loss, arterial blood pressure, and renal function were made during the three phases. RESULTS: Twenty-eight (87%) of the 32 infants underwent the three homeostatic phases. The median ages of onset and cessation of diuresis were 25 and 96 hours, respectively. There was no correlation between onset of diuresis and change of thermal environment. During the prediuretic phase, V averaged 1.6 mL/kg per hour, and 17 of 28 infants had at least one collection period in which V was less than 1 mL/kg per hour; urinary sodium excretion was 0.1 mEq/kg per hour; the glomerular filtration rate (GFR) was 0.22 mL/kg per hour; fractional excretion of sodium (FENa) was 6.2%; and urine osmolality was dilute (221 mOsm/kg). During the diuretic phase, V and sodium excretion more than tripled; GFR and FENa doubled; and there was no change in urine osmolality. During postdiuresis, V and Na excretion decreased to values intermediate between the prediuretic and diuretic phases, and FENa fell to prediuretic levels, but there was no change in GFR or urine osmolality. There was poor correlation between blood pressure and GFR. Insensible water loss was high and variable during all phases, exceeding 190 mL/kg per day in the smallest infants. CONCLUSIONS: Extremely low birth weight infants manifest three phases of fluid and electrolyte homeostasis, as do more mature infants, independent of thermal environment. Diuresis and natriuresis are the result of abrupt increases in GFR and FENa. We speculate that this may be the result of expansion of the neonatal extracellular space as fetal lung fluid is reabsorbed.

A quantitative review of mortality and developmental disability in extremely premature newborns.

OBJECTIVES: To summarize the literature on mortality rates and prevalences of major neurodevelopmental disabilities and to examine trends of these outcomes over time in extremely premature neonates. DATA SOURCES: MEDLINE was used to search the English literature for studies published since 1970 reporting on both mortality and disability in infants born at or before 26 weeks' gestation (extremely immature [EI] cohort), with a birth weight of 800 g or less (extremely small [ES] cohort), or subgroups of these. STUDY SELECTION: Studies were included in the analysis if all of the following were reported: mortality; direct examination of 75% or more of the survivors; and the proportion of patients with at least 1 of the following disabilities: cerebral palsy, mental retardation, blindness, and deafness. Studies reporting cohorts included as a subset of cohorts in another study were excluded. Forty-two studies providing mortality and disability data for 20 cohorts of 4116 EI infants and 38 cohorts of 4345 ES infants born after 1972 met the inclusion criteria. DATA EXTRACTION: Data were abstracted from all studies that met these criteria by two of us (J.M.L. and D.E.W.), independently; the data were then cross-checked to ensure accuracy. RESULTS: Survival averaged 41% for EI infants and 30% for ES infants, and it increased significantly with time. In contrast to mortality, the prevalences of major neurodevelopmental disabilities among survivors have not changed over time. The most common major disability was mental retardation, found in 14% of EI and ES survivors. Cerebral palsy was found in 12% of EI survivors and 8% of ES survivors, blindness was found in 8% of EI and ES survivors, and deafness was found in 3% of EI and ES survivors. Overall, 22% of EI survivors and 24% of ES survivors were classified as having at least 1 major disability. Each 100 EI or ES livebirths yielded 7 children with major disabilities; this prevalence was correlated with survival across cohorts. CONCLUSIONS: The prevalence of disabilities had not changed among EI or ES survivors with increasing survival. However, increasing survival of these infants has resulted in a steadily increasing prevalence of children with disabilities.

The outcome of extreme prematurity.

Significant advances in perinatology and neonatology in the last decade have resulted in increased survival of extremely premature infants. Survival rates for infants born in tertiary perinatal and neonatal care centers in the United States in the 1990s increase with each week of gestational age from 22 through 26 weeks. Reported survival rates at 22 weeks range from 0% to 21% in the few reporting studies. Reported survival rates at 23 and 24 weeks range from 5% to 46% and from 40% to 59%, respectively. These may not be the maximum survival rates possible because at these gestational ages information is either insufficient to determine that obstetric and neonatal intensive care strategies to maximize neonatal survival were used or it is specified that such strategies were not used. Reported survival rates at 25 and 26 weeks range from 60% to 82% and from from 75% to 93%, respectively. The literature regarding the prevalence of major neurodevelopmental disabilities among extremely premature survivors in the last 25 years is heteogeneous, and the reported prevalances of major disability vary much more than do survival rates. However, the majority of extremely premature infants who survive will be free of major disability. Overall, approximately one fifth to one quarter of survivors have at least one major disability-impaired mental development, cerebral palsy, blindness, or deafness. Impaired mental development is the most prevalent disability (17%-21% [95% CI] of survivors affected), followed by cerebral palsy (12%-15% of survivors affected). Blindness and deafness are less common (5% to 8% and 3% to 5% of survivors affected, respectively). Approximately one half of disabled survivors have more than one major disability. Based on studies of infants less than 750 to 1,000 grams birth weight, it can be anticipated that approximately another half of all extremely premature survivors will have one or more subtle neurodevelopmental disabilities in the school and teenage years. There is little evidence to suggest that long-term neurodevelopmental outcome has changed from the late 1970s to the early 1990s or with increasing survival. Survival of individual extremely premature infants cannot be accurately predicted in the immediate perinatal period. Major disability cannot be accurately predicted for individual survivors during the course in the newborn intensive care unit.

Correlates of low thyroxine values at newborn screening among infants born before 32 weeks gestation.

We assessed the relation of perinatal factors to severe hypothyroxinemia of prematurity, defined as thyroxine value more than 2.6 standard deviations below the mean for newborns. The 365 survivors of birth before 32 weeks gestation were enrolled in a population-based study of the correlates of neonatal brain injury. In this historical cohort study, mothers were interviewed; perinatal data were abstracted from medical records and neonatal data were collected prospectively. Neonatal thyroxine screening values were retrieved from the New Jersey State Department of Health. Associated with severe hypothyroxinemia were: gestational age 23-27 weeks vs. 31 weeks (OR = 5.1, 95% CI 1.7, 15.2), later age at thyroxine test (OR = 1.6 per day, 95% CI 1.2, 2.1), fraction inspired oxygen at age 24 h > 40% (OR = 3.2, 95% CI 1.1, 8.8), mechanical ventilation (OR = 5.1, 95% CI 1.3, 19.4), diastolic blood pressure < 20 mmHg (OR = 2.3, 95% CI 1.2, 4.3), and > 12 years of maternal education (OR = 0.4, 95% CI 0.22, 1.0). Infants with severe hypothyroxinemia had higher mortality, more days of oxygen supplementation, ventilation and hospitalization and were 11 times more likely to require oxygen supplementation at the postnatal age equivalent to 36 weeks gestational age (odds ratio 10.6, 95% CI 2.3, 48.8). In preterm infants, neonatal thyroxine levels obtained at newborn screening in the first week of life may convey important prognostic information about mortality, morbidity, and the risk for bronchopulmonary dysplasia.

Survival of the extremely preterm infant in North America in the 1990s.

Survival of extremely premature infants has been significantly higher in the last decade than previously, and may well have improved during this time. The majority of infants greater than or equal to 25 weeks' gestation survive today. Survival of infants 23 and 24 weeks' gestation is significantly lower, but is by no means negligible. Reports of survival of infants less than 23 weeks or less than 500-g birth weight are not unique. Moreover, the maximum survival of infants less than or equal to 25 weeks possible with current state-of-the-art care is not known. Currently available data do not allow survival of the individual extremely low-birth weight or extremely premature infant to be predicted with clinically acceptable accuracy. The concept of a limit of viability is vague and clinically and ethically simplistic. The provision of neonatal intensive care is not necessarily beneficial or justified merely because it affords some minimal chance of survival. This phrase should not be used to summarize the complex issues involved in balancing maternal and neonatal risks and benefits of intrapartum and neonatal care of the extremely low-birth weight or the extremely premature fetus and infant, the suffering of the infant and family, parental values and autonomy, and consumption of limited communal resources. It should be deleted from our vocabulary.

Neonatal outcomes of fetuses diagnosed with life-limiting conditions when individualized comfort measures are proposed.

OBJECTIVE: To describe the neonatal outcomes of a case series of infants who were prenatally diagnosed with potential life-limiting conditions and to whom individualized comfort measures were offered. STUDY DESIGN: This is a retrospective analysis of the postnatal outcomes of a selected population of 49 infants prenatally diagnosed with potential life-limiting conditions whose parents were prenatally referred for counseling to the comfort care team. RESULT: The prenatal diagnosis was confirmed postnatally in 45 infants. The only four survivors had a significant discrepancy between prenatal and postnatal diagnosis. Whether they were treated with individualized comfort measures (n=28) or intensive care (n=17), all the newborns died with similar median age at death (2 days). CONCLUSION: Diagnostic accuracy is the main determinant of outcomes. Provision of intensive care neither prevents the death of infants affected by life-limiting conditions nor prolongs life compared with that of infants treated with individualized comfort measures.

Assessing fluid and electrolyte status in the newborn. National Academy of Clinical Biochemistry.

Fluid and electrolyte assessment during the first week of life is complicated by rapid changes in fluid and electrolyte balance during the transition from fetal to neonatal life and by the newborn's small size. A physiologic decrease in extracellular water volume, as well as a transient increase in serum potassium and transient decreases in plasma glucose and total plasma ionized calcium concentrations must be taken into account. In general, the more immature the newborn, the greater the changes that can be expected. The use of plasma creatinine as an indicator of glomerular filtration rate is limited because it is a function of maternal renal function at birth and because of non-steady-state conditions in the immediate postnatal period. Guidelines for monitoring schedules are provided on the basis of these physiologic considerations and the author's experience. Method of blood sampling and time to separation of serum are important considerations in interpreting results. Minimization of sample volume is critical to minimize blood transfusion requirements. Clinicians should be aware of the analytical error associated with these measurements in their own institutions. Reference ranges are provided.

Effects of euvolemic and hypervolemic hyperbicarbonemia on segmental nephron HCO3 reabsorption in the newborn dog.

Studies were undertaken to determine the effect of elevated plasma bicarbonate concentration (PHCO3) with and without volume expansion on segmental nephron HCO3 reabsorption in newborn and adult dogs using the technique of distal blockade. Reabsorption of bicarbonate per mL glomerular filtrate (RHCO3/GFR) in the proximal nephron was more suppressed in euvolemic newborns than euvolemic adults as PHCO3 was increased from baseline to 50-70 mM. Inasmuch as total nephron reabsorption has been shown to be essentially complete under these conditions in both newborns and adults, distal nephron HCO3 delivery and the fraction of the distal HCO3 load reabsorbed must have been greater in euvolemic newborns than adults when PHCO3 was elevated. Total nephron RHCO3/GFR was less suppressed by NaHCO3 volume expansion in the newborn than it was in the adult. However, proximal nephron RHCO3/GFR was similarly suppressed by NaHCO3 volume expansion in newborns and adults. Thus, the NaHCO3-expanded newborn must have reabsorbed a greater proportion of the increased distal HCO3 load than did the NaHCO3-expanded adult. Proximal nephron HCO3 reabsorption is a balance between reabsorption effected by active proton secretion and passive HCO3 back leak. Euvolemic increase in peritubular HCO3 concentration has been shown to suppress proximal tubular proton secretion; volume expansion increases proximal tubule HCO3 permeability and back leak.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracellular pH modifies adaptive response to high K+ in cultured canine kidney cells.

The chronic interactive and independent effects of extracellular pH and K+ on renal Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity and active K+ transport were studied in the Madin-Darby canine kidney (MDCK) cell line. Confluent cell monolayers were incubated for 24 h in control (4 mM) or high (7.5 mM) K+ medium at acid (6.8) or neutral (7.4) pH. Under acid pH conditions, exposure to high K+ elicited a rise of 133% in maximum Na(+)-K(+)-ATPase activity and 66% in active K+ uptake. In contrast, high K+ had no effect on enzyme activity or K+ uptake at neutral pH. Detergent-activated Na(+)-K(+)-ATPase assay demonstrated a latent pool of enzyme at acid pH-control K+, which seemed to account entirely for the increase in Na(+)-K(+)-ATPase activity after exposure to high K+. The effects of pH appeared unrelated to HCO3- and Cl- concentration in the extracellular environment. We conclude that the upregulatory effect of high K+ on renal Na(+)-K(+)-ATPase is pH dependent. The data suggest that a pool of catalytically inactive enzyme exists only at acid extracellular pH at K+ concentrations in the normal physiological range and that K+ adaptation, at least initially, is the result of recruitment of this latent intracellular pool. In the intact cell extracellular K+ and luminal pH may interact to modify catalytic turnover rate as well as bioavailability of Na(+)-K(+)-ATPase.

A standard protocol for blood pressure measurement in the newborn.

OBJECTIVES: Improvements in neonatal care have resulted in increasing survival of extremely premature infants whose hospital course often runs into weeks or months. Some interventions during the acute care of these neonates, such as umbilical catheterization and use of steroids, not infrequently result in elevation of blood pressure (BP). It is, therefore, essential that these infants be monitored accurately for possible hypertension during their convalescence. Unfortunately, normative data on BP in this population are scant and comparison of data from various studies is hampered by methodologic differences in design. Studies in adults address the necessity for a restful state, adopting a comfortable position, and attempts to reduce the startle response to initial cuff inflation. Studies in the newborn using the oscillometric technique have not addressed these concerns. A standard BP measurement protocol was studied to determine the effect of ensuring a restful state, startle response to cuff inflation, and infant position on BP in clinically stable low birth weight infants after the first week of life. STUDY DESIGN: The Dianamap oscillometer was used to measure BP in infants with a birth weight <2500 g between 7 and 42 days postnatal age. Each infant was studied only once when they were clinically stable. BP was measured in two positions, prone and supine, in random order. Infants were studied at least 11/2 hours after their last feeding or medical intervention. An appropriate sized cuff was applied to the right upper arm and the infant was positioned according to randomization. The infant was then left undisturbed for at least 15 minutes or until the infant was sleeping or in a quiet awake state. Three successive BP recordings were taken at 2-minute intervals. The infant's position was then reversed and another 15 minutes of quiet time was allowed. Thereafter, a second set of three successive BP recordings were obtained. The most recent routine nursing BP measurement was also recorded. Data were analyzed using analysis of variance and are presented as means and standard errors of the mean. RESULTS: Sixty-four infants were studied. Birth weights ranged from 901 to 2423 g and gestational ages from 26 to 37 weeks. Overall, mean BP was significantly lower in the prone than supine positions (45.7 +/- 0.7 vs 47.8 +/- 0.8 mm Hg, P < .002). In either position, the first measurement was significantly higher than the third (average difference was 3 mm Hg, P < .003). In general, the relationships among position and order of measurement were similar for systolic and diastolic BP. Mean BPs obtained by routine nurse measurements were significantly higher than those in either position using our standard protocol (54.4 vs 47.0 or 49.1 mm Hg, P < .003). Moreover, the routine nurse measurements varied more widely than did those obtained using the standard protocol. The standard deviation for the routine mean BP measurements by nurses was 11.4 compared with 6.8 and 8.2 for the first measurements in the prone and supine positions, respectively, with the standard protocol. The mean BP measurements made in the supine position (the highest measurements obtained) using the standard protocol were also significantly lower than published values: 57 of 64 measurements were less than the average mean BP for age described by Tan (J Pediatr. 1988; 112:266-270). CONCLUSION: The statistically significant difference between the prone and supine position and among successive measurements in each position are not clinically relevant. The clinically significant differences between measurements obtained with this standard protocol and routine nursing measurements or published data are the result of ensuring a restful state after cuff application. We believe that measurements thus obtained are more representative of true resting BPs in these infants. (ABSTRACT TRUNCATED)

Chronic potassium supplementation of newborn dogs increases cortical Na,K-ATPase but not urinary potassium excretion.

The distal nephron of the newborn dog cannot secrete an acute potassium load as efficiently as can that of the adult dog. Distal nephron potassium secretion is dependent upon basolateral Na,K-ATPase activity. Because Na,K-ATPase activity is lower in the immature than the mature distal nephron, it was hypothesized that lower Na,K-ATPase activity may be responsible for the lower potassium secretory capacity of the immature nephron. In the adult, chronic high dietary potassium intake increases renal tubular potassium secretory capacity by increasing Na/K pump abundance in distal nephron segments responsible for potassium secretion. Therefore, in order to test the above hypothesis, renal cortical and outer medullary Na,K-ATPase activity under Vmax conditions (a measure of pump abundance) and urinary potassium excretion during acute potassium loading were determined in 7 age-matched, litter mate pairs (chronically potassium supplemented versus control) newborn dogs. The potassium supplemented member of each pair received 6 mmol.day-1.kg-1 of KCl as a 150 mM solution for 7-21 days after birth and the control member received an equal volume of water for the same period of time. This protocol resulted in a doubling of renal cortical Vmax Na,K-ATPase activity in the potassium supplemented animals (from 369 +/- 186 to 718 +/- 286 nmol Pi liberated.h-1.micrograms DNA-1, P = 0.025). There was no significant change in outer medullary enzyme activity. Contrary to the above hypothesis, this increase in cortical enzyme activity was not associated with increased potassium excretion at baseline or during acute potassium loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of anion effect on volume expansion natriuresis in the developing canine kidney.

The renal response to volume expansion with sodium chloride or sodium bicarbonate was studied in 15 newborn and 13 adult dogs. Proximal and distal nephron function were estimated using the technique of distal nephron blockade. Fractional sodium reabsorption was 99.0 +/- 0.3% in newborn and 96.6 +/- 0.06% in adult during the NaCl expansion (P less than 0.01) and 98.1 +/- 0.7% in the newborn and 93.2 +/- 0.7% in the adult during NaHCO3 expansion (P less than 0.001). With either anion the higher fractional sodium reabsorption in the newborn was due to reabsorption of a greater fraction of the load presented to the distal nephron segment. The percent of the distal sodium load that was reabsorbed was 98.0 +/- 0.6% in the newborn and 92.2 +/- 1.0% in the adult during NaCl expansion, and 96.1 +/- 1.3% in the newborn and 81.5 +/- 2.4% in the adult during NaHCO3 expansion. Differences in distal nephron chloride, potassium and bicarbonate reabsorption among the groups support the hypothesis that the enhanced distal sodium reabsorption in the newborn occurred largely in the ascending loop of Henle with NaCl expansion, while it occurred in the late distal and cortical collecting tubules with NaHCO3 expansion. There was no difference between the natriuretic responses to NaCl or NaHCO3 in the newborn (P greater than 0.20); however, the natriuretic response to NaCl was less than that to NaHCO3 in the adult (P less than 0.001). This suggests that the bulk of the sodium that escaped reabsorption in Henle's loop during NaHCO3 expansion was reabsorbed in the late distal tubule in the newborn, but not in the adult.

The role of cortical Na,K-ATPase in distal nephron potassium secretion by the immature canine kidney.

Amiloride-sensitive potassium secretion in response to acute potassium loading is lower in the newborn than in the adult. Potassium secretion is a function of late distal tubule and cortical collecting tubule Na,K-ATPase activity. Na,K-ATPase activity in vivo is determined by enzyme abundance and catalytic turnover. Chronic potassium supplementation increases potassium secretory capacity in the adult by increasing enzyme abundance in the late distal and cortical collecting tubules. We hypothesized that the lower potassium secretory capacity of the newborn was the result of lower late distal and cortical collecting tubule Na,K-ATPase activity and could be similarly enhanced. To test this hypothesis, newborn dogs were supplemented with 6 mmol KCl.d-1.kg-1 for 1 wk; age-matched litter mate controls were not (n = 8 pairs). Potassium supplementation resulted in a mean increase in Vmax Na,K-ATPase activity in vitro (proportional to pump abundance) of 70 +/- 42%. Mean Na,K-ATPase activities +/- SEM were 279 +/- 58 versus 198 +/- 44 nmol inorganic P. h-1.microgram DNA-1, p = 0.05. However, amiloride-sensitive potassium secretion after an acute potassium load of 20 mumol.min-1.kg-1 over 150 min was not enhanced (9.6 +/- 1.8 versus 8.9 +/- 0.8 mumol.min-1.kg-1, potassium-supplemented versus control animals). We conclude that lower enzyme abundance is not primarily responsible for the newborn's lower potassium secretory capacity. We speculate that the factor that limits secretion in the newborn during acute potassium loading does so by restricting catalytic turnover of the enzyme in vivo.

Potassium metabolism in extremely low birth weight infants in the first week of life.

OBJECTIVE: Nonoliguric hyperkalemia has been reported to occur in the first week of life in as many as 50% of extremely low birth weight (ELBW) infants. We studied potassium balance and renal function in the first 5 days of life to characterize potassium metabolism during the three phases of fluid and electrolyte homeostasis that we have described in ELBW infants and to elucidate the factors that contribute to the development of nonoliguric hyperkalemia. STUDY DESIGN: Plasma potassium concentration (PK), potassium intake and output, and renal clearances were obtained for the first 6 days of life in 31 infants with a birth weight of 1000 gm or less. Collection periods in which urine flow rate was greater than or equal to 3 ml/kg per hour and weight loss was greater than or equal to 0.8 gm/kg per hour were denoted to be diuretic. Prediuresis includes all collection periods before the first diuretic period; diuresis includes all collection periods between the first and last diuretic periods; postdiuresis includes all collection periods after the last diuretic period. Infants with a PK greater than 6.7 mmol/L on at least one measurement were denoted to have hyperkalemia. RESULTS: PK increased initially after birth--despite the absence of potassium intake- and then decreased and stabilized by the fourth day of life. Diuresis occurred in 27 of 31 infants. The age at which PK peaked was closely related to the onset of diuresis. PK decreased significantly during diuresis as the result of a more negative potassium balance, despite a significant increase in potassium intake. In fact, PK fell to less than 4 mmol/L in 13 of 27 infants during diuresis. After the cessation of diuresis, potassium excretion decreased even though there was a significant increase in potassium intake, potassium balance was zero, and PK stabilized. Hyperkalemia developed in 11 of 31 infants. The pattern of change in PK with age was similar in infants with normokalemia and hyperkalemia: PK initially increased (essentially in the absence of potassium intake) and then decreased and stabilized by the fourth day of life. However, the rise in PK after birth was greater in infants with hyperkalemia than in those with normokalemia: 0.7 +/- 0.2 versus 1.8 +/- 0.2 mmol/L (p < 0.001). No differences in fluid and electrolyte homeostasis or renal function were identified as associated with hyperkalemia. CONCLUSIONS: PK increases in most ELBW infants in the first few days after birth as a result of a shift of potassium from the intracellular to the extracellular compartment. The increase in the glomerular filtration rate and in the fractional excretion of sodium, with the onset of diuresis, facilitates potassium excretion, and PK almost invariably decreases. Hyperkalemia seems to be principally the result of a greater intracellular to extracellular potassium shift immediately after birth in some ELBW infants.

Renal response of newborn dog to potassium loading.

The renal response to potassium loading was studied in 14 newborn (6-20 days of age) and 14 adult mongrel dogs in order to determine the capacity of the newborn to excrete potassium load. Eight newborn and eight adult dogs were infused with 20 mueq of potassium chloride X min-1 X kg body wt-1 for 240 min. Adults excreted a significantly greater proportion of the potassium load during the 240-min infusion than did newborns (72 +/- 4 vs. 52 +/- 4%, P = 0.003). The infusion resulted in a significantly greater increase in plasma potassium concentration in the newborn (3.9 +/- 0.3 meq/liter) than in the adult (2.8 +/- 0.4 meq/liter), P = 0.05. Average potassium excretion rate per body weight was greater in the adult than newborn during potassium loading (15.0 +/- 1.0 vs. 10.4 +/- 0.7 mu eq X min-1. kg body wt-1, P = 0.003); however, average potassium excretion corrected for glomerular filtration rate was not significantly different between the adult and newborn (3.2 +/- 0.2 vs. 3.0 +/- 0.2 mu eq/ml filtered, P greater than 0.20). In another six newborn and six adult dogs, blockade of distal nephron potassium secretion with amiloride in the potassium-loaded state inhibited more than 90% of potassium excretion in both the newborn and adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamically significant PDA: an echocardiographic and clinical assessment of incidence, natural history, and outcome in very low birth weight infants maintained in negative fluid balance.

Fifty very low birth weight (VLBW) infants (750-1500 g, 27-33 weeks gestational age) were assigned at random to one of two groups of negative fluid balance and underwent prospective clinical and echocardiographic examinations during the first month of life. The purpose was to determine: the effect of fluid restriction on the incidence of ductal shunting, the reliability of the physical examination in diagnosing significant ductal shunting, and the relationship between significant ductal shunting and outcome in such infants. None of the infants had manipulations to close the ductus during the first week of life. Using routine structural and functional echocardiographic indices as criteria for the diagnosis of hemodynamically significant ductal shunting (hsPDA), we found that the two fluid-balance groups (8%-10% weight loss vs 13%-15% weight loss) did not significantly differ in incidence of hsPDA, duration of ventilation, or development of BPD. These two groups were then combined for further analysis: 32 (64%) of 50 VLBW infants had hsPDA during the first week of life. The group of infants with hsPDA did not differ significantly from that without hsPDA in birth weight or gestational age, but had a significantly lower Apgar score (P less than 0.04) and was significantly more likely to require ventilator support for RDS (P less than 0.01). Although when present a typical ductal murmur was specific for the development of significant ductal shunting, no murmur was heard in 21 (66%) of 32 infants with early hsPDA.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of management strategies for extreme prematurity in New Jersey and the Netherlands: outcomes and resource expenditure.

OBJECTIVE: To quantify differences in resource expenditure in the perinatal period and long-term outcome of extremely premature infants who received systematically different approaches to neonatal intensive care. METHODS: Perinatal management, mortality, prevalence of disabling cerebral palsy (DCP), and resource expenditure of 2 population-based inception cohorts of extremely premature infants born in the mid-1980s were compared. Electronic fetal monitoring, tocolysis, cesarean section delivery, and assisted ventilation were used to characterize management approaches. Participants included all live births at 23 to 26 weeks' gestation in a 3-county area of central New Jersey (NJ) from 1984 to 1987 (N = 146) and throughout the Netherlands (NETH) in 1983 (N = 142). Mortality and the prevalence of DCP were the primary outcomes. Numbers of hospital days with and without assisted ventilation were the measures of resource expenditure. RESULTS: Electronic fetal monitoring (100% vs 38%), cesarean section (28% vs 6%), and assisted ventilation (95% vs 64%) were all more commonly used in NJ than in NETH. Ten percent of NJ deaths occurred without assisted ventilation, compared with 45% of Dutch deaths. A total of 1820 ventilator days were expended per 100 live births in NJ, compared with 448 in NETH. The increase in the number of nonventilator days (3174 vs 2265 days per 100 live births) did not reach statistical significance. Survival to age 2 (46 vs 22%) and the prevalence of DCP among survivors (17.2 vs 3.4%) were significantly greater in NJ at age 2 than in NETH at age 5. CONCLUSIONS: Near universal initiation of intensive care in NJ, compared with selective initiation of intensive care in NETH, was associated with 24.1 additional survivors per 100 live births, 7.2 additional cases of DCP per 100 live births, and a cost of 1372 additional ventilator days per 100 live births.

Radiologic placement of implantable chest ports in pediatric patients.

OBJECTIVE: We evaluated the technical success and complications associated with radiologic placement of implantable chest ports in children for long-term central venous access. MATERIALS AND METHODS: Between May 1, 1996 and January 11, 2000, 29 chest ports were placed in 28 children (15 girls, 13 boys; age range, 2-17 years; mean, 11.7 years). The patient's right internal jugular vein was used for access in 93% (27/29) of the procedures, and a collateral neck vein was used as a conduit to recanalize the central veins in two procedures because of bilateral jugular and subclavian vein occlusion. All procedures were performed in interventional radiology suites. Both real-time sonography and fluoroscopy were used to guide venipuncture and port insertion. Follow-up data were obtained through the clinical examination and electronic review of charts. RESULTS: Technical success was 100%. Fourteen percent of the catheters were removed prematurely, including one catheter removed 17 days after placement because the patient's blood cultures were positive for Candida albicans. No patients experienced hematoma, symptomatic air embolism, symptomatic central venous thrombosis, catheter malposition, or pneumothorax. The median number of days for catheter use by patients was 280 days (total, 9043 days; range, 17-869 days). The rate of confirmed catheter-related infection was 14% or 0.04 per 100 venous access days. One catheter occluded after 132 days. CONCLUSION: In pediatric patients, radiologists can insert implantable chest ports using real-time sonographic and fluoroscopic guidance with high rates of technical success and low rates of complication.