Stephen Baumgart

Sodium restriction versus daily maintenance replacement in very low birth weight premature neonates: A randomized, blind therapeutic trial

To test the hypothesis that restriction of sodium intake during the first 3 to 5 days of life will prevent the occurrence of hypernatremia and the need for administration of large fluid volumes, we prospectively and randomly assigned 17 babies (mean +/- SD: 850 +/- 120 gm; 27 +/- 1 weeks of gestation) to receive in blind fashion either daily maintenance sodium or salt restriction with physician-prescribed parenteral fluid intake. Maintenance-group infants received 3 to 4 mEq of sodium per kilogram per day; restricted infants received no sodium supplement other than with such treatments as transfusion. Sodium balance studies conducted for 5 days demonstrated that maintenance salt intake resulted in a daily sodium balance near zero, whereas sodium-restricted infants continued to excrete urinary sodium at a high rate, which promoted a more negative balance (average daily sodium balance -0.30 +/- 1.78 SD in maintenance group vs -3.71 +/- 1.47 mEq/kg per day in restriction group; p less than 0.001). Care givers tended to prescribe daily increases in parenteral fluids for the salt-supplemented infants, perhaps because serum sodium concentrations were elevated in these infants after the first day of the study (p less than 0.001). Hypernatremia developed in two sodium-supplemented infants (greater than 150 mEq/L), and hyponatremia developed in two sodium-restricted infants (less than 130 mEq/L); however, the restricted infants were more likely to have normal serum osmolality (p less than 0.05). Both groups of infants produced urine that was neither concentrated nor dilute, with a high fractional excretion of sodium; renal failure was not observed. The mortality rate was not affected, but the incidence of bronchopulmonary dysplasia was significantly less in the sodium-restricted babies (p less than 0.02). We conclude that in tiny premature infants, a fluid regimen that restricts sodium may simplify parenteral fluid therapy targeted to prevent hypernatremia and excessive administration of parenteral fluids.

Surface colonization with coagulase-negative staphylococci in premature neonates

To follow the emergence of surface colonization with coagulase-negative staphylococci in neonates, we sampled four surface sites (axilla, ear, nasopharynx, and rectum) in 18 premature infants during the first 4 weeks of life. Swabs were obtained on the first day of life, twice weekly for 2 weeks, and weekly thereafter. Isolates were characterized by species, biotype, antibiotic susceptibility patterns, and slime production. Over 4 weeks the percentage of infants with Staphylococcus epidermidis as the only surface coagulase-negative staphylococci rose from 11% to 100%. Predominance of a single S. epidermidis biotype increased from none to 89%. Multiple antibiotic resistance rose from 32% to 82% of isolates, and the prevalence of slime production increased from 68% to 95%. This microbiologic pattern was established by the end of the first week of life and persisted throughout the month of study. In three infants, S. epidermidis sepsis developed with organisms identical to their predominant surface isolate. We conclude that species, multiple antibiotic resistance, and slime production appear to confer a selective advantage for the surface colonization of premature newborn infants in the intensive care nursery environment. Infants so colonized may be at greater risk for subsequent infection with these strains of coagulase-negative staphylococci.

Nonoliguric hyperkalemia in the premature infant weighing less than 1000 grams

Eighteen very low birth weight premature infants born before 28 weeks gestation and weighing less than 1000 gm were evaluated prospectively for disturbances in serum electrolyte concentrations and for renal glomerular and tubular functions. Clinically symptomatic hyperkalemia resulting in significant electrocardiographic dysrhythmias developed in eight of these infants; 10 babies remained normokalemic. Peak serum potassium concentration ranged from 6.9 to 9.2 mEq/L in the hyperkalemic group; all potassium values in the normokalemic group were less than 6.6 mEq/L. Indices of renal glomerular function and urine output were similar in both groups; no infant had oliguria. Serum creatinine concentrations were the same in both groups (1.04 +/- 0.16 SD mg/dl in normokalemic vs 1.19 +/- 0.24 mg/dl in hyperkalemic infants, beta less than 0.2 at alpha = 0.05), and glomerular filtration rates did not differ significantly (6.29 +/- 1.78 ml/min/1.73 m2 in normokalemic vs 5.70 +/- 1.94 ml/min/1.73 m2 in hyperkalemic infants, beta less than 0.2 at alpha = 0.05). In contrast, indicators of tubular function revealed a significantly larger fractional excretion of sodium in hyperkalemic infants: 13.9 +/- 5.4% versus 5.6 +/- 0.9% in normokalemic control subjects (p less than 0.001). Hyperkalemic infants also had a tendency toward lower urine concentrations of potassium, although there was no significant difference in their net potassium excretion in comparison with that in the normokalemic group. We speculate that hyperkalemia in the tiny baby is in part the result of immature distal tubule function with a compromise in ability to regulate potassium balance.

Effect of heat shielding on convective and evaporative heat losses and on radiant heat transfer in the premature infant.

Ten premature infants nursed on servocontrolled radiant warmer beds were studied in three environments designed to alter one or more factors affecting heat transfer (convection, evaporation, and radiation). In the control environment, infants were nursed supine on an open warmer bed. The second environment (walled chamber) was designed to reduce convection and evaporation by placing plastic walls circumferentially around the bed. In the third environment convection and evaporation were minimized by covering infants with a plastic blanket. Air turbulence, insensible water loss, and radiant warmer power were measured in each environment. There was a significant reduction in mean air velocity in the walled chamber and under the plastic blanket when compared to the control environment. A parallel decrease in insensible water loss occurred. In contrast, radiant power demand was the same for control and walled environments, but decreased significantly when infants were covered by the plastic blanket. This study suggests that convection is an important factor influencing evaporation in neonates nursed under radiant warmers. The thin plastic blanket was the most effective shield, significantly reducing radiant power demand.

The diuretic phase of respiratory distress syndrome and its relationship to oxygenation

To determine the relationship between improvement in pulmonary function and diuresis in respiratory distress syndrome, ten consecutive premature infants requiring mechanical ventilation for severe RDS were studied. Every infant had a diuresis (output/intake greater than 80%), which began at 26 to 34 hours of life and which lasted for an additional 64-72 hours. The diuresis preceded significant improvement in AaDo2 and ventilator settings (IMV, PIP, PEEP) by 52 hours. There was a significant decrease in body weight among all study infants during the first four days of life despite an increase in fluid intake. This study suggests a relationship in RDS between improvement in oxygenation and removal of interstitial lung edema.

Cardiac malposition, redistribution of fetal cardiac output, and left heart hypoplasia reduce survival in neonates with congenital diaphragmatic hernia requiring extracorporeal membrane oxygenation☆☆☆★

OBJECTIVE To evaluate cardiac position, left ventricular (LV) mass, and distribution of fetal cardiac output in infants with congenital diaphragmatic hernia (CDH) who required extracorporeal membrane oxygenation (ECMO), and in control subjects. STUDY DESIGN Echocardiograms were performed on 23 neonates with CDH shortly after birth, and repeated within 5 days of repair on ECMO in 21 infants,aand on 12 infants receiving ECMO for other diagnoses, and on 10 healthy, term neonates. Cardiac angle between the midline saggital plane and the interventriculak septum was measured, and deviation from normal (45 degrees) was determined. The ratio of cross-sectional areas (proportional to flows) across the pulmonary (PV) and aortic (AV) valves was determined (PV2/AV2) in 19 infants with CDH and in the healthy control subjects. RESULTS Thirteen (57%) infants with CDH survived and 10 (43%) died, with no difference in cardiac deviation before surgical repair (35 +/- 13 degrees vs Cardiac deviation persisted after repair in nonsurvivors (27 +/- 14 degrees vs 800.01 and LV mass was significantly less (1.68 +/- 0.39 vs 3.05 +/- 1.20 gm/kg, p00.0005). Neonates requiring ECMO for other diagnoses and well term babies did not have cardiac angle deviations; both these groups had a greater LV mass than did the infants with CDH. The PV2/AV2 flow ratios were higher in infants with CDH (median, 1.73; range, 1.25 to 16.50) compared with those of the healthy infants (0.96, 0.79 to 1.69, p < 0.0002). CONCLUSIONS Cardiac malposition persisted despite CDH repair in nonsurvivors with low LV mass, and fetal cardiac output was redistributed away from the left ventricle. Lung hypoplasia with reduced pulmonary flow returning to the left atrium and altered left atrial hemodynamics may result in LV hypoplasia

Clinical Antecedents of Neurologic and Audiologic Abnormalities in Survivors of Neonatal Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation is an effective rescue treatment for severe cardiorespiratory failure in term or near-term neonates, although cerebral palsy, mental retardation, and sensorineural hearing loss are observed in 10 to 20% of survivors. The objective of the present study was to identify potential risk factors that may explain the neurologic and audiologic sequelae noted in 19% of 181 survivors of neonatal extracorporeal membrane oxygenation from our hospital. Our results suggest the following findings in survivors of severe cardiorespiratory failure treated with neonatal extracorporeal membrane oxygenation: (1) hypotension or the need for cardiopulmonary resuscitation before extracorporeal membrane oxygenation significantly increases the risk of spastic cerebral palsy, (2) profound hypocarbia before extracorporeal membrane oxygenation is associated with a significantly increased risk of hearing loss, (3) mental retardation in the absence of spastic cerebral palsy is unexplained except when due to abnormal fetal brain development, and (4) hypoxemia in the absence of hypotension does not increase the risk of neurologic or audiologic sequelae. (J Child Neurol 1997;12:415-422).

MRI, MRA, and neurodevelopmental outcome following neonatal ECMO ☆

Cranial magnetic resonance imaging (MRI) of 31 newborn infants treated with venoarterial cardiopulmonary bypass for severe but reversible respiratory failure, revealed major focal parenchymal lesions in 7 of 31 infants (23%) and demonstrated abnormal enlargement of extra-axial and ventricular cerebrospinal fluid spaces in 16 of 31 (51%). No preferential left versus right lateralization of focal injury was observed in conjunction with right common carotid artery and jugular vein ligation. No statistically significant relationships were found between major brain lesions on MRI scans and the clinical characteristics of the pre-extracorporeal membrane oxygenation (ECMO), ECMO, and post-ECMO course. Major focal brain lesions were significantly associated with an asymmetric cerebrovascular response to carotid ligation of the right versus left middle cerebral arteries as detected by magnetic resonance angiography (P < .05). Enlarged cerebrospinal fluid spaces were not significantly related to the presence of parenchymal MRI lesions, but were associated with lower Bayley neurodevelopmental scores for mental (MDI) and psychomotor evaluations (PDI) at 6 and 12 months (P < .05). It is concluded that asymmetries of cerebral vascular adaptation detected by magnetic resonance angiography after ECMO may be associated with major brain lesions revealed by MRI. Thereafter, the presence of enlarged cerebrospinal fluid spaces on MRI is associated with a poor shortterm developmental outcome.

Modern Fluid and Electrolyte Management of the Critically Ill Premature Infant

In this article, the authors introduce the concept of a transitional physiology which governs fluid and electrolyte balance in the immediate postnatal period. The important impact of the extrauterine environment on fluid balance is also discussed. Finally, the pathophysiology of diuresis in RDS, and fluid shifts in the VLBW infant with therapeutic recommendations are presented.

Fluid, Electrolyte, and Glucose Maintenance in the Very Low Birth Weight Infant

The low birth weight premature newborn, less than 1000 gm, represents a dif ficult problem in the management of parenteral fluid, electrolyte, and glucose maintenance. To assess this problem, six infants (mean weight 720 gm, range 575- 835 gm; mean gestation 26.5 ± 0.4 SEM wk) nursed under radiant warmers were evaluated during the first three days of life to determine volume of fluid intake, sodium and dextrose intakes, and urine output. Insensible water loss (IWL) was measured on a metabolic scale. In accordance with current recommendations, infants received fluid volumes of 111 ± 10, 152 ± 16, and 191 ± 27 ml/kg/day on days 1, 2, and 3, respectively. Sodium intake (usually as 0.2% saline) ranged 0-8.5 mEq/kg/day. Dextrose infusions (as 10% solution) ran from 3.3 to 13.7 mg/kg/ min. Insensible water loss measured 159 ± 15 ml/kg/day. Despite increasing fluid intake, serum sodium concentration increased from 141 ± 3 mEq/l on day 1 to 155 ± 7 mEq/l on day 3 (p < 0.05). None of the infants became oliguric and only two urine specimens had specific gravity greater than 1.015. These data demon strate a larger insensible water loss than reported previously in small infants, but increasing the administration of standard 10% dextrose and 0.2% saline solution to balance insensible losses may result in sodium and glucose overload. Recom mendations are made for adjusting parenteral fluid therapy for birth weight groups 600-800, 801-1000, 1001-1500, and 1501-2000 grams and for environmental con ditions or radiant warmer or incubator, with or without plastic shielding or pho totherapy.