Supportive management of the sick neonate. Parenteral calories, water, and electrolytes

Intravenous lipids for preterm infants: a review

Extremely low birth weight infants (ELBW) are born at a time when the fetus is undergoing rapid intrauterine brain and body growth. Continuation of this growth in the first several weeks postnatally during the time these infants are on ventilator support and receiving critical care is often a challenge. These infants are usually highly stressed and at risk for catabolism. Parenteral nutrition is needed in these infants because most cannot meet the majority of their nutritional needs using the enteral route. Despite adoption of a more aggressive approach with amino acid infusions, there still appears to be a reluctance to use early intravenous lipids. This is based on several dogmas that suggest that lipid infusions may be associated with the development or exacerbation of lung disease, displace bilirubin from albumin, exacerbate sepsis, and cause CNS injury and thrombocytopena. Several recent reviews have focused on intravenous nutrition for premature neonate, but very little exists that provides a comprehensive review of intravenous lipid for very low birth and other critically ill neonates. Here, we would like to provide a brief basic overview, of lipid biochemistry and metabolism of lipids, especially as they pertain to the preterm infant, discuss the origin of some of the current clinical practices, and provide a review of the literature, that can be used as a basis for revising clinical care, and provide some clarity in this controversial area, where clinical care is often based more on tradition and dogma than science.

The development of pediatric fluid resuscitation: an interview with Dr. Frederic A. 'Fritz' Berry

Dr. Frederic A. 'Fritz' Berry (1935), Professor Emeritus of Anesthesiology and Pediatrics at the University of Virginia, has played a pioneering role in the development of pediatric anesthesiology through training generations of anesthesiologists. He identifies his early advocacy of balanced electrolyte solution for perioperative fluid resuscitation as his defining contribution. Based on his clinical experiences, he pushed to extend the advances in adult fluid resuscitation into pediatric practice. He imparted these and other insights to his colleagues although textbooks, book chapters, original journal publications, and decades of Refresher Course Lectures at the American Society of Anesthesiologists' annual meetings. A model educator, clinician, and researcher, he shaped the careers of hundreds of physicians-in-training while advancing the field of pediatric anesthesiology.

Development of water transport in the collecting duct

The ability of the immature kidney to concentrate urine is lower than in adults. This can lead to severe water and electrolyte disorders, especially in premature babies. Resistance to AVP and lower tonicity of the medullary interstitium seem to be the major factors limiting urine concentration in newborns. AVP-stimulated cAMP generation is impaired. This is the result of inhibition of the production by PGE(2) acting through EP3 receptors and increased degradation by phosphodiesterase IV. The expression of aquaporin-2 (AQP2) in the immature kidney is low; however, under conditions of water deprivation and after stimulation with DDAVP, it rises to adult levels. The expression of AQP3 and AQP4 is intact at birth and does not seem to contribute to the hyporesponsiveness to AVP. Low sodium transport by thick ascending loops of Henle, immaturity of the medullary architecture, and adaptations in the transport of urea contribute to the lower tonicity of the medullary interstitium. This paper reviews the alterations in the AVP signal transduction pathway in the immature kidney.

Aggressive nutrition of the very low birthweight infant

We propose an approach to nutrition of the VLBW infant that aims at minimizing the interruption of nutrient uptake engendered by premature birth. Our approach is aggressive in that it goes beyond current practice in several key aspects. The gap in nutrient intakes between the proposed aggressive approach and current practice will most likely disappear over the next few years as today's aggressive practice becomes tomorrow's standard practice. As the gap diminishes, so will the threat that nutritional deprivation poses to growth and development of VLBW infants.

Early postoperative alterations in infant energy use increase the risk of overfeeding

AIM OF STUDY

Energy needs in infants are decreased after surgery because of growth inhibition (resulting from catabolic stress metabolism), decreased insensible losses, and inactivity. Using standardized formulas that account for growth, activity, and insensible losses during this stress period can lead to overfeeding in excess of 200% of the actual measured requirement. Overfeeding during this acute injury period can result in increased CO2 production from lipogenesis. This study determined the effects of a reduced rate of mixed caloric repletion on infant energy use during the early postoperative period.

METHODS

C-reactive protein (CRP), oxygen consumption (VO2), carbon dioxide production (VCO2), measured energy expenditure (MEE), and total urinary nitrogen (TUN) were measured serially in seven infants (average age, 78 days) during the first 72 hours after abdominal or thoracic surgery. Nonprotein respiratory quotient (RQnp), and values for oxidation of carbohydrate (Ce) and fat (Fe) were calculated. Injury severity was stratified based on serum CRP concentrations of > or = 6.0 mg/dL (high stress) or < 6.0 mg/dL (low stress). Recovery from acute stress was analyzed by comparing studies in which CRP had decreased to < or = 2.0 mg/dL (resolving stress group) with those in which CRP values were greater than 2.0 mg/dL (acute stress group).

RESULTS

Average total caloric intake (64.56 +/- 18.51 kcal/kg/d; approximately 50% of predicted energy requirement) exceeded average MEE (42.90 +/- 9.98 kcal/kg/d) by approximately 50%. Average TUN was 0.18 +/- 0.07 g/kg/d (high stress 0.2 +/- 0.05 versus low stress 0.16 +/- 0.09 g/kg/d). Average RQnp was 1.05 +/- 0.13 and average Ce was 37.28 +/- 16.86 kcal/kg/d. The average calculated Fe was 0.0 +/- 12.27 kcal/kg/d, reflecting approximately equal amounts of fat oxidized compared with fat generated from excess glucose (lipogenesis). When individual studies were analyzed at a CRP cutpoint of 2.0 mg/dL, overfeeding (RQ > 1.0) was significantly less likely in the resolving (2/6 studies, 33.4%) versus acute stress (9/13 studies, 69.2%, Z test P < .001) group. Five of seven (5/7) patients (9/19 individual studies) had negative Fe values (average -9.89 +/- 10.02) reflecting net lipogenesis. The RQnp for these nine studies was 1.14 +/- 0.11 versus 0.97 +/- 0.09 for the remaining 10, and this difference was significant (P < .01). A significant correlation existed between carbohydrate intake and VCO2 (Pearson r = .6951, P < .01). In addition, there was a good correlation between carbohydrate intake and VCO2 (Pearson r = .6591, P < .01). The coefficient of variation for MEE was 8.0% (low stress) versus 30.2% (high stress).

CONCLUSION

Lipogenesis with increased CO2 production is substantial, even at reduced caloric delivery rates that exceeded MEE by only 50%, during the early postoperative acute metabolic stress period in infants. These data suggest that caloric requirements during stress are likely equal to or only minimally in excess of actual MEE. Intersubject variability, especially in more severely stressed infants, underscores the importance of serial measurements of energy expenditure to enable precise caloric delivery and avoid overfeeding. In the absence of calorimetric measurement, the data suggest that PBMR (predicted basal metabolic rate) should be used to estimate caloric delivery until CRP values are < or = 2.0 mg/dL.

Role of the source of phosphate salt in improving the mineral balance of parenterally fed low birth weight infants

Because the monobasic potassium phosphate salt (monobasic) improves the solubility of calcium and phosphorus in amino acid plus dextrose solutions, compared with the current mixtures of monobasic plus dibasic salts (dibasic), we tested the bioavailability and clinical effects of monobasic in 16 parenterally fed low birth weight infants at standard (n = 8) and high levels (n = 8) of mineral intakes. A constant infusion of macronutrients and vitamin D was provided in a crossover design of two four-day periods. With standard intakes of calcium (35 mg/kg/day, 0.9 mmol/kg/day) and phosphorus (30 mg/kg/day, 1 mmol/kg/day), there was no difference between monobasic and dibasic regimens on balance data or plasma biochemical monitoring (calcium, phosphorus, pH, carbon dioxide pressure, base excess, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D). With the use of the monobasic regimen, the mineral intakes were doubled without precipitation in the infusate: calcium, 70 mg/kg/day (1.8 mmol/kg/day), and phosphorus, 55 mg/kg/day (1.7 mmol/kg/day). This led to increased apparent retention of both calcium (63 +/- 5 mg/kg/day, 1.58 +/- 0.12 mmol/kg/day) and phosphorus (52 +/- 4 mg/kg/day, 1.67 +/- 0.14 mmol/kg/day) compared with that for standard levels of mineral intake. The improvement of calcium-phosphorus balance was accompanied by more severe calciuria (9 +/- 2 mg/kg/day, 0.2 +/- 0.05 mmol/kg/day) and by metabolic compensation for an increased acid load. In addition to the possibility of exceeding the buffering capacity of the infant, this relative acidosis could also be evidence of improved bone mineralization.

Measured energy expenditure in critically ill infants and young children

Technological limitations have impeded accurate energy expenditure assessment in critically ill infants and young children. Instead, a predicted energy expenditure (PEE) is derived based on weight, heat loss, activity, growth requirements, and degree of stress. This study compared actual measured energy expenditure (MEE) with conventional predicted values in 20 critically ill infants and children using a validated metabolic cart designed for use in this age group. All patients were studied either within 4 days of major surgery or during an acute disease process necessitating intensive care. All were severely stressed clinically and were studied while mechanically ventilated in a temperature-controlled environment. The study interval ranged from 1 to 12 hr and averaged 4 hr after a stabilization period of 30 min. The mean MEE was significantly lower than the mean PEE (52.2 +/- 16 kcal/kg/day vs 101.8 +/- 17 kcal/kg/day, P less than 0.001) with a mean MEE/PEE of 52.6 +/- 17% (range 26 to 92%). In a subgroup of 7 paralyzed patients, the mean MEE was significantly lower than in the 13 nonparalyzed patients when compared with PEE and predicted basal metabolic rate (PBMR). The coefficient of variance, conventionally recognized to be approximately 15% for PEE, averaged 6.35% for MEE in this study. These data indicate that if PEE is used as the sole guide for caloric repletion in the stressed infant or child, these patients will be substantially overfed.

Growth and total body water in premature infants fed "in-utero" or "ex-utero"

Total body water and anthropometric measurements were compared in two groups of premature infants. The first group included infants with birthweights less than 1,501 g who were fed under usual clinical circumstances and studied at a bodyweight of 1,800-2,100 g ("Ex-utero"); the second group of infants had a birthweight of 1,800 to 2,100 g and were studied within the first week of life ("In-utero"). Triceps and subscapular skinfold thicknesses were significantly greater in "Ex-utero" infants than in "In-utero" infants, whereas body length was significantly greater in the latter group compared to the former. There were no difference in total body water, abdominal skinfold thickness, or midarm circumference between the two groups. These data suggest that feeding premature infants a standard premature infant formula under established guidelines leads to differences in body and fat distribution but not total body water compared to infants nourished "in utero".

Controversies in neonatal nutrition

The assessment of growth parameters remains one of the most practical and valuable tools to estimate nutritional status in neonates. Growth assessment in full-term infants is performed by using charts developed by the National Center for Health and Statistics. The assessment of post-natal growth in premature infants is controversial and can be performed by using either intrauterine or extrauterine standards. The selection of appropriate growth charts should be based on clinical, demographic, ethnic, and socioeconomic similarities of the population used for reference. Daily energy intakes ranging from 100 to 120 kcal/kg/day have been recommended for full-term infants, while higher intakes ranging from 114 to 181 kcal/kg/day have been recommended for premature neonates. Full-term infants should be nursed or nipple fed on demand; however, premature infants should ideally be tube fed by intermittent gastric feeding (gavage). Continuous gastric and transpyloric feedings are indicated in selected infants. Human milk is a preferred food for full-term infants during the first six months of life; however, this precept does not suggest that all infants who are exclusively breast-fed will grow adequately. Preterm human milk is also a preferred food for the low birthweight infant, provided nutritional supplements are used. It is unclear whether the supplementation of vitamin D, iron, and fluoride in full-term breast-fed infants should be started at birth, at the time of initiation of solid foods, or at the age of six months. The routine supplementation of multivitamins, folic acid, and vitamin E to all low birthweight infants is controversial. Most investigators suggest vitamin supplementation be given until the intake of formula or breast milk is sufficient to meet daily requirements. Vitamin E appears to exert a protective effect in premature infants against the development of severe retinopathy. The supplementation of vitamin E should be dependent upon the serum vitamin E concentration. It is controversial whether iron supplementation for premature infants should be initiated soon after birth or at two months of age, or whether higher doses of iron should be given to very low birthweight infants. If iron supplementation is started at birth, vitamin E status should be closely monitored. Although the optimal intakes of calcium and phosphorus in infant feedings have not been firmly established, the levels of calcium and phosphorus in human milk appear to be inadequate for the growing low birthweight infant.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Mechanics and energetics of breathing helium in infants with bronchopulmonary dysplasia

The mechanics and energetics of breathing were studied in preterm infants with bronchopulmonary dysplasia while spontaneously breathing control gas and helium-oxygen (Heliox) gas mixtures. During Heliox breathing, there was a significant decrease in pulmonary resistance, resistive work of breathing, and mechanical power of breathing, whereas ventilation remained unchanged. Breathing a lower density gas mixture (Heliox) may have therapeutic value by decreasing the demands on the respiratory muscles and the caloric requirements for breathing. Therefore, this modality may reduce potential respiratory muscle fatigue and avail additional calories for growth and recovery in the preterm infant with bronchopulmonary dysplasia.

Meeting zinc and copper intake requirements in the parenterally fed preterm and full-term infant

To determine the intravenous zinc and copper intakes required to build up body stores in the preterm infant and achieve positive retention in full-term infants, balance studies were completed in 38 preterm, full-term, and full-term SGA infants who received complete intravenously delivered nutrient formulations excluding zinc and copper. Zinc as ZnSo4 and copper as CuCl2 were then added to individual infants' formulations, with intakes ranging from 91 to 824 micrograms/kg/day (zinc) and 8 to 92 micrograms/kg/day (copper). Samples of infusate as well as urine, stool, and aspirate were collected for 72 hours and analyzed for zinc and copper by atomic absorption spectrophotometry. Zinc and copper retention correlated significantly with intake (r = 0.89; 0.82, P less than 0.01) and were independent of gestational age, postnatal age, and birth weight. In full-term and full-term SGA infants, intakes of zinc at greater than 150 and copper at greater than 16 micrograms/kg/day were adequate to replace ongoing losses and prevent acute deficiencies. The dosage for copper is similar to the current recommendation of the American Medical Association; the zinc dosage is 50% higher. Preterm infants receiving intakes of zinc at 438 and copper at 63 micrograms/kg/day achieve in utero retention rates. These dosages are significantly higher than AMA recommendations. Both combinations can be delivered by peripheral or central line without complications.

The preterm infant: Breast or bottle?

The long term survival of preterm infants has greatly improved in the last decade. Clinicians have consequently been able to concentrate more on their optimal nutrition and this has led to a controversy regarding the best milk for these infants. Current theory and practice suggests that the fastest growth and the best energy retention is obtained if a highly modified preterm formula milk is used. Banked mature human breast milk appears nutritionally inadequate and has no proven advantages. The use of fresh mothers' own milk merits further investigation, although its widespread use will usually be impractical.

Selected topics in therapeutic nutrition

Although parenteral and enteral nutrition has advanced rapidly in the last 5 years, prevention of nutritional problems in children still depends on the practice of basic nutritional principles. Breast-feeding remains the best alimentation for the infant. Increased support of breast-feeding in children with cleft lip and/or palate is a simple application of basic therapeutic nutrition. Proper feeding can avert the need for parenteral or enteral nutrition. As our knowledge of nutritional therapeutics expands, the practitioner will be able to play a greater role in both preventive and therapeutic nutrition.

Intravenous nitrogen and energy intakes required to duplicate in utero nitrogen accretion in prematurely born human infants

In order to determine the intravenous energy and nitrogen intakes required to achieve intrauterine rates of nitrogen accretion and growth, 30 studies were completed in 22 premature infants who were provided with various intakes of amino acids and energy (glucose +/- lipid) by peripheral vein infusion. At constant nitrogen intake, increasing energy intake (as lipid) from 50 to 80 nonprotein kcal/kg/day resulted in significant increases in nitrogen retention and weight gain. Increasing nitrogen intake from 494 to 655 mg/kg/day at constant low energy intake (mean = 53 kcal/kg/day) had no effect on nitrogen retention or weight change; however, at higher energy intakes (mean = 81 kcal/kg/day) increasing nitrogen intake correlated significantly with increasing nitrogen retention. At energy intakes greater than 70 kcal/kg/day the major determinant of nitrogen retention was nitrogen intake. When energy intake was greater than 70 kcal/kg/day, the infusion of nitrogen providing 430 to 560 mg/kg/day (2.7 to 3.5 gm protein/kg/day) resulted in the duplication of intrauterine nitrogen accretion rates.

Parenteral nutrition in paediatric practice: a review

The special problems associated with parenteral nutrition in childhood are reviewed. A regime for administration is outlined and specific areas for further research are suggested.

Metabolic response to postoperative parenteral nutrition in infants

Thirty-five infants who had tracheoesophageal fistula, esophageal stenosis, anal atresia, or Hirschsprung's disease were managed with various types of parenteral solution after their radical operations. The infants were divided into 6 groups and given 1) the usual low calorie infusion consisting of 5% glucose, water, and electrolytes, 2) high calorie formula consisting of 21 g/kg/day glucose, and 4 g/kg/day synthesized crystalline L-amino acids, 3) solutions without phosphate, 4) solutions of Cal/N ratio 200 providing 4 g/kg/day amino acids, 5) solutions of Cal/N ratio 400 providing 2 g/kg/day amino acids, and 6) a regimen containing fat emulsion. Nitrogen (N) and phosphorus (P) balances, blood urea nitrogen (BUN), blood glucose, plasma phosphate, immunoreactive insulin (IRI), and non-esterified fatty acid (NEFA) values were investigated. Parenteral solutions, providing 100 Cal/kg/day of Cal/N ratio 200, yielded sufficient positive N balance (120 mg/kg/day average). High calorie solutions without phosphate caused marked hypophosphatemia (0.3 mEq/1) with undetectable P in 24-hr urine. P balance correlated with N balance. Solutions of Cal/N 400 induced a lower BUN level, although there was a cumulative negative N balance. Solutions of Cal/N 200 induced higher levels of IRI and lower glucose than those of Cal/N 400. Increased IRI response and remarkedly decreased NEFA levels were seen in the group administered solutions without fat. Solutions with fat emulsion suppressed IRI response and improved the level of plasma NEFA.

Transepidermal water loss in newborn infants. I. Relation to ambient humidity and site of measurement and estimation of total transepidermal water loss

Insensible water loss (IWL) is an important factor in the thermoregulation and water balance of the newborn infant. A method for direct measurement of the rate of evaporation from the skin surface has been developed. The method, which is based on determination of the vapour pressure gradient close to the skin surface, allows free evaporation. From measurements performed on 19 newborns placed in incubators, a linear relation was found between the evaporation rate (ER) and the humidity of the environment at a constant ambient temperature. A 40% lower ER was recorded at a high relative humidity (60%) than at a low one (20%) in the incubator. At measurements on different sites of the body, a high ER was observed on the face and peripheral parts of the extremities, while ER at other sites was relatively low. By determining ER from different parts of the body and calculating the areas of the corresponding surfaces, the total cutaneous insensible water loss for the infant in question could be obtained. The transepidermal water loss (TEWL) for the whole body surface area was calculated to be 8.1 g/m2h. On the basis of measurements performed it was found that the total cutaneous insensible water loss can be estimated with a reasonable degree of accuracy by recording ER from only three easily accessible measurement points.

[Different caloric intake in 75 "low birth weights": effect on weight gain, blood sugar, serum protein, and serum bilirubin (author's transl)]

A prospective study on oral feeding was started in 75 low birth weights (below 2500 g) with adapted milk. Early feeding was given in two groups with different feeding volume and caloric intake. The infants were grouped alternately. Both groups were comparable concerning birth weight, gestational age, and intrauterine growth. Due to partially different variances, covariate correction was applied to analysis of the data. The high caloric group had excellent weight gain, the maximum weight loss was less, and birth weight was regained earlier than in the control group. Blood sugar and serum protein were similar in both groups. Mean serum bilirubin levels were lower in the group with high caloric intake, but differences failed to be significant. Early high caloric feeding was well tolerated and is preferable to parenteral nutrition in low birth weights.

Renal control of sodium and fluid balance in newborn infants during intravenous maintenance therapy

Changes in accumulated fluid and sodium balance during intravenous maintenance fluid therapy has been studied in 38 newborn infants with different clinical disorders and gestational ages 28-42 weeks. The results from the infants born before 36 weeks of gestation (preterm) have been compared with the result from infants born after 36 weeks. Three different saline infusions 10, 20 and 40 mEq Na1/2/1000 ml 5.5% glucose have been given. The infusion rate has in preterm neonates been 3.3 ml/kg and hour and in the more full-term neonates been 3.6 ml/kg and hour. The study lasted for 5-8 hours. Urine was collected by spontaneous voidings in plastic bags. The balances were calculated as the difference between the amount given intravenously, and the amount excreted in the urine. In the more full-term neonates Na1/2 balance became increasingly negative with the 10 mEq solution, just balanced with the 20 mEq solution and increasingly positive with the 40 mEq solution. A different response was found in the preterm neonates. The natriuresis was higher and the sodium balances were increasingly negative with both the 10 and 20 mEq solutions. With the 40 mEq solution the negative balance tended to level off. The fluid balances were fairly well maintained in all infants regardless of the sodium concentration in the infusate.