Controversies in neonatal nutrition

The Use of Transpyloric Enteral Nutrition in the Critically Ill Child

To assess the use and complications of transpyloric enteral nutrition (TEN) in the critically ill child we evaluated prospectively all children who received TEN in a pediatric intensive care unit (PICU) of a tertiary university hospital. The type of nutrition used, its duration, medication administered, tolerance, gastrointestinal complications (vomiting, abdominal distension or excessive gastric residue, diarrhea, and pulmonary aspiration), nongastrointestinal complications, and mortality were assessed. A comparative analysis was made between the first 2 years of the study and the remaining period. Over a period of 4.5 years, 152 patients between the ages of 3 days and 17 years received TEN for a duration of 19 ± 32.3 days (range 1–240 days). Forty-one patients received TEN during the first 2 years; 100 patients received TEN in the postoperative period after cardiac surgery (66%). One hundred seventeen patients (77%) received sedation and 65 (43%) received muscle relaxants, presenting no extra complications. Twenty-four patients (15.8%) presented with gastrointestinal complications: abdominal distension and/or excessive gastric residue in 17 and diarrhea in 11. Gastrointestinal intolerance was associated with pulmonary infection ( p < 0.05), altered hepatic function ( p < 0.001), and hypokalemia or hypocalcemia ( p < 0.05). Diarrhea was more frequent in patients with shock ( p < 0.05), altered hepatic function ( p < 0.05), excessive gastric residue ( p < 0.001), and hypokalemia or hypocalcemia ( p < 0.05). In the second study period, the number of patients on TEN and the doses of sedatives, muscle relaxants, and vasoactives were higher ( p < 0.05), with no increase in the incidence of complications. TEN is a useful method of nutrition with few complications in the critically ill child.

Serial composition of human milk in preterm and term mothers

Human milk samples were collected from 86 mothers induced in the study on days 3, 7, 14 and 28 of lactation. The mothers were divided into three groups on the basis of gestation viz. group 1: 37-41 weeks (n=41), group II: 33-36 (n=23) and group III: <33 weeks gestation (n=22). All the samples were analysed for the estimation of fat, lactose and protein. The results obtained from the investigations were statistically analysed. The analysis of the results revealed a lower amount of fat and lactose in preterm milk as compared to term milk (p<0.01). These were found to increase in amount with increasing postnatal age (p<0.05). The protein levels were observed to be significantly higher in preterm than term milk (p<0.01). These were observed to decrease significantly with increase in postnatal age (p<0.01).

A high prevalence of metabolic bone disease in exclusively breastfed very low birthweight infants in Dar-es-Salaam, Tanzania

Metabolic bone disease (MBD), or rickets, is common in very low birthweight infants. A descriptive, cross-sectional, hospital-based study was carried out at Muhimbili Medical Centre, Dar-es-Salaam from 15 April to 30 June, 1995 to discover the magnitude, contributory factors, morbidity and suitable biochemical diagnostic tests for MBD. One hundred infants with a postnatal age of 6-12 weeks, whose birthweights were 1500 g or less were studied. Thirty-three of 100 (33%) infants, 16 boys and 17 girls, were radiographically diagnosed as having metabolic bone disease. The mean (SD) gestational age of those infants was 30.4 (2.7) weeks, while that of the infants without metabolic bone disease was 32.4 (3) weeks (p = 0.003). There was no significant difference in birthweight, serum calcium and serum phosphate levels between those infants with MBD and those without. The mean (SD) serum alkaline phosphatase in infants with MBD was 1052.9 (493.3) U/l and 766.8 (301.7) in those without MBD (p = 0.006). Thus, metabolic bone disease is common in very low birthweight infants. Wrist radiography and serum alkaline phosphatase levels remain important diagnostic tools. MBD should be considered seriously in very low birthweight infants.

Breast-feeding in neonatal intensive care

OBJECTIVE

To determine the incidence of breast-feeding in very preterm babies while in neonatal intensive care.

METHODOLOGY

A retrospective records analysis of all 151 babies with gestational age less than 35 weeks admitted to the neonatal intensive care unit (NICU) of a major teaching hospital in 1993.

RESULTS

On discharge 64% of babies were having some breast milk (45% having breast milk alone, 19% both breast milk and formula), and 38% some breast-feeding (17% being solely breast-fed, the other 21% combining breast-feeding with either bottle-feeding or an intragastric tube [IGT]. Breast milk was the first milk for 41% of babies, with 83% having breast milk at some stage. Increasing gestational age was associated with a decreased likelihood of first milk being breast milk (73% of those less than 29 weeks compared to 21% of those aged 33-34 weeks, P < 0.001), but with increased rates of breast-feeding (23 compared to 59%, P = 0.01) and breast milk consumption (42 compared to 73%, P = 0.04).

CONCLUSIONS

Breast-feeding rates in NICU are well below those found on discharge for full term babies. Both maternal and staff-related factors contribute to this. More and better education of mothers, doctors and nurses as well as changes to some unit practices could increase these rates.

Techniques of enteral feeding in the newborn

Among techniques of enteral feeding, gastric bolus feeding still appears to be the method of choice for most newborn babies because it is both practical and inexpensive. Unstable preterm infants and those with severe respiratory diseases or with delayed gastric emptying time may not tolerate intermittent gastric feedings and may benefit from continuous gastric feedings. Transpyloric feedings do not seem to offer any advantage over continuous gastric feedings and should be reserved for infants at risk of aspiration, such as those with gastroesophageal reflux or delayed gastric emptying. Early low-volume feedings appear beneficial and are not associated with increased morbidity. Once enteral feedings are established, daily increments of 10-20 ml/kg appear to be safe and not associated with an increased risk of necrotizing enterocolitis.

Nutritional factors in milk from Brazilian mothers delivering small for gestational age neonates

The composition of breast milk from brazilian mothers delivering low birthweight infants and its adequacy as a source of nutrients for this group has not yet been fully elucidated. A total of 209 milk samples from 66 women were analysed. The mothers were divided into three groups: G1, mothers delivering term babies of low birthweight (TSGA, n = 16); G2, mothers delivering preterm babies of appropriate birthweight (PTAGA, n = 20); G3, mothers delivering term babies of appropriate birthweight (TAGA, n = 30). The following factors were analysed: osmolarity, total proteins and protein fractions, creamatocrit, sodium, potassium, calcium and magnesium. Milk samples were collected 48 h and 7, 15, 30 and 60 days after delivery. The groups did not differ significantly in terms of osmolarity, total proteins and fractions, creamatocrit, calcium, magnesium or potassium throughout the study period. Sodium levels were higher in all samples from mothers of TSGA infants and in samples from mothers of PTAGA infants on the 7th, 15th and 30th days than in milk from the TAGA group. The authors consider the needs of the low birthweight and TAGA infants and that these high sodium levels may be necessary for growth of low birthweight infants.

Advances in neonatology. View from a practicing pediatrician

After reviewing the many problems that may be seen by the physician in follow-up care of the preterm infant and family, it is important to take a step back and evaluate the infant as a whole. In the vast majority of instances, the preterm infant will turn out to be normal. In an unfortunate minority, there may be difficult problems that the baby, parents, and caretakers must face. The pediatrician must remain diligent to attend to those problems that are correctable and to assist patients to their full potential.

Risk-benefit assessment of anaesthetic agents in the puerperium

A critical evaluation of anaesthetic agents in the puerperium is difficult because systematic, relevant studies are still lacking. Current knowledge of the effects of different agents used in labour and caesarean section indicates that significant residual effects on the mother and newborn are limited. In the early puerperium, based on physiological and/or hormonal changes, the mother could be more sensitive to inhalational anaesthetic agents and local analgesics. To date there is no evidence that any anaesthetic agent is excreted in breast milk in clinically significant amounts when given as a single dose. The only exception is perhaps in the case of very premature neonates whose mothers have had multidrug therapy before labour. Even then the importance of breast milk should be carefully assessed against possible adverse drug effect. However, repeated administration of long-acting benzodiazepines and continuous epidural administration of pethidine (meperidine) can have adverse effects on the neonate. The essential conclusion of this review is that breast-feeding is best. The different anaesthetic agents are excreted in the milk in amounts so low that detrimental effects on the neonate should not be expected.

Scientifically-based strategies for nutrition of the high-risk low birth weight infant

Technological advances in the intensive care of low birth weight (LBW) infants have resulted in major increases in their survival. New challenges in meeting their nutritional needs have emerged. Very low birth (VLBW) weight infants have very little body fat or glycogen reserves at birth, making them susceptible to starvation. If fed enterally, they require at least 120 calories/kg per day for growth. Numerous immaturities in the gastrointestinal tract and liver limit protein digestion, absorption, and metabolism. Several amino acids not considered essential to the older child or adult are essential to the VLBW infant. Supplying a high protein load with an inappropriate amino acid composition may lead to metabolic imbalances. The digestion and absorption of fats differs from the older child or adult. Lingual and gastric lipases are important, and the lack of bile acids limits fat absorption. Lipoprotein lipase deficiency causes problems when too much fat or fat of incorrect composition is provided. There are controversies regarding the most appropriate carbohydrate source, but research shows that lactose remains an important carbohydrate source for most of these infants. Calcium, magnesium, and phosphorus requirements pose questions in both enterally and parenterally nourished infants. Studies of iron usage suggest that VLBW infants fed either human milk or formula should receive iron supplements. Vitamin E may be helpful in preventing oxygen toxicity. Vitamin D deficiency contributes to bone demineralization and rickets. Controversy exists regarding the correlation between vitamin A nutrition and development of chronic lung disease. Guidelines have been developed for recommended intakes, but much needs to be learned to provide a sound scientific basis upon which to provide optimal nourishment for the high risk, LBW infant.

Breast milk for infants who cannot breastfeed

Controversy exists regarding feeding the preterm infant. Milk banks serve as one source of human milk for preterm infants. Milk banks are discussed in terms of the benefits of human milk, the potential hazards, and ways that milk banks are attempting to avoid those hazards. This article focuses on the feeding needs of preterm and sick infants. A brief history of artificial feeding and milk banks is presented.

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.

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.

Drugs in human milk. Clinical pharmacokinetic considerations

Drugs ingested by a lactating mother would be expected to appear in human milk to some extent and be ingested by a breast-feeding infant. Drugs pass from maternal plasma into milk by passive diffusion and are distributed within the aqueous, protein and lipid phases of milk. Distribution into milk will be affected by physiochemical characteristics of the drug: acid-base characteristics, relative protein binding in plasma and milk, and lipid solubility, as well as milk composition. The milk-to-plasma concentration ratio is the most commonly quoted index of drug distribution into human milk. However, calculation of the daily infant dose of drug ingested in milk, and from this the dose in milk relative to the maternal dose on a weight-adjusted basis, is a more relevant indicator of infant exposure to a drug. This is particularly true for drugs with a high volume of distribution, for which only a small proportion of the mother's dose is contained within the plasma and available for distribution into milk. A better indication of infant exposure to a drug is the steady-state plasma drug concentration in a breast-feeding infant, the major determinants of which are the dose rate (via milk) and the oral availability and clearance in the infant. Although in neonates the rate of absorption may be different from adults, there is little evidence that its extent is significantly different. Clearance, however, is impaired in very young infants, particularly if premature. The decreased clearance would result in a proportional increase in steady-state plasma concentrations in the breast-feeding infant. Consideration of the dose ingested in milk and the approximate clearance in infants of different ages allows estimation of likely steady-state plasma concentrations in breast-feeding infants. From these considerations, recommendations regarding the safety of drugs during breast-feeding can be made. Drugs which are very toxic or have dose-independent toxicity should be considered separately. Recommendations regarding 'social' drugs such as nicotine, alcohol, caffeine and theobromine are particularly difficult, as doses are uncontrolled and vary variable.

Principles of drug biodisposition in the neonate. A critical evaluation of the pharmacokinetic-pharmacodynamic interface (Part I)

Rational pharmacotherapy is dependent upon an understanding of the clinical pharmacokinetic and pharmacodynamic properties of the drugs employed. Although the available data on drug biodisposition and action in the neonate have increased considerably in the last few years, pharmacokinetic-pharmacodynamic interactions for many drugs remain poorly understood. The ontogeny of drug absorption, distribution, metabolism, and elimination are addressed in this review. Drug absorption from any site depends upon both the physicochemical properties of the drug and a variety of patient factors. Absorption of orally administered drugs may be affected by changes in gastric acidity and emptying time as well as by bile salt pool size, bacterial colonisation, and extraintestinal disease states such as congestive heart failure. Factors affecting drug absorption following intramuscular, percutaneous, and rectal administration are also discussed. Drug distribution in the neonate is influenced by a variety of important and predictable age-dependent factors. The developmental aspects of protein binding and body water compartments are described. Additionally, hepatic drug metabolism assumes an important role in understanding the pharmacokinetic and pharmacodynamic properties of many compounds. Certain biotransformation pathways, including hydroxylation by the P450 mono-oxygenase system and glucuronidation, demonstrate only limited activity at birth, while other pathways, such as sulphate or glycine conjugation, appear very efficient at birth. Elimination of drugs excreted unchanged in the urine is dramatically reduced in the newborn, compared with older infants and children, due to immaturity of both glomerular filtration and tubular secretory processes. The glomerular filtration rate remains markedly reduced prior to 34 weeks gestational age, increasing as a function of post-conceptual age until adult values are achieved by approximately 2.5 to 5 months of age. Tubular secretory capacity is also limited at birth, approaching adult values by approximately 7 months of age. Published reports describing the pharmacokinetics and pharmacodynamics of commonly used drugs in the neonatal period, as well as differences in drug biodisposition among premature infants, full term neonates, and older infants and children, are reviewed. Our recommendations for neonatal drug therapy are based upon a critical interpretation of these data, an understanding of fetal development and maturational processes, and an understanding of how disease states may affect drug biodisposition in the neonate.