The improved survival of low birth weight infants has also placed the burden on the physician of more optimal nutrition management of these infants. The appropriate goals of low birth weight feed includes ensuring adequate short term growth, preventing feeding related morbidities, optimizing long term outcomes including its impact on adult onset diseases (e.g. coronary artery disease, diabetes mellitus, etc).Enteral feeding of the low birth weight (LBW) newborn has been beset with controversies relating to a variety of issues-time to start, type of milk, frequency, rapidity of increment, mode of feeding, suckling at breast, fortification of human milk, etc. Several reasons could be ascribed to existence of differences of opinion. Firstly, LBW newborns constitute a heterogeneous population of preterm and term growth retarded infants, whose maturity and nutritional needs differ. The advances in our understanding of the gut physiology of the neonate, their nutritional needs and long-term growth implications have also undergone a sea change in the past couple of decades. The present communication attempts an evidence-based review of some of the controversial issues related to LBW (especially preterm) enteral feeding.</sec><sec id="sec002"><title>Early enteral trophic/priming feeding

Journal of Neonatology

0971-2179

National Neonatology Forum

jn-21-2-013

REVIEW ARTICLE

Enteral feeding of low birth weight infants

Ramji

Siddarth

Department of Neonatology, Maulana Azad Medical College New Delhi 100 002, India.

*E-mail: sumsid@vsnl.com

4–62007

212136138

The improved survival of low birth weight infants has also placed the burden on the physician of more optimal nutrition management of these infants. The appropriate goals of low birth weight feed includes ensuring adequate short term growth, preventing feeding related morbidities, optimizing long term outcomes including its impact on adult onset diseases (e.g. coronary artery disease, diabetes mellitus, etc).Enteral feeding of the low birth weight (LBW) newborn has been beset with controversies relating to a variety of issues-time to start, type of milk, frequency, rapidity of increment, mode of feeding, suckling at breast, fortification of human milk, etc. Several reasons could be ascribed to existence of differences of opinion. Firstly, LBW newborns constitute a heterogeneous population of preterm and term growth retarded infants, whose maturity and nutritional needs differ. The advances in our understanding of the gut physiology of the neonate, their nutritional needs and long-term growth implications have also undergone a sea change in the past couple of decades. The present communication attempts an evidence-based review of some of the controversial issues related to LBW (especially preterm) enteral feeding.</sec><sec id="sec002"><title>Early enteral trophic/priming feeding

The general consensus till recently had been that enteral feeding should be deferred for a few days in LBW infants who are less than 30 weeks or less than 1200g in birth weight or are sick (e.g. severe respiratory distress, birth asphyxia, sepsis, etc) till they appear to ‘stabilize’. The reason for this imposed starvation of the gut was the physician's concern of the risk of necrotizing enterocolitis. However, evidence from physiologic studies favour addition of nutritionally insignificant amounts of enteral substrates prior to initiation of full enteral feeds in order to stimulate/prime the motor, endocrine, vascular and mucosal aspects of the preterm gut in order to improve tolerance to subsequent enteral feeding.

There is now sufficient evidence from published medical literature that demonstrate improved tolerance to enteral feeding amongst infants primed with trophic feeding and no increased risk of necrotizing enterocolitis. In most studies the neonates were provided with trophic feeding (volumes of 10–15 ml/kg/day) during the first week of life before standard increments in enteral feeding volumes were initiated (volume increments ranged from 15–20 ml/kg/day)(1–5). A randomized controlled study by McClure et al (5) on 100 preterm infants with birth weights < 1750g recruitedfor trophic feeding on day 3 of life observed significantly greater energy intake, better growth, fewer episodes of sepsis, shorter duration of parenteral nutrition and shorter days to maximal enteral feeding volumes in the trophic fed group.

A systematic review by Kennedy and Tyson (6) of randomized controlled trials evaluating early or delayed initiation of enteral feedings in LBW or preterm infants concluded that early feeding had no effect on necrotizing enterocolitis, weight gain, mortality or age at discharge. The current evidence supports the view that the gut must be allowed to carry out it function of feeding and digestion for which it has been designed.

Rapid versus slow advancements

The rapidity of feed volume increments has been best with controversies. A more rapid increase should result in faster weight gain and a shorter hospital stay. The proponents of slow feed advancements have cited risk of necrotising enterocolitis in their defense, while those in favour of rapid advancements have cited better growth in their defense. Controlled trials prior to the 1990s’ had observed an association between rapid feed advancement and increased risk of NEC. Table 1 summarizes the results of rapid feed advancement trials on NEC in preterm neonates. It is evident that none of the recent randomized controlled trials demonstrated any increased risk of NEC. Kennedy et al (12) in a systematic review of randomized controlled trials comparing rapid versus slow feed advancements observed no increased risk of NEC attributable to feed advancement volumes. But, they observed a shorter duration to full enteral feeding and an overall reduction in days to regain birth weight in the rapid advancement groups. The lack of effect on NEC could be a result of differences in study design, improved neonatal care resulting in decrease in NEC risk factors and shift in feeding protocols from formula to human milk. The present evidence favors more rapid advancements of feeds (@ 30 ml/kg/day) in stable preterm infants with no increased risk of NEC in these infants. Table 1

Summary of slow versus fast feed advancement trials in preterm neonates

Trial (year)	Sample size	Study Design	Volume increments	Effect on NEC	Comments

Brook (1976)⁷	29	RCT	10ml/kg/d versus 20ml/kg/d	Not significant
McKeown (1992)⁸	118	Matched case-control	46ml/kg/d versus 23ml/kg/d	Significantly more in rapid advancement	Age at NEC significantly associated with earlier age of feeding
Wright (1993)⁹	498	Case-control	12 ml/kg/d versus 15.5 ml/kg/d	Significantly more in rapid advancement	Small difference significant due to large sample size
Caple (1997)10	150	RCT	20 ml/kg/d versus 30 ml/kg/d	Not significant	Rapid group acquired faster weight gains and shorter days on IV fluids
Rayyis (1999)¹¹	185	RCT	15 ml/kg/d versus 35 ml/kg/d	Not significant	Significantly faster weight gain in rapid group

It appears that it should be possible to make rapid advances in enteral feeds in stable VLBW infants after 4/5 days of life as long as the infant is able to tolerate it. Tolerance to enteral feeding can be judged by absence of abdominal distention and gastric residues < 20% of previous feeds.

Intermittent versus continuous nasogastric feeding

Concerns have been expressed about very low birth weight infant's tolerate to intermittent bolus feeds as the relatively incompetent gastroesophageal sphincter could result in reflux of feeds and increased risk of feed aspirations and apnea. The studies that have evaluated intermittent versus continuous feeding protocols have not observed any increased risk of feed intolerance, NEC or time to reach full enteral feeds. However, all these studies have had small sample sizes and one may have to be cautious in extrapolating the results from these studies. However, clinical experience at large has observed the VLBW infants have tolerated intermittent feeding quite well. There may however be some infants < 1000g who may not tolerate intermittent feeding and they may be candidates for continuous enteral feeding.

Human milk, nutrient supplementation and human milk fortification

There have been several recommendations on the vitamin and mineral requirements for preterm and low birth weight babies. These form the bases of composition of preterm formulae. During the years when human milk banking gained popularity, there was a need for supplementing micro and macronutrients because pooled human milk had a large proportion of term human milk (the availability of vitamins and minerals being inadequate for the needs of the preterm infant). The resurgence of maternal interest in feeding preterm infants with their own preterm milk demands a critical reappraisal of nutritional supplementation in these infants. On a theoretical basis preterm infants fed on atleast 180 ml/kg/day of preterm human milk should be receiving each day 120–130 Kcal/kg energy, 3.0–3.7 g/kg protein, 2.3–4.0 mmol/kg sodium and 2.7–3.0 mmol/kg potassium. These match the of the programming of cardiovascular risk factors by early diet and the long-term benefit of breast milk.

The issue of adequacy of human milk in term growth retarded low birth weight is more complex due to the non-availability of any trials that have evaluated the adequacy of breast milk and supplementation in these infants. In impoverished conditions, mothers are known to be marginal with regards to micro and macronutrients. The breast milk of these mothers may contain insufficient nutrients to meet the needs of both term and preterm infants in developing nations.

Enteral feeding techniques

The traditional mode of feeding in LBW infants centered around gavage or tube feeding, which gradually transited to bottle feeding before full breast feeding was established. In the developing countries, this practice resulted in disastrous outcomes- low breast feeding rates at discharge consequent to the infant's “nipple confusion” experience resulting in increased risk of diarrheas. The Indian experience has led to the discovery of an alternative strategy that overcomes these handicaps. Feeding the VLBW infant >32 weeks with spoon, cup or traditional feeding devices such as the ‘paladai’ resulted in decreased rates of infection and improved breast feeding rates at discharge. A recently published study evaluated the safety of cup feeding compared to bottle-feeding in infants > 33 weeks. It was observed that during cup feeding premature infants were more physiologically stable, with lower heart rates, higher oxygen saturation and less desaturations than bottle-fed babies. The study supports the use of cup feeding as a safe strategy for feeding preterms while transiting from tube to breast feeding.

During postnatal life suckling can be enhanced by use of ‘nonnutritive sucking’ (NNS) as an additional strategy that would enhance the transition from gavage to breast-feeding. It has been observed that when preterms are allowed NNS before, during and after intermittent nasogastric feeding, it enhances the suckling activity of the infant. A systematic review of 20 trials (20) revealed that NNS resulted in faster transit from tube to oral feeding and also resulted in shortened hospital stay. None of the studies reported any negative effects. There is at present sufficient evidence to promote NNS in neonatal unit protocols to aid transition from tube to breast-feeding.

There has also been concern about whether preterm infants >34 weeks should be allowed ad-lib compared to fixed time feeding schedules. Recent trials (21) have suggested that the infant has the capacity to develop self-regulation and do gain weight adequately on ad-lib feeding regimen. Therefore infants >34 weeks should be allowed ad-lib feeding provided that have developed good sucking.

Conclusion

Provision of breast milk is the choice for feeding low birth weight newborns. Evidence supports the practice of trophic feeding with human milk in VLBW neonates at volumes of 0.5–1.0 ml/hr as early as the first day of life. Once these infants stabilize, the feeding volumes can be increased rapidly (upto 30–35 ml/kg/day) without any increased risk of adverse outcomes such as NEC (Table 2). In preterm neonates less than 34 weeks, transition from nasogastric intermittent feeding can be facilitated by use of nonnutritive sucking and spoon/cup feeding techniques. All these preterm neonates should receive multivitamin supplementation and also sufficient amount of calcium and phosphorous to prevent osteopenia. There is insufficient evidence for the routine use of human milk fortifiers. Iron supplementation should begin at 4–6 weeks of life in all preterm neonates. The researchable issues include need for routine multivitamin supplements in preterms on exclusive human milk feeding and also in term low birth weight infants. Table 2

Enteral feeding protocol (birth weight, volume and frequency of feeding)

Day	> 1600 g (3 h)	1200-1600g (2 h)	<1200 g (2 h)

1	60 ml/kg	60 ml/kg	160 ml/kg
2	90 ml/kg	90 ml/kg	30 ml/kg
3	120 ml/kg	120 ml/kg	50 ml/kg
4	150 ml/kg	150 ml/kg	70 ml/kg
5	150 ml/kg	180 ml/kg	90 ml/kg
6	150 ml/kg	180 ml/kg	180 ml/kg

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