Practical preterm parenteral nutrition: systematic literature review and recommendations for practice

Current practice in relation to the prescribing, compounding and administration of parenteral nutrition for extremely preterm infants is inconsistent and based on largely historical evidence. Increasingly there are calls for more 'aggressive' nutritional interventions to prevent 'postnatal growth failure'. However the evidence base for these recommendations is weak, and there are no long-term studies examining the impact of such practices. Here we summarise the evidence for preterm parenteral nutrition interventions. We suggest principles to guide practice based on evidence from a systematic search and review of evidence to date, and recommend actions necessary to advance the understanding of this important aspect of preterm care.

Neonatal intrahepatocellular lipid

There is increasing evidence that preterm birth is a risk factor for the development of adiposity associated disease, although the pathophysiological basis is unclear. We have previously shown that preterm infants have increased internal abdominal (visceral) adiposity by term. In adults increased internal adiposity is associated with elevated intrahepatocellular lipid (IHCL). We measured IHCL using (1)H NMR spectroscopy in 26 infants (eight healthy preterm-at-term and 18 term-born) and compared values with a reference group of 32 adults. There was no significant difference between adult and term-born IHCL content. In preterm-at-term infants IHCL was significantly elevated when compared with term-born infants and with adults (IHCL CH2/water median (interquartile range): preterm 1.69 (1.04-3.53), term 0.21 (0-0.54) and adult 0.55 (0.08-1.57).

Accelerated postnatal head growth follows preterm birth

BACKGROUND

Poor growth after preterm birth, particularly poor head growth, is associated with impaired neurodevelopmental outcome.

OBJECTIVE

To evaluate weight gain and head growth between birth and term in a contemporary cohort of preterm infants, taking into account breast milk intake and illness severity.

METHODS

Subjects were inborn infants <or=32 weeks gestation who remained in the neonatal unit up to >or=37 weeks postmenstrual age. Weight and head circumference (HC) were expressed as standard deviation score (SDS), growth between birth and discharge as SDS gain (SDSG), and illness severity and breast milk exposure as the number of days of level 1 (full) intensive care (%L1IC) and the number of days on which breast milk was received (%BM) as a percentage of days from birth to discharge.

RESULTS

Infants showed poor postnatal weight gain but accelerated head growth. There was a highly significant fall in mean (SD) weight SDS between birth and discharge (-0.31 (0.96) and -1.32 (1.02) respectively, p<0.001) and a highly significant increase in HC SDS (-0.52 (0.95) and -0.03 (1.25) respectively, p = 0.003). %L1IC had a highly significant negative impact on weight SDSG (p = 0.006), and %BM had a significant positive impact on HC SDSG (p = 0.043).

CONCLUSIONS

Accelerated postnatal head growth suggests catch up after antenatal restraint. This raises the possibility that poor neurocognitive outcomes after extremely preterm birth may in part be consequent on poor intrauterine brain growth. As postnatal head growth may be facilitated by breast milk, there is an urgent need to evaluate the optimal use of breast milk in preterm neonates. Illness severity is a significant determinant of poor postnatal weight gain.