Responses of Preterm Pigs to an Oral Fluid Supplement During Parenteral Nutrition.

BACKGROUND: Nutrients and electrolytes in amniotic fluid swallowed by fetuses are important for growth and development. Yet, preterm infants requiring parenteral nutrition (PN) receive minimal or no oral inputs. With the limited availability of amniotic fluid, we evaluated the responses of preterm pigs receiving PN to an oral fluid supplement (OFS) based on the electrolyte and nutrient composition of amniotic fluid. MATERIALS AND METHODS: Preterm pigs (92% of term) received a combination of PN (6 mL/kg-h) and 4 mL/kg-h of supplemental fluid as an experimental OFS (n = 9), lactated Ringer's either enterally (n = 10) or intravenously (n = 8). Outcome measures after 96 hours were weight gain, blood chemistry, organ weights, and small intestine mass and brush-border membrane carbohydrases. RESULTS: The OFS did not improve weight gain compared with providing lactated Ringer's orally or intravenously, or increase serum urea nitrogen values, but resulted in higher serum total and low-density lipoprotein cholesterol, as well as improved glucoregulation and heavier intestines, livers, kidneys, and brains and lighter lungs. CONCLUSIONS: Providing supplemental fluid and electrolytes during PN either intravenously or orally increases weight gain after preterm birth. An oral fluid supplement based on amniotic fluid may accelerate development and maturation of organs critical for extrauterine life after preterm birth and may enhance neurodevelopment.

A preterm pig model of lung immaturity and spontaneous infant respiratory distress syndrome.

Respiratory distress syndrome (RDS) and bronchopulmonary dysplasia remain the leading causes of preterm infant morbidity, mortality, and lifelong disability. Research to improve outcomes requires translational large animal models for RDS. Preterm pigs delivered by caesarian section at gestation days (GD) 98, 100, 102, and 104 were provided 24 h of neonatal intensive care, monitoring (pulse oximetry, blood gases, serum biomarkers, radiography), and nutritional support, with or without intubation and mechanical ventilation (MV; pressure control ventilation with volume guarantee). Spontaneous development of RDS and mortality without MV are inversely related with GD at delivery and correspond with inadequacy of tidal volume and gas exchange. GD 98 and 100 pigs have consolidated lungs, immature alveolar architecture, and minimal surfactant protein-B expression, and MV is essential at GD 98. Although GD 102 pigs had some alveoli lined by pneumocytes and surfactant was released in response to MV, blood gases and radiography revealed limited recruitment 1-2 h after delivery, and mortality at 24 h was 66% (35/53) with supplemental oxygen provided by a mask and 69% (9/13) with bubble continuous positive airway pressure (8-9 cmH2O). The lungs at GD 104 had higher densities of thin-walled alveoli that secreted surfactant, and MV was not essential. Between GD 98 and 102, preterm pigs have ventilation inadequacies and risks of RDS that mimic those of preterm infants born during the saccular phase of lung development, are compatible with standards of neonatal intensive care, and are alternative to fetal nonhuman primates and lambs.