Jan Erik H Bunt

Prospective evaluation of surfactant composition in bronchoalveolar lavage fluid of infants with congenital diaphragmatic hernia and of age-matched controls.

OBJECTIVES Infants with congenital diaphragmatic hernia may have biochemically immature lungs. However, normal lecithin/sphingomyelin ratios and phosphatidylglycerol concentrations have been reported in the amniotic fluid of congenital diaphragmatic hernia patients. We hypothesized that if the lungs of congenital diaphragmatic hernia patients are surfactant deficient, that this condition would be reflected in an altered surfactant composition in the bronchoalveolar lavage fluid compared with that composition in age-matched controls. DESIGN Prospective, controlled study. SETTING Surgical intensive care unit in a Level III pediatric university hospital. PATIENTS Four groups were studied: two groups of congenital diaphragmatic hernia patients (conventionally ventilated, n = 13; treated with extracorporeal membrane oxygenation, n = 5); and two control groups (conventionally ventilated, n = 13; extracorporeal membrane oxygenation, n = 6). INTERVENTIONS Bronchoalveolar lavage, using a blind, standardized technique, was performed in conventionally ventilated congenital diaphragmatic hernia patients, extracorporeal membrane oxygenation-treated congenital diaphragmatic hernia patients, age-matched conventionally ventilated controls without pulmonary abnormalities, and extracorporeal membrane oxygenation-treated infants without congenital diaphragmatic hernia. MEASUREMENTS AND MAIN RESULTS The concentrations of different surfactant phospholipids and the fatty acid composition of phosphatidylcholine in bronchoalveolar lavage fluid were measured. No significant differences between the concentrations of phosphatidylcholine and phosphatidylglycerol, and the lecithin/sphingomyelin ratios, were found between the four groups. The fatty acid composition of phosphatidylcholine in conventionally ventilated patients showed a median percentage of palmitic acid within the normal range for age in both groups: 68% in congenital diaphragmatic hernia patients and 73% in controls (p < .001). CONCLUSIONS Our findings indicate that the concentrations of different phospholipids are similar in congenital diaphragmatic hernia patients and controls without congenital diaphragmatic hernia. A primary surfactant deficiency is unlikely in infants with congenital diaphragmatic hernia. However, secondary surfactant deficiency after respiratory failure may be involved.

Endogenous surfactant metabolism in critically ill infants measured with stable isotope labeled fatty acids

Little is known about endogenous surfactant metabolism in infants, because radioactive isotopes used for this purpose in animals cannot be used in humans. We developed a novel and safe method to measure the endogenous surfactant kinetics in vivo in humans by using stable isotope labeled fatty acids. We infused albumin-bound [U-13C]palmitic acid (PA) and [U-13C]linoleic acid (LLA) for 24 h in eight critically ill infants (mean ± SD; weight: 3.7 ± 1.3 kg; age: 51.3 ± 61.6 d) who required mechanical ventilation. The 13C enrichment of PA and LLA in surfactant phosphatidylcholine (PC), obtained from tracheal aspirates, was measured by gas chromatography combustion interface-isotope ratio mass spectrometry. We measured a significant incorporation of both 13C-PA and 13C-LLA into surfactant PC. PC-PA and PC-LLA became enriched after 8.7 ± 4.9 h (range: 3.4-17.3) and 10.0 ± 7.2 h (range: 3.0-22.4), respectively; the times at maximum enrichment were 49.2 ± 8.9 and 45.6 ± 19.3 h, respectively. The fractional synthesis rate of surfactant PC-PA ranged from 0.4 to 3.4% per h, whereas the fractional synthesis rate of PC-LLA ranged from 0.5 to 3.8% per h. The surfactant PC-PA and PC-LLA half-lives ranged from 16.8 to 177.7 and 23.8 to 144.4 h, respectively. This method provides new data on surfactant metabolism in infants requiring mechanical ventilation. We found that synthesis of surfactant from plasma PA and LLA is a slow process and that there were marked differences in PC kinetics among infants. This variability could be related to differences in lung disease and could affect the clinical course of the respiratory failure.

Effect of Prenatal Steroids on Glucose Metabolism and Lipogenesis of Ventilated Premature Infants on the First Day of Life

Effect of Prenatal Steroids on Glucose Metabolism and Lipogenesis of Ventilated Premature Infants on the First Day of Life

Surfactant Metabolism Studied with Stable Isotopes in Preterm Baboons Exposed to Prenatal Betamethasone † 1619

Surfactant Metabolism Studied with Stable Isotopes in Preterm Baboons Exposed to Prenatal Betamethasone † 1619

Differences in the Metabolism of Selected Fatty Acids in Surfactant Phosphatidylcholine in Preterm Infants. |[dagger]| 1620

Differences in the Metabolism of Selected Fatty Acids in Surfactant Phosphatidylcholine in Preterm Infants. † 1620

ENDOGENOUS SURFACTANT TURNOVER IN PRETERM INFANTS MEASURED WITH STABLE ISOTOPES, A NOVEL AND SAFE METHOD. |[dagger]| 1473

We studied surfactant synthesis and turnover in vivo in preterm infants using the stable isotope [U-13C]glucose, as a precursor for the synthesis of palmitic acid in surfactant phosphatidylcholine (PC). Six preterm infants (birth weight, 916 +/- 244 g; gestational age, 27.7 +/- 1.7 wk) received a 24-h [U-13C]glucose infusion on the first day of life. The 13C-enrichment of palmitic acid in surfactant PC, obtained from tracheal aspirates, was measured by gas chromatography-combustion interface-isotope ratio mass spectrometry. We observed a significant incorporation of carbon-13 from glucose into surfactant PC palmitate. PC palmitate became enriched after 19.4 +/- 2.3 (16.5 to 22.3) h and reached maximum enrichment at 70 +/- 18 (48 to 96) h after the start of the label infusion. The fractional synthesis rate (FSR) of surfactant PC palmitate from glucose was 2.7 +/- 1.3%/d. We calculated the absolute production rate of surfactant PC to be 4.2 mg/kg/d, and the half-life to be 113 +/- 25 (87 to 144) h. Data on endogenous surfactant production and turnover were obtained for the first time in human infants with the use of stable isotopes. This novel and safe method could be applied to address many important issues concerning surfactant metabolism in preterm infants, children, and adults.

CHANGES IN FATTY ACID COMPOSITION OF SURFACTANT PHOSPHATIDYL-CHOLINE IN PRETERM INFANTS AFTER SURFACTANT THERAPY AND I.V.-LIPIDS † 1474

CHANGES IN FATTY ACID COMPOSITION OF SURFACTANT PHOSPHATIDYL-CHOLINE IN PRETERM INFANTS AFTER SURFACTANT THERAPY AND I.V.-LIPIDS † 1474