Paola Cogo

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.

Parenteral Nutrition of Preterm Infants with a Lipid Emulsion Containing 10% Fish Oil: Effect on Plasma Lipids and Long-Chain Polyunsaturated Fatty Acids

OBJECTIVE To compare plasma lipids in preterm infants given a new lipid emulsion containing 10% fish oil, 50% medium-chain triacylglycerols, and 40% soybean oil, compared with a standard preparation containing 50:50 medium-chain triacylglycerols: soybean oil. STUDY DESIGN Preterm infants weighing <1250 g at birth (n=47) were randomly assigned to receive parenteral nutrition with a fish oil lipid (n=23) or soybean oil (n=24). Plasma lipid classes and plasma and red blood cell fatty acids were determined by gas chromatography in cord blood and on postnatal days 7 and 14. RESULTS On day 7, the infants receiving fish oil lipid had significantly lower plasma phospholipids, cholesterol esters, and free cholesterol but similar triglyceride concentrations. They also had significantly higher phospholipid docosahexaenoic acid (2.77 ± 0.08 versus 2.46 ± 0.01 mol%, P<.01) and eicosapentaenoic acid (1.58 ± 0.01 versus 0.25 ± 0.01 mol%, P<.01) as well as lower arachidonic acid (10.64 ± 0.29 versus 11.93 ± 0.29 mol%, P<.01) compared with those receiving soybean oil. Similar differences were found in red blood cells. CONCLUSIONS The fish oil lipid emulsion was well tolerated, and infants receiving fish oil had lower plasma lipids and improved fatty acids status. The effect of these changes on inflammation, growth, and neurodevelopment should be explored.

Pulmonary Surfactant Disaturated-Phosphatidylcholine (DSPC) Turnover and Pool Size in Newborn Infants with Congenital Diaphragmatic Hernia (CDH)

In animal CDH models, surfactant deficiency contributes to the pathophysiology of the condition but information on human disease is very limited. The aim of our study was to investigate surfactant kinetics in CDH newborns. We studied surfactant disaturated-phosphatidylcholine (DSPC) half-life, turnover and apparent pool size by stable isotope methodology in CDH newborns with no ExtraCorporeal Membrane Oxygenation (ECMO) support (n = 13, birth weight (BW) 3.2 ± 2.2 kg, gestational age (GA) 39 ± 0.4 wks, postnatal age 43 ± 11 h) and in 8 term infants with no lung disease (CONTROLS, BW 2.7 ± 0 kg, GA 38 ± 0.8 wks, postnatal age 96 ± 26 h). We administered a trace dose of 13C-palmitic acid dipalmitoyl-phosphatidylcholine (DPPC) through the endotracheal (ET) tube and we measured DSPC kinetics by gas chromatography-mass spectrometry from DSPC13C-enrichment decay curves obtained from sequential tracheal aspirates. DSPC amount from tracheal aspirates (TA-DSPC) was measured by gas chromatography. In CDH infants DSPC half-life was shorter (24 ± 4 and 53 ± 11 h, p = 0.01), turnover faster (0.6 ± 0.1 and 1.5 ± 0.3 d−1p = 0.01), apparent pool size smaller (34 ± 6 and 57 ± 7 mg/kg body weight, p = 0.02) and tracheal aspirates DSPC amount lower (2.4 ± 0.4 and 4.6 ± 0.5 mg/mL Epithelial Lining Fluid (ELF), p = 0.007) than in CONTROLS. In conclusion surfactant kinetics is grossly abnormal in mechanically ventilated CDH. Whether alterations of DSPC kinetics in CDH infants are caused by a primary surfactant deficiency or are secondary to oxygen therapy and ventilator support has still to be determined.

The effect of 5 intravenous lipid emulsions on plasma phytosterols in preterm infants receiving parenteral nutrition: a randomized clinical trial

BACKGROUND Elevated plasma phytosterol concentrations are an untoward effect of parenteral nutrition (PN) with vegetable oil-based lipid emulsions (LEs). Phytosterols are elevated in neonatal cholestasis, but the relation remains controversial. OBJECTIVE The objective was to study the effect of 5 LEs on plasma phytosterols in preterm infants. DESIGN One hundred forty-four consecutive admitted preterm infants (birth weight: 500-1249 g) were studied. Patients were randomly assigned to receive 1 of 5 different LEs: S [100% soybean oil (SO)], MS [50% medium-chain triglycerides (MCTs) and 50% SO], MSF (50% MCTs, 40% SO, and 10% fish oil (FO)], OS (80% olive oil and 20% SO), or MOSF (30% MCTs, 25% olive oil, 30% SO, and 15% FO). Phytosterols in the LEs and in plasma (on postnatal day 7 and day 14) were measured by gas chromatography-mass spectrometry. RESULTS Patients in the S group had significantly higher total phytosterol intakes than did the other study groups. On PN days 7 and 14, plasma phytosterol concentrations were highest in the S group and lowest in the MOSF group. Despite similar β-sitosterol intakes between the MS and MSF groups, plasma concentrations were significantly lower in the MSF than in the MS group. Only 3 patients (2.1%) developed cholestasis: 1 in the MS, 1 in the MSF, and 1 in the MOSF group. No cases of cholestasis were observed in the S and OS groups. CONCLUSIONS In uncomplicated preterm infants receiving routine PN, we found a correlation between phytosterol intake and plasma phytosterol concentrations; however, cholestasis was rare and no difference in liver function at 6 wk was observed.

A dual stable isotope tracer method for the measurement of surfactant disaturated-phosphatidylcholine net synthesis in infants with congenital diaphragmatic hernia.

The aim of the study was to measure for the first time in humans surfactant disaturated-phosphatidylcholine (DSPC) net synthesis and kinetics by using a novel, dual stable isotope tracer approach. Ten infants with congenital diaphragmatic hernia [CDH; birth weight, 3.4 ± 0.2; gestational age, 39.8 ± 0.4 wk] and 6 age-matched control subjects with no lung disease (birth weight, 3.2 ± 0.3 kg; gestational age, 39.1 ± 1.1 wk), all of whom were admitted to the neonatal intensive care unit (Padua, Italy), were studied. A ll infants received simultaneously an intratracheal (carbon-13 di-palmitoyl-phosphatidylcholine) and an i.v. (deuterated palmitic acid) stable isotope tracer. Isotopic enrichment curves of DSPC from sequential tracheal aspirates were analyzed by mass spectrometry. DSPC kinetic data were expressed as mean ± SEM and compared by the Mann-Whitney test. DSPC net synthesis from plasma palmitate was nearly identical in infants with CDH and control subjects (8.6 ± 2.2 and 8.1 ± 1.5 mg·kg−1·d−1; P = 0.7). DSPC apparent pool size was 36.7 ± 7.5 and 58.5 ± 9.1 mg/kg (P = 0.07) and half-life was 26.7 ± 4.5 and 50.3 ± 9.7 h (P = 0.03) in infants with CDH and control subjects, respectively. Both DSPC turnover and percentage of catabolism/recycling significantly correlated with duration of mechanical ventilation. In conclusion, the measurements of net DSPC synthesis and catabolism/recycling were reported for the first time in humans. Mean net DSPC synthesis was ∼8 mg·kg−1·d−1. No significant differences were found between control subjects and infants with CDH. DSPC turnover was faster in infants with CDH, presumably reflecting an increased DSPC catabolism/recycling. Whether this may ultimately lead to a secondary surfactant deficiency in infants with CDH is still to be ascertained.

Surfactant kinetics in preterm infants on mechanical ventilation who did and did not develop bronchopulmonary dysplasia

ObjectiveTo characterize surfactant kinetics in vivo in two groups of premature infants on different levels of mechanical ventilation and at different risk of developing bronchopulmonary dysplasia. DesignControlled observational study in two independent groups of infants. SettingNeonatal intensive care unit. PatientsThirteen preterm infants (26 ± 0.5 wks, birth weight 801 ± 64 g) on high ventilatory setting and who finally all developed bronchopulmonary dysplasia (MechVentBPD), and eight (26 ± 0.5 wks, birth weight 887 ± 103 g) who had minimal or no lung disease and of whom none developed bronchopulmonary dysplasia (MechVentNoBPD). Measurements and Main ResultsEndotracheal 13C-labeled dipalmitoyl-phosphatidylcholine was administered and subsequent measurements of the 13C enrichment of surfactant-disaturated phosphatidylcholine (DSPC) from serial tracheal aspirates were made by gas chromatography-mass spectrometry. We calculated disaturated phosphatidylcholine pharmacokinetic variables in terms of half-life and apparent pool size from the enrichment decay curves over time. DSPC concentration from tracheal aspirates was expressed as milligrams/milliliter epithelial lining fluid (ELF-DSPC). Data are presented as mean ± se. In MechVentBPD infants vs. MechVentNoBPD, ELF-DSPC was much reduced, 2.9 ± 0.6 vs. 9.4 ± 3.0 mg/mL ELF (p = .03), half-life was shorter, 19.4 ± 2.8 vs. 42.5 ± 6.3 hrs (p = .002), and apparent pool size larger, 136 ± 21 vs. 65.8 ± 16.0 mg/kg (p = .057). In MechVentBPD, apparent DSPC pool size positively correlated with mean airway pressure × Fio2 and inversely correlated with ELF-DSPC. ELF-DSPC was inversely correlated with mean airway pressure × Fio2. No significant correlations were found in the MechVentNoBPD group. ConclusionsMechVentBPD infants showed profound alteration of surfactant kinetics compared with preterm infants with minimal lung disease, and these alterations were correlated with severity of ventilatory support.

Protein turnover, lipolysis, and endogenous hormonal secretion in critically ill children.

Objectives The catabolic state is a major contributor to morbidity and mortality of critical illness and may be related to endocrine changes. We studied whether protein and lipid turnover correlate with insulin and growth and thyroid hormone plasma levels in critically ill infants. Design Prospective clinical study. Setting Pediatric intensive care unit. Patients Twelve critically ill children and ten age-matched controls. Measurements We measured lipolysis and protein turnover by infusing albumin-bound uniformly 13C palmitic acid and 2H3-leucine for 3 hrs and 2H5-glycerol for 5 hrs to critically ill infants. Simultaneously, we measured serum growth hormones, insulin, C-peptide, thyroid-stimulating hormone, T4, T3, albumin, retinol binding protein (RBP), and prealbumin. Hormone and serum protein levels were also measured in six children when recovered from critical illness. Ten healthy age-matched children served as controls for hormone serum levels comparison. Results Palmitic acid and glycerol turnover were 5.6 ± 2.2 &mgr;mol/kg/min and 12.2 ± 7.3 &mgr;mol/kg/min, respectively, whereas &agr;-ketoisocaproic turnover was 4.9 ± 2.8 &mgr;mol/kg/min. &agr;-Ketoisocaproic turnover positively correlated (R = 0.7, p = .03) with duration of pediatric intensive care unit admission and with prealbumin and RBP serum levels (R = 0.9, p = .001). Insulin-like growth factor binding protein (IGFBP)-2 was significantly higher and IGFBP-3 was significantly lower in critically ill children (p = .03 and p = .04 vs. recovery phase, respectively). No other hormonal differences were found. Serum albumin was significantly lower in sick children. We found a significant correlation between prealbumin and RBP and IGFBP-3 (R = 0.6, p = 0.03 and R = 0.6, p = .04, respectively). &agr;-Ketoisocaproic turnover positively correlated with IGFBP-1 (R = 0.79, p = .01) and did not correlate with insulin-like growth factor I (R = −0.5, p = .15 [ not significant]) No other correlations were found. Lipid turnover measurements did not correlate with any endogenous hormone levels or with duration of critical illness. Conclusion Protein turnover but not lipolysis correlated with a persisting critically ill condition, serum prealbumin, RBP, and plasma IGFBP-1.

Impact of severe sepsis on serum and urinary biomarkers of acute kidney injury in critically ill children: an observational study.

Background/Aims: We hypothesized that sepsis could have an impact on the sensitivity of serum and urinary neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C (CysC) for acute kidney injury (AKI) diagnosis in critically ill children. Methods: Serum NGAL (sNGAL) and urinary NGAL (uNGAL) and CysC were measured daily in the first 48 h from pediatric intensive care unit admission in 11 consecutive critically ill children with severe sepsis; a single measurement was made in a population of 10 healthy controls undergoing minor ambulatory surgery to exclude possible biases in the laboratory methods. Results: uNGAL, serum CysC (sCysC), and urinary CysC (uCysC) levels were significantly increased in patients with septic AKI compared with septic patients without AKI, while sNGAL levels were not significantly different between septic patients with and without AKI. Median serum creatinine levels did not show significant differences between AKI and non-AKI patients. Conclusions: uNGAL, sCysC and uCysC were not altered by sepsis and were good predictors of AKI. In a septic state, sNGAL alone did not discriminate patients with AKI from those without AKI.

Secretory phospholipase A2 pathway during pediatric acute respiratory distress syndrome: A preliminary study

Objective: To verify if secretory phospholipase A2 (sPLA2) is increased in pediatric acute respiratory distress syndrome (ARDS) triggered or not by respiratory syncytial virus infection and to clarify how the enzyme may influence the disease severity and the degree of ventilatory support. Design: Prospective pilot study. Setting: Two academic pediatric intensive care units. Patients: All infants <6 months old hospitalized for severe respiratory syncytial virus bronchiolitis, who developed ARDS (respiratory syncytial virus-ARDS group); all infants <6 months old diagnosed with ARDS secondary to other causes (ARDS group); and infants <6 months old who needed ventilation for reasons other than any lung disease (control group). Interventions: None. Measurements and Main Results: We enrolled six respiratory syncytial virus -ARDS babies, five ARDS babies, and six control infants. The sPLA2 activity and tumor necrosis factor (TNF)-&agr; were significantly higher in the bronchoalveolar lavage of ARDS infants. Worst oxygenation, ventilation, and longer pediatric intensive care unit stay and ventilation time were present in ARDS babies. No differences were found in Clara cell secretory protein and in serum cytokines levels. Because there is no correlation between bronchoalveolar lavage protein content (a marker of permeability) and sPLA2, the enzyme seems mainly produced in the alveoli. TNF-&agr;, the main inductor of sPLA2 expression, significantly correlates with the enzyme level in the bronchoalveolar lavage. Significant positive correlations exist between sPLA2, TNF-&agr; and oxygen need, mean airway pressure, ventilatory index, and the Murrays lung injury score. Negative correlations were also found between sPLA2, TNF-&agr;, and Pao2/Fio2 ratio. Conclusions: The sPLA2 and TNF-&agr; are increased in ARDS and seem correlated with clinical severity, higher oxygen requirement, and more aggressive ventilation. This correlation confirms findings from adult experience and should guide further investigations on pediatric ARDS pathophysiology.

Implantation of a left ventricular assist device as a destination therapy in Duchenne muscular dystrophy patients with end stage cardiac failure: management and lessons learned.

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder, characterized by progressive skeletal muscle weakness, loss of ambulation, and death secondary to cardiac or respiratory failure. End-stage dilated cardiomyopathy (DCM) is a frequent finding in DMD patients, they are rarely candidates for cardiac transplantation. Recently, the use of ventricular assist devices as a destination therapy (DT) as an alternative to cardiac transplantation in DMD patients has been described. Preoperative planning and patient selection play a significant role in the successful postoperative course of these patients. We describe the preoperative, intraoperative and postoperative management of Jarvik 2000 implantation in 4 DMD pediatric (age range 12-17 years) patients. We also describe the complications that may occur. The most frequent were bleeding and difficulty in weaning from mechanical ventilation. Our standard protocol includes: 1) preoperative multidisciplinary evaluation and selection, 2) preoperative and postoperative non-invasive ventilation and cough machine cycles, 3) intraoperative use of near infrared spectroscopy (NIRS) and transesophageal echocardiography, 4) attention on surgical blood loss, use of tranexamic acid and prothrombin complexes, 5) early extubation and 6) avoiding the use of nasogastric feeding tubes and nasal temperature probes. Our case reports describe the use of Jarvik 2000 as a destination therapy in young patients emphasizing the use of ventricular assist devices as a new therapeutic option in DMD.