Tracheal ligation increases mitogen-activated protein kinase activity and attenuates surfactant protein B mRNA in fetal sheep lungs

Background: Tracheal ligation has been shown to accelerate fetal pulmonary growth in normal and hypoplastic lungs. Our aim was to study the effects of tracheal ligation on established molecular markers of growth and differentiation [mitogen-activated protein (MAP) kinase] and maturity [surfactant protein B (SPB) and fatty acid synthase (FAS)].Materials and methods: Tracheal ligation was performed on four 100-day-gestation fetal sheep, with four age-matched fetuses undergoing maternal laparotomy and hysterotomy as control. Lungs from surviving fetuses (n = 2 in each group) were harvested after 4 days and frozen in liquid nitrogen. Protein lysates were prepared, and MAP kinase enzymatic assays [extracellular signal regulated protein kinase (ERK)-1 and -2] and Western blots were performed. Total RNA was isolated, and a fetal sheep lung cDNA library was created. The sheep SPB and FAS genes were cloned and sequenced. Northern blots were performed with the new clones, normalizing to beta-actin.Results: Tracheal ligation lungs contained a larger volume of fluid (40 ml) compared with age-matched controls (8 ml). MAP kinase enzymatic ERK-1 activity was increased and SPB mRNA expression was reduced in fetal lungs after tracheal ligation. Neither ERK-2 enzymatic activities and FAS mRNA nor ERK protein levels were affected by tracheal ligation, by Western blot analysis.Conclusion: Tracheal ligation-induced fetal lung growth may be mediated in part via the MAP kinase pathway. Expression of SPB mRNA is attenuated by tracheal ligation, whereas FAS, one of the key enzymes that synthesizes the lipid portion of surfactant, is not affected

Diltiazem reduces pulmonary arterial pressures in recurrent pulmonary hypertension associated with pulmonary hypoplasia

Background/purpose: Recurrent pulmonary hypertension in the neonatal population is an unusual event with dire consequences. Pulmonary hypertension seen in association with pulmonary hypoplasia may be refractory to conventional medical management. The effect of the calcium channel antagonist diltiazem was studied in five patients with severe pulmonary hypertension.Methods: A retrospective review of the hospital records was performed to determine the efficacy of diltiazem for refractory pulmonary hypertension. All five patients experienced and did not respond to maximal conventional therapy, which included inhaled nitric oxide, intravenous nitrates, and extracorporeal membrane oxygenation (ECMO). Right ventricular pressures were determined by transthoracic echocardiograms and were used to document improvement in the pressure gradients. Statistical analyses were performed using a paired Student\u27s ttest. A P value of less than .05 was considered significant.Results: Diltiazem significantly reduced the right ventricular systolic pressure (RVSP) from 82 +/- 8.4 mm Hg to 58.4 +/- 7 mm Hg (P = .008). Two patients died; one had a large ventricular septal defect, and the other suffered multisystem organ failure secondary to sepsis. The surviving patients were weaned off diltiazem and did not experience recurrent pulmonary hypertension.Conclusions: In cases of pulmonary hypoplasia with recurrent pulmonary hypertension, diltiazem may be considered as a therapy. A multicenter prospective trial is advocated

Tracheal resection and reanastomosis in the neonatal period

Background/purpose: Severe congenital tracheal stenosis is rare. Most of these can be managed conservatively before elective repair. Focal tracheal stenosis has been treated with resection of the involved trachea and primary reanastomosis in older infants. The authors found no reports of repair of this lesion in neonates. Two patients are presented with severe respiratory failure on the first day of life that required extracorporeal life support (ECLS) who underwent successful tracheal resection and reanastomosis (TRR) during the first week of life.Methods: A retrospective review was conducted.Results: Both babies had severe pulmonary hypertension and carbon dioxide retention despite maximal therapy and were placed on ECLS shortly after transfer. One had an isolated stenosis of the upper trachea, and the other had agenesis of the right lung, esophageal atresia with tracheoesophageal fistula, and a tracheal stenosis at the end of a short trachea with a long, narrow left bronchus. Both underwent diagnostic studies and had surgical repair while on ECLS at day 3 and 7 of life without bleeding complications. They were weaned off ECLS 1 and 8 days after surgery. One patient was extubated and did well. The other was extubated transiently, but required a tracheostomy because of left mainstem bronchomalacia. Both are alive and well at 18 and 38 months of age, with no narrowing of the repairs.Conclusion: In the setting of severe respiratory failure requiring ECLS support, TRR can be performed safely and successfully in the neonate with focal tracheal stenosis

Extracorporeal membrane oxygenation for nonneonatal acute respiratory failure

Hypothesis: Extracorporeal membrane oxygenation (ECMO) is effective in nonneonatal acute respiratory failure under certain circumstances.Design: Retrospective medical record review.Setting: The intensive care unit of a tertiary care hospital.Patients: Thirty-four nonneonatal patients (mean age, 22 years; range, 8 days to 56 years), with ratios of the PaO2 to the fraction of inspired oxygen persistently below 70, who were treated with ECMO after maximal ventilator therapy had failed (mean time of ventilator therapy, 6.9 days; range, 1-41 days). The mean ECMO duration was 304 hours (range, 56-934 hours). Patients were grouped into 7 categories based on their diagnosis: sepsis or sepsis syndrome (n = 3), bacterial or fungal pneumonia (n = 10), viral pneumonia (n = 5), trauma or burn (n = 2), inhalation injury without burn (n = 1), immunocompromised state (due to transplantation or chemotherapy) (n = 8), and acute respiratory failure of unknown origin (n = 5).Main outcome measure: Survival to hospital discharge following ECMO therapy.Results: Overall survival was 53% (18 patients). All 6 patients (100%) with viral pneumonias or isolated inhalation injuries survived. Of 13 patients with bacterial pneumonia, sepsis, or sepsis syndrome not complicated by multiorgan failure, 10 (77%) survived. In contrast, all but 1 of the immunocompromised patients died. Survival in patients who were intubated for less than 9 days before ECMO was 64%, whereas survival fell precipitously to 22% for patients who experienced mechanical ventilation for 9 or more days before the implementation of ECMO. Finally, the proportion of patients who died while receiving ECMO therapy was greater when the ECMO duration exceeded 300 hours (62% vs. 38%; P\u3c.05).Conclusions: Nonneonatal survival with ECMO therapy is strongly dependent on the diagnosis. Pre-ECMO intubation for less than 9 days had little effect on survival. Survival rates decreased when the length of time of receiving ECMO exceeded 300 hours

Prenatal vitamin E treatment improves lung growth in fetal rats with congenital diaphragmatic hernia

Purpose: Congenital diaphragmatic hernia (CDH) is associated with pulmonary hypoplasia. To discover factors that would accelerate fetal lung growth, the authors developed models of hypoplasia, found that antioxidants improved lung growth in vitro, and then proceeded to in vivo studies.Methods: Timed-pregnant rats were fed nitrofen (100 mg) on gestational day 9.5 (term, 22), and fetal lungs were harvested at day 13.5 and placed in organ culture in serum-free media with (n = 10) or without (n = 9) additional vitamin E (0.134 IU/mL). Camera lucida tracings were made daily on live, unstained lungs for 4 days, scanned, digitized, and analyzed for multiple growth parameters. Similar nitrofen-exposed rats were fed an optimized total dose of 150 IU vitamin E (n = 19) or olive oil (n = 13) from days 16.5 to 20.5, and fetal lungs were harvested at day 21.5, weighed and fixed for histology, or homogenized and biochemically analyzed.Results: Vitamin E accelerated hypoplastic fetal lung growth in vitro as measured by area, perimeter, lung bud count, perimeter over square root area, and fractal dimension. In vivo vitamin E significantly increased lung weights, total DNA, and protein contents.Conclusions: Vitamin E accelerates hypoplastic fetal rat lung growth and complexity in vitro, and prenatal vitamin E treatment in vivo improves pulmonary hypoplasia in fetal rats with CDH

Decreased mitogen activated protein kinase activities in congenital diaphragmatic hernia-associated pulmonary hypoplasia

Background/purpose: The mechanisms that cause pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH) currently are unknown. The authors proposed that the reduced size and immaturity of these lungs may be associated with differences in the levels of mitogen activated protein (MAP) kinase phosphorylation (extracellular signal regulated protein kinases, ERK-1 and -2).Methods: ERK-1 activities were measured using immune-complex kinase assays on fetal whole-lung lysates obtained from both nitrofen and olive oil-treated (control) pregnant rats. In addition, ERK-1 and ERK-2 functional activities were estimated by semiquantitative Western blot analysis, using an antibody specific for the diphosphorylated (dp-ERK, activated) forms of the enzymes.Results: ERK-1 activities, measured using immune-complex kinase assays, were reduced in CDH lungs compared with olive oil-treated controls (P \u3c.02). In addition, dp-ERK-1 and dp-ERK-2 levels were found to be reduced in CDH lungs compared with controls (dp-ERK-1, P =.003; dp-ERK-2, P =.04), whereas ERK-1 and ERK-2 protein levels were unchanged.Conclusions: The lower values of ERK-1 activity and reduced amounts of dp-ERK-1 and dp-ERK-2 in lung tissue from CDH animals, suggests that ERK-1 and ERK-2 activities are reduced in pulmonary hypoplasia associated with CDH. The observed reduction in ERK-1 and ERK-2 activities implicates attenuated cell signaling upstream of the ERK-1 and -2 enzymes