Uso convencional de surfactante en recién nacidos con enfermedad de membrana hialina / Conventional use of surfactant in newborns with hyaline membrane disease

La enfermedad de membrana hialina se debe a la deficiencia de surfactante en los pulmones de los recién nacidos especialmente los menores de 37 semanas de gestación. El manejo materno con corticoides prenatales en este grupo, disminuye la morbimortalidad asociada a esta patología neonatal. Se analiza desde el punto de la evidencia actualmente existente la administración de surfactante a estos prematuros y se revisa el tipo de surfactante a administrar, cuando es el mejor momento para administrarlo, la dosis y la forma de administrarlo.

Hyaline membrane disease is due to surfactant deficiency in the lungs of newborns, especially those younger than 37 weeks gestation. Maternal management with prenatal corticosteroids in this group reduces the morbidity and mortality associated with this neonatal pathology. The administration of surfactant to these preterm infants is analyzed from the point of the currently existing evidence and the type of surfactant to be administered is reviewed, when is the best time to administer it, the dose and the form of administration.

Chest physiotherapy in preterm infants with lung diseases.

BACKGROUND: In neonatology the role of chest physiotherapy is still uncertain because of the controversial outcomes. METHODS: The aim of this study was to test the applicability in preterm infants of 'reflex rolling', from the Vojta method, in preterm neonates with lung pathology, with particular attention to the effects on blood gases and oxygen saturation, on the spontaneous breathing, on the onset of stress or pain. The study included 34 preterm newborns with mean gestational age of 30.5 (1.6) weeks - mean (DS) - and birth weight of 1430 (423) g - mean (DS) -, who suffered from hyaline membrane disease, under treatment with nasal CPAP (continuous positive airways pressure), or from pneumonia, under treatment with oxygen-therapy. The neonates underwent phase 1 of 'reflex rolling' according to Vojta method three times daily. Respiratory rate, SatO2, transcutaneous PtcCO2 e PtcO2 were monitored; in order to evaluate the onset of stress or pain following the stimulations, the NIPS score and the PIPP score were recorded; cerebral ultrasound scans were performed on postnatal days 1-3-5-7, and then weekly. RESULTS: In this population the first phase of Vojta's 'reflex rolling' caused an increase of PtcO2 and SatO2 values. No negative effects on PtcCO2 and respiratory rate were observed, NIPS and PIPP stress scores remained unmodified during the treatment; in no patient the intraventricular haemorrhage worsened in time and none of the infants developed periventricular leucomalacia. CONCLUSIONS: Our experience, using the Vojta method, allows to affirm that this method is safe for preterm neonates, but further investigations are necessary to confirm its positive effects and to evaluate long-term respiratory outcomes.

Auditory neuropathy associated with postnatally acquired cytomegalovirus infection in a very preterm infant.

Neurosensory hearing loss is a well-known complication of antenatally acquired cytomegalovirus (CMV) infection. We here report an infant who developed auditory neuropathy after a postnatally acquired CMV infection. Infection probably occurred through ingestion of infected breast milk. Following a cochlear implant, there is normal language perception and a mildly delayed language expression at age 4. We speculate that the long-term effects of perinatal CMV infections are more dependent on the postconceptional age at which infection occurs than on whether the infection occurs antenatally or postnatally. An early acquired neonatal CMV infection in very preterm infants may therefore have long-term neurological sequelae, including auditory deficits.

Surfactant Metabolism Dysfunction and Childhood Interstitial Lung Disease (chILD).

Surfactant deficiency and the resultant respiratory distress syndrome (RDS) seen in preterm infants is a major cause of respiratory morbidity in this population. Until recently, the contribution of surfactant to respiratory morbidity in infancy was limited to the neonatal period. It is now recognised that inborn errors of surfactant metabolism leading to surfactant dysfunction account for around 10% of childhood interstitial lung disease (chILD). These abnormalities can be detected by blood sampling for mutation analysis, thereby avoiding the need for lung biopsy in some children with chILD.

[Dynamic change in respiratory mechanic dynamics and its clinical significance during mechanical ventilation in hyaline membrane disease of children].

OBJECTIVE: To explore the characteristics of changes in respiratory mechanic dynamics and clinical significance in hyaline membrane disease (HMD) under mechanical ventilation. METHODS: One hundred and twenty-six newborns with HMD undergoing mechanical ventilation were divided into two groups: complication group with 43 cases and no-complication group with 83 cases. The blood gases and indices of respiratory mechanic dynamics were monitored 2, 24, 48 and 72 hours after the first ventilation and before the first weaning from ventilation. RESULTS: Pulmonary compliance [(0.55+/-0.10) ml.cm H(2)O(-1).kg(-1), (0.43+/-0.10) ml.cm H(2)O(-1).kg(-1)] and minute volume [MV, (0.65+/-0.10) L/min, (0.62+/-0.30) L/min] were elevated compared with that after ventilation for 2-72 hours, however the oxygenation index [OI, (10.2+/-1.9)mm Hg vs. (13.6+/-4.3) mm Hg] significantly lower. The compliance and MV in no-complication group were higher than that in complication group 24 and 48 hours after ventilation. There were no differences in the airway resistance and lung inflation index between two groups. The pulmonary compliance was negatively correlated with OI (r=-0.208, P<0.01) and corrected with MV (r=0.218, P<0.01). In no-complication group, all cases ventilation was weaned successfully at once in all the patients,and their mean compliance and MV were (0.55+/-0.10) ml.cm H(2)O(-1).kg(-1) and (0.65+/-0.20) L/min respectively. However, in complication group, weaning failed 38 patients, their mean compliance and MV were (1.03+/-0.30) ml.cm H(2)O(-1).kg(-1) and (0. 33+/-0.30) L/min respectively. CONCLUSION: Respiratory mechanic dynamics monitoring is beneficial in evaluating the severity of hyaline membrane disease and complications, guiding mechanical ventilation management and weaning.

[High-frequency oscillatory lung ventilation in complex therapy for congenital pneumonia and hyaline membrane disease in newborns].

Fifty-eight neonatal infants with hyaline membrane disease (HMD) and congenital pneumonia were examined in the critical status. In 32 of them, high-frequency oscillatory lung ventilation (HFOLV) was employed. The use of HFOLV was found to reduce the length of stay in neonates on toxic oxygen concentrations by more than 2 times and to accelerate the normalization of ventilation-perfusion relationships by more than 3 times. A study of the basic parameters of central and regional hemodynamics showed that HFOLV failed to affect the patients' hemodynamic status. The efficiency of correction of severe respiratory disorders in neonatal infants with HMD was ascertained to increase with the combined use of the Russian surfactant and HFOLV. A formula was developed to calculate the starting amplitude of oscillations when HFOLV was employed. The maximum allowable values of mean airway pressure at which HFOLV could be discontinued were determined, which prevented the regimens from toughening when HFOLV was changed to the routine artificial ventilation. The use of HFOLV was established to reduce the risk of severe cerebral structural and vascular lesions and mortality rates.

The association between hyaline membrane disease and preeclampsia.

OBJECTIVE: The purpose of this study was to determine whether hyaline membrane disease is increased in newborn infants who are born to women with preeclampsia compared with control subjects. STUDY DESIGN: This was a historic cohort study of deliveries between 24 and 37 weeks of gestation at the Medical University of South Carolina from 1996 through 2002. Singleton infants who were born to women with preeclampsia were compared with nonpreeclamptic control subjects. The incidence of hyaline membrane disease was compared by chi 2 analysis and Fisher exact test, with significance at a probability value of <.05. Logistic regression analysis was performed to address potential confounders. RESULTS: There were 814 women with preeclampsia and 3021 control subjects. When we controlled for confounding factors, there was a significant increase in the incidence of hyaline membrane disease in the preeclamptic group overall (odds ratio, 1.35; 95% CI, 1.03-1.78). The risk was more pronounced in neonates who were born at 32 weeks of gestation (odds ratio, 1.93; 95% CI, 1.28-2.91). CONCLUSION: The risk of hyaline membrane disease in neonates at < 32 weeks of gestation is increased in patients with preeclampsia. This supports the contention that fetal lung maturity is not accelerated in preeclampsia.

Gelatinase activities in the airways of premature infants and development of bronchopulmonary dysplasia.

Matrix-degrading metalloproteinases may play a role in the pathophysiology of bronchopulmonary dysplasia (BDP). We, therefore, evaluated correlations between gelatinase activities [metalloproteinase (MMP)-2 and MMP-9] or tissue inhibitor of metalloproteinase (TIMP)-1 levels present in the airways during the initial phase of hyaline membrane disease and the onset of BPD. Tracheal aspirates were obtained within 6 h of birth (day 0) from 64 intubated neonates with a gestational age < or =30 wk. Forty-five neonates were resampled on day 3 or 5. Total MMP-2 level measured by zymography fell with time, whereas total MMP-9 level and TIMP-1 levels, assayed by ELISA, increased; the MMP-9 increase correlated with the increase in airway inflammatory cell numbers. Among the parameters measured on day 0, 3, or 5, lower total MMP-2 level, lower birth weight, and higher fraction of inspired oxygen on day 0 were significantly and independently associated with the development of BPD. In conclusion, MMP-9 level and TIMP-1 levels increased after birth but are not linked to BPD outcome. In contrast, low MMP-2 level at birth is strongly associated with the development of BPD.

Pulmonary oxygen consumption: a hypothesis to explain the increase in oxygen consumption of low birth weight infants with lung disease.

OBJECTIVE: We determined pulmonary oxygen consumption (VO2lung) in low-birthweight infants with acute lung disease to help explain the greater whole-body oxygen consumption (VO2wb) in these infants with than in those without lung disease. METHODS AND MATERIALS: Eleven infants (birth weight 1,076+/-364 g; gestational age 28+/-3 weeks) undergoing mechanical ventilation for respiratory distress syndrome were studied in their first week of life. We measured VO2wb by indirect calorimetry and simultaneously determined systemic oxygen uptake (VO2Fick) as the product of cardiac output (echocardiography) and the arterial-mixed venous oxygen content difference (cooximetry) assuming that VO2wb-VO2Fick accounts for VO2lung. Right atrial blood samples were used to determine mixed venous oxygenation, and infants were excluded if samples returned saturations greater than 89%. RESULTS: VO2lung was 1.92+/-1.74 ml x kg(-1) x min(-1), representing 25% of their VO2wb (7.58+/-1.48 ml x kg(-1) x min(-1)). VO2lung was not correlated with clinical measures of acute disease severity. However, infants with the most severe changes on follow-up radiography (Edwards score 5 as assessed by radiologist blinded for VO2 data) all had a VO2lung level greater than 2.0 ml x kg(-1) x min(-1). CONCLUSION: VO2lung can account for the elevated metabolic rate in low-birthweight infants with lung injury. We speculate that this reflects in part inflammatory pulmonary processes and may herald chronic lung disease.

The science of neonatal high-frequency ventilation.

Despite improvements in respiratory care, ventilator-induced lung injury remains an important cause of morbidity and mortality in neonates who require assisted ventilation. Animal data clearly demonstrate that high-frequency ventilation can be used successfully to reduce lung injury in experimental models of acute lung injury. These models and human research show that the efficacy of high-frequency ventilation is dependent on optimizing functional residual capacity and avoiding lung overinflation. When used with a strategy that promotes lung recruitment, high-frequency ventilation effectively reduces the occurrence of chronic lung disease and is not associated with significant brain injury. When used with a strategy that allows the lung to collapse or is associated with hyperventilation, however, high-frequency ventilation does not reduce lung injury and is associated with significant brain injury. Like every tool we use to support critically ill neonates, high-frequency ventilation needs a careful carpenter. As therapies and health care strategies evolve, there remains nothing more important than the health care team at the bedside. Critical evaluation of the patient and his or her response to the therapy being offered is essential to promotion of the patient health outcome.

Effects of inhaled nitric oxide on gas exchange and acute lung injury in premature lambs with moderate hyaline membrane disease.

OBJECTIVE: The purpose of this study was to examine whether inhaled nitric oxide (iNO) may change lung injury in moderate hyaline membrane disease (HMD). METHODS: Fifteen moderately premature lambs (128 days gestation, term=147 days) were randomly assigned to treatment with 20 ppm inhaled NO (n=7) from the onset of ventilation or control (n=8). Except for inhaled NO, treatments were intentionally similar to those applied in clinical situations. After porcine surfactant administration (Curosurf, 100 mg/kg), mechanical ventilator settings were modified during the course of the study to maintain PaCO(2) between 40 and 50 mmHg and post-ductal SpO(2) between 90 and 95%. The main studied parameters were gas exchanges parameters, respiratory mechanics (static compliance and functional residual capacity) and pulmonary vascular permeability and/or filtration rate indices. RESULTS: We found that 20 ppm of inhaled NO for 5 h significantly reduce ventilatory and oxygen requirements, but only during the first hour of mechanical ventilation. No increase in extravascular lung water content (5.41+/-0.96 vs. 5.46+/-1.09 ml/g bloodless dry lung in the control group and in the NO group, respectively) and no impairment of the respiratory mechanics could be found in the NO-treated group. However, inhaled NO increased the albumin lung leak index in this model (6.09+/-1.51 in the NO-treated group vs. 4.08+/-1.93 in the control group; P<0.05). CONCLUSIONS: Our results do not therefore support a detrimental effect of short-term exposure to low doses of NO inhalation in moderate HMD. However, it may induce an increase in lung vascular protein leakage. The pathophysiological consequences of this finding remain to be elucidated.

Pulmonary outcome in extremely low birth weight infants.

OBJECTIVE: To determine whether infants with hyaline membrane disease (HMD) superimposed on immature lung disease (ILD) have more abnormal lung function and respiratory drive during the evolution of chronic neonatal lung disease (CNLD) in extremely low birth weight infants (ELBW; <1000 g). METHODS: We measured lung mechanics (respiratory frequency, tidal volume, minute ventilation, lung resistance, lung compliance, lung impedance, and work of breathing per minute) and respiratory drive (airway opening pressure 100 milliseconds after initiation of breath [P(0.1)] and maximal inspiratory pressure generated during airway occlusion) on 3 occasions before term in 24 ELBW infants. RESULTS: Ten infants with ILD (mean [95% CI] gestation: 24.3 weeks [23.1,25.4]; birth weight: 675 g [553,798]) were studied at 27, 31, and 35 weeks of postconceptional age and 14 infants with HMD superimposed on ILD (gestation: 25.1 weeks [24.4,25.9]; birth weight: 687 g [601,773]) were studied at 28, 32, and 35 weeks of postconceptional age. There were no statistically significant differences between the groups for respiratory frequency, tidal volume, minute ventilation, lung resistance, lung compliance, lung impedance, work of breathing per minute, P(0.1), and maximal inspiratory pressure generated during airway occlusion. With increasing age, both groups demonstrated increased respiratory drive as measured by P(0.1) without significant changes in respiratory frequency or CO(2). Work of breathing per minute increased in the HMD group with age and was higher in extubated subjects. A similar trend with age was demonstrated in ILD infants. Regardless of whether the initial lung disease was ILD alone or HMD + ILD, ELBW infants developed a mildly reduced lung compliance/kg (.8-1.1 mL/cm.H(2)O/kg) and high lung resistance (75-125 cm.H(2)O/L/second) pattern of CNLD, which changed little after 3 weeks of age. Survival to 6 months was 23/24 (96%). Oxygen dependency was 16/24 (67%) at 35 weeks, yet only 5/23 (22%) survivors required oxygen at discharge from the neonatal unit (43 weeks). CONCLUSIONS: The visco-elastic and flow-resistive properties of the lungs in ELBW infants with CNLD remain only mildly abnormal, suggesting a more favorable prognosis for lung function in later years than previously reported.

Effects of birthweight and oxygen supplementation on lung function in late childhood in children of very low birth weight.

Impaired respiratory function has been found frequently in ex-premature children, but it is unclear which specific factors influence this impairment the most. The aim of this study was to determine the importance of the contributions of birth weight, gestational age, neonatal respiratory disease, and its treatment on subsequent childhood lung function at age 11 years in a cohort of children of very low birth weight (VLBW; 2,000 g) of similar age. VLBW children were shorter and lighter than controls (P < 0.0001) at 11 years of age, and had reduced expiratory flows (P < 0.00001) and forced vital capacities (P < 0.001). The residual volume to total lung capacity ratio (RV/TLC ratio) was increased (P < 0.00001), while total lung capacity (TLC) remained unchanged. Those with bronchopulmonary dysplasia (BPD) had the lowest mean expiratory flows. Males had lower expiratory flows than females. On univariate analysis, gestational age by itself accounted for 8.8% of the explained variance in FEV(1) at 11 years of age, but birth weight accounted for 16% on its own; both together accounted for a further 0.2% (16.2%), suggesting that the latter was the dominant factor. On multivariate analysis, the contribution of birth weight and gestational age was small, and the best predictors at 11 years of age, which together explained 43.4% of the total variance in FEV(1), were log days of supplemental oxygen (9.6%) and a reported history of asthma (10.8%). For FEF(25-75), these predictors explained 7.2% and 13.4%, respectively, of the total explained variance of 40.6%. The relation between neonatal oxygen supplementation and childhood FEV(1) was such that up to 20 days of supplemental oxygen had little effect on subsequent FEV(1) at 11 years of age, but each additional week of supplemental oxygen after that time was associated with a progressive reduction in FEV(1) of 3%. These data confirm the significant role of supplemental oxygen in the neonatal period and a history of asthma on the subsequent reduction of expiratory flows in VLBW children. Birth weight was a more important prenatal factor than gestational age, but both were of lesser predictive significance than either supplemental oxygen or a reported history of asthma.

Cardiopulmonary exercise performance in prematurely born children.

Prematurely born children have reduced peak VO2 compared with their peers, inferentially attributed to ventilatory limitation. The primary purpose of this study was to compare exercise ventilation and cardiac output in a sample of childhood survivors of lung disease of prematurity with those of a control group to elucidate reasons for lower peak VO2. A secondary aim was to describe and compare the ventilatory response to incremental exercise. Thirty-two children, aged 8-9 y, were recalled for lung function and progressive exercise tests. Fifteen of them also performed submaximal exercise with measurement of cardiac output (indirect [CO2] Fick) and physiologic dead space. Results were compared with those of term-born, age- and sex-matched, control children. Pulmonary function tests showed mild airflow limitation. Peak VO2 was lower in prematurely born children compared with control children, and was correlated with lean body mass. Their heart rate-VO2 relationship and stroke volume were similar to that of term-born control children. Children with a history of bronchopulmonary dysplasia and hyaline membrane disease as infants exhibited greater exercise hyperpnea than did healthy control children, because of higher breathing frequency, and maintained lower end-tidal PCO2 during submaximal exercise. Physiologic dead space normalized for body weight was similar in preterm and term-born children. Lower peak VO2 in this population is not caused by cardiopulmonary factors, but is best predicted by lean body mass. Ventilation did not limit exercise performance, although it appears that breathing during exercise is regulated differently in prematurely born children than in term-born children.

A rat model of acute respiratory distress syndrome (ARDS) Part 2, influence of lavage volume, lavage repetition, and therapeutic treatment with rSP-C surfactant.

UNLABELLED: The influence of lavage volume, and lavage repetition with physiological saline solution (groups 1-3: 3x4, 4x4, 5x4, groups 7-9: 3x8, 5x8, 7x8, mL per animal) was studied in a rat lung lavage model of the acute respiratory distress syndrome (ARDS). Anesthetized and tracheotomized rats (12 rats/group) were pressure-controlled ventilated with 100% oxygen at a respiratory rate of 30 breaths/min, inspiration: expiration ratio of 1:2, peak inspiratory pressure of 28 cm H2O at positive end-expiratory pressure of 8 cm H2O during the whole experimental period. To investigate the influence of therapeutic treatment, a recombinant surfactant protein C (rSP-C) containing surfactant was used. Therefore, rats which received a lavage of 4x4 mL per animal (groups 4 to 6) or 7x8 mL per animal (groups 10-12) were treated intratracheally with surfactant doses of 12.5, 25, or 100 mg phospholipids (PL) per kg body weight (bw). In all groups, partial arterial oxygen pressures (PaO2, mm Hg) and partial arterial carbon dioxide pressures (PaCO2, mm Hg) were determined 30 min before, directly after, and 5, 30, 60, 90, 120, 150, 180, and 210 min after the last lavage. Additionally, animals were euthanized 210 min after the last lavage for semiquantitative histopathological grading of coded lung slides. Grading was performed with respect to the severity of hyaline membrane formation (HM), margination and infiltration of polymorphonuclear neutrophil leukocytes (PMNL) into the lung alveoli and interstitial and intraalveolar edema (E). The intrapulmonary distribution of intratracheally applied rSP-C was estimated in selected lung slides stained with polyclonal anti-rSP-C antibody and was compared to unlavaged control rats and unlavaged rats which received 100 mg/kg bw rSP-C. The repetitive lavage depleted the lung from its natural surfactant resources leading to a pathophysiological cascade similar to that of the acute respiratory distress syndrome. PaO2 levels and HM formation showed a lavage-induced decrease. Both changes were significantly dependent on the repetition and volume of the lavage; however, the parameters PMNL and E did not show such a dependence. Treatment with rSP-C surfactant significantly improved oxygenation and reduced HM-formation in a dose-dependent manner independent from the lavage volume. All doses of rSP-C surfactant showed no clear influence on the parameters PMNL and E independently from the lavage volume. In lavaged rat lungs (ARDS-model), the exogenously applied rSP-C was distributed homogeneously along the alveolar lining. Unlavaged rats that received a similar dose of rSP-C showed a marked inhomogeneous extracellular distribution, mainly associated with larger bronchi, while the type II pneumocytes were stained positively in unlavaged control and unlavaged rSP-C treated rats. CONCLUSION: This model mimics very closely the wide spectrum of the clinical situation of human acute lung injury (ALI) because the variation of lavage volume and repetition lead to reproducible different severity grades and states of ALI. The significant reduction of pathognomic changes due to treatment with rSP-C surfactant showed that this is a useful model to estimate the influence of therapeutic concepts in ALI and ARDS.

[For or against the early use of nasal continuous positive pressure and exogenous surfactant in hyaline membrane disease. Physiopathologic arguments]. / Pour ou contre une utilisation précoce de la pression positive continue nasale et du surfactant exogène au cours de la maladie des membranes hyalines. Arguments physiopathologiques.

The use of nasal CPAP in the treatment of respiratory distress syndrome in very premature newborns follows pathophysiological basis. The authors emphasize the usefulness of nasal CPAP and surfactant in the treatment of respiratory distress syndrome. The aim of this strategy is to reduce alveolar atelectasis, thus reducing the incidence and the severity of respiratory distress syndrome, together with a possible reduction of the incidence of bronchopulmonary dysplasia.

Haemodynamic effects of altering arterial oxygen saturation in preterm infants with respiratory failure.

AIMS: To examine the haemodynamic effects of brief alteration in arterial oxygenation in preterm infants with respiratory failure. METHODS: Eighteen preterm infants with respiratory failure, aged 9-76 hours, underwent detailed Doppler echocardiographic assessment at 86%, 96%, and 100% SaO2, achieved by altering the FIO2. Sixteen were receiving intermittent positive pressure ventilation, median FIO2 0.45 (0.20-0.65), median mean airway pressure 12 cm H2O (0-20). SaO2 was stable for 15 minutes at each stage. Four parameters of pulmonary arterial pressure were measured: peak velocity of tricuspid regurgitation and peak velocity of left to right ductal flow, TPV:RVET ratio and PEP:RVET ratio, measured at the pulmonary valve, along with flow velocity integrals at the aortic and pulmonary valves, and systemic arterial pressure. Ductal size was graded into closed, small, moderate, large with imaging, pulsed and continuous wave Doppler. RESULTS: Between 86% and 96% SaO2, there were no consistent changes, but in three of the 12 with a patent ductus arteriosus (PDA) there was ductal constriction, with complete closure in one. Between 96% and 100% SaO2, peak ductal flow velocity rose significantly in four of eight with a PDA. Ductal constriction occurred in four infants; in three this was associated with a significant fall in aortic flow integral and a rise in aortic pressure (4-6 mm Hg). Overall, 11 infants went from 86% to 100% SaO2 and pulmonary arterial pressure fell significantly in seven. CONCLUSION: A brief rise in SaO2 within the range maintained by most neonatal units can cause significant ductal constriction. The fall in pulmonary arterial pressure with 100% SaO2 seen in most infants was associated with a fall in pulmonary blood flow (or no change), rather than a rise, indicating that the dominant haemodynamic effect was ductal constriction rather than pulmonary vasodilation.