Doppler assessment of pulmonary artery pressure and extrapulmonary shunting in the acute phase of hyaline membrane disease

Association of umbilical venous catheters vs peripherally inserted central catheters with death or severe intraventricular hemorrhage among preterm infants < 30 weeks: A randomized clinical trial

BACKGROUND

Umbilical venous catheters (UVCs) or peripherally inserted central catheters (PICCs) are routinely inserted in preterm infants for total parenteral nutrition and medications. We aimed to examine whether the rates of severe intraventricular hemorrhage (IVH) or death vary among preterm infants receiving UVCs compared to PICCs.

METHODS

This randomized controlled trial included preterm infants <  30 weeks gestation assigned after birth to either UVC placement group or PICC group.

RESULTS

A total of 233 preterm infants (117 infants in UVC group, 116 infants in PICC group) were randomized and collected data was available for intention-to-treat analysis. There were no differences in baseline population characteristics. Severe IVH occurred in 16 infants (13.6%) in the UVC group and 11(9.5%) in the PICC group (risk difference [RD], 4.1% [5% CI, -4 to 12.3]; P = 0.42). The incidence of death before 28 days of life did not differ significantly between groups (10 [8.5% ] in UVC vs 6 [5.1%] in PICC; RD, 3.4% [95% CI, -3.0 to 9.84]; P = 0.44). Seventeen percent (20/117) of the UVC group died or developed severe IVH compared with 12% (14/116) of the PICC group (risk difference, 5% [95% CI, -4.01 -14.06]; P = 0.36). The incidence of necrotizing enterocolitis (NEC) was significantly higher in the UVC group infants than in the PICC group infants (7.7% vs. 1.7%); p = 0.03.

CONCLUSIONS

The incidence of severe IVH or death did not differ significantly among preterm m infants <  30 weeks gestation subjected to UVC or PICC placement. Early inotropic support was a significant risk factor for the development of severe IVH. UVC maybe an additional risk factor for the development of NEC, but further research is required to validate this finding.

Controversies in neonatology: The efficacy of inhaled nitric oxide in preterm infants with persistent pulmonary hypertension

Introduction: There is limited and conflicting information in literature regarding use of inhaled nitric oxide (iNO) in preterm infants. In this study we examined the characteristics of preterm infants with persistent pulmonary hypertension (PHT) who responded and did not respond to iNO therapy . Material and Method: We retrospectively reviewed data of infants

Assessing pulmonary circulation in severe bronchopulmonary dysplasia using functional echocardiography

Pulmonary hypertension (PH) is common in infants with severe bronchopulmonary dysplasia (BPD) and increases the risk of death. The objectives of this preliminary study were to compare responses of pulmonary circulation parameters to 100% oxygen (O₂) and inhaled nitric oxide (iNO) in infants with BPD and PH using echocardiography. Responses between fetal growth restriction (FGR) and appropriate for gestational age infants were compared. Ten infants <28 weeks GA at birth were assessed at ≥36 weeks corrected gestation. Baseline echocardiography1 was performed which was repeated (echocardiography2) after 30 minutes of O₂. After a gap of 2–3 hours, iNO was administered for 15 minutes and echocardiography3 was performed, followed by iNO weaning. The gestation and birthweight of the cohort were 25.9 ± 1.6 weeks and 612 ± 175 g. Assessments were performed at 38.7 ± 1.4 weeks corrected gestational age. Baseline time to peak velocity: right ventricular ejection time (TPV/RVETc) increased from 0.24 ± 0.02 to 0.27 ± 0.02 (O₂, p = .01) and 0.31 ± 0.03 (iNO, p < .001), indicating a decrease in pulmonary vascular resistance [PVR]. Baseline tricuspid annular plane systolic excursion (TAPSE) increased from 8.1 ± 0.6 mm to 9.3 ± 0.7 mm (O₂, p = .01) and 10.5 ± 1.1 mm (iNO, p = .0004), indicating improved ventricular systolic performance. Percentage change for all parameters was greater with iNO. Significant correlations between cardiac performance and PVR were noted. FGR infants noted higher baseline PVR (TPV/RVETc, 0.21 ± 0.02 vs. 0.25 ± 0.01, p = .002), lower ventricular performance (TAPSE, 7 ± 1.2 mm vs. 8.6 ± 6 mm, p = .003), and lower percentage change with O₂ and iNO. A reactive component of pulmonary circulation provides real‐time physiological information, which could rationalize treatment decisions.

Echocardiographic Assessment of Right Ventricular Afterload in Preterm Infants: Maturational Patterns of Pulmonary Artery Acceleration Time Over the First Year of Age and Implications for Pulmonary Hypertension

BACKGROUND

Assessment of pulmonary hemodynamics is critical in the diagnosis and management of cardiopulmonary disease of premature infants, but reliable noninvasive indices of pulmonary hemodynamics in preterm infants are lacking. Because pulmonary artery acceleration time (PAAT) is a validated noninvasive method to assess right ventricular (RV) afterload in infants and children, the aim of this study was to investigate the maturational changes of PAAT measures in preterm infants over the first year of age and to discern the impact of typical cardiopulmonary abnormalities on these measures.

METHODS

In a prospective multicenter study of 239 preterm infants (<29 weeks at birth), PAAT was assessed at days 1, 2, and 5 to 7, at 32 and 36 weeks' postmenstrual age, and at 1-year corrected age. To account for heart rate variability, PAAT was adjusted for RV ejection time. Premature infants who developed bronchopulmonary dysplasia or had echocardiographic findings of pulmonary hypertension were analyzed separately. Intra- and interobserver reproducibility analysis was performed.

RESULTS

PAAT was feasible in 95% of the image acquisitions, and there was high intra- and interobserver agreement (intraclass correlation coefficients > 0.9 and coefficients of variation < 6%). In uncomplicated preterm infants (n = 103 [48%]) PAAT and PAAT adjusted for RV ejection time increased longitudinally from birth to 1-year corrected age (P < .001) and were linearly associated with gestational age at birth (r = 0.81 and r = 0.82, P < .001) and increasing postnatal weight and postnatal age (r > 0.81, P < .001). PAAT measures were significantly reduced (P < .001) in infants with bronchopulmonary dysplasia and/or pulmonary hypertension (n = 119 [51%]) beyond 1 week of age.

CONCLUSIONS

PAAT measures increase in preterm infants from birth to 1-year corrected age, reflective of the physiologic postnatal drop in RV afterload. Bronchopulmonary dysplasia and pulmonary hypertension have a negative impact on PAAT measures. By demonstrating excellent reliability and establishing reference patterns of PAAT in preterm infants, this study suggests that PAAT and PAAT adjusted for RV ejection time can be used as complementary parameters to assess physiologic and pathologic changes in pulmonary hemodynamics in neonates.

Early versus delayed continuous positive airway pressure (CPAP) for respiratory distress in preterm infants

BACKGROUND

The application of continuous positive airway pressure (CPAP) has been shown to have some benefits in the treatment of preterm infants with respiratory distress. CPAP has the potential to reduce lung damage, particularly if applied early before atelectasis has occurred. Early application may better conserve an infant's own surfactant stores and consequently may be more effective than later application.

OBJECTIVES

• To determine if early compared with delayed initiation of CPAP results in lower mortality and reduced need for intermittent positive-pressure ventilation in preterm infants in respiratory distress ○ Subgroup analyses were planned a priori on the basis of weight (with subdivisions at 1000 grams and 1500 grams), gestation (with subdivisions at 28 and 32 weeks), and according to whether surfactant was used ▫ Sensitivity analyses based on trial quality were also planned ○ For this update, we have excluded trials using continuous negative pressure SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2020, Issue 6), in the Cochrane Library; Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations Daily and Versions(R); and the Cumulative Index to Nursing and Allied Health Literatue (CINAHL), on 30 June 2020. We also searched clinical trials databases and the reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-RCTs.

SELECTION CRITERIA

We included trials that used random or quasi-random allocation to either early or delayed CPAP for spontaneously breathing preterm infants in respiratory distress.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane and Cochrane Neonatal, including independent assessment of trial quality and extraction of data by two review authors. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We found four studies that recruited a total of 119 infants. Two were quasi-randomised, and the other two did not provide details on the method of randomisation or allocation used. None of these studies used blinding of the intervention or the outcome assessor. Evidence showed uncertainty about whether early CPAP has an effect on subsequent use of intermittent positive-pressure ventilation (IPPV) (typical risk ratio (RR) 0.77, 95% confidence interval (CI) 0.43 to 1.38; typical risk difference (RD) -0.08, 95% CI -0.23 to 0.08; I² = 0%, 4 studies, 119 infants; very low-certainty evidence) or mortality (typical RR 0.93, 95% CI 0.43 to 2.03; typical RD -0.02, 95% CI -0.15 to 0.12; I² = 33%, 4 studies, 119 infants; very low-certainty evidence). The outcome 'failed treatment' was not reported in any of these studies. There was an uncertain effect on air leak (pneumothorax) (typical RR 1.09, 95% CI 0.39 to 3.04, I² = 0%, 3 studies, 98 infants; very low-certainty evidence). No trials reported intraventricular haemorrhage or necrotising enterocolitis. No cases of retinopathy of prematurity were reported in one study (21 infants). One case of bronchopulmonary dysplasia was reported in each group in one study involving 29 infants. Long-term outcomes were not reported.

AUTHORS' CONCLUSIONS

All four small trials included in this review were performed in the 1970s or the early 1980s, and we are very uncertain whether early application of CPAP confers clinical benefit in the treatment of respiratory distress, or whether it is associated with any adverse effects. Further trials should be directed towards establishing the appropriate level of CPAP and the timing and method of administration of surfactant when used along with CPAP.

How Do We Monitor Oxygenation during the Management of PPHN? Alveolar, Arterial, Mixed Venous Oxygen Tension or Peripheral Saturation?

Oxygen is a pulmonary vasodilator and plays an important role in mediating circulatory transition from fetal to postnatal period. Oxygen tension (PO₂) in the alveolus (PAO₂) and pulmonary artery (PaO₂) are the main factors that influence hypoxic pulmonary vasoconstriction (HPV). Inability to achieve adequate pulmonary vasodilation at birth leads to persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen therapy is the mainstay of PPHN management. However, optimal monitoring and targeting of oxygenation to achieve low pulmonary vascular resistance (PVR) and optimizing oxygen delivery to vital organs remains unknown. Noninvasive pulse oximetry measures peripheral saturations (SpO₂) and a target range of 91-95% are recommended during acute PPHN management. However, for a given SpO₂, there is wide variability in arterial PaO₂, especially with variations in hemoglobin type (HbF or HbA due to transfusions), pH and body temperature. This review evaluates the role of alveolar, preductal, postductal, mixed venous PO₂, and SpO₂ in the management of PPHN. Translational and clinical studies suggest maintaining a PaO₂ of 50-80 mmHg decreases PVR and augments pulmonary vasodilator management. Nevertheless, there are no randomized clinical trials evaluating outcomes in PPHN targeting SpO₂ or PO₂. Also, most critically ill patients have umbilical arterial catheters and postductal PaO₂ may not be an accurate assessment of oxygen delivery to vital organs or factors influencing HPV. The mixed venous oxygen tension from umbilical venous catheter blood gas may assess pulmonary arterial PO₂ and potentially predict HPV. It is crucial to conduct randomized controlled studies with different PO₂/SpO₂ target ranges for the management of PPHN and compare outcomes.

Cardiovascular response and sequelae after minimally invasive surfactant therapy in growth-restricted preterm infants

OBJECTIVE

To study cardiovascular response to minimally invasive surfactant therapy in preterm infants with and without foetal growth restriction (FGR).

DESIGN

Poractant alfa was administered and echocardiograms were performed before and 30 min after. FGR infants were compared with those appropriate for gestational age (AGA).

RESULTS

Ten FGR infants were compared with 20 AGA infants (gestation [weeks], 28.9 ± 2 vs. 28.6 ± 1, p = 0.55 and birthweight [g], 813 ± 157 vs. 1141 ± 257, p = 0.01, respectively). The change in echocardiographic parameters was more prominent in AGA infants ([global contractility] fractional area change [FAC, %], FGR, 24.7 ± 2.2 to 27.9 ± 0.4, p = 0.08 vs. AGA, 26.6 ± 3 to 30.5 ± 1, p < 0.01, and [longitudinal contractility] tricuspid annular plane systolic excursion [mm], FGR, 3.9 ± 0.3 to 4.6 ± 0.5, p = 0.003 vs. AGA, 4.6 ± 0.3 to 5.5 ± 0.4, p = 0.0001). Significant difference was noted for change in FAC (%), FGR 2.1 ± 1.7 vs. AGA 4.1 ± 1.2, p = 0.02.

CONCLUSIONS

Differential cardiovascular response to minimally invasive surfactant therapy amongst FGR infants may reflect an in-utero maladaptive state.

Standardization of nitric oxide inhalation in extremely preterm infants in Japan

BACKGROUND

In perinatal medicine, inhaled nitric oxide (iNO) has been an important tool for the treatment of full-term and late-preterm infants with persistent pulmonary hypertension of the newborn (PPHN) and hypoxemic respiratory failure (HRF). Its use in more premature infants, however, is controversial. To evaluate the current clinical practices regarding use of acute iNO in extremely preterm infants, a nationwide survey was conducted in Japan.

METHODS

A questionnaire survey was conducted from May to September, 2015. Questionnaires about PPHN and iNO treatment were sent to the doctor in charge of the neonatal care unit in 213 perinatal medical centers (PMC) that possessed iNO equipment in Japan.

RESULTS

A total of 143 of the 213 PMC provided responses (67.1%). A diagnosis of PPHN was made exclusively on echocardiography in all PMC. On definitive PPHN diagnosis, iNO was selected in the majority of the PMC (72%) and started from ≤10 p.p.m. in most PMC (49.7%) for extremely preterm infants. During iNO therapy, cardiac function was checked on echocardiography by a neonatologist every ≤8 h. iNO weaning was started when differential peripheral oxygen saturation (SpO₂ ) disappeared, or when SpO₂ reached 100% and so on. After iNO concentration reached 5 p.p.m., it was decreased gradually and carefully in five steps, taking 12-24 h to go from 5 to 0 p.p.m.

CONCLUSIONS

Inhaled nitric oxide was predominantly used in extremely preterm infants as early rescue therapy for PPHN based on echocardiography performed by a neonatologist.

Cardiorespiratory Physiology following Minimally Invasive Surfactant Therapy in Preterm Infants

INTRODUCTION

Surfactant replacement therapy through the endotracheal tube has been shown to improve lung compliance and reduce pulmonary pressures. Minimally invasive surfactant therapy (MIST) combines the benefits of continuous positive airway pressure (CPAP) and surfactant for spontaneously breathing preterm infants. We aimed to characterize the haemodynamic changes accompanying the first dose of MIST in preterm infants.

METHODS

Poractant alfa (200 mg/kg) was administered as MIST while on CPAP support. Echocardiograms were performed before (T1) and 30 (T2) and 60 min (T3) after MIST to assess serial change.

RESULTS

Twenty infants (mean gestational age 29.5 ± 2.8 weeks, median birth weight 1,102 g, IQR 840-1,940) received MIST at a median age of 16 h (IQR 3-24). FiO2 decreased significantly at 30 min (0.41 ± 0.08 to 0.27 ± 0.03, p < 0.001). Significant changes were noted at T2 for ductal parameters (decreased % time right to left shunt: 25% [15-33] to 14.5% [6-22], p = 0.013). Reduced pulmonary vascular resistance (PVR; increased pulmonary artery time velocity ratio 0.23 ± 0.05 to 0.28 ± 0.04 ms, p = 0.004) and improved longitudinal (tricuspid annular plane systolic excursion 4.5 ± 0.8 to 5.3 ± 0.9 mm, p = 0.004) and global (fractional area change 25 ± 2.3 vs. 27 ± 2%, p = 0.002) ventricular function were noted.

CONCLUSIONS

This is the first study assessing cardiovascular adaptation to MIST, a procedure fast gaining acceptance in the neonatal community. Increased pulmonary blood flow is likely due to a combined effect of increased ductal flow, reduced PVR, and increased ventricular function.

Facilitated tucking during early neonatologist-performed echocardiography in very preterm neonates

AIM

To assess the effect of facilitated tucking (FT), a nonpharmacologic nursing intervention, on echocardiographic parameters and infant comfort collected prospectively during neonatologist-performed echocardiography.

METHODS

Echocardiography was performed twice, in standard conditions and with FT; the order was randomised by computer. Echocardiography provided data on pulmonary artery flow and pressure, right and left ventricular function, and persistent ductus arteriosus. Comfort was assessed by a behavioural scale of pain, variations in heart rate (HR) and SpO₂ , and a newborn infant parasympathetic evaluation index based on the high-frequency variability in HR.

RESULTS

Fifty newborns, with mean gestational age of 28 [26.6-29.0] weeks and mean birthweight of 950 [780-1190] g, were studied at a postnatal age of 13 [9-27] hours. FT was associated with longer acceleration time/right ventricular ejection time in the main pulmonary artery (p = 0.006), reduced averaged HR variations (p = 0.03) and lower pain scores (p < 0.001). The other haemodynamic parameters and the parasympathetic index were not influenced by FT.

CONCLUSION

Echocardiography performed soon after birth in very premature neonates may generate mild discomfort. FT during echocardiography is associated with lower pulmonary artery pressures and improves infant's comfort during this examination.

Early postnatal echocardiographic assessment of pulmonary blood flow in newborns with congenital diaphragmatic hernia

Objective:

Echocardiography is the most important tool to assess infants with congenital diaphragmatic hernia (CDH) for pulmonary hypertension (PH). The pattern of blood flow in the pulmonary artery [described as time to peak velocity (TPV)/right ventricular ejection time (RVET) ratio] provides distinct information about pulmonary arterial pressure. The aim of our study was to investigate the correlation of TPV/RVET measurements with the most commonly used classification system for PH in CDH newborns and the association of these measurements with outcome parameters.

Methods:

Echocardiographic measurements were obtained in 40 CDH newborns within 6 h of life. The obtained measurements were correlated with the decision for or against extracorporeal membrane oxygenation (ECMO); early mortality; total duration of mechanical ventilation and total duration of oxygen supplementation.

Results:

The correlation coefficient between severity of PH and TPV/RVET measurements was −0.696 (P<0.001). Using receiver operating characteristic (ROC) analyses the optimal cutoff for TPV/RVET in order to predict the necessity for ECMO or early mortality without ECMO was 0.29 with a sensitivity of 86.7%, a specificity of 68%, a positive predictive value of 61.9% and a negative predictive value of 89.5%. Newborns with a TPV/RVET below the cutoff had a 5.9-fold risk for ECMO or early mortality, a significantly longer duration of mechanical ventilation (13.4 days vs. 7.4 days, P=0.003) and oxygen supplementation (22.4 days vs. 9.0 days, P=0.019), and a lower survival rate (76.2% vs. 100%, P=0.021).

Conclusions:

TPV/RVET is a feasible parameter to assess PH in CDH newborns with close correlation to outcome parameters.

Preterm growth restriction and bronchopulmonary dysplasia: the vascular hypothesis and related physiology

KEY POINTS

Approximately 5-10% pregnancies are affected by fetal growth restriction. Preterm infants affected by fetal growth restriction have a higher incidence of bronchopulmonary dysplasia. The present study is the first to measure pulmonary artery thickness and stiffness. The findings show that impaired vasculogenesis may be a contributory factor in the higher incidence of bronchopulmonary dysplasia in preterm growth restricted infants. The study addresses the mechanistic link between fetal programming and vascular architecture and mechanics.

ABSTRACT

Bronchopulmonary dysplasia is the most common respiratory sequelae of prematurity and histopathologically features fewer, dysmorphic pulmonary arteries. The present study aimed to characterize pulmonary artery mechanics and cardiac function in preterm infants with fetal growth restriction (FGR) compared to those appropriate for gestational age (AGA) in the early neonatal period. This prospective study reviewed 40 preterm infants between 28 to 32 weeks gestational age (GA). Twenty infants had a birthweight <10th centile and were compared with 20 preterm AGA infants. A single high resolution echocardiogram was performed to measure right pulmonary arterial and right ventricular (RV) indices. The GA and birthweight of FGR and AGA infants were 29.8 ± 1.3 vs. 30 ± 0.9 weeks (P = 0.78) and 923.4 g ± 168 vs. 1403 g ± 237 (P < 0.001), respectively. Assessments were made at 10.5 ± 1.3 days after birth. The FGR infants had significantly thicker right pulmonary artery inferior wall (843.5 ± 68 vs. 761 ± 40 μm, P < 0.001) with reduced pulsatility (51.6 ± 7.6 μm vs. 59.7 ± 7.5 μm, P = 0.001). The RV contractility [fractional area change (28.7 ± 3.8% vs 32.5 ± 3.1%, P = 0.001), tricuspid annular peak systolic excursion (TAPSE) (5.2 ± 0.3% vs. 5.9 ± 0.7%, P = 0.0002) and myocardial performance index (0.35 ± 0.03 vs. 0.28 ± 0.02, P < 0.001)] was significantly impaired in FGR infants. Significant correlation between RV longitudinal contractility (TAPSE) and time to peak velocity/RV ejection time (measure of RV afterload) was noted (r²  =  0.5, P < 0.001). Altered pulmonary vascular mechanics and cardiac performance reflect maladaptive changes in response to utero-placental insufficiency. Whether managing pulmonary vascular disease will alter clinical outcomes remains to be studied prospectively.

Cardiac Function Assessments in Left Bochdalek's Hernia: Clinical Relevance

The objectives of this study were to characterize peri-operative echocardiographic (ECHO) assessments of right ventricular (RV) function and pulmonary hypertension (PH) and ascertain correlation with clinical outcomes in infants with left Bochdalek's hernia (LBH). This retrospective study in a quaternary neonatal intensive care unit involved electronic database search for infants with LBH during January 2009 to July 2017. Demographics, outcomes, and ECHO parameters were accessed from archived databases. Thirty-one infants with mean gestational age and birthweight (BW) 38.4 ± 1.4 weeks and 3079 ± 450 g were included. Postnatal age at surgery was 4.3 ± 2 days. Two infants died before surgery (none after surgery). The survival rate in this cohort of late preterm and term infants with LBH not accompanied by congenital heart disease was 29/31 (93.5%). PH was noted in 28 (90%). Significant changes in biventricular function and pulmonary vascular haemodynamics were noted when reassessed after surgery [RV area change (%), 28 ± 3 vs. 34 ± 4, p = 0.007 and pulmonary artery capacitance (PAC) (ml³ × mmHg^-1), 0.05 ± 0.03 vs. 0.09 ± 0.05, p = 0.02]. The median duration of all respiratory support in those who were operated was 14.7 days (8.5, 25). Significant correlations were noted between pre-operative ECHO assessments and the duration of respiratory support (tricuspid regurgitation, r = 0.63, p = 0.0001 and PAC, r = - 0.52, p = 0.004). Peri-operative functional ECHO provided information about the evolution of cardiac function in infants with LBH.

Nitric oxide for the treatment of preterm infants with severe RDS and pulmonary hypertension

BACKGROUND

Inhaled nitric oxide (iNO) cannot be recommended for the routine treatment of respiratory failure in premature neonates, but it has been suggested that the effectiveness of iNO therapy should be further studied in more select preterm infants, such as those with persistent pulmonary hypertension of the newborn (PPHN).

OBJECTIVE

To evaluate the frequency of PPHN in very preterm infants with severe respiratory distress syndrome (RDS), to assess the effectiveness of iNO in these patients, and to individuate possible predictive factors for the response to iNO in preterm infants with RDS.

STUDY DESIGN

We retrospectively studied infants <30 weeks of gestational age or birth weight <1250 g, who were affected by severe RDS and treated with iNO during the first week of life. Clinical characteristics of infants with or without echocardiographic diagnosis of PPHN were compared, as well as those of responder or no responder to iNO therapy. Effectiveness of iNO was evaluated by recording changes of MAP, FiO₂ , SpO₂ /FiO₂ ratio, and oxygenation index (OI) before, and 3 ± 1, 6 ± 1, 12 ± 3, 24 ± 6, 48 ± 6, and 72 ± 12 h after beginning therapy.

RESULTS

We studied 42 (4.6%) infants, of whom 28 (67%) had PPHN and 14 (33%) did not. iNO therapy was associated with improved oxygenation in both the groups but it was quicker in the PPHN than in the no PPHN group. Multivariate analysis showed that FiO₂ >0.65, diagnosis of PPHN, and birth weight >750 g independently predicts effectiveness of iNO in very preterm infants with RDS.

CONCLUSION

We found that PPHN is a frequent complication of severe RDS in very preterm infants and iNO therapy can improve their oxygenation earlier than in infants without PPHN. iNO therapy is not recommended for the routinely treatment of RDS in premature neonates but in cases of concurrent diagnosis of PPHN it should be considered carefully.

Feasibility and utility of portable ultrasound during retrieval of sick preterm infants

AIM

Document the incidence of haemodynamic pathology in critically ill preterm newborns requiring transport.

METHOD

A transport neonatologist performed cardiac and cerebral ultrasound before and after transportation of infants born ≤30 weeks gestation.

RESULTS

Forty-four newborns were studied in 2008-2015; of them, 21 were transported by road, 19, by helicopter and four, by fixed wing: median birthweight, 1130 g (680-1960 g) and median gestation, 27 weeks (23-30); 30 of 44 were male babies. Antenatal steroid course was complete in two babies. Ultrasound in the referring hospital was at a mean of two hours: 47 minutes (00:15-7:00) of age. Low systemic blood flow was common: 50% had right ventricular output <150mL/kg/min and 23%, a superior vena cava flow <50mL/kg/min. at stabilisation. Cranial US: 10 Grade I IVH, 2 Grade II IVH, 1 Grade IV IVH and 32 normal scans pretransport. After transport, three further Grade I IVH were reported. Mortality was higher in the babies with low systemic blood flow: 4 of 12 (33%) died vs 1 of 31 (6%) in the normal flow group (OR = 7.2, 95% CI: 1.1 to 47, p = 0.022).

CONCLUSION

Point-of-care ultrasound during the retrieval of preterm infants confirms a high incidence of haemodynamic pathology. The use of ultrasound during transport may provide an opportunity for earlier targeted circulatory support.

A new look at bronchopulmonary dysplasia: postcapillary pathophysiology and cardiac dysfunction

Pulmonary hypertension (PH) and right ventricular function are the focus of cardiovascular effects of bronchopulmonary dysplasia (BPD). We assessed cardiac indexes reflecting systemic afterload and pulmonary venous back pressure as pathophysiologic factors. Cardiac parameters were measured by conventional echocardiography in 20 preterm infants with severe BPD and compared with those of 10 preterm infants with no BPD and 20 healthy term infants. In infants with severe BPD, PH was noted in 5 (25%) by tricuspid regurgitation Doppler jet ≥2.8 m/s and in 15 (75%) by time to peak velocity/right ventricular ejection time <0.34. Among systemic cardiac indexes, significant impairment of diastolic measures was noted in the BPD group compared with infants with no BPD and term infants. The significance persisted after adjusting for gestational age and birth weight. These included transmitral E/A ratio (1.07 ± 0.07 vs. 0.91 ± 0.04 vs. 0.89 ± 0.09; P < 0.0001), isovolumic relaxation time (68.8 ± 3.9 vs. 58.5 ± 7.8 vs. 54.2 ± 5.7 ms ; P < 0.0001), mitral valve stroke volume (4.7 ± 0.7 vs. 5.6 ± 0.6 vs. 5.9 ± 0.1; P = 0.002), and myocardial performance index (0.33 ± 0.05 vs. 0.28 ± 0.01 vs. 0.27 ± 0.05; P = 0.03). Left ventricular output was significantly lower in the BPD cohort (183 ± 45 vs. 189 ± 9 vs. 191 ± 32 mL/kg/min; P = 0.03). Altered systemic (left-sided) cardiac function was noted in infants with BPD, which may lead to pulmonary venous congestion contributing to a continued need for respiratory support.

Feasibility and utility of portable ultrasound during retrieval of sick term and late preterm infants

AIM

To determine the role of clinician performed ultrasound (CPU) during the retrieval and transport of critically ill term and near term newborns.

METHODS

A neonatologist with portable ultrasound accompanied a sample of newborn retrievals to perform cardiac and cerebral ultrasound before and after transportation.

RESULTS

A total of fifty-five babies were studied. Median birthweight: 3350 g (2220-5030 g). CPU led to a change in the planned receiving hospital in ten babies. Eleven babies were suspected congenital heart disease (CHD) prior to retrieval: eight confirmed CHD by CPU and three normal structure. One transported to a children's hospital for cardiology review was confirmed as having normal structure; one to a perinatal hospital where normal structure was confirmed and one baby died at the referring hospital and postmortem confirmed normal structure. In five babies with clinical pulmonary hypertension, CPU revealed unsuspected CHD. The destination was changed to a paediatric cardiology centre, avoiding a second retrieval. Eleven babies had evidence of haemodynamic compromise allowing targeting of inotropes.

CONCLUSION

This is the first study of CPU during retrieval of high-risk infants. Ultrasound in retrieval is feasible, allows accurate triage of babies to cardiac centres and may allow more accurate targeting of fluid and inotrope support.

Sildenafil therapy in bronchopulmonary dysplasia-associated pulmonary hypertension: a retrospective study of efficacy and safety

Bronchopulmonary dysplasia (BPD) is associated with a high incidence of pulmonary artery hypertension (PAH) and is frequently treated with sildenafil. The objective was to investigate the echocardiographic and clinical efficacy and safety of sildenafil in this setting. The hypothesis was that treatment would result in significant echocardiographic and clinical improvements. This was a retrospective study of the cohort of infants who were born between 2004 and 2012 and administered sildenafil as in-patients for BPD-associated PAH. Medical records and archived echocardiographic data were reviewed. Twenty-two infants fulfilled the inclusion criteria and had a mean (±SD) gestation age and birth weight of 25.6 (±1.3) weeks and 631 (±181) g, respectively. Six (27 %) infants died before discharge (predominantly due to respiratory failure; in three of them, a concomitant viral respiratory infection was thought to be an aggravating factor). Amongst survivors, no mortality was noted up to 1 year follow-up. Significant improvement in echocardiographic markers of pulmonary hypertension was noted in the echocardiogram performed 27.5 days (interquartile range 24, 31) post-initiation of therapy, two thirds showing ≥20 % decline in the right ventricular systolic pressure. Left ventricular fractional shortening did not alter significantly. At initiation, all infants had 'severe' BPD. The fraction of inspired oxygen (FiO2) decreased significantly from 0.57 (SE ± 0.05) to 0.42 (SE ± 0.03) (p = 0.02), and no significant alteration was noted over the timeframe in mean pCO2 (64.4 ± 3.3 to 63.2 ± 3.3 mmHg). The number of infants needing endotracheal intubation and mechanical ventilation decreased (from 3 to 1) over the same time. No serious adverse effects were noted.

CONCLUSION

Sildenafil therapy was associated with a significant improvement in the echocardiographic markers of PAH and a reduction in FiO2. The medication was well tolerated.

Neonatal echocardiography

Echocardiography is a technique within neonatal care increasingly used in acute management of patients because of its potential to guide care and hemodynamic management. However, its use continues to provoke controversy, as it was originally within the purview of pediatric cardiologists trained to identify structural as well as functional heart disease. This article examines some of the echocardiographic techniques available to the neonatologist, their applications, and the concerns surrounding their use on neonatal units.

Vasopressin as an adjunct therapy for pulmonary hypertension: a case report

Vasopressin is emerging as a therapeutic adjunct option towards treatment of shock states in the pediatric population. Its effects on pulmonary vasculature are less well understood. This report describes a 5-month-old infant with nitric oxide-unresponsive pulmonary hypertension, oxygenation failure, and systemic hypotension. Vasopressin therapy improved oxygenation and blood pressure and biventricular function, allowing weaning of nitric oxide and inotropic support. No decrease in coronary flow was noted.

CONCLUSIONS

Vasopressin could be considered as an adjunct option in infants with pulmonary hypertension and systemic hypotension. Echocardiographic monitoring during treatment is recommended.

Pulmonary hypertension in preterm infants: prevalence and association with bronchopulmonary dysplasia

OBJECTIVE

To determine whether early pulmonary hypertension (PH) at 10-14 days of life in preterm infants is associated with bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age (PMA).

STUDY DESIGN

This was a prospective observational cohort study of infants <28 weeks' gestation. Exclusion criteria were any major anomaly, genetic syndrome, or death before the initial echocardiogram. Echocardiograms were performed between 10 and 14 days of life and at 36 weeks' PMA to assess PH. BPD and its severity were determined at 36 weeks PMA by the National Institutes of Health workshop definition.

RESULTS

From March 2011 to April 2013, of 146 consecutively admitted infants <28 weeks, 120 were enrolled. One infant was excluded, 17 did not consent, and 8 died before undergoing a study echocardiogram. At 10-14 days of life, 10 infants had early PH (8%). Male sex (56% vs 40%), gestational age (26(+2) ± 1(+2) vs 25(+6) ± 1(+4) weeks), birth weight (837 ± 205 g vs 763 ± 182 g), and small for gestational age (14% vs 20%) were not significantly different among infants with no PH and early PH, respectively. Infants with early PH required >0.3 fraction of inspired oxygen by day 10 of life (70% vs 27%, P < .01). Moderate/severe BPD or death was greater among infants with early PH (90%) compared with no PH (47%, relative risk 1.9, 95% CI 1.43-2.53).

CONCLUSION

In this prospective, single-center cohort, early PH was associated with moderate/severe BPD or death at 36 weeks' PMA.

Cardiovascular function in children who had chronic lung disease of prematurity

OBJECTIVES

Although increased pulmonary arterial pressure is common in infancy in preterm infants who develop chronic lung disease of prematurity (CLD), it is unknown if the increase persists into childhood. We, therefore, assessed if 8-12-year-old children with documented CLD in infancy had evidence of right ventricular dysfunction or pulmonary arterial hypertension at rest or in response to acute hypoxia when compared to preterm and term-born controls.

METHODS

We studied 90 children: 60 born at ≤32 weeks of gestation (28 with CLD and 32 preterm controls), and 30 term-born controls. All had echocardiography including myocardial velocity imaging, at rest and while breathing 15% oxygen and 12% oxygen for 20 min each.

RESULTS

Baseline oxygen saturation, heart rate, blood pressure and echocardiographic markers of left and right ventricular function were similar in all three groups. While breathing 12% oxygen, the oxygen saturation decreased to 81.9% in the CLD group compared to 85.1% (p<0.05) and 84.7% (p<0.01) in the preterm and term controls, respectively. In response to hypoxia, all three groups showed increases in velocity of tricuspid regurgitation, end-diastolic velocity of pulmonary regurgitation, and right ventricular relaxation time; and decreases in pulmonary arterial acceleration time and the ratio of right ventricular acceleration time to ejection time. However, there were no differences between groups.

CONCLUSIONS

Childhood survivors of CLD have comparable left and right ventricular function at 8-12 years of age to preterm and term-born children, and no evidence of increased pulmonary arterial pressure even after hypoxic exposure.

Hypoxic pulmonary hypertension of the newborn

Hypoxic pulmonary hypertension of the newborn is characterized by elevated pulmonary vascular resistance and pressure due to vascular remodeling and increased vessel tension secondary to chronic hypoxia during the fetal and newborn period. In comparison to the adult, the pulmonary vasculature of the fetus and the newborn undergoes tremendous developmental changes that increase susceptibility to a hypoxic insult. Substantial evidence indicates that chronic hypoxia alters the production and responsiveness of various vasoactive agents such as endothelium-derived nitric oxide, endothelin-1, prostanoids, platelet-activating factor, and reactive oxygen species, resulting in sustained vasoconstriction and vascular remodeling. These changes occur in most cell types within the vascular wall, particularly endothelial and smooth muscle cells. At the cellular level, suppressed nitric oxide-cGMP signaling and augmented RhoA-Rho kinase signaling appear to be critical to the development of hypoxic pulmonary hypertension of the newborn.

Endothelial NOS gene Glu298Asp polymorphism in preterm neonates with respiratory distress syndrome

RATIONALE

Respiratory Distress Syndrome (RDS) due to prematurity is one of the most important causes of morbidity and mortality in Neonatal Intensive Care Units. According to few studies in recent years, endothelial nitric oxide synthase (eNOS) gene polymorphisms are found to be partially responsible for liability to RDS. The purpose of this study was to determine the association between eNOS gene polymorphism and RDS in preterm neonates.

PATIENTS AND METHODS

The patient group consisted of 152 premature neonates born before 37 weeks of gestation and diagnosed as RDS. The control group consisted of 125 premature neonates born before 37 weeks of gestation, but was not diagnosed as RDS. Genomic DNA from patients and controls was analyzed by polymerase chain reaction.

RESULTS

It was found that Glu/Glu, Glu/Asp, and Asp/Asp genotype frequencies of the eNOS gene polymorphism were 35.2%, 59.2%, and 5.6% of the control group, and 32.9%, 65.1%, and 2.0% of the patient group, respectively (P > 0.05). However, significant increases in Glu/Glu genotype and Glu allele frequencies were noted in the RDS groups when the preterm neonates were divided into two groups (24-30 weeks and 31-36 weeks) by gestational age. Additionally, Glu/Asp genotype and Asp allele were markedly less frequent among the RDS groups (P < 0.05). Asp allele frequency in boys and Glu allele frequency in girls were significantly high in RDS group (P < 0.05).

CONCLUSIONS

These data suggest that there were significant gestational age-related differences between RDS and control groups in terms of Glu298Asp polymorphism. Therefore, RDS seems to develop with alterations in eNOS Glu298Asp genotype frequencies in the Turkish population.

Nitric oxide for the treatment of preterm infants with respiratory distress syndrome

INTRODUCTION

Inhaled Nitric oxide (iNO) has been proposed as effective treatment for improving oxygenation in preterm infants with respiratory distress syndrome (RDS), and for preventing the development of bronchopulmonary dysplasia (BPD).

AREAS COVERED

This drug evaluation mainly reviews the results of clinical studies on the effects of iNO in preterm infants with RDS which have provided contradictory results probably due to their different designs. Three recent meta-analyses of these studies have concluded that iNO therapy is not effective in decreasing the risk of death and BPD and cannot be recommended as routine treatment. The same meta-analyses suggest that some strategy of iNO treatment and some subgroups of patients, such as infants with persistent pulmonary hypertension of the newborn (PPHN), should be further studied.

EXPERT OPINION

At present, the available evidence does not support the use of iNO in preterm infants with RDS, and iNO therapy cannot be recommended for the routine treatment of respiratory failure in premature neonates. In the future, further studies in selected populations using adequate doses and investigating the effectiveness of other drugs, such as sildenafil, might affect the use and diffusion of iNO.

Global myocardial function is compromised in infants with pulmonary hypertension

AIM

Persistent pulmonary hypertension of the newborn is a serious clinical entity with significant mortality and long-term morbidity. The objective was to study the profile of myocardial function, especially diastolic function, in term infants with pulmonary hypertension treated with nitric oxide.

METHODS

Unit electronic database was accessed to identify infants ≥34 weeks gestation who were administered nitric oxide for pulmonary hypertension over the last 6 years. Medical records and archived echocardiographic images were retrieved. Those with no echocardiogram on the day of administration of nitric oxide, concomitant congenital heart disease or ≥2 weeks of age at the time of nitric administration were excluded.

RESULTS

Low biventricular outputs were noted in >2/3rd infants. Tricuspid regurgitation was noted in 20/25 (80%) infants, and ductal shunt was bidirectional in the majority of cases. Right ventricular diastolic function was assessed by systolic to diastolic duration ratio; dysfunction was widely prevalent.

CONCLUSIONS

A large percentage of infants were haemodynamically severely compromised. This is the first study to detail right ventricular diastolic dysfunction in infants with pulmonary hypertension and highlights the therapeutic role of milrinone, a lusitropic drug with myocardial relaxation properties. Comprehensive evaluation of cardiovascular haemodynamics can optimize clinical care.

Pulmonary hypertension in chronic neonatal lung disease

Pulmonary hypertension is an uncommon but significantly challenging complication of chronic neonatal lung disease [CNLD] as it occurs in the "new bronchopulmonary dysplasia [BPD]". The presence of pulmonary hypertension may be sub-clinical and is often overlooked as it is not considered in all but the more severe cases of children with CNLD. Whilst the mainstays of therapy are supplemental oxygen and time and the majority of children will have resolution of their pulmonary hypertension with lung growth, the advent of newer pharmacological treatments has offered stability and perhaps a better prognosis for more severe cases of pulmonary hypertension.

Pulmonary hypertension during acute respiratory diseases in infants

OBJECTIVES

The study was undertaken to assess whether previously healthy infants with acute respiratory diseases develop elevated pulmonary artery pressures and to identify which type of disease is associated with pulmonary hypertension.

MATERIAL AND METHODS

We performed 2D and Doppler echocardiography in 137 infants, aged between 1 and 12 month, from November 2007 to December 2009. 75 infants had acute respiratory diseases (49 bronchiolitis, 16 interstitial pneumonia, 3 bronchopneumonia, 6 episodic wheezing, 1 lobar pneumonia) and 62 were in the control group. We excluded children with congenital heart diseases and other conditions associated with pulmonary hypertension. The method of time to peak velocity corrected for heart rate was used to estimate pulmonary arterial pressure (PAP). We analysed 2 age-subgroups: 1-2 months and 2-12 months. A Student's t-test for independent samples was used to compare the mean values of variables.

OUTCOMES

Increased mean pulmonary pressures (>25mmHg) were measured in 18 infants with respiratory diseases, with the next distribution: 14 bronchiolitis, 2 bronchopneumonia, 1 episodic wheezing, 1 interstitial pneumonia. The values were categorized as mild-moderate pulmonary hypertension. Mean PAP were significantly increased in subjects with clinically bronchoobstructive disease (bronchiolitis, episodic wheezing, bronchopneumonia) vs. control (p=0.05 in first age-subgroup and<0.001 in second age-subgroup). In infants with bronchoobstructive disease hospitalization was significantly longer in patients with pulmonary hypertension vs. normal PAP (p= 0.04 in first age-subgroup and 0.005 in second age-subgroup). In patients with bronchoobstructive diseases, mean PAPm and PAPs were significantly increased in subjects with a moderate/severe episode of wheezing at admission vs. a mild episode (p=0.02). Mean PAPm and PAPs were increased in subjects with interstitial pneumonia vs. control, but without statistic significance.

CONCLUSION

Echocardiography is a non-invasive investigation, which brings valuable information regarding pulmonary hypertension in infantile acute respiratory pathology. We found increased PAP almost exclusively in bronchoobstructive diseases; the mechanic effect of hyperinflation on pulmonary vessels is probably the dominant mechanism. PHT could be a criterion in establishing the severity of an acute wheezing episode, a prognosis factor and an element of therapeutic guidance.

Reproducibility of myocardial velocity and deformation imaging in term and preterm infants

AIMS

Myocardial velocity imaging has been validated in adults for assessment of ventricular function and indirect indices of pulmonary arterial pressure. To establish whether it could also be used in infants, we investigated the reproducibility of myocardial velocities and deformation indices in term and preterm neonates.

METHODS AND RESULTS

Myocardial velocity loops acquired from 16 infants were analysed by four observers for inter-observer variability, and re-analysed after 6 months by one observer for intra-observer variability. For myocardial velocities, the coefficients of variation (CVs) for the left ventricle (LV) were 10-11 (intra-observer) and 14-20% (inter-observer) and for the right ventricle (RV) 15-19 and 18-24%, respectively. Reproducibility for annular displacements was <13% (intra-observer) and <18% (inter-observer). CVs for LV strain were 14-17 (intra-observer) and 36-43% (inter-observer) and for RV 19-24 and 25-37%. CVs for isovolumic acceleration were in general >40%. In comparison, the CVs for blood pool indices were 3-15%.

CONCLUSION

Intra-observer reproducibility for myocardial velocity and deformation indices in neonates is adequate for these parameters to be used in clinical research. Inter-observer reproducibility is sub-optimal suggesting that these measurements should be used in clinical practice with caution. Myocardial acceleration, a marker of contractile function, was poorly reproducible.

Contribution of xanthine oxidase-derived superoxide to chronic hypoxic pulmonary hypertension in neonatal rats

Xanthine oxidase (XO)-derived reactive oxygen species (ROS) formation contributes to experimental chronic hypoxic pulmonary hypertension in adults, but its role in neonatal pulmonary hypertension has received little attention. In rats chronically exposed to hypoxia (13% O2) for 14 days from birth, we examined the effects of ROS scavengers (U74389G 10 mg·kg−1·day−1 or Tempol 100 mg·kg−1·day−1 ip) or a XO inhibitor, Allopurinol (50 mg·kg−1·day−1 ip). Both ROS scavengers limited oxidative stress in the lung and attenuated hypoxia-induced vascular remodeling, confirming a critical role for ROS in this model. However, both interventions also significantly inhibited somatic growth and normal cellular proliferation in distal air spaces. Hypoxia-exposed pups had evidence of increased serum and lung XO activity, increased vascular XO-derived superoxide production, and vascular nitrotyrosine formation. These changes were all prevented by treatment with Allopurinol, which also attenuated hypoxia-induced vascular remodeling and partially reversed inhibited endothelium-dependent arterial relaxation, without affecting normal growth and proliferation. Collectively, our findings suggest that XO-derived superoxide induces endothelial dysfunction, thus impairing pulmonary arterial relaxation, and contributes to vascular remodeling in hypoxia-exposed neonatal rats. Due to the potential for adverse effects on normal growth, targeting XO may represent a superior “antioxidant” strategy to ROS scavengers for neonates with pulmonary hypertension.

Inhaled nitric oxide for the treatment of preterm infants with respiratory distress syndrome

Many authors have hypothesized that inhaled nitric oxide (iNO) might acutely improve oxygenation in preterm neonates with infant respiratory distress syndrome (iRDS) and decrease the risk of bronchopulmonary dysplasia. The studies on the effects of iNO in preterm infants with iRDS have given contradictory results. We report their main methodological characteristics and the observed effects of iNO in preterm infants. Moreover, we discuss the infants' age at the beginning of the study, the dose and duration of iNO therapy, its potential effect on neurodevelopment, its relationship with surfactant properties, and the need to identify patients who are likely to respond to this therapy. We advise caution against the widespread use of iNO in preterm infants with iRDS. At present, it appears to be premature to have specific recommendations regarding the indications for iNO therapy in this group of patients. The conclusion of current trials and the follow-up studies of recently completed trials will give further data to guide neonatologists' decisions, and until then it is likely that clinicians will continue to make case-by-case decisions for the treatment of iNO in preterm infants with hypoxia that is unresponsive to other therapies. However, this decision should always be discussed with the parents.

Characteristics of pulmonary hypertension in preterm neonates

OBJECTIVE

Characteristics of preterm infants who develop pulmonary hypertension (PHT) and their response to inhaled nitric oxide (iNO) are not well described. Our objective was to identify risk factors for PHT in infants <37 weeks gestational age (GA) and to evaluate their response to iNO.

STUDY DESIGN

A retrospective chart review was conducted in infants <37 weeks GA born from July/2000 to October/2005 who had an echocardiographic diagnosis of PHT in the first 4 weeks of life. A comparison non-PHT group was generated matched for GA and birth date. Data on prenatal and postnatal characteristics, response to iNO and mortality were collected.

RESULTS

Low Apgar scores, preterm premature rupture of membranes, oligohydramnios, pulmonary hypoplasia and sepsis were independently predictive of PHT. Mortality was significantly higher in the PHT group (26.2% versus 4.1%; P<0.0001) compared to the control group. Low birth weight, severe intraventricular hemorrhage and male sex were significantly associated with death in infants with PHT. Thirty-seven percent (23/61) of infants with PHT were treated with inhaled NO. Infants < 29-week GA had poor response to iNO and the response to iNO increased with GA (P<0.02).

CONCLUSIONS

Low Apgar scores, oligohydramnios and pulmonary hypoplasia are associated with the development of PHT in premature infants. The percentage of infants responding to iNO increases with advancing GA.

Inhaled nitric oxide in very preterm infants with severe respiratory distress syndrome

AIM

To test the hypothesis that inhaled nitric oxide therapy can decrease the incidence of bronchopulmonary dysplasia and death in preterm infants with severe respiratory distress syndrome; to evaluate the possible predictive factors for the response to inhaled nitric oxide therapy.

METHODS

Preterm infants (less than 30 weeks' gestation) were randomized to receive during the first week of life inhaled nitric oxide, or nothing, if they presented severe respiratory distress syndrome. Then, the treated infants were classified as non responders and responders.

RESULTS

Twenty infants were enrolled in the inhaled nitric oxide therapy group and 20 in the control group. Bronchopulmonary dysplasia and death were less frequent in the inhaled nitric oxide group than in the control group (50 vs. 90%, p=0.016). Moreover, nitric oxide treatment was found to decrease as independent factor the combined incidence of death and BPD (OR=0.111; 95% C.I. 0.02-0.610). A birth weight lower than 750 grams had a significant predictive value for the failure of responding to inhaled nitric oxide therapy (OR 12; 95% C.I. 1.3-13.3).

CONCLUSION

Inhaled nitric oxide decreases the incidence of bronchopulmonary dysplasia and death in preterm infants with severe respiratory distress syndrome. Birth weight may influence the effectiveness of inhaled nitric oxide therapy in promoting oxygenation improvement in preterm infants.

Blood L-arginine levels in early respiratory distress syndrome

L-arginine is the precursor of nitric oxide which plays an important role on pulmonary circulation and pulmonary vascular tone. Our aim was to compare the levels of L-arginine between infants with respiratory distress syndrome and infants without respiratory distress syndrome and to determine the relationship between plasma L-arginine concentrations and severity of disease. Thirty premature infants who were admitted to our neonatal intensive care unit were included the study. Seventeen of these infants with respiratory distress syndrome were study group and the other 13 infants without respiratory distress syndrome served as controls. Blood collection was made before any treatment or intervention given to infants and tandem mass spectrometry was used for laboratory testing. In the respiratory distress syndrome group mean L-arginine level was 33.0 (+/- 11.5) mM/l, and in controls it was 79.0 (+/- 23) mM/l. This difference was statistically significant (P < 0.05). There was a reverse relationship between L-arginine levels and oxygenation index (r = 0.732, P = 0.001). If level of L-arginine is low or insufficient in respiratory distress syndrome patients' nitric oxide level would decrease in pulmonary circulation and results increased pulmonary resistance and severity of respiratory distress syndrome. We concluded that L-arginine levels are low in patients with rspiratory distress syndrome and for further investigations, supplementation of respiratory distress syndrome patients with L-arginine may decrease disease severity.

Inhaled nitric oxide for premature infants with severe respiratory failure

BACKGROUND

Inhaled nitric oxide is a controversial treatment for premature infants with severe respiratory failure. We conducted a multicenter, randomized, blinded, controlled trial to determine whether inhaled nitric oxide reduced the rate of death or bronchopulmonary dysplasia in such infants.

METHODS

We randomly assigned 420 neonates, born at less than 34 weeks of gestation, with a birth weight of 401 to 1500 g, and with respiratory failure more than four hours after treatment with surfactant to receive placebo (simulated flow) or inhaled nitric oxide (5 to 10 ppm). Infants with a response (an increase in the partial pressure of arterial oxygen of more than 10 mm Hg) were weaned according to protocol. Treatment with study gas was discontinued in infants who did not have a response.

RESULTS

The rate of death or bronchopulmonary dysplasia was 80 percent in the nitric oxide group, as compared with 82 percent in the placebo group (relative risk, 0.97; 95 percent confidence interval, 0.86 to 1.06; P=0.52), and the rate of bronchopulmonary dysplasia was 60 percent versus 68 percent (relative risk, 0.90; 95 percent confidence interval, 0.75 to 1.08; P=0.26). There were no significant differences in the rates of severe intracranial hemorrhage or periventricular leukomalacia. Post hoc analyses suggest that rates of death and bronchopulmonary dysplasia are reduced for infants with a birth weight greater than 1000 g, whereas infants weighing 1000 g or less who are treated with inhaled nitric oxide have higher mortality and increased rates of severe intracranial hemorrhage.

CONCLUSIONS

The use of inhaled nitric oxide in critically ill premature infants weighing less than 1500 g does not decrease the rates of death or bronchopulmonary dysplasia. Further trials are required to determine whether inhaled nitric oxide benefits infants with a birth weight of 1000 g or more.

Inhaled nitric oxide therapy in neonatal hypoxic respiratory failure: insights beyond primary outcomes

The Neonatal Research Network developed and initiated 3 multicenter randomized controlled clinical trials evaluating inhaled nitric oxide therapy. Additional projects evolved from these efforts including basic science research and observational investigations. This article provides a historical prospective of the Network's investigations related to the diagnosis and management of neonatal hypoxic respiratory failure, especially those related to inhaled nitric oxide therapy. It will review the Network's contributions toward advancing the clinical care of the newborn with severe hypoxic respiratory failure.

The pulmonary circulation in bronchopulmonary dysplasia

Abnormalities of the pulmonary circulation are increasingly being recognized as a major contributor to the high morbidity and mortality of bronchopulmonary dysplasia. Historically, studies have focused on the importance of pulmonary hypertension to the pathophysiology of BPD, with the assumption that pulmonary vascular abnormalities are a secondary consequence of primary injury to the airspace. Recent studies suggest, however, that abnormalities of the pulmonary vasculature, including altered growth and structure, may directly contribute to the abnormal alveolarization that characterizes the condition. In this article, we briefly outline mechanisms of pulmonary vascular injury in infants at risk of BPD. We then focus on the recognition and management of pulmonary hypertension in these infants. Finally, we review how disordered pulmonary vascular growth may contribute to the pathogenesis of BPD and emphasize the importance of the reciprocal development of the airspace and the pulmonary circulation.

Efficacy and safety of tolazoline for treatment of severe hypoxemia in extremely preterm infants

OBJECTIVE

To determine the efficacy of tolazoline as a rescue treatment for hypoxemia in preterm infants with respiratory distress syndrome.

METHODS

Retrospective chart review on case series of infants weighing < 750 g at birth who received tolazoline during a severe hypoxemic episode while receiving maximal ventilator support for respiratory distress syndrome. A slow bolus infusion of low dose tolazoline (0.5 mg-2 mg/kg) mixed with plasmanate or normal saline (10 mL/kg) was administered. Outcome measures evaluated included an increase in PaO(2) > or =20 mm Hg from pretreatment value and an increase in oxygen saturation to > or =90%.

RESULTS

Forty-three infants with a mean gestational age and birth weight of 24 weeks and 581 g, respectively, received tolazoline. All infants were mechanically ventilated and required a fraction of inspired oxygen of 1.0. Oxygenation improved in 72% (31/43) of infants with a tolazoline dose of 0.5 to 1.0 mg/kg. Of those who responded, PaO(2) values (mean +/- standard deviation) pretolazoline and posttolazoline were 32 +/- 7.5 mm Hg and 156 +/- 114.9 mm Hg, respectively. In all responders, oxygen saturation increased to > or =90% within 30 minutes of tolazoline administration. Improvement in pH, pCO(2), oxygenation index, and mean airway pressure was also noted. Among nonresponders, pH decreased and pCO(2) increased after tolazoline. Minimal change in blood pressure was noted in both responders and nonresponders. Heart rate decreased by 19 beats per minute among nonresponders compared with an increase of 3 beats per minute in those who responded to tolazoline.

CONCLUSION

Tolazoline is an effective treatment of severe resistant hypoxemia in preterm infants who are already on vigorous ventilatory support.

Early versus delayed initiation of continuous distending pressure for respiratory distress syndrome in preterm infants

BACKGROUND

The application of a continuous distending pressure (CDP) has been shown to have some benefits in the treatment of pre-term infants with respiratory distress syndrome (RDS). CDP has the potential to reduce lung damage, particularly if applied early before atelectasis has occurred. Early application of CDP may better conserve an infant's own surfactant stores and consequently be more effective than CDP applied later in the course of RDS.

OBJECTIVES

In pre-term infants with RDS to determine if early compared with delayed initiation of CDP results in lower mortality and reduced need for intermittent positive pressure ventilation.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register (Issue 1, 2002), MEDLINE (1966-2001), previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, journal hand searching mainly in the English language.

SELECTION CRITERIA

Trials among pre-term infants with respiratory distress syndrome spontaneously breathing at trial entry, which used random or quasi-random allocation to either early or delayed CDP.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and its Neonatal Review Group were used, including independent assessment of trial quality and extraction of data by two authors.

MAIN RESULTS

In six studies on a total of 165 infants, early CDP was associated with a significant reduction in subsequent use of intermittent positive pressure ventilation, typical RR 0.55, RD -0.16, NNT 6, but there was no evidence of effect on overall mortality. There was no evidence of effect on the rates of pneumothorax (five studies) or bronchopulmonary dysplasia (one study). Early CDP resulted in a reduction in duration of oxygen therapy in the single study reporting this outcome.

REVIEWER'S CONCLUSIONS

Early application of CDP has a clinical benefit in the treatment of RDS in that it reduces subsequent use of IPPV and thus may be useful in preventing the adverse effects of this treatment. However, many of the trials were done in the 1970s and 1980s and re-evaluation of the strategy of early CDP in the era of antenatal steroid use and early surfactant administration is indicated.

Randomised controlled trial of postnatal sodium supplementation in infants of 25-30 weeks gestational age: effects on cardiopulmonary adaptation

BACKGROUND

It has previously been shown that, in preterm babies, routine sodium supplementation from 24 hours after birth is associated with increased risk of oxygen dependency and persistent expansion of the extracellular compartment.

OBJECTIVE

To explore whether this is mediated by a delayed fall in pulmonary artery pressure (PAP). Postnatal changes in PAP, estimated as the ratio of time to peak velocity to right ventricular ejection time, corrected for heart rate (TPV:RVET(c)), were compared in preterm infants who received routine sodium supplements that were either early or delayed.

METHODS

Infants were randomised, stratified according to sex and gestation, to receive a sodium intake of 4 mmol/kg/day starting either from 24 hours after birth or when a weight loss of 6% of birth weight was achieved. Echocardiographic assessment was made on the day of delivery (day 0), and on days 1, 2, 7, and 14. Babies with congenital heart disease were excluded.

RESULTS

There was no difference between the two groups in TPV:RVET(c) measured sequentially after birth. On within group testing, when compared with values at birth, the ratio was higher by day 3 in the early supplemented group, suggesting a more rapid fall in PAP compared with the late supplemented group, in whom a significant fall did not occur until day 14.

CONCLUSIONS

The timing of sodium supplementation after preterm birth does not appear to affect the rate of fall in PAP as measured by the TPV:RVET(c) ratio. The previous observation linking routine sodium supplementation from 24 hours after birth with increased risk of continuing oxygen requirement therefore does not appear to be mediated by a delayed fall in PAP. Instead, the increased risk of continuing oxygen requirement is likely to be a direct consequence of persistent expansion of the extracellular compartment and increased pulmonary interstitial fluid, resulting from a sodium intake that exceeded sodium excretory capacity. This adds further weight to the view that clinical management, in this case the timing of routine sodium supplementation, should be individually tailored and delayed until the onset of postnatal extracellular volume contraction, marked clinically by weight loss.

Neonatal pulmonary hypertension--urea-cycle intermediates, nitric oxide production, and carbamoyl-phosphate synthetase function

BACKGROUND

Endogenous production of nitric oxide is vital for the decrease in pulmonary vascular resistance that normally occurs after birth. The precursor of nitric oxide is arginine, a urea-cycle intermediate. We hypothesized that low concentrations of arginine would correlate with the presence of persistent pulmonary hypertension in newborns and that the supply of this precursor would be affected by a functional polymorphism (the substitution of asparagine for threonine at position 1405 [T1405N]) in carbamoyl-phosphate synthetase, which controls the rate-limiting step of the urea cycle.

METHODS

Plasma concentrations of amino acids and genotypes of the carbamoyl-phosphate synthetase variants were determined in 65 near-term neonates with respiratory distress. Plasma nitric oxide metabolites were measured in a subgroup of 10 patients. The results in infants with pulmonary hypertension, as assessed by echocardiography, were compared with those in infants without pulmonary hypertension. The frequencies of the carbamoyl-phosphate synthetase genotypes in the study population were assessed for Hardy-Weinberg equilibrium.

RESULTS

As compared with infants without pulmonary hypertension, infants with pulmonary hypertension had lower mean (+/-SD) plasma concentrations of arginine (20.2+/-8.8 vs. 39.8+/-17.0 micromol per liter, P<0.001) and nitric oxide metabolites (18.8+/-12.7 vs. 47.2+/-11.2 micromol per liter, P=0.05). As compared with the general population, the infants in the study had a significantly skewed distribution of the genotypes for the carbamoyl-phosphate synthetase variants at position 1405 (P<0.005). None of the infants with pulmonary hypertension were homozygous for the T1405N polymorphism.

CONCLUSIONS

Infants with persistent pulmonary hypertension have low plasma concentrations of arginine and nitric oxide metabolites. The simultaneous presence of diminished concentrations of precursors and breakdown products suggests that inadequate production of nitric oxide is involved in the pathogenesis of neonatal pulmonary hypertension. Our preliminary observations suggest that the genetically predetermined capacity of the urea cycle--in particular, the efficiency of carbamoyl-phosphate synthetase--may contribute to the availability of precursors for nitric oxide synthesis.

The persistently patent arterial duct in the premature infant

The presence of a persistently patent arterial duct is common in premature neonates and may be associated with high morbidity. Early accurate diagnosis, assessment of the significance of the left to right shunt and prompt treatment are required to improve the outcome in this infant population.

Changes in pulmonary arterial pressure in preterm infants with chronic lung disease

BACKGROUND

Pulmonary arterial pressure (PAP) is raised in preterm infants with respiratory distress syndrome who subsequently develop chronic lung disease. The natural history of pulmonary hypertension in infants with chronic lung disease is unknown.

OBJECTIVES

To investigate changes in PAP, assessed non-invasively using Doppler echocardiography, in infants with chronic lung disease during the 1st year of life.

METHODS

Serial examinations were performed in infants with chronic lung disease and healthy preterm infants. The Doppler derived acceleration time to right ventricular ejection time ratio (AT/RVET) was calculated from measurements made from the pulmonary artery velocity waveform.

RESULTS

A total of 248 examinations were performed in 54 infants with chronic lung disease and 44 healthy preterm infants. The median AT/RVET was significantly lower in infants with chronic lung disease than in healthy preterm infants (0.31 v 0.37). AT/RVET significantly correlated with age corrected for prematurity in both infants with chronic lung disease (r = 0.67) and healthy infants (r = 0.55). There was no significant difference between the rate of change in AT/RVET between the two groups. In infants with chronic lung disease, multivariate analysis showed that AT/RVET was significantly independently associated with age and inversely with duration of supplemental oxygen treatment. Median AT/RVET was significantly lower in infants with chronic lung disease until 40-52 weeks of age corrected for prematurity.

CONCLUSIONS

Although PAP falls with increasing age in both infants with chronic lung disease and healthy preterm infants, it remains persistently raised in infants with chronic lung disease until the end of the 1st year of life.

Mechanisms of blood pressure increase induced by dopamine in hypotensive preterm neonates

AIMS

To compare changes in global haemodynamics as well as anterior cerebral and superior mesenteric artery perfusion after dopamine treatment.

METHODS

Anterior cerebal and superior mesenteric artery perfusion was measured using Doppler ultrasonography in hypotensive preterm neonates in whom cardiac output increased (group 1, n=10) or decreased (group 2, n=40) after dopamine treatment.

RESULTS

Despite a lower dopamine infusion rate, the blood pressure increase (mm Hg) in group 2 [Delta=13(1); mean(SE)] exceeded that in group 1 [Delta=8(1)], while systemic vascular resistance (mm Hg/l/min/kg) rose in group 2 [Delta=106 (37)], but was unchanged in group 1 [Delta=9 (6)]. Anterior cerebral artery blood velocity and resistance were unaffected by dopamine. However, compared with unchanged values in group 1, superior mesenteric artery blood velocity fell by 14.7(4.8) cm/s and resistance increased by 4.1(0.7) mm Hg/cm in group 2.

CONCLUSIONS

These results suggest that, in a portion of hypotensive preterm neonates, the increase in blood pressure induced by dopamine is related to a predominant vasoconstrictor action and is associated with a fall in bowel perfusion.

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.

Endotracheal inhalatory sodium nitroprusside in severely hypoxic newborns

This study examined the response of 10 newborns admitted to the Neonatal Intensive Care Unit of Hospital Universitário, UFMS, Campo Grande, MS, Brazil, submitted to mechanical ventilation under the following ventilator parameters: FiO2 = 100%, PIP (24 mmHg, rate > 30 mpm. All had severe hypoxia and were treated with a solution of sodium nitroprusside (SNP) administered through a special adapter for continuous endotracheal inhalation. Significant increases in PaO2, SaO2 and in PaO2/FiO2 ratio were observed at 1 h and at 6-8 h of treatment, whereas blood pressure did not change significantly while treatment was being delivered. No side effects such as methemoglobinemia or cyanogen accumulation were observed. Although appropriate studies using animal models have still to be conducted, present results suggest that endotracheal inhalation of SNP could constitute a valid form of treatment for newborns with persistent pulmonary hypertension or severe hypoxia of difficult management.

Plasma L-arginine concentration, oxygenation index, and systemic blood pressure in premature infants

OBJECTIVE

To determine the relationships between plasma L-arginine concentrations and the severity of respiratory distress syndrome (RDS) or systemic blood pressure in premature infants.

DESIGN

Prospective, observational study.

SETTING

Neonatal intensive care, tertiary referral hospital.

SUBJECTS

Fifty-three premature infants.

INTERVENTIONS

We measured arginine and nutritional intake, plasma arginine concentration, total amino acid concentrations, and blood pressure on days 3, 7, 14, and 21 of life. In 33 infants who received assisted ventilation, oxygenation index could be calculated to reflect the severity of RDS. The relationships between plasma arginine and oxygenation index or blood pressure were analyzed using multiple linear regression.

MEASUREMENTS AND MAIN RESULTS

On day 3, plasma arginine concentrations were decreased compared with normal published values. Arginine concentrations increased with the day of life of measurement (p < .001) and with arginine intake (p < .001). After adjusting for arginine intake and day of life, an inverse relationship was found between oxygenation index and plasma arginine concentrations: (p = .025). No similar relationship was found between oxygenation index and the concentration of total amino acids. A weak positive relationship was found between plasma arginine concentration and systemic blood pressure.

CONCLUSIONS

Increments in the oxygenation index, reflective of an increased severity of RDS, are associated with a decrease in plasma arginine concentration. This finding may reflect arginine consumption by the nitric oxide synthase pathway in the lungs of premature infants with RDS, or may be explained by increased arginine catabolism. The lack of a similar relationship between total plasma amino acids and oxygenation index supports the first interpretation.

Changes in pulmonary artery pressure during the acute phase of respiratory distress syndrome treated with three different types of surfactant

We studied the changes in acceleration time/right ventricular ejection time ratio (AT/RVET; indicative of changes in pulmonary artery pressure) calculated from Doppler ultrasound examinations performed before and 1, 6, and 12 h after the first and second doses of surfactant following the administration of each of three different surfactants during the acute phase of the respiratory distress syndrome. Maximum fractional inspired oxygen concentration (F(I,O2)) and peak inspiratory pressure (PIP) were recorded during each 4 h period from birth for the first 24 h and subsequently every 24 h until 72 h. Eighty-three infants were studied. Fifty patients weighing > 1 kg received Exosurf (n = 29) or ALEC (n = 21) and 33 weighing < or = 1 kg received Exosurf (n = 22) or Survanta (n = 11). The AT/RVET rose rapidly after administration of all three surfactants. There was no significant difference in the change in AT/RVET between those > 1 kg who received Exosurf and those who received ALEC (a synthetic surfactant). Similarly, there was no difference between those infants < or = 1 kg who received Exosurf and those who received Survanta. The F(I,O2) requirements, but not PIP, were lower in those infants who received Survanta at 12 and 20 h compared with those who received Exosurf. There was no significant difference in the F(I,O2) or PIP requirements between infants > 1 kg who received Exosurf compared with those who received ALEC. The rise in AT/RVET found in this study after administration of ALEC, Exosurf, or Survanta suggests that similar and rapid falls in pulmonary artery pressure occur after all three surfactant administrations, despite the difference in clinical response demonstrated between Exosurf and Survanta.