Improving pulmonary function does not decrease oxygen consumption in infants with bronchopulmonary dysplasia

Inhaled bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants and is associated with respiratory morbidity. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increased compliance and tidal volume, and decreased airway resistance, have been documented with the use of bronchodilators in infants with CLD. Therefore, bronchodilators are widely considered to have a role in the prevention and treatment of CLD, but there remains uncertainty as to whether they improve clinical outcomes. This is an update of the 2016 Cochrane review.

OBJECTIVES

To determine the effect of inhaled bronchodilators given as prophylaxis or as treatment for chronic lung disease (CLD) on mortality and other complications of preterm birth in infants at risk for or identified as having CLD.

SEARCH METHODS

An Information Specialist searched CENTRAL, MEDLINE, Embase, CINAHL and three trials registers from 2016 to May 2023. In addition, the review authors undertook reference checking, citation searching and contact with trial authors to identify additional studies.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials involving preterm infants less than 32 weeks old that compared bronchodilators to no intervention or placebo. CLD was defined as oxygen dependency at 28 days of life or at 36 weeks' postmenstrual age. Initiation of bronchodilator therapy for the prevention of CLD had to occur within two weeks of birth. Treatment of infants with CLD had to be initiated before discharge from the neonatal unit. The intervention had to include administration of a bronchodilator by nebulisation or metered dose inhaler. The comparator was no intervention or placebo.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane. Critical outcomes included: mortality within the trial period; CLD (defined as oxygen dependency at 28 days of life or at 36 weeks' postmenstrual age); adverse effects of bronchodilators, including hypokalaemia (low potassium levels in the blood), tachycardia, cardiac arrhythmia, tremor, hypertension and hyperglycaemia (high blood sugar); and pneumothorax. We used the GRADE approach to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included two randomised controlled trials in this review update. Only one trial provided useable outcome data. This trial was conducted in six neonatal intensive care units in France and Portugal, and involved 173 participants with a gestational age of less than 31 weeks. The infants in the intervention group received salbutamol for the prevention of CLD. The evidence suggests that salbutamol may result in little to no difference in mortality (risk ratio (RR) 1.08, 95% confidence interval (CI) 0.50 to 2.31; risk difference (RD) 0.01, 95% CI -0.09 to 0.11; low-certainty evidence) or CLD at 28 days (RR 1.03, 95% CI 0.78 to 1.37; RD 0.02, 95% CI -0.13 to 0.17; low-certainty evidence), when compared to placebo. The evidence is very uncertain about the effect of salbutamol on pneumothorax. The one trial with usable data reported that there were no relevant differences between groups, without providing the number of events (very low-certainty evidence). Investigators in this study did not report if side effects occurred. We found no eligible trials that evaluated the use of bronchodilator therapy for the treatment of infants with CLD. We identified no ongoing studies.

AUTHORS' CONCLUSIONS

Low-certainty evidence from one trial showed that inhaled bronchodilator prophylaxis may result in little or no difference in the incidence of mortality or CLD in preterm infants, when compared to placebo. The evidence is very uncertain about the effect of salbutamol on pneumothorax, and neither included study reported on the incidence of serious adverse effects. We identified no trials that studied the use of bronchodilator therapy for the treatment of CLD. Additional clinical trials are necessary to assess the role of bronchodilator agents in the prophylaxis or treatment of CLD. Researchers studying the effects of inhaled bronchodilators in preterm infants should include relevant clinical outcomes in addition to pulmonary mechanical outcomes.

Postnatal diuretics, weight gain and home oxygen requirement in extremely preterm infants

OBJECTIVES

Diuretics are often given to infants with evolving/established bronchopulmonary dysplasia (BPD) with the hope of improving their pulmonary outcomes. We aimed to determine if diuretic use in preterm infants was associated with improved pulmonary outcomes, but poorer weight gain.

METHODS

An observational study over a 5 year period was undertaken of all infants born at less than 29 weeks of gestation and alive at discharge in all neonatal units in England who received consecutive diuretic use for at least 7 days. Postnatal weight gain and home supplementary oxygen requirement were the outcomes. A literature review of randomised controlled trials (RCTs) and crossover studies was undertaken to determine if diuretic usage was associated with changes in lung mechanics and oxygenation, duration of supplementary oxygen and requirement for home supplementary oxygen.

RESULTS

In the observational study, 9,457 infants survived to discharge, 44.6% received diuretics for at least 7 days. Diuretic use was associated with an increased probability of supplementary home oxygen of 0.14 and an increase in weight gain of 2.5 g/week. In the review, seven of the 10 studies reported improvements only in short term lung mechanics. There was conflicting evidence regarding whether diuretics resulted in short term improvements in oxygenation.

CONCLUSIONS

Diuretic use was not associated with a reduction in requirement for supplemental oxygen on discharge. The literature review highlighted a lack of RCTs assessing meaningful long-term clinical outcomes. Randomised trials are needed to determine the long-term risk benefit ratio of chronic diuretic use.

Mechanical Power: A New Concept in Mechanical Ventilation

Mechanical ventilation is a potentially life-saving therapy for patients with acute lung injury, but the ventilator itself may cause lung injury. Ventilator-induced lung injury (VILI) is sometimes an unfortunate consequence of mechanical ventilation. It is not clear however how best to minimize VILI through adjustment of various parameters including tidal volume, plateau pressure, driving pressure, and positive end expiratory pressure (PEEP). No single parameter provides a clear indication for onset of lung injury attributable exclusively to the ventilator. There is currently interest in quantifying how static and dynamic parameters contribute to VILI. One concept that has emerged is the consideration of the amount of energy transferred from the ventilator to the respiratory system per unit time, which can be quantified as mechanical power. This review article reports on recent literature in this emerging field and future roles for mechanical power assessments in prospective studies.

Pharmacologic Management of Severe Bronchopulmonary Dysplasia

Few medications are available and well tested to treat infants who already have developed or inevitably will develop severe bronchopulmonary dysplasia (sBPD). Infants who develop sBPD clearly have not benefited from decades of research efforts to identify clinically meaningful preventive therapies for very preterm infants in the first days and weeks of their postnatal lives. This review addresses challenges to individualized approaches to medication use for sBPD. Specific challenges include understanding the combination of an individual infant's postmenstrual and postnatal age and the developmental status of drug-metabolizing enzymes and receptor expression. This review will also explore the reasons for the variable responsiveness of infants to specific therapies, based on current understanding of developmental pharmacology and pharmacogenetics. Data demonstrating the remarkable variability in the use of commonly prescribed drugs for sBPD are presented, and a discussion about the current use of some of these medications is provided. Finally, the potential use of antifibrotic medications in late-stage sBPD, which is characterized by a profibrotic state, is addressed.

Power to mechanical power to minimize ventilator-induced lung injury?

Mechanical ventilation is a life-supportive therapy, but can also promote damage to pulmonary structures, such as epithelial and endothelial cells and the extracellular matrix, in a process referred to as ventilator-induced lung injury (VILI). Recently, the degree of VILI has been related to the amount of energy transferred from the mechanical ventilator to the respiratory system within a given timeframe, the so-called mechanical power. During controlled mechanical ventilation, mechanical power is composed of parameters set by the clinician at the bedside—such as tidal volume (V_T), airway pressure (Paw), inspiratory airflow (V′), respiratory rate (RR), and positive end-expiratory pressure (PEEP) level—plus several patient-dependent variables, such as peak, plateau, and driving pressures. Different mathematical equations are available to calculate mechanical power, from pressure-volume (PV) curves to more complex formulas which consider both dynamic (kinetic) and static (potential) components; simpler methods mainly consider the dynamic component. Experimental studies have reported that, even at low levels of mechanical power, increasing V_T causes lung damage. Mechanical power should be normalized to the amount of ventilated pulmonary surface; the ratio of mechanical power to the alveolar area exposed to energy delivery is called “intensity.” Recognizing that mechanical power may reflect a conjunction of parameters which may predispose to VILI is an important step toward optimizing mechanical ventilation in critically ill patients. However, further studies are needed to clarify how mechanical power should be taken into account when choosing ventilator settings.

Bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increased compliance and tidal volume and decreased pulmonary resistance have been documented with the use of bronchodilators in infants with CLD. Therefore, bronchodilators might have a role in the prevention and treatment of CLD.

OBJECTIVES

To determine the effect of bronchodilators given as prophylaxis or as treatment for CLD on mortality and other complications of preterm birth in infants at risk for or identified as having CLD.

SEARCH METHODS

On 2016 March 7, we used the standard strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 2), MEDLINE (from 1966), Embase (from 1980) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; from 1982). We searched clinical trials databases, conference proceedings and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. We applied no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials involving preterm infants were eligible for inclusion. Initiation of bronchodilator therapy for prevention of CLD had to occur within two weeks of birth. Treatment of patients with CLD had to be initiated before discharge from the neonatal unit. The intervention had to include administration of a bronchodilator by nebulisation, by metered dose inhaler (with or without a spacer device) or by intravenous or oral administration versus placebo or no intervention. Eligible studies had to include at least one of the following predefined clinical outcomes: mortality, CLD, number of days on oxygen, number of days on ventilator, patent ductus arteriosus (PDA), pulmonary interstitial emphysema (PIE), pneumothorax, intraventricular haemorrhage (IVH) of any grade, necrotising enterocolitis (NEC), sepsis and adverse effects of bronchodilators.

DATA COLLECTION AND ANALYSIS

We used the standard method described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Two review authors extracted and assessed all data provided by each study. We reported risk ratio (RR), risk difference (RD) and number needed to treat for an additional beneficial outcome (NNTB) with 95% confidence interval (CI) for dichotomous outcomes and mean difference (MD) for continuous data. We assessed the quality of the evidence by using the GRADE approach.

MAIN RESULTS

For this update, we identified one new randomised controlled trial investigating effects of bronchodilators in preterm infants. This study, which enrolled 73 infants but reported on 52 infants, examined prevention of CLD with the use of aminophylline. According to GRADE, the quality of the evidence was very low. One previously included study enrolled 173 infants to look at prevention of CLD with the use of salbutamol. According to GRADE, the quality of the evidence was moderate. We found no eligible trial that studied the use of bronchodilator therapy for treatment of individuals with CLD. Prophylaxis with salbutamol led to no statistically significant differences in mortality (RR 1.08, 95% CI 0.50 to 2.31; RD 0.01, 95% CI -0.09 to 0.11) nor in CLD (RR 1.03, 95% CI 0.78 to 1.37; RD 0.02, 95% CI -0.13 to 0.17). Results showed no statistically significant differences in other complications associated with CLD nor in preterm birth. Investigators in this study did not comment on side effects due to salbutamol. Prophylaxis with aminophylline led to a significant reduction in CLD at 28 days of life (RR 0.18, 95% CI 0.04 to 0.74; RD -0.35, 95% CI -0.56 to -0.13; NNTB 3, 95% CI 2 to 8) and no significant difference in mortality (RR 3.0, 95% CI 0.33 to 26.99; RD 0.08, 95% CI -0.07 to 0.22), along with a significantly shorter dependency on supplementary oxygen in the aminophylline group compared with the no treatment group (MD -17.75 days, 95% CI -27.56 to -7.94). Tests for heterogeneity were not applicable for any of the analyses, as each meta-analysis included only one study.

AUTHORS' CONCLUSIONS

Data are insufficient for reliable assessment of the use of salbutamol for prevention of CLD. One trial of poor quality reported a reduction in the incidence of CLD and shorter duration of supplementary oxygen with prophylactic aminophylline, but these results must be interpreted with caution. Additional clinical trials are necessary to assess the role of bronchodilator agents in prophylaxis or treatment of CLD. Researchers studying the effects of bronchodilators in preterm infants should include relevant clinical outcomes in addition to pulmonary mechanical outcomes. We identified no trials that studied the use of bronchodilator therapy for treatment of CLD.

Exploration of the Contribution of Biobehavioral Variables to the Energy Expenditure of Preterm Infants

Variation in energy expended by preterm infants may be due to infant maturity and history of resolved acute lung disease (respiratory distress syndrome [RDS]) as well as growth, caloric intake, and activity. Indirect calorimetry was used in this exploratory, short-term longitudinal study to estimate energy expenditure (EE) from measures of inspired and expired O2 and CO2 .The sample included 35 assessments for 10 preterm infants (5 with and 5 without RDS history). Lung disease history (resolved RDS, no RDS diagnosis), weight gain (g/d) from the day on which birth weight had been regained to the study day, mean activity level, the number of the assessment (1 6), and the interaction of lung disease history and time were included in a linear mixed model for repeated measures. Time was an index of postconceptional and postnatal age; all 3 were highly correlated. Because of high correlation with weight gain, caloric intake was not included in the analytic model. Lung disease history, mean activity level, and time were significant contributors to EE. A more precise measure of medical status than absence or presence of lung disease history, evenly spaced repetitions of EE assessment, and exploration of contexts in which the infants exhibit a higher activity level are needed in a replication study with a larger sample.

Bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increase in compliance and tidal volume and decrease in pulmonary resistance have been documented with use of bronchodilators in studies of pulmonary mechanics in infants with CLD. Therefore, it is possible that bronchodilators might have a role in the prevention and treatment of CLD.

OBJECTIVES

To determine the effect of bronchodilators given either prophylactically or as treatment for CLD on mortality and other complications of prematurity in preterm infants at risk for or having CLD.

SEARCH METHODS

For this update of the review, searches of The Cochrane Library, Issue 3, 2012; MEDLINE 1966; EMBASE; CINAHL; personal files and reference lists of identified trials were performed in March 2012. In addition Web of Science and abstracts from the Annual meetings of the Pediatric Academic Societies were searched electronically from 2000 to 2012 on PAS Abstracts2view(TM.) No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials involving preterm infants were eligible for inclusion. Initiation of bronchodilator therapy had to occur within two weeks of birth for prevention of CLD. For treatment of CLD, treatment had to be initiated before discharge from the neonatal unit. The intervention had to include the administration of a bronchodilator either by nebulisation, metered dose inhaler (with or without a spacer device), intravenously or orally versus placebo or no intervention. Eligible studies had to include at least one of the predefined clinical outcomes (mortality, CLD, number of days on oxygen, number of days on ventilator, patent ductus arteriosus (PDA), pulmonary interstitial emphysema (PIE), pneumothorax, any grade of intraventricular haemorrhage (IVH), necrotising enterocolitis (NEC), sepsis and adverse effects of bronchodilators. Adverse effects of bronchodilators included hypokalaemia, tachycardia, cardiac arrhythmias, tremor, hypertension and hyperglycaemia).

DATA COLLECTION AND ANALYSIS

We used the standard method described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Two investigators extracted and assessed all data for each study. We reported risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CI) for dichotomous outcomes and weighted mean difference (WMD) for continuous data.

MAIN RESULTS

In this update we identified four randomised controlled trials investigating the effects of bronchodilators in preterm infants. None of these studies fulfilled our inclusion criterion that clinical outcomes should be reported. One eligible study was previously found dealing with prevention of CLD; this study used salbutamol and enrolled 173 infants. No eligible studies were found dealing with treatment of CLD. Prophylaxis with salbutamol did not show a statistically significant difference in mortality (RR 1.08; 95% CI 0.50 to 2.31; RD 0.01; 95% CI -0.09 to 0.11) or CLD (RR 1.03; 95% CI 0.78 to 1.37; RD 0.02; 95% CI -0.13 to 0.17). No statistically significant differences were seen in other complications associated with CLD or preterm birth. No side effects due to salbutamol were commented on in this study.

AUTHORS' CONCLUSIONS

There are insufficient data to reliably assess the use of salbutamol for the prevention of CLD. Further clinical trials are necessary to assess the role of salbutamol or other bronchodilator agents in prophylaxis or treatment of CLD. Researchers studying the effects of bronchodilators in preterm infants should include relevant clinical outcomes in addition to pulmonary mechanical outcomes.

Diuretics acting on the distal renal tubule for preterm infants with (or developing) chronic lung disease

BACKGROUND

Lung disease in preterm infants is often complicated with lung edema.

OBJECTIVES

To assess the risks and benefits of diuretics acting on distal segments of the renal tubule (distal diuretics) in preterm infants with or developing chronic lung disease (CLD).

SEARCH STRATEGY

The standard method of the Cochrane Neonatal Review Group were used. Initially, MEDLINE (1966 to November 2001), EMBASE (1974 to November 2001) and the Cochrane Controlled Trials Register (CENTRAL,The Cochrane Library, Issue 4, 2001) were searched. In addition, several abstract books of national and international American and European Societies were hand searched. Updated searches in April 2003, April 2007, and December 2010 did not yield any additional trials.

SELECTION CRITERIA

Included in this analysis are trials in which preterm infants with or developing CLD and at least five days of age were randomly allocated to receive a diuretic acting on the distal renal tubule. Eligible studies needed to assess at least one of the outcome variables defined a priori for this systematic review.

DATA COLLECTION AND ANALYSIS

The standard method for the Cochrane Collaboration described in the Cochrane Collaboration Handbook were used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion. Parallel and cross-over trials were combined. Whenever possible, baseline and final outcome data measured on a continuous scale was transformed into change scores using Follmann's formula.

MAIN RESULTS

Of the six studies fulfilling entry criteria, most focused on pathophysiological parameters and did not assess effects on important clinical outcomes defined in this review, or the potential complications of diuretic therapy.In preterm infants > 3 weeks of age with CLD, a four week treatment with thiazide and spironolactone improved lung compliance and reduced the need for furosemide. A single study showed thiazide and spironolactone decreased the risk of death and tended to decrease the risk for remaining intubated after eight weeks in infants who did not have access to corticosteroids, bronchodilators or aminophylline.

AUTHORS' CONCLUSIONS

In preterm infants > 3 weeks of age with CLD, acute and chronic administration of distal diuretics improve pulmonary mechanics. However, positive effects should be interpreted with caution as the numbers of patients studied are small in surprisingly few randomized controlled trials.

Effect of caffeine on respiratory muscle strength and lung function in prematurely born, ventilated infants

The aims of this study were to determine whether caffeine administration increased respiratory muscle function and if this was associated with lung function improvement in prematurely born infants being weaned from mechanical ventilation. Respiratory muscle function was assessed by measurement of the maximum pressures generated during occlusions at end inspiration (Pemax) and end expiration (Pimax) and lung function by measurement of lung volume (functional residual capacity (FRC)) and respiratory system compliance (CRS) and resistance (RRS) in 18 infants with a median gestational age of 28 (range 24-36) weeks. Measurements were made immediately prior to caffeine administration (baseline) and 6 h later. Six hours after caffeine administration compared to baseline, the median Pemax (p = 0.017), Pimax (p = 0.004), FRC (p < 0.001), CRS (p = 0.002) and RRS (p = 0.004) had significantly improved. Our results suggest that caffeine administration facilitates weaning of prematurely born infants from mechanical ventilation by improving respiratory muscle strength.

The Effects of helium/oxygen mixture (heliox) before and after extubation in long-term mechanically ventilated very low birth weight infants

OBJECTIVES

Our goal was to evaluate the effects of a helium/oxygen mixture (heliox) on pulmonary mechanics and gas exchange in preterm infants during both conventional and noninvasive ventilation.

PATIENTS AND METHODS

Ten preterm infants, ventilated from birth, were enrolled. Resistive work of breathing, pulmonary compliance, static compliance, respiratory rate, minute ventilation, ventilatory support, and gas exchange were measured before and during treatment. One hour after heliox therapy, subjects who showed a decrease of peak inspiratory pressure of >20% of the initial value were extubated and shifted to nasal bilevel positive airway pressure with heliox for the following 3 hours. Pulmonary mechanics and ventilatory parameters were measured during air/oxygen ventilation and again 10 minutes and 1 hour after starting heliox. Transcutaneous pressure of O(2) and CO(2), oxygen saturation, and respiratory rate were recorded continuously. Arterial blood gases were measured immediately before and 1 hour after initiating bilevel positive airway pressure. To maintain oxygen saturation at >92% during the bilevel positive airway pressure phase, the mean fraction of inspired oxygen was increased from 0.34 to 0.36.

RESULTS

Mean peak inspiratory pressure decreased from 21.4 to 17.4 cmH(2)O, work of breathing decreased from 0.46 to 0.22 joule/L, and transcutaneous pressure of CO(2) decreased from 52.3 to 49.1 mmHg. Mean transcutaneous pressure of O(2) improved from 42.8 to 46.7 mmHg, and minute ventilation improved from 332 to 478 mL/kg per minute. No significant differences were observed in mean airway pressure, respiratory rate, oxygen saturation, pulmonary compliance, and static compliance. Eight infants were extubated. One of them needed to be reintubated after 5 hours.

CONCLUSIONS

Our data show that mechanical ventilation with heliox reduces resistive work of breathing and ventilatory support requirements and improves gas exchange in preterm infants.

Energy requirements

The determination of the appropriate energy and nutritional requirements of a newborn infant requires a clear goal of the energy and other compounds to be administered, valid methods to measure energy balance and body composition, and knowledge of the neonatal metabolic capacities. Providing an appropriate amount of energy to newborn infants remains a challenge considering the great number of newborn infants who suffer in-hospital growth retardation. The energy requirements of a newborn infant are influenced by several factors - basal metabolism, growth, energy expenditure, and energy losses - which change continuously during development. Calculating the energy requirements of preterm infants is subject to error if general recommendations are applied without recognition of the large variation in factors that influence, for example, energy expenditure. Therefore, energy recommendations should be individualized and preferably based on measurements of energy expenditure. In particular, extremely low birth-weight and very low birth-weight infants are prone to develop negative energy and nutrient balances, due to low energy intake, low energy reserves and high energy demands. Early energy accretion is not only essential for growth but also influences neurodevelopmental outcome and physical health in the long term, thereby underlining the importance of adequate neonatal nutrition.

Comparison of resting energy expenditure in bronchopulmonary dysplasia to predicted equation

OBJECTIVE

Children with bronchopulmonary dysplasia (BPD) often suffer from growth failure because of disturbances in energy balance with an increase of resting energy expenditure (REE). Evaluation of REE is a useful tool for nutritional management. Indirect calorimetry is an elective method for measuring REE, but it is time consuming and requires rigorous procedure. The objective of this study was to test accuracy of prediction equation to evaluate REE in BPD children.

PATIENTS AND METHODS

Fifty-two children aged 4-10 years with BPD (30 boys and 22 girls) and 30 healthy lean children (20 boys and 10 girls) were enrolled. In this study, indirect calorimetry was compared to four prediction equations (Schoffield-W, Schoffield-HW, Harris-Benedict and Food and Agriculture Organization equation) using Bland-Altman pair wise comparison.

RESULTS

The Harris-Benedict equation was the best equation to predict REE in children with BPD, and Schoffield-W was the best in healthy children. For the children with chronic lung disease of prematurity the Harris-Benedict equation showed the lowest mean predicted REE-REE measured by indirect calorimetry difference (difference = 15 kcal/day; limits of agreement -266 and 236 kcal/day; 95% confidence interval for the bias -207 to 177 kcal/day), and graphically, the best agreement. For the group of healthy children, it was the Schofield-W equation (-2.9 kcal/day; limits of agreement -275 and 269 kcal/day; 95% confidence interval for the bias -171 to 165 kcal/day), and graphically, the best agreement.

CONCLUSION

Differences in prediction equation are minimal compared to calorimetry. Prediction equation could be useful in the management of children with BPD.

Energy expenditure and plasma catecholamines in preterm infants with mild chronic lung disease

The present study examined the hypothesis that the energy expenditure (EE) increases during the development of chronic lung disease (CLD) together with serum catecholamines as indicator of stress. Sixteen spontaneously breathing infants with gestational age of 28-34 weeks and birth weight of 870-1920 g were studied. Eight patients were at risk for CLD, eight were healthy controls. Measurements of indirect calorimetry were done weekly at postnatal ages of 2, 3, 4 and 5 weeks. Serum concentrations of adrenaline and noradrenaline were measured by means of a high-pressure liquid chromatography (HPLC) method. The eight CLD risk infants developed mild CLD with FiO(2) of 0.27-0.31 and characteristic radiographic signs at 28 days. Compared to the healthy controls, preterm infants with mild CLD showed increases in EE from week 3 (+67%) to week 5 (+46%). Plasma noradrenaline was increased significantly in the CLD infants when compared to the controls at week 3 (0.7+/-0.3 vs. 0.5+/-0.1 ng/ml; P<0.05) and more pronounced at week 4 (1.4+/-0.2 vs. 0.6+/-0.2 ng/ml; P<0.001) and 5 (1.1+/-0.3 vs. 0.7+/-0.2 ng/ml; P<0.01). Plasma adrenaline was markedly higher in the CLD risk group (mean overall value: 0.64+/-0.1 ng/ml) than in the controls (<0.1 ng/ml in all controls) from week 2 to 5. Regression analysis for the combined values of the infants with and without CLD showed that EE was directly correlated with heart rate, noradrenaline and adrenaline concentration at each of the four study weeks and with respiratory rate at weeks 2 and 3. Increased plasma catecholamine concentrations in preterm infants with CLD suggest that these infants experienced marked stress during the early stages of the disease. Increased EE may in part be a result of this stress.

Diuretics acting on the distal renal tubule for preterm infants with (or developing) chronic lung disease

OBJECTIVES

The aim of this review is to assess the risks and benefits of diuretics acting on distal segments of the renal tubule (distal diuretics) in preterm infants with or developing chronic lung disease (CLD). Primary objectives are to assess changes in need for oxygen or ventilatory support and effects on long-term outcome, and secondary objectives are to assess changes in pulmonary mechanics and potential complications of therapy.

SEARCH STRATEGY

We used the standard method of the Cochrane Neonatal Review Group. We searched MEDLINE (1966-November 2001), EMBASE (1974-November 2001) and the Cochrane Controlled Trials Register (CCTR) (Cochrane Library Issue 4, 2001). In addition, we hand searched several abstract books of national and international American and European Societies.

SELECTION CRITERIA

We included in this analysis trials in which preterm infants with or developing CLD and at least five days of age were all randomly allocated to receive a distal diuretic (i.e., a diuretic acting on the distal renal tubule). Eligible studies needed to assess at least one of the outcome variables defined a priori for this systematic review. Primary outcome variables included changes in need for respiratory support and oxygen supplementation, mortality, bronchopulmonary dysplasia (BPD), death or BPD, chronic lung disease at 36 weeks of postconceptional age (gestational age + postnatal age), length of stay, and number of rehospitalizations during the first year of life. Secondary outcome variables included pulmonary mechanics and potential complications of therapy.

DATA COLLECTION AND ANALYSIS

We used the standard method for the Cochrane Collaboration which is described in the Cochrane Collaboration Handbook. Two investigators extracted, assessed and coded separately all data for each study, using a form that was designed specifically for this review. Any disagreement was resolved by discussion. We combined parallel and cross-over trials and, whenever possible, transformed baseline and final outcome data measured on a continuous scale into change scores using Follmann's formula.

MAIN RESULTS

Of six studies fulfilling entry criteria, most focused on pathophysiological parameters and did not assess effects on important clinical outcomes defined in this review, or the potential complications of diuretic therapy. In preterm infants > 3 weeks of age with CLD, a four-week treatment with thiazide and spironolactone improved lung compliance and reduced the need for furosemide. Thiazide and spironolactone decreased the risk of death and tended to decrease the risk for lack of extubation after 8 weeks in intubated infants who did not have access to corticosteroids, bronchodilators or aminophylline. However, there is little or no evidence to support any benefit of diuretic administration on need for ventilatory support, length of hospital stay, or long-term outcome in patients receiving current therapy. There is no evidence to support the hypothesis that adding spironolactone to thiazide or that adding metolazone to furosemide improves the outcome of preterm infants with CLD.

REVIEWER'S CONCLUSIONS

In preterm infants > 3 weeks of age with CLD, acute and chronic administration of distal diuretics improve pulmonary mechanics. Studies are needed to assess (1) whether thiazide administration improves mortality, duration of oxygen dependency, ventilator dependency, length of hospital stay and long-term outcome in patients exposed to corticosteroids and bronchodilators (2) whether adding spironolactone to thiazides or adding metolazone to furosemide has any beneficial effect.

Energy expenditure in infants with pulmonary insufficiency: is there evidence for increased energy needs?

The observed growth failure in infants with pulmonary insufficiency is postulated to be a consequence of elevated rates of energy expenditure. Assessment of energy expenditure by the classical technique of indirect calorimetry has yielded conflicting results. The adoption of the newer, doubly labeled water technique has provided evidence to support increased rates of energy expenditure in infants with chronic lung disease, congenital heart disease and in minimally ill, extremely low birth weight infants. The doubly labeled water technique holds great promise for the detailed study of energy expenditure in a variety of clinical conditions, including very ill as well as free-living subjects.

Bronchodilators for the prevention and treatment of chronic lung disease in preterm infants

BACKGROUND

Chronic lung disease (CLD) occurs frequently in preterm infants (< 37 weeks gestational age) and has a multifactorial etiology. Bronchodilators have the potential effect of dilating small airways with muscle hypertrophy. Increase in compliance and tidal volume and decrease in pulmonary resistance have been documented with use of bronchodilators in short term studies of pulmonary mechanics in infants with CLD. Therefore it is possible that bronchodilators might have a role in the prevention and treatment of CLD.

OBJECTIVES

To evaluate the effect of bronchodilators, given prophylactically or as treatment for chronic lung disease, on mortality and other complications of preterm births.

SEARCH STRATEGY

The search strategy used to identify studies was according to the guidelines of the Cochrane Neonatal Review Group. Searches were made of MEDLINE 1966 to December 2000, EMBASE 1980 to January 2001, CINAHL 1982 to December 2000, the Cochrane Library Issue 1, 2001, personal files and reference lists of identified trials. The following terms were used: bronchopulmonary dysplasia, chronic lung disease, bronchodilator agents, adrenergic agents, anticholinergic agents, albuterol, aminophylline, atropine, caffeine, clenbuterol, cromakalim, ephedrine, epinephrine, fenoterol, hexoprenaline, ipratropium, isoetharine, isoproterenol, orciprenaline, procaterol, terbutaline, theophylline, tretoquinol.

LIMITS

newborn, infant; human, clinical trial or controlled clinical trial, meta analysis, multicenter study or randomised controlled trial. No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled clinical trials involving preterm infants. Initiation of bronchodilator therapy had to occur within two weeks of birth for prevention of CLD. For treatment of CLD treatment should have been initiated before discharge from the neonatal unit. The intervention had to include the randomised administration of a bronchodilator either by nebulisation, metered dose inhaler with or without a spacer device, intravenously or orally, versus placebo or no intervention. Eligible studies had to include at least one of the following outcomes: mortality, CLD at 28 days or at 36 weeks corrected GA, number of days on oxygen, number of days on ventilator, patent ductus arteriosus (PDA), pulmonary interstitial emphysema (PIE), pneumothorax, any grade of intraventricular haemorrhage, necrotizing enterocolitis (NEC), sepsis and adverse effects of bronchodilators.

DATA COLLECTION AND ANALYSIS

We used the standard method for the Cochrane Collaboration as described in the Cochrane Collaboration handbook. Two investigators (GN, AO) extracted and assessed all data for each study. Any disagreement was resolved by discussion. Relative risk (RR) and risk difference (RD) with 95% confidence intervals (CI) are reported for dichotomous outcomes and mean difference (WMD) for continuous data.

MAIN RESULTS

One eligible study was found dealing with prevention of CLD; this study used salbutamol and enrolled 173 infants. No eligible studies were found dealing with treatment of CLD. Prophylaxis with salbutamol did not show a statistically significant difference in mortality [RR 1.08 (95% CI 0.50, 2.31); RD 0.01 (95% CI -0.09, 0.11)], CLD (mild, moderate or severe) [RR 1.03 (95% CI 0.78, 1.37); RD 0.02 (95% CI -0.13, 0.17)], need for iv dexamethasone [RR 0.77 (95% CI 0.49, 1.19); RD -0.08 (95% CI -0.22, 0.05)], respiratory infections [RR 0.61 (95% CI 0.27, 1.39); RD -0.06 (95% CI -0.16, 0.04)] or positive blood culture [RR 1.06 (95% CI 0.54, 2.06); RD 0.01 (95% CI -0.10, 0.12)]. There was no statistically significant difference in duration of ventilatory support [MD -1.63 days (95% CI -5.63, 2.37)], duration of oxygen supply [MD -2.82 days (95% CI -11.91, 6.27)] or age of weaning from respiratory support (defined as assisted ventilation or oxygen supplementation) [MD -2.87 days (95% CI -11.28, 5.54)]. No side effects due to salbutamol were commented on in this study.

REVIEWER'S CONCLUSIONS

There are insufficient data to reliably assess the use of salbutamol for the prevention of CLD. Further clinical trials are necessary to assess the role of salbutamol or other bronchodilator agents in prophylaxis or treatment of CLD.

Sleep, respiratory rate, and growth hormone in chronic neonatal lung disease

This study assessed whether respiratory rates (RRs) correlate with urinary growth hormone (U-GH) excretion and sleep architecture in infants with chronic neonatal lung disease (CNLD) in early (1 month), middle (6 months), and late (10 months) infancy. Twenty-three preterm infants (CNLD=16, controls=7) were studied on 51 occasions. CNLD infants were stratified according to mean non-REM sleep respiratory rate (NREM RR) in early infancy into "High RR CNLD" infants (mean NREM RR >2 SD higher than controls) and "Normal RR CNLD" infants (mean NREM RR within 2 SD of controls' mean). "High RR CNLD" infants (RR >45) had a lower mean birthweight (P=0.015), current weight (P=0.042), current length (P=0.02), and growth velocity in early infancy (grams/week gained: P=0.042) than "Normal RR CNLD" and control infants. Mean (95% CI) U-GH excretion (ng U-GH/g urinary creatinine) was higher in "High RR CNLD" infants in air or their usual O2 (1,932 [459, 3,406]) than "Normal RR CNLD" (394 [147, 642]) and controls (320 [147, 492]) (P=0.024). With resolution of tachypnea by mid-infancy, hemoglobin oxygen saturation (SaO2) >93%, mean growth parameters and U-GH excretion for the "High RR CNLD" group were not significantly different from "Normal RR CNLD" and control groups. CNLD infants demonstrated increased sleep efficiency (P=0.016), whereas controls had similar sleep efficiency between early and middle infancy (P=0.452). Mean percent time in REM sleep (REM%) and slow wave sleep (SWS%) were not significantly different between early and middle infancy and did not vary in relation to respiratory rate. We conclude that tachypneic infants with CNLD have slower growth and elevated U-GH excretion in early infancy. With resolution of tachypnea, growth improved, U-GH excretion decreased, and sleep consolidation occurred. An elevated U-GH in tachypneic CNLD infants may reflect stress, compromised nutrition (GH resistance), or a feedback loop involving a direct effect of GH on lung growth and repair.

Myocardial, erythropoietic, and metabolic adaptations to anemia of prematurity in infants with bronchopulmonary dysplasia

OBJECTIVES

The effects of anemia of prematurity during bronchopulmonary dysplasia (BPD) as well as on the metabolic and erythropoietic functions were determined before and after a transfusion. Fourteen anemic (Hb range: 65-88 gm/L), oxygen dependent (fraction of inspired oxygen < or = 35%), nonventilated, preterm infants with BPD were studied at a postnatal age of 6 +/- 2 weeks.

STUDY DESIGN

Cardiac output, heart rate, mean velocity of circumferential fiber shortening, shortening fraction (SF), and stroke volume were assessed by pulsed and continuous wave Doppler echocardiography. Values for resting oxygen consumption, carbon dioxide production, and energy expenditure were obtained by indirect calorimetry. The affinity of oxygenated hemoglobin was determined by a blood oxygen dissociation analyzer.

RESULTS

An increased hemoglobin level resulted in a suppression of erythropoietin secretion (p < 0.001), whereas heart rate, cardiac output, stroke volume, and SF decreased (p < 0.05). Weight gain before and after transfusion were similar. Plasma lactate levels decreased from 1.6 +/- 0.3 to 1.2 +/- 0.3. Oxygen consumption, carbon dioxide production, and energy expenditure were not affected.

CONCLUSIONS

Anemia of prematurity and BPD increase heart rate, cardiac output, stroke volume, and SF. These hemodynamic compensatory responses are normalized by transfusion.

Assessing the effect of disease on nutrition of the preterm infant

OBJECTIVE

To review existing data on nutritional requirements of extremely low birth weight (ELBW) and very low birth weight (VLBW) preterm infants (those who weigh < 1000 g and 1000-1500 g at birth, respectively), and the effects of diseases on these nutritional requirements.

DATA SOURCES

A literature search was conducted on applicable articles related to nutritional requirements of preterm ELBW and VLBW infants and the effects of diseases in these infants on their nutritional and metabolic requirements.

DATA SYNTHESIS

The literature was analyzed to determine nutritional requirements of preterm ELBW and VLBW infants, to select the most common diseases that have significant and important effects on nutrition and metabolism in these infants, and to make recommendations about diagnostic and therapeutic approaches to nutritional problems as affected by diseases in ELBW and VLBW infants.

CONCLUSIONS

Many diseases unique to preterm infants, either directly or by enhancing the effects of stress on the metabolism of such infants, provide important changes in the nutrient requirements. The overriding observation from all studies, however, is that ELBW and VLBW preterm infants are underfed during the early postnatal period and that this condition, combined with additional stresses from various diseases, increases the risk of long-term neurological sequelae. The value of achieving a specific body composition and growth weight is less certain. There remains a critical need for determining the right quality as well as quantity of nutrients for these infants.

Influence of energy substrates on respiratory gas exchange during conventional mechanical ventilation of preterm infants

OBJECTIVE

The purpose of this study was to determine the optimal parenteral feeding regimen for infants with compromised respiratory function.

METHODS

We studied the influence of varying the source of energy on respiratory gas exchange in 10 infants who were supported by mechanical ventilation and who received intravenous feedings. Two isoenergetic parenteral regimens were infused consecutively; the level of fat intake was varied inversely with that of glucose. Under similar ventilator settings, transcutaneous partial pressures of oxygen and carbon dioxide, as well as indirect calorimetry were measured during each regimen.

RESULTS

Despite the higher carbon dioxide production during the glucose-rich regimen (8.9 +/- 0.7 vs 7.9 +/- 0.4 ml/kg per minute, p < 0.05 by analysis of variance), transcutaneous partial pressure of carbon dioxide remained unaffected, suggesting ventilatory compensation as documented by the increased (p < 0.002) alveolar ventilation. This was not associated with a detectable rise in oxygen consumption, but with a significant change in partial pressure of oxygen (77 +/- 5 vs 66 +/- 3 mm Hg, p < 0.05).

CONCLUSIONS

Ventilator-dependent infants with early and mild bronchopulmonary dysplasia, who receive intravenous feedings of a moderate load of glucose-based energy, can compensate for enhanced carbon dioxide production by increasing their respiratory drive, with a beneficial effect on oxygenation compared with that observed when energy is derived from lipid-based solutions.

Energy requirements in sick preterm babies

The energy requirements of healthy preterm babies are well documented in the literature. However, the clinical load in neonatal intensive care units is due to sick preterm infants requiring prolonged mechanical ventilation, many of whom will develop bronchopulmonary dysplasia. It is this group in which knowledge of energy requirements is scanty. This group also has poor energy reserves and is often intolerant of enteral and parenteral nutrition. In this article, we will review methods of measurement of energy expenditure, methodological problems when applied to ill infants and published results of energy expenditure measurements in sick preterm babies. We will review the link between energy reserves, energy intake and energy expenditure. The problems of undernutrition in early postnatal life and possible consequences in adult life will be discussed.

Prolonged mechanical ventilation in children

Improvements in neonatal and pediatric intensive care have produced a growing population of children dependent on mechanical ventilation for survival. Long-term mechanical ventilation has become a realistic alternative to death from progressive respiratory failure for many children with chronic respiratory illness. This article reviews the pathophysiology, etiology, and management of chronic respiratory failure in childhood.

Pathophysiology and treatment of bronchopulmonary dysplasia. Current issues

Although much has been learned about BPD in the 25 years since its initial description, BPD remains a significant complication of prematurity. Substantial advances into the understanding of its pathophysiology and pathogenesis have been made and are reflected in new therapeutic interventions. Much current research is directed towards the role of prevention, exploring new approaches for accelerating lung maturation with combined maternal steroid and thyrotropin releasing hormone (TRH) therapy, surfactant replacement therapy, high frequency oscillatory ventilation, antioxidant administration, manipulation of endogenous antioxidants, and other pharmacologic strategies to minimize lung injury. The impact of other technologies, such as synchronized intermittent mandatory ventilation, perfluorocarbon (liquid) ventilation, and perhaps inhaled nitric oxide therapy may become additional parts of the clinical regimen for some cases of severe neonatal respiratory failure. Less information is available on mechanisms which can hasten lung healing. Ongoing studies of inflammatory products, growth factors, and cytokines may lead to new therapies which will favorably influence the fibroproliferative phase of disease. In the meantime, the medical and social impact of BPD continues to remain a significant problem not only during infancy but also throughout life. Mildred Stahlman, MD, recently wrote that (a)s sanguine as the future looks for surfactant therapy, it may leave us with more very low-birth weight infants who survive, whose potential for normal pulmonary growth and development is unknown, and whose very immature organ systems, besides the lung, are still susceptible to metabolic, neurologic, and other problems. As more survivors are reaching young adulthood, respiratory and neurodevelopmental complications persist. Thus, as advances in the care of the premature newborn with respiratory distress have dramatically improved survival, the management of chronic lung disease and related problems remains a continuing challenge.

Use of high-fat formula for premature infants with bronchopulmonary dysplasia: metabolic, pulmonary, and nutritional studies

The use of dietary fat in preference to carbohydrate offers the theoretic advantage of diminishing carbon dioxide production and thus the respiratory quotient, which may be beneficial for babies with chronic lung disease. Ten premature infants (birth weight (mean +/- SEM), 1.13 +/- 0.12 kg; postnatal age, 9 +/- 1 weeks) with bronchopulmonary dysplasia were alternately fed a high-fat and a high-carbohydrate formula each for 1 week, in randomized order. Lower rates of carbon dioxide production (6.6 +/- 0.3 versus 7.4 +/- 0.4 ml/kg per minute; p < 0.05), and consequently lower respiratory quotients (0.80 +/- 0.02 versus 0.94 +/- 0.01 ml/kg per minute; p < 0.005), were observed during the administration of the high-fat formula. There were no significant differences in results of pulmonary function tests with the use of either formula. Both formulas were equally well tolerated and able to promote adequate growth and normal biochemical profiles. However, weight gain was significantly greater with the administration of the high-carbohydrate formula, possibly because of an increase in the accretion of body fat. We conclude that the short-term use of high-fat formula for infants with bronchopulmonary dysplasia decreases carbon dioxide production while maintaining adequate growth and nutritional status.

Growth retardation after dexamethasone administration: assessment by knemometry

Knemometry has been used to measure lower leg growth during 32 nine day courses of dexamethasone in 26 babies ranging from 24 to 32 weeks' gestation at birth. Mean leg length velocity was 0.37 mm/day in the 10 days before steroids. Administration of dexamethasone was associated with a decrease in velocity in all babies, and in 15 leg shortening was documented. Mean leg length velocity during steroid treatment was -0.003 mm/day. After the course of dexamethasone was completed there was an immediate increase in leg length velocity to a mean of 0.52 mm/day over the first 10 days then falling to a value similar to the growth velocity observed before treatment. Leg length had reached the value predicted by growth before steroids about 30 days after dexamethasone. The reduction in leg length velocity occurred despite a significant increase in energy intake and decrease in oxygen requirements.

Relative contribution of physical activity to neonatal oxygen consumption

To explore the relevance of distinguishing between resting and global energy expenditure in newborn infants, oxygen consumption (VO2) was measured during extremes of physical activity in 17 parenterally fed newborn infants with a large range of body weights (1.0-3.4 kg) and gestational ages (28-41 weeks). Under constant nutrient intakes, each infant served as his/her own control when comparing VO2 during resting conditions and spontaneous intense physical activity, called exercise. VO2 was significantly correlated with body weight at rest (r = 0.96). But during intense activity, the better predictor of exercise-induced VO2 was body weight in the smaller infants (< 2.0 kg) and gestational age in the larger infants (> 35 weeks). The difference in VO2 between both levels of activity represented the oxygen cost of exercise, which decreased (P < 0.01) with body weight. For clinical purposes, the physical activity of low-birth-weight infants does not contribute substantially to their energy balance.

Energy expenditure and severity of respiratory disease in very low birth weight infants receiving long-term ventilatory support

We attempted to determine whether the hypermetabolism of infants with bronchopulmonary dysplasia was detectable during assisted ventilation. Respiratory gas exchange variables were measured with a metabolic gas monitor in 10 infants under similar nutritional conditions. Oxygen consumption increased linearly with the need for ventilatory support (R2 = 0.75), as documented by the ventilatory index.

Energy expenditure during synthetic surfactant replacement therapy for neonatal respiratory distress syndrome

Little information is available on the energy expenditure of infants with increased work of breathing from respiratory distress syndrome (RDS). A study was carried out to determine whether surfactant replacement therapy modifies respiratory gas exchange in newborn infants with RDS and an arterial-alveolar oxygen tension ratio of less than 0.22. In a double-blind, placebo-controlled, rescue trial, infants received either two 5 ml/kg doses of a synthetic surfactant, Exosurf Neonatal, or air placebo. Of 23 infants ventilated for RDS, 11 were randomly assigned to receive air and 12 to receive surfactant. Oxygen consumption, carbon dioxide production, respiratory quotient, and metabolic rate were measured by computerized, closed-circuit, indirect calorimetry. Concomitantly, transcutaneous oxygen and carbon dioxide tension were continuously recorded. Oxygen consumption and carbon dioxide production remained constant during the period infants received surfactant. In patients randomly assigned to surfactant, a decrease in respiratory quotient was observed after the first (p less than 0.025) but not the second dose. This decrease was possibly related to a change in substrate utilization. The improved clinical outcomes reported among infants receiving surfactant were not accompanied by changes in energy expenditure.

Total parenteral nutrition in the newborn infant: energy substrates and respiratory gas exchange

The hypothesis that a high-fat parenteral regimen was beneficial for respiratory gas exchanges, in comparison with a high-glucose regimen, was tested in a paired crossover design. Ten parenterally fed newborn infants with no respiratory problems received two 5-day isoenergetic and isonitrogenous regimens that differed in their nonprotein source of energy; the level of fat intake (low fat (LF) 1 gm.kg-1.day-1; high fat (HF) 3 gm.kg-1.day-1) varied inversely with that of glucose. Continuous transcutaneous PO2 (tcPO2) and PCO2 (tcPCO2), respiratory gas exchange (indirect calorimetry), and plasma arachidonate metabolites were measured at the end of each regimen. Oxygen consumption and resting energy expenditure were not affected by modification of the source of energy. However, carbon dioxide production (VCO2) was higher during LF than during HF (6.9 +/- 0.2 vs 6.2 +/- 0.1 ml.kg-1.min-1; p less than 0.01), as was the respiratory quotient (1.08 +/- 0.02 vs 0.96 +/- 0.02; p less than 0.001). Despite the differences in VCO2, the tcPCO2 was not affected, suggesting adequate pulmonary compensation during LF, as documented by the higher minute ventilation (160 +/- 7 vs 142 +/- 5 ml.kg-1.min-1; p less than 0.01). The lower tcPO2 during the HF regimen (73.8 +/- 2.8 vs 68.8 +/- 2.6 mm Hg; p less than 0.015) indicated a disturbance at the alveolocapillary level induced by the lipid emulsion. No differences were found in circulating levels of prostaglandins and thromboxanes. The substitution of glucose for lipid did not modify fat storage (2.1 +/- 0.3 vs 2.1 +/- 0.3 gm.kg-1.day-1). We conclude that the supposed beneficial effect of a fat emulsion on respiratory gas exchange is questionable.

Drug therapy for bronchopulmonary dysplasia

With improved survival of critically ill premature infants, BPD has become an important sequela of neonatal intensive care. A variety of medications are used in the management of BPD. In this article we have attempted to summarize clinical efficacy, pharmacokinetics, and side effects of many of these medications. Longer-term studies on the efficacy of drug therapy are needed and may be facilitated by the development of accurate and reproducible computerized techniques for the measurement of pulmonary mechanics in neonates. Ultimately, new pharmacologic agents or other strategies that will prevent lung injury from hyperoxia and mechanical ventilation or accelerate tissue repair once injury occurs will play a major role in the prevention and treatment of infants with BPD.

Effects of intravenous glucose loading on oxygen consumption, carbon dioxide production, and resting energy expenditure in infants with bronchopulmonary dysplasia

To determine the effects of intravenous glucose loading on basal oxygen consumption, resting energy expenditure, and basal carbon dioxide production in infants with bronchopulmonary dysplasia who were still oxygen dependent, we administered intravenous glucose loads of 4 and 12 mg/kg-1/min-1 on 2 consecutive days, under identical experimental conditions, to six infants with bronchopulmonary dysplasia and six healthy control subjects. Infants were not fed for 9 hours before and during the 4- to 6-hour study periods; the intravenous glucose infusion, along with an amino acid mixture (2 gm.kg-1.24 hr-1), was started at the beginning of the fasting period. Oxygen consumption and carbon dioxide production and resting energy expenditure were measured by a flow-through indirect calorimetry technique under basal conditions. Infants with oxygen-dependent bronchopulmonary dysplasia had significantly higher basal oxygen consumption and resting energy expenditure than did control infants and significantly higher basal carbon dioxide production during the high glucose infusion. With glucose loading, infants with bronchopulmonary dysplasia had a significant rise in basal oxygen consumption (7.91 +/- 0.91 ml.kg-1.min-1 to 9.65 +/- 1.35 ml.kg-1.min-1, p less than 0.05), basal carbon dioxide production (5.93 +/- 0.72 ml.kg-1.min-1 to 7.10 +/- 1.04 ml.kg-1.min-1), and resting energy expenditure (53.8 +/- 5.75 kcal.kg-1.24 hr-1 to 65.3 +/- 7.0 kcal.kg-1.24 hr-1, all p values less than 0.05). Control infants had no significant changes with intravenous glucose loading. We conclude that intravenous glucose loading in infants with bronchopulmonary dysplasia resulted in a net increase in resting energy expenditure, which should be taken into account in assessing their energy intake during nutritional management. The risk of pulmonary stress caused by an increase in basal oxygen consumption and carbon dioxide production resulting from glucose load should also be considered.

Metabolic rate and energy balance in infants with bronchopulmonary dysplasia

To determine energy use and growth of infants with bronchopulmonary dysplasia (BPD), we studied metabolic rate and energy balance in five infants with stage III-IV BPD (birth weight 1309 +/- 530 gm, gestational age 32 +/- 3 weeks, postnatal age 59.8 +/- 14.2 days) and in five control infants (birth weight 1540 +/- 213 gm, gestational age 33 +/- 2 weeks, postnatal age 42.0 +/- 4.2 days). Infants with BPD had significantly lower energy intake but higher energy expenditure than did control infants. Weight gain and energy cost of growth were significantly less in BPD infants than in control infants, as were urine output and output/intake ratio. We conclude that infants with BPD (1) absorbed caloric intake as well as did normal control infants, (2) had low energy intake and high energy expenditure, resulting in poor weight gain, and (3) had low energy cost of growth, suggesting an alteration in composition of tissue gain, with relatively high water content.