Short- and long-term effects of furosemide on lung function in infants with bronchopulmonary dysplasia

Diuretics use in the management of bronchopulmonary dysplasia in preterm infants: A systematic review

AIM

Bronchopulmonary dysplasia (BPD), a respiratory complication associated with neonatal prematurity, presents opportunities for pharmacological intervention due to its contributing risk factors. Despite diuretics' controversial usage in BPD treatment and varying institutional practices, this review aims to consolidate evidence from clinical trials regarding diuretic use in BPD.

METHODS

We conducted a systematic review following PRISMA guidelines, searching EMBASE, Medline, Web of Science and CINAHL databases (PROSPERO 2022: CRD42022328292). Covidence facilitated screening and data extraction, followed by analysis and formatting in Microsoft Excel.

RESULTS

Among 430 screened records, 13 were included for analysis. Three studies assessed spironolactone and chlorothiazide combinations, two studied spironolactone and hydrochlorothiazide, while eight examined furosemide. All studies evaluated drug effects on dynamic pulmonary compliance and pulmonary resistance, serving as comparative measures in our review.

CONCLUSION

Diuretics' effectiveness in treating bronchopulmonary dysplasia remains uncertain. The limited number of identified randomised controlled trials (RCTs) hampers high-level evidence-based conclusions when applying the Population, Intervention, Comparison, Outcome (PICO) approach. Conducting large prospective studies of good quality could provide more definitive insights, but the rarity of outcomes and eligible patients poses challenges. Further research, primarily focusing on RCTs assessing diuretics' safety and efficacy in this population, is warranted.

Respiratory management in the premature neonate

INTRODUCTION

Advances in neonatal care have made possible the increased survival of extremely preterm infants. Even though there is widespread recognition of the harmful effects of mechanical ventilation on the developing lung, its use has become imperative in the management of micro-/nano-preemies. There is an increased emphasis on the use of less-invasive approaches such as minimally invasive surfactant therapy and non-invasive ventilation that have been proven to result in improved outcomes.

AREAS COVERED

Here, we review the evidence-based practices surrounding the respiratory management of extremely preterm infants including delivery room interventions, invasive and non-invasive ventilation approaches, and specific ventilator strategies in respiratory distress syndrome and bronchopulmonary dysplasia. Adjuvant relevant respiratory pharmacotherapies used in preterm neonates are also discussed.

EXPERT OPINION

Early use of non-invasive ventilation and use of less invasive surfactant administration are key strategies in the management of respiratory distress syndrome in preterm infants. Ventilator management in bronchopulmonary dysplasia must be tailored according to the individual phenotype. There is strong evidence to start caffeine early to improve respiratory outcomes, but evidence is lacking on the use of other pharmacological agents in preterm neonates, and an individualized approach has to be considered for their use.

Lung ultrasound assessment of pulmonary edema in neonates with chronic lung disease before and after diuretic therapy

INTRODUCTION

Bronchopulmonary dysplasia (BPD) is characterized by lung injury with varying degrees of disrupted alveolarization, vascular remodeling, inflammatory cell proliferation, and pulmonary edema. Diuretics are often used to ameliorate the symptoms or progression of BPD. Our primary objective was to use lung ultrasound (LUS) to determine if diuretics decrease pulmonary edema in infants with BPD. The secondary objective was to assess changes in respiratory support during the first week after initiation of diuretics.

METHODS

Premature infants requiring noninvasive respiratory support and starting diuretic therapy for evolving BPD were compared with a similar group of infants not receiving diuretics (control). For the diuretic group, LUS exams were performed before and on Days 1, 3, and 6 after initiation of treatment. For the control group, LUS was performed at equivalent time points. A composite pulmonary edema severity (PES) score of 0-5 was calculated based on the total number of B-lines in six scanned areas. Respiratory support parameters (FiO₂ , nasal cannula flow, or CPAP) were also recorded.

RESULTS

Infants in the diuretic (n = 28) and control (n = 23) groups were recruited at median corrected gestational ages of 34.2 (33.3-35.9) and 34.0 (33.4-36.3) weeks, respectively (p = 0.82). PES scores, FiO₂ , and respiratory flow support decreased significantly from Days 0 to 6 (p < 0.0001, p = 0.001, and p = 0.01, respectively) in the diuretic group, but not in the control group.

CONCLUSION

Diuretic use is associated with decreased pulmonary edema and improved oxygenation in infants with BPD during the first week of treatment.

Fifteen-minute consultation: Neonatal hypertension

Neonatal hypertension is a rare but well recognised condition, especially in newborns needing invasive monitoring in the intensive care unit. Recognition of newborns with hypertension remains challenging because of natural variability in blood pressure with postconceptional age and the lack of reference data for different gestational ages. Investigation of neonates with hypertension can be challenging in light of the myriad differing aetiologies. This may be simplified by a systematic approach to investigation. There remains a relative paucity of data to guide the use of pharmacological therapies for hypertension in neonates. Clinicians rely on empirical management protocols based on experience and expert opinion. Much of the information on dosing regimens and protocols has simply been derived from the use of antihypertensive agents in older children and in adults, despite fundamental pathophysiological differences.

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.

An Update on the Prevention and Management of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a common morbidity affecting preterm infants and is associated with substantial long-term disabilities. There has been no change in the incidence of BPD over the past 20 years, despite improvements in survival and other outcomes. The preterm lung is vulnerable to injuries occurring as a result of invasive ventilation, hyperoxia, and infections that contribute to the development of BPD. Clinicians caring for infants in the neonatal intensive care unit use multiple therapies for the prevention and management of BPD. Non-invasive ventilation strategies and surfactant administration via thin catheters are treatment approaches that aim to avoid volutrauma and barotrauma to the preterm developing lung. Identifying high-risk infants to receive postnatal corticosteroids and undergo patent ductus arteriosus closure may help to individualize care and promote improved lung outcomes. In infants with established BPD, outpatient management is complex and requires coordination from several specialists and therapists. However, most current therapies used to prevent and manage BPD lack solid evidence to support their effectiveness. Further research is needed with appropriately defined outcomes to develop effective therapies and impact the incidence of BPD.

Loop Diuretics in Severe Bronchopulmonary Dysplasia: Cumulative Use and Associations with Mortality and Age at Discharge

OBJECTIVES

To measure between-center variation in loop diuretic use in infants developing severe bronchopulmonary dysplasia (BPD) in US children's hospitals, and to compare mortality and age at discharge between infants from low-use centers and infants from high-use centers.

STUDY DESIGN

We performed a retrospective cohort study of preterm infants at <32 weeks of gestational age with severe BPD. The primary outcome was cumulative loop diuretic use, defined as the proportion of days with exposure between admission and discharge. Infant characteristics associated with loop diuretic use at P < .10 were included in multivariable models to adjust for center differences in case mix. Hospitals were ranked from lowest to highest in adjusted use and dichotomized into low-use centers and high-use centers. We then compared mortality and postmenstrual age at discharge between the groups through multivariable analyses.

RESULTS

We identified 3252 subjects from 43 centers. Significant variation between centers remained despite adjustment for infant characteristics, with use present in an adjusted mean range of 7.3% to 49.4% of days (P < .0001). Mortality did not differ significantly between the 2 groups (aOR, 0.98; 95% CI, 0.62-1.53; P = .92), nor did postmenstrual age at discharge (marginal mean, 47.3 weeks [95% CI, 46.8-47.9 weeks] in the low-use group vs 47.4 weeks [95% CI, 46.9-47.9 weeks] in the high-use group; P = .96).

CONCLUSIONS

A marked variation in loop diuretic use for infants developing severe BPD exists among US children's hospitals, without an observed difference in mortality or age at discharge. More research is needed to provide evidence-based guidance for this common exposure.

Bronchopulmonary dysplasia requiring tracheostomy: A review of management and outcomes

Bronchopulmonary Dysplasia (BPD) is a pulmonary disease affecting newborns, commonly those with prematurity or low birth weight. Its pathogenesis involves underdevelopment of lung tissue with subsequent limitations in ventilation and oxygenation, resulting in impaired postnatal alveolarization. Despite advances in care with improved survival, BPD remains a prevalent comorbidity of prematurity. In severe cases, management may involve mechanical ventilation via tracheostomy. BPD's demand for multidisciplinary care compounds the challenges in management of this condition. Here, we review existing literature: the history of disease, criteria for diagnosis, pathogenesis, and modes of treatment with a focus on the severe subtype: that which is associated with pulmonary hypertension (PAH) for which tracheostomy is often required to facilitate long-term mechanical ventilation. We review the current recommendations for tracheostomy and decannulation.

Diuretic use in infants with developing or established chronic lung disease: A practice looking for evidence

AIM

The objective was to assess respiratory efficacy of hydrochlorothiazide and spironolactone and ascertain any adverse effects.

METHODS

Data from 2014 to 2018 was analysed for infants <28 weeks' gestational age (GA) administered oral diuretics. Impact on respiratory support, weight gain and electrolyte status was assessed as a pre-post intervention study.

RESULTS

Of 491 infants, 117 (24%) were administered diuretics for evolving or established bronchopulmonary dysplasia. GA and birthweight of the cohort were 25.7 ± 1.1 weeks and 779 ± 172 g, respectively. Median (interquartile range) chronological age and GA at the start of diuretics was 45 (22, 62) days and 32.1 (30.1, 35.1) weeks, respectively. In 71/117 (61%) infants, diuretics were started at <36 weeks GA. Of them 63 (88.7%) went on to develop bronchopulmonary dysplasia. Median duration of diuretics was 38 (18-52) days. Modest improvement was noted in respiratory parameters (ventilator pressure (cm of H₂ O), 8.8 ± 0.4 vs. 8.8 ± 0.5, P = 0.39, oxygen requirement (%), 32 ± 1 vs. 30 ± 1, P = 0.07 and pO₂ (mm Hg) 34.5 ± 1.3 vs. 36.6 ± 1, P = 0.04. Ninety-eight (84%) infants developed hyponatraemia (<135 mmol/L); sodium supplements were administered in 58/98 (59%) infants. In one third infants, phosphate levels dropped below 1.8 mmol/L, needing supplementation. Weight gain (g/kg/day) slowed down significantly (18.2 ± 2.1 to 10 ± 2.9, P = <0.001).

CONCLUSIONS

Use of diuretics was associated with modest improvements in respiratory support requirements but was associated with significant electrolyte abnormalities and slowdown in weight gain (or weight loss).

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.

Association Between Furosemide Exposure and Clinical Outcomes in a Retrospective Cohort of Critically Ill Children

Furosemide is commonly prescribed in critically ill patients to increase the urine output and prevent fluid overload (FO) and acute kidney injury (AKI), but not supported by conclusive evidence. There remain conflicting findings on whether furosemide associates with AKI and adverse outcomes. Information on the impact of furosemide on adverse outcomes in a general population of pediatric intensive care unit (PICU) is limited. The aim of the cohort study was to investigate the associations of furosemide with AKI and clinical outcomes in critically ill children. Study Design: We retrospectively reviewed a cohort of 456 critically ill children consecutively admitted to PICU from January to December 2016. The exposure of interest was the use of furosemide in the first week after admission. FO was defined as ≥5% of daily fluid accumulation, and mean FO was considered significant when mean daily fluid accumulation during the first week was ≥5%. The primary outcomes were AKI in the first week after admission and mortality during PICU stay. AKI diagnosis was based on Kidney Disease: Improving Global Outcomes criteria with both serum creatinine and urine output. Results: Furosemide exposure occurred in 43.4% of all patients (n = 456) and 49.3% of those who developed FO (n = 150) in the first week after admission. Patients who were exposed to furosemide had significantly less degree of mean daily fluid accumulation than those who were not (1.10 [-0.33 to 2.61%] vs. 2.00 [0.54-3.70%], P < 0.001). There was no difference in the occurrence of AKI between patients who did and did not receive furosemide (22 of 198 [11.1%] vs. 36 of 258 [14.0%], P = 0.397). The mortality rate was 15.4% (70 of 456), and death occurred more frequently among patients who received furosemide than among those who did not (21.7 vs. 10.5%, P = 0.002). Furosemide exposure was associated with increased odds for mortality in a multivariate logistic regression model adjusted for body weight, gender, illness severity assessed by PRISM III score, the presence of mean FO, and AKI stage [adjusted odds ratio (AOR) 1.95; 95%CI, 1.08-3.52; P = 0.026]. Conclusion: Exposure to furosemide might be associated with increased risk for mortality, but not AKI, in critically ill children.

Pharmacotherapy for the Prevention of Bronchopulmonary Dysplasia: Can Anything Compete with Caffeine and Corticosteroids?

Bronchopulmonary dysplasia (BPD) is a morbidity of prematurity with implications for respiratory and neurologic health into adulthood. Multiple risk factors contribute to the development of BPD leading to examination of various prevention strategies. The roles of systemic corticosteroids and caffeine have been addressed by the American Academy of Pediatrics. The place in therapy of other agents commonly utilized in clinical practice remains unclear. Inhaled nitric oxide has been the subject of numerous large, randomized controlled trials in preterm infants. Despite sound rationale, these trials have largely failed to document benefit, suggesting a limited role for inhaled nitric oxide therapy in the preterm population. In contrast, intramuscular vitamin A has been documented to reduce the incidence of BPD in randomized trials. However, the invasiveness and the sporadic availability of this therapy have led to decreased utilization. All macrolide antibiotics do not appear to have a similar impact on the incidence of BPD; however, azithromycin administered to infants colonized with Ureaplasma may have impact. Questions remain about the optimal dosing approach and long-term safety of this intervention. Finally, diuretic therapy is widely used in clinical practice despite significant toxicities and limited data supporting a role in BPD prevention. Taken together, available data suggest that caffeine and selective use of corticosteroids remain the mainstays of pharmacologic BPD prevention.

An update on the post-NICU discharge management of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease which develops as a result of neonatal/perinatal lung injury. It is the commonest cause of chronic lung disease in infancy and the most frequent morbidity associated with prematurity. The incidence of BPD has continued to rise despite many advances in neonatal care and this increase has been attributed to the increased survival of younger and more premature babies. There have been many advances in the care of patients with early and evolving BPD, yet there is a paucity of data regarding outpatient management of patients with established BPD. There are limited adequately-powered high-quality studies/randomized controlled trials which assess commonly used therapies such as supplemental oxygen, bronchodilators, steroids and diuretics in patients with BPD, beyond short-term effects. Further research is needed to improve our understanding of the role of currently used treatments on the long-term outcomes of patients with established BPD, post-discharge from the neonatal intensive care unit.

Acute Responses to Diuretic Therapy in Extremely Low Gestational Age Newborns: Results from the Prematurity and Respiratory Outcomes Program Cohort Study

OBJECTIVE

To determine if daily respiratory status improved more in extremely low gestational age (GA) premature infants after diuretic exposure compared with those not exposed in modern neonatal intensive care units.

STUDY DESIGN

The Prematurity and Respiratory Outcomes Program (PROP) was a multicenter observational cohort study of 835 extremely premature infants, GAs of 23^0/7-28^6/7 weeks, enrolled in the first week of life from 13 US tertiary neonatal intensive care units. We analyzed the PROP study daily medication and respiratory support records of infants ≤34 weeks postmenstrual age. We determined whether there was a temporal association between the administration of diuretics and an acute change in respiratory status in premature infants in the neonatal intensive care unit, using an ordered categorical ranking of respiratory status.

RESULTS

Infants in the diuretic exposed group of PROP were of lower mean GA and lower mean birth weight (P < .0001). Compared with infants unexposed to diuretics, the probability (adjusted for infant characteristics including GA, birth weight, sex, and respiratory status before receiving diuretics) that the exposed infants were on a higher level of respiratory support was significantly greater (OR, >1) for each day after the initial day of diuretic exposure.

CONCLUSIONS

Our analysis did not support the ability of diuretics to substantially improve the extremely premature infant's respiratory status. Further study of both safety and efficacy of diuretics in this setting are warranted.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT01435187.

Updates on Functional Characterization of Bronchopulmonary Dysplasia - The Contribution of Lung Function Testing

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that predominantly affects prematurely born infants. Initially, BPD was described in infants who had suffered severe respiratory failure and required high pressure, mechanical ventilation with high concentrations of supplementary oxygen. Now, it also occurs in very prematurely born infants who initially had minimal or even no signs of lung disease. These differences impact the nature of the lung function abnormalities suffered by “BPD” infants, which are also influenced by the criteria used to diagnose BPD and the oxygen saturation level used to determine the supplementary oxygen requirement. Key also to interpreting lung function data in this population is whether appropriate lung function tests have been used and in an adequately sized population to make meaningful conclusions. It should also be emphasized that BPD is a poor predictor of long-term respiratory morbidity. Bearing in mind those caveats, studies have consistently demonstrated that infants who develop BPD have low compliance and functional residual capacities and raised resistances in the neonatal period. There is, however, no agreement with regard to which early lung function measurement predicts the development of BPD, likely reflecting different techniques were used in different populations in often underpowered studies. During infancy, lung function generally improves, but importantly airflow limitation persists and small airway function appears to decline. Improvements in lung function following administration of diuretics or bronchodilators have not translated into long-term improvements in respiratory outcomes. By contrast, early differences in lung function related to different ventilation modes have led to investigation and demonstration that prophylactic, neonatal high-frequency oscillation appears to protect small airway function.

Unexpected extra-renal effects of loop diuretics in the preterm neonate

The loop diuretics furosemide and bumetanide are commonly used in neonatal intensive care units (NICUs). Furosemide, because of its actions on the ubiquitous Na(+) -K(+) -2Cl(-) isoform cotransporter and its promotion of prostanoid production and release, also has non-diuretic effects on vascular smooth muscle, airways, the ductus arteriosus and theoretically the gastrointestinal tract. Loop diuretics also affect the central nervous system through modulation of the GABA-A chloride channel.

CONCLUSION

  The loop diuretics have a variety of biological effects that are potentially harmful as well as beneficial. Care should be taken with the use of these agents because the range of their effects may be broader than the single action sought by the prescribing physician.

Neonatal diuretic therapy: furosemide, thiazides, and spironolactone

Diuretics are commonly used to treat infants with oxygen-dependent chronic lung disease. However, there are limited data suggesting a beneficial effect of long-term diuretic therapy on pulmonary function or clinical outcome in this population. Furthermore, data available for review were primarily obtained before the widespread use of antenatal steroids or surfactant replacement therapy, before recognition of the new bronchopulmonary dysplasia. If used in this population, limitations of diuretic therapy as well as significant side effects need to be understood and a rationale approach to clinical use developed on a patient-centered basis.

Hypertension in infancy: diagnosis, management and outcome

Advances in the ability to identify, evaluate, and care for infants with hypertension, coupled with advances in the practice of Neonatology, have led to an increased awareness of hypertension in modern neonatal intensive care units. This review will present updated data on blood pressure values in neonates, with a focus on the changes that occur over the first days and weeks of life in both term and preterm infants. Optimal blood pressure measurement techniques as well as the differential diagnosis of hypertension in the neonate and older infants will be discussed. Recommendations for the optimal immediate and long-term evaluation and treatment, including potential treatment parameters, will be presented. We will also review additional information on outcome that has become available over the past decade.

Intravenous or enteral loop diuretics 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 administration of a diuretic acting on the loop of Henle (loop diuretic) in preterm infants with or developing chronic lung disease (CLD).

SEARCH STRATEGY

Standard search method of the Cochrane Neonatal Review Group was used. Initial search included the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2003), MEDLINE (1966 to April 2003), EMBASE (1974 to 1998). In addition, several abstract books of national and international American and European Societies were hand searched. The MEDLINE and the Cochrane Central searches were updated in March 2007 and December 2010.  The EMBASE search was completed in April 2007 and December 2010. Additional searches in CINAHL, clinicaltrials.gov and controlled-trials.com was completed in December 2010.

SELECTION CRITERIA

Trials in which preterm infants with or developing chronic lung disease and at least five days of age were all randomly allocated to receive a loop diuretic either enterally or intravenously were included in this analysis.

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. Parallel and cross-over trials were combined and, whenever possible, transformed baseline and final outcome data measured on a continuous scale into change scores using Follmann's formula.

MAIN RESULTS

The only loop diuretic used in the six studies that met the selection criteria was furosemide. Most studies 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 developing CLD, furosemide administration has either inconsistent effects or no detectable effect. In infants > 3 weeks of age with CLD, a single intravenous dose of 1 mg/kg of furosemide improves lung compliance and airway resistance for one hour. Chronic administration of furosemide improves both oxygenation and lung compliance.

AUTHORS' CONCLUSIONS

In view of the lack of data from randomized trials concerning effects on important clinical outcomes, routine or sustained use of systemic loop diuretics in infants with (or developing) CLD cannot be recommended based on current evidence. Randomized trials are needed to assess the effects of furosemide administration on survival, duration of ventilatory support and oxygen administration, length of hospital stay, potential complications and long-term outcome.

Adjunctive pharmacotherapy in neonates with respiratory failure

Whereas oxygen, continuous positive airway pressure (CPAP) and mechanical ventilation are the mainstays of treatment of pulmonary conditions in newborns, there are a number of adjunctive therapies that may improve the pulmonary function of these infants. These include the use of bronchodilators and diuretics given either systemically or through the inhaled route, mucolytic agents, and anti-inflammatory agents. This chapter gives an overview of the use of the most-studied agents including aerosolized bronchodilators, systemic and inhaled diuretics, and systemic and inhaled corticosteroids in the treatment and prevention of, where appropriate, respiratory distress syndrome, bronchopulmonary dysplasia, and meconium aspiration syndrome. Evidence on the use of mucolytic agents including acetylcysteine and deoxyribonuclease, and the anti-inflammatory agents including the macrolide antibiotics, cromolyn, pentoxyfylline, and recombinant human Clara cell protein are also reviewed.

Treatment of patent ductus arteriosus

Patent ductus arteriosus (PDA) continues to be one of the most common problems found in premature infants. The incidence is inversely related to gestation, but may be reduced by use of antenatal steroids, lower volume fluid regimen and judicious use of phototherapy. However, there continues to be controversy as to the appropriate indications for treatment, varying from prophylaxis on the basis of gestation to treatment only when a PDA is demonstrably significant. The situation is further complicated by differing diagnostic criteria for ductal patency or significance. Prophylactic treatment is likely to result in up to 64% of babies being treated unnecessarily. Early treatment of significant or symptomatic PDA depends upon accurate diagnosis. PDA closure can then be achieved using medical means, with surgery reserved for patients in whom this fails or in whom there are contra-indications. However, the optimum timing for intervention remains unknown.

Bronchopulmonary dysplasia (chronic lung disease of infancy): an update for the pediatrician

This paper is a review of the changes that have occurred over the past 35 years in the clinical and radiologic presentation of bronchopulmonary dysplasia (BPD), now more commonly referred to as chronic lung disease of infancy (CLD). Curent thoughts on etiology are only briefly discussed. The major focus is the management of the patient with CLD by the primary care physician once the patient has been discharged from hospital. Oxygen, diuretic, bronchodilator, antiinflammatory and nutritional therapies are discussed in detail. Finally, current information on long-term prognosis and recommendations for the prevention of RSV and influenza infections are reviewed.

Intravenous or enteral loop diuretics for preterm infants with (or developing) chronic lung disease

BACKGROUND

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

OBJECTIVES

The aim of this review was to assess the risks and benefits of administration of a diuretic acting on the loop of Henle (loop diuretic) in preterm infants with or developing chronic lung disease (CLD). Primary objectives were to assess changes in need for oxygen or ventilatory support and effects on long-term outcome, and secondary objectives were to assess changes in pulmonary mechanics and potential complications of therapy.

SEARCH STRATEGY

We used the standard search method of the Cochrane Neonatal Review Group. We searched MEDLINE (1966-October 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 chronic lung disease and at least 5 days of age were all randomly allocated to receive a loop diuretic either enterally or intravenously. Eligible studies needed to assess at least one of the outcome variables defined a priori for this systematic review. Primary outcome variables included important clinical outcomes, and secondary outcome variables included toxicity and pulmonary mechanics (e.g., lung compliance and airway resistance).

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

The only loop diuretic used in the studies which met the selection criteria was furosemide. Most studies 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 developing CLD, furosemide administration has either inconsistent effects or no detectable effect. In infants > 3 weeks of age with CLD, a single intravenous dose of 1 mg/kg of furosemide improves lung compliance and airway resistance for 1 hour. Chronic administration of furosemide improves both oxygenation and lung compliance.

REVIEWER'S CONCLUSIONS

In preterm infants > 3 weeks of age with CLD, acute and chronic administration of furosemide improve lung compliance. Chronic administration of intravenous or enteral furosemide improves oxygenation. In view of the lack of data from randomized trials concerning effects on important clinical outcomes, routine or sustained use of systemic loop diuretics in infants with (or developing) CLD cannot be recommended based on current evidence. Randomized trials are needed to assess the effects of furosemide administration on survival, duration of ventilatory support and oxygen administration, length of hospital stay, potential complications and long-term outcome.

Chronic lung injury in preterm lambs: abnormalities of the pulmonary circulation and lung fluid balance

Chronic lung disease of early infancy, or bronchopulmonary dysplasia, is a frequent complication of prolonged mechanical ventilation after premature birth. Pulmonary hypertension and edema are common features of this condition, which is often attributed to long-term, repetitive overinflation of incompletely developed lungs. The overall objective of this work was to examine the effects on the pulmonary circulation and lung fluid balance of different ventilation strategies using large versus small inflation volumes in an animal model of bronchopulmonary dysplasia. We studied 16 newborn lambs that were delivered prematurely (124+/-3 d gestation, term = 147 d) by cesarean section and mechanically ventilated for 3 to 4 wk. Ten lambs were ventilated at 20 breaths/min, yielding a tidal volume of 15+/-5 mL/kg, and six lambs were ventilated at 60 breaths/min, yielding a tidal volume of 6+/-2 mL/kg. All lambs received surfactant at birth and had subsequent surgery for closure of the ductus arteriosus and catheter placement to allow serial measurements of pulmonary vascular resistance and lung lymph flow. Chronic lung injury, documented by serial chest radiographs and postmortem pathologic examination, developed in all lambs irrespective of the pattern of assisted ventilation. Pulmonary vascular resistance, which normally decreases during the month after birth at term, did not change significantly from the first to the last week of study. Lung lymph flow, an index of net transvascular fluid filtration, increased with time in lambs that were ventilated at 20 breaths/min, but not in lambs ventilated at 60 breaths/min. Lymph protein concentration decreased with time, indicative of increased fluid filtration pressure, without evidence of a change in lung vascular protein permeability. Postmortem studies showed interstitial lung edema, increased pulmonary arteriolar smooth muscle and elastin, decreased numbers of small pulmonary arteries and veins, and decreased capillary surface density in distal lung of chronically ventilated lambs compared with control lambs that were killed either 1 d (same postconceptional age) or 3 wk (same postnatal age) after birth at term. Thus, chronic lung injury from prolonged mechanical ventilation after premature birth inhibits the normal postnatal decrease in pulmonary vascular resistance and leads to lung edema from increased fluid filtration pressure. These abnormalities of the pulmonary circulation may contribute to the abnormal respiratory gas exchange that often exists in infants with bronchopulmonary dysplasia.

Effect of lung water content, manipulated by intratracheal furosemide, surfactant, or a mixture of both, on compliance and viscoelastic tissue forces in lung-lavaged newborn piglets

OBJECTIVE

To study the impact of lung water content and its reduction by a topically applied diuretic on respiratory and lung tissue mechanics in comparison with surfactant administration in surfactant-deficient newborn piglets with lavage-induced lung injury.

DESIGN

Controlled, randomized study.

SETTING

Animal research facility.

SUBJECTS

Newborn piglets. TREATMENT Piglets were surfactant depleted by lung lavage and, after a pretreatment period, randomly treated with intratracheal furosemide, furosemide and surfactant, or with surfactant alone.

MEASUREMENTS AND MAIN RESULTS

Dynamic compliance (C(DYN)), static compliance (C(ST)), stress-adaptation pressures (P(DIFF)) and post mortem lung water content were determined. Static compliance in the furosemide-surfactant group was not significantly higher than in the surfactant group. At the end of the study, C(ST) did not differ between the three groups because C(ST) in the furosemide group had increased to values similar to those of the surfactant-containing treatment groups: C(ST) F+S: 0.73 +/- 0.2 mL/cm H2O/kg body weight (BW); C(ST) S: 0.61 +/- 0.11 mL/cm H2O/kg BW; and C(ST) F: 0.60 +/- 0.19 mL/cm H2O/kg BW). Compliance was inversely and P(DIFF) was directly correlated to lung water (LW) content (C(ST) vs. LW: r2 = .59, p = .001; C(DYN) vs. LW: r2 = .49, p = .006; P(DIFF) vs. LW: r2 = .37, p = .059), independent of the type of treatment. Changes in C(ST) and C(DYN) were inversely related to changes in P(DIFF). Intrapulmonary furosemide was more rapidly absorbed when administered to the surfactant-depleted lung alone compared with the mixture with surfactant, and intrapulmonary furosemide had a rapid systemic effect.

CONCLUSION

Although the combination of surfactant with a diuretic failed to increase respiratory compliance to a significantly larger extent than surfactant alone, furosemide at the end of the study increased respiratory compliance to a level similar to surfactant-containing treatments. Lung water content and, to a lesser extent, the absence or presence of surfactant appeared to determine lung mechanics, and its impact on lung mechanics was similar to surfactant administration.

A risk-benefit assessment of drugs used for neonatal chronic lung disease

Improvements in neonatal intensive care have resulted in more extremely low birthweight babies surviving who are at risk of developing chronic lung disease. The preterm lung is vulnerable as it is both structurally immature and deficient in surfactant and antioxidant defences. Mechanical ventilation and high inspired oxygen concentrations are often necessary for preterm babies to survive but they can cause pulmonary inflammation which leads to lung damage. Abnormal healing in the presence of ongoing inflammation leads to airways remodelling which can result in protracted respiratory problems in these babies. A commonly used definition for chronic lung disease is the requirement for supplemental oxygen beyond 36 weeks' postconception. Many drugs that are commonly used for chronic lung disease have not been subjected to proper randomised controlled trials but are widely used on the basis of small studies showing short term benefits. They can be broadly divided into 2 groups. First, there are preventative drugs that are administered early to reduce oxygen toxicity and pulmonary inflammation. Secondly, there are those administered in established chronic lung disease, designed to reduce respiratory morbidity. Pulmonary inflammation in the neonate is reduced by systemic corticosteroids. Corticosteroid therapy within the first 2 weeks of life enables earlier extubation of preterm babies with subsequent reduced chronic lung disease and improved neonatal survival when given between 7 and 14 days. However, there is an increased risk of gastrointestinal haemorrhage, metabolic derangement, ventricular hypertrophy and potential effects on long term growth and brain development. Diuretics and inhaled bronchodilators improve pulmonary compliance and reduce oxygen requirements in established chronic lung disease but probably have little effect in reducing the incidence. In babies with established chronic lung disease, home oxygen therapy enables earlier discharge and prophylaxis against respiratory syncytial virus can reduce morbidity from bronchiolitis. All of the above therapies have adverse effects that need to be considered before initiating treatment. Recently, new drugs have become available which may be beneficial. These include inhaled nitric oxide for reduction of ventilation-perfusion mismatching, recombinant human superoxide dismutase for protection against oxidative stress and alpha-1 proteinase inhibitor which may reduce airways remodelling. At present these therapies are undergoing clinical trials. Exogenous surfactant is beneficial in respiratory distress syndrome and may reduce the risk of chronic lung disease but there have been no randomised controlled trials of its use in established chronic lung disease. Drugs which have been tried unsuccessfully include erythromycin, ambroxol and mast cell stabilisers.

Aerosolized furosemide in the treatment of acute respiratory distress and possible bronchopulmonary dysplasia in preterm neonates

OBJECTIVE

To review the efficacy and safety of inhaled furosemide in the treatment of acute respiratory distress and possible bronchopulmonary dysplasia (BPD) in preterm neonates receiving ventilator and oxygen support.

DATA SOURCES

A MEDLINE search was performed from January 1966 to December 1998 using the key words inhaled or aerosolized furosemide, BPD, preterm, neonate, and infant newborn.

STUDY SELECTION AND DATA EXTRACTION

All clinical trials involving the use of inhaled furosemide in ventilator- and oxygen-dependent preterm neonates with acute respiratory distress and possible BPD were evaluated.

DATA SYNTHESIS

Inhaled furosemide 1 and 2 mg/kg has improved pulmonary function in preterm neonates without significant adverse effects. However, only a single dose of inhaled furosemide was used in these trials, and pulmonary functions were monitored for only two or four hours after administration.

CONCLUSIONS

Inhaled furosemide may be effective, but studies are needed to determine the optimal dosage regimen and long-term risks and benefits of its use in these patients.

A new method to analyze lung compliance when pressure-volume relationship is nonlinear

Changes in dynamic lung compliance during inspiration and expiration cannot be modeled accurately with conventional algorithms. We developed a simple method to analyze pressure-volume (P/V) relationships under condition of nonlinearity (APVNL) and tested it in a lung model with known resistance and nonlinear P/V relationship. In addition, pulmonary mechanics in 22 infants, 11 of them with nonlinear P/V relationships, were analyzed with the new method. The findings were compared with those obtained by a recently introduced algorithm, multiple linear regression analysis (MLR) of the equation of motion. The APVNL method described the changing compliance (C) of the lung model accurately, whereas the MLR method underestimated C especially in the first half of the breath. In infants the MLR method gave highly variable, often nonphysiological C values in the beginning of a breath. In contrast, the coefficient of variability of measurements obtained by the APVNL method was significantly smaller (p < 0.02), and the indices of model-fit showed better agreement between calculated and observed pressure than for the MLR method (p < 0.02). We conclude that the APVNL method accurately describes nonlinear P/V relationships present during spontaneous breathing or mechanical ventilation. The method may be helpful in identifying and preventing pulmonary overdistention.

The new obstetrics: its integration into neonatal clinical practise, teaching and research

Most neonatologists have not yet incorporated into their teaching, clinical service and research the advances in high risk obstetrics particularly as it relates to fetal surveillance. This brief review emphasizes some of the "new obstetrics" from the viewpoint of perinatal medicine, particularly in terms of neonatal teaching and the design of future neonatal research. The information that can be obtained about an infant prenatally by the use of ultrasound. power doppler, computerized fetal heart rate monitoring, cordocentesis, etc is extensive and yet, has rarely been utilized in the design of neonatal research protocols. It is becoming imperative that the "new obstetrics" be recognized and utilized in modern neonatal thinking if a truly "perinatal medicine" is to be practised.

Changes in body water compartments with diuretic therapy in infants with chronic lung disease

The effects of diuretic therapy on body water compartments were studied in preterm infants with chronic lung disease. Gestational age of the infants ranged from 24 to 28 weeks, while the median postnatal age at the time of study was 40 days. Infants were randomized to receive furosemide (1.0 mg/kg/day) alone (n = 5) or combined with metolazone (0.2 mg/kg/day, n = 7) for 4 consecutive days. Treatment in both groups produced a significant decrease (P < 0.05) in extracellular water (ECW) without changes in plasma volume, total body water or body weight. The decrease in ECW with furosemide (503 +/- 28 to 446 +/- 19 ml/kg initial body weight) was of similar magnitude to that seen with combined furosemide plus metolazone (522 +/- 30 to 454 +/- 15 ml/kg initial body weight). Water and electrolyte intakes were similar in both groups and unchanged over the course of the study. These findings suggest that in infants with chronic lung disease, diuretic therapy induces intercompartmental shifts in body water, ultimately decreasing interstitial water while preserving PV. Only combined treatment with furosemide plus metolazone produced a significant increase in urine output, confirming the increased efficacy of combination therapy in inducing diuresis.

Pulmonary effect of inhaled furosemide in ventilated infants with severe bronchopulmonary dysplasia

BACKGROUND

When administered parenterally, furosemide, a loop diuretic, results in improved lung compliance and decreased airway resistance in infants with bronchopulmonary dysplasia (BPD). However, furosemide-induced diuresis results in hypokalemia, chloride deficiency, hypercalciuria, nephrocalcinosis, and rickets. In patients with asthma, inhaled furosemide has recently been demonstrated to inhibit the bronchoconstrictive effects of exercise, cold air hyperventilation, and antigen challenge. We hypothesized that inhaled furosemide will result in improved pulmonary mechanics in ventilated infants with BPD and will prevent the systemic complications of parenteral furosemide.

OBJECTIVE

To determine the efficacy and safety of a single dose of inhaled furosemide on pulmonary mechanics in infants with severe BPD who are ventilator dependent at 21 days of age.

DESIGN AND METHODS

A randomized, double-blind, crossover study was performed on 9 infants with BPD, each serving as his own control. Each patient was randomized to receive an aerosol dose of furosemide (1 mg/kg in 2 mL of saline) or placebo (2 mL of saline) on the first day of the study and the other agent the following day of the study. Pulmonary mechanics were measured before and 1 and 2 hours after the inhalation using the Pulmonary Evaluation and Diagnostics System.

RESULTS

Gestational age (mean +/- SEM) was 29 +/- 1 weeks; birth weight was 1.1 +/- 0.1 kg; age at study was 47 +/- 6 days; and weight at study was 1.8 +/- 0.2 kg. There was no significant change in the pulmonary function measurements before treatment and 1 or 2 hours after treatment with either placebo or furosemide. Baseline and 2-hour values were: dynamic compliance (mL/ cm H2O per kilogram): 0.46 +/- .03 to 0.50 +/- .03 (placebo) and 0.50 +/- 0.02 to 0.51 +/- 0.02 (furosemide); dynamic resistance (cm H2O/L per second): 118 +/- 9 to 106 +/- 7 (placebo) and 111 +/- 8 to 105 +/- 7 (furosemide); and tidal volume (mL/kg): 8.6 +/- 0.5 to 8.9 +/- 0.5 (placebo) and 8.9 +/- 0.2 to 9.4 +/- 0.3 (furosemide).

CONCLUSION

We conclude that, under the conditions of our study, a single dose of 1 mg/kg inhaled furosemide does not improve the pulmonary mechanics in ventilator-dependent infants with severe BPD.

Intrasubject variability of repeated pulmonary function measurements in preterm ventilated infants

This study set out to describe the variability and assess the reproducibility of repeated pulmonary function measurements in ventilated preterm infants. We measured tidal volume (VT), lung compliance (CL), and resistance (RL) in 16 infants (mean +/- SD: birthweight 1222 +/- 343 g) during spontaneous breathing and during mechanical ventilation, suppressing breathing efforts by mild hyperventilation. CL and RL were calculated from the equation of motion using linear regression analysis (LR), and by the Mead and Wittenberger method (MW). Flow and transpulmonary pressure were recorded for at least two consecutive periods, after which the esophageal tube was removed and replaced 1 hour later for a second set of recordings. The mean percent change (% delta) between the initial and the repeated measurements with their respective 95% confidence intervals were calculated. Reproducibility was assessed by the intraclass correlation coefficient (ICC) (total agreement = 1, good reproducibility > or = 0.75). The mean % delta between initial and repeat measurements during spontaneous breathing ranged from 11% to 14% for CL and VT, and from 22% to 32% for RL. The variation for RL was even higher when the analysis was done separately for the inspiratory and expiratory phase. CL and VT had good reproducibility (ICC > 0.9), while RL was significantly less reproducible (ICC < 0.75). Measurements obtained from mechanical breaths had less variability than from spontaneous breaths, ranging from 8% to 15% for CL and VT, and from 13% to 21% for RL. Reproducibility assessed by the ICC was good for most measurements during mechanical breaths. The variability and reproducibility of measurements were similar for both methods of analysis during mechanical ventilation, but during spontaneous breathing variability was larger with the MW method than with LR analysis. We concluded that VT and CL were reproducible during spontaneous and mechanical breathing. However, RL measurements were reproducible only during mechanical ventilation. The high variability of RL in spontaneously breathing preterm infants may reduce the clinical usefulness of this measurement for individual patients.

Mineral excretion following furosemide compared with bumetanide therapy in premature infants

Mineral excretion following single doses of furosemide were compared with bumetanide in a random cross-over trial in 17 premature infants. The mean birthweight and gestational age were 889 +/- 85 g and 27 +/- 2 weeks. Following furosemide therapy, significantly higher chloride losses and urine volumes were noted in the first 8-h period compared with the second or third 8-h periods. Following bumetanide therapy, sodium, calcium, and chloride losses and urine volumes were significantly higher in the first 8 h compared with the second or third 8-h periods. Hourly sodium and chloride losses were significantly lower following bumetanide than furosemide during the first two 8-h periods. During the final 8-h period sodium, potassium, chloride, and calcium losses were significantly lower following bumetanide than following furosemide. Sodium loss per urine volume was lower with bumetanide than furosemide but calcium loss tended to be higher. Hence, bumetanide does not appear to be a calcium-sparing diuretic following single-dose therapy.

Randomized trial of long-term diuretic therapy for infants with oxygen-dependent bronchopulmonary dysplasia

STUDY OBJECTIVE

To determine whether long-term oral diuretic therapy would improve the pulmonary function of preterm infants with bronchopulmonary dysplasia.

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

Level III intensive care nursery.

INTERVENTION

We randomly selected 43 stable patients with oxygen-dependent bronchopulmonary dysplasia to receive either orally administered spironolactone and chlorothiazide or placebo. These drugs were continued until the patients no longer required supplemental oxygen. Both groups received furosemide as needed.

MEASUREMENTS AND RESULTS

Each infant had pulmonary function tests at study entry, 4 weeks after study entry, 1 week and 8 weeks after being weaned to room air and off study drugs, and at 1 year of corrected age. Pulmonary function tests include dynamic pulmonary compliance, airway resistance, thoracic gas volume, and maximal expiratory flow at functional residual capacity; most of the infants had functional residual capacity measured. Between the first and second pulmonary function tests (while the infants were receiving diuretic or placebo), the infants in the diuretic group had a significant improvement in dynamic pulmonary compliance (46%; p < 0.001) and airway resistance (31%; p < 0.05); there were no changes in compliance or resistance in the placebo group. Although patients in both the diuretic and the placebo groups required progressively less supplemental oxygen, by 4 weeks after study entry the patients in the diuretic group needed less supplemental oxygen than did those in the placebo group (p < 0.01). There were no significant differences in results of serial pulmonary function tests in either group after discontinuation of diuretic therapy. Despite the significant differences in pulmonary function between the two groups, there was no significant difference between them in the total number of days that supplemental oxygen was required. Significantly more infantsin the placebo group received more than 10 doses of furosemide on an as-needed basis.

CONCLUSIONS

Long-term diuretic therapy in stable infants with oxygen-dependent bronchopulmonary dysplasia, after extubation, improves their pulmonary function and decreases their fractional inspired oxygen requirement, but does not decrease the number of days that they require supplemental oxygen. The improvement in pulmonary function associated with diuretic therapy is not maintained after treatment is discontinued.

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.

Addition of metolazone to overcome tolerance to furosemide in infants with bronchopulmonary dysplasia

A decreased response to the loop diuretic furosemide develops within a few doses in young infants. We tested the hypothesis that the use of the thiazide-like diuretic metolazone, in combination with furosemide, would inhibit water and electrolyte reabsorption and overcome pharmacologic tolerance to furosemide alone. Infants with bronchopulmonary dysplasia of similar gestational and postnatal ages were randomly assigned to one of three groups. Group 1 (n = 6) received furosemide (1 mg/kg per dose) intravenously every 24 hours for a total of five doses. Group 2 (n = 8) received the same treatment as group 1, but in addition metolazone (0.2 mg/kg per dose) was given enterally with doses 3 and 4 of furosemide. Group 3 (n = 8) received metolazone (0.2 mg/kg per dose) enterally every 24 hours for five doses. Urine was collected before the first diuretic dose and throughout the study for determination of the urine flow rate; urinary excretion of sodium, chloride, and potassium; and creatinine clearance. Urinary flow rate and urinary sodium and chloride excretion increased after the first dose in all groups. In the infants treated with either furosemide or metolazone, urinary flow rate and urinary and chloride excretion returned to baseline values after the last three doses. In contrast, when furosemide was administered with metolazone, urinary flow rate and urinary excretion of sodium, chloride, and potassium were greater than the values for baseline and for the previous dose, as well as for the corresponding doses of furosemide in group 1 and metolazone in group 3. Tolerance to furosemide (group 1) and metolazone (group 3) appeared to be explained by compensatory increased sodium and chloride reabsorption without changes in creatinine clearance. We conclude that the administration of metolazone with furosemide enhances diuresis, natriuresis, and chloruresis and overcomes the rapid development of tolerance to furosemide in infants with bronchopulmonary dysplasia by blocking the compensatory increase in renal sodium and chloride absorption.

Neonatal sensorineural hearing loss associated with furosemide: a case-control study

Thirty-five neonates with sensorineural hearing loss (SNHL), identified by brainstem auditory evoked response (BAER), and 70 matched controls with normal BAERs were studied. All infants had had BAERs before discharge from hospital as part of a screening program for high-risk neonates. Infants with SNHL showed no response to a 60dBnHL click stimulus and all had these results confirmed on at least one occasion after hospital discharge. Based on the screening program results, over-all prevalence of non-hereditary hearing loss was estimated to be 0.93 per 1000 live births, and in neonates weighing less than 2000g at birth to be 15.54 per 1000 live births. Several factors, including seizures, exposure to anticonvulsant drugs, furosemide and kanamycin were associated with SNHL, but after multivariate analysis, only exposure to furosemide remained significant. Peak serum bilirubin concentration and benzyl alcohol exposure did not appear to be related to hearing loss.

Bronchopulmonary dysplasia. Pharmacologic treatments and prediction of outcome

Bronchopulmonary dysplasia (BPD) is a progressive disorder of the lungs of newborn infants initially involving distal airways, but followed in weeks by the development of abnormalities in all parts of the lung architecture. BPD develops primarily but not exclusively in premature infants. The incidence in the general population has never been assessed accurately in a prospective manner. One retrospectively calculated incidence figure is 1.2 infants per 1,000 total live births per year in the United States (17). With approximately 4 million births annually in North America, there are about 5,000 babies each year who develop BPD. The additional weeks, months, and, in some cases, years of hospitalization, the frequent rehospitalizations, and the mortality of 20–50% beyond 1 month of age (17) underscore the disproportionate financial and emotional toll of BPD not only on patients and families but caregivers as well. The glacial rates of improvement in the illness, the frequent setbacks, and the profound disruption to family life all support the contention that BPD is a major public health problem.

Double-blind, placebo-controlled trial of alternate-day furosemide therapy in infants with chronic bronchopulmonary dysplasia

To test the hypothesis that alternate-day administration of furosemide will result in a sustained improvement in pulmonary function without causing alterations in electrolyte or mineral homeostasis, we conducted a randomized, double-blind, placebo-controlled study of 11 hospitalized, oxygen-dependent, spontaneously breathing infants with chronic bronchopulmonary dysplasia. Infants were randomly selected to receive either furosemide, 4 mg/kg in two divided doses on alternate days orally, or placebo for 8 days, followed by crossover to the alternate-therapy for an additional 8-day period. The two study periods were separated by a 48-hour washout period. Dynamic compliance, total pulmonary resistance, the concentration of electrolytes in serum, and the concentrations of calcium and creatinine in urine were measured on nontreatment days. Alternate-day furosemide therapy increased dynamic lung compliance by 76 +/- 112% and decreased total pulmonary resistance by 20 +/- 39%, compared with placebo (both variables p = 0.032). Alternate-day furosemide therapy did not result in increased urine output, electrolyte abnormalities, or increased urinary calcium excretion. We conclude that this simplified treatment regimen may be useful in the management of infants with chronic bronchopulmonary dysplasia. The results support our previous speculation that furosemide improves pulmonary function by mechanisms unrelated to its diuretic properties.

The pharmacology and therapeutics of diuretics in the pediatric patient

Selection of appropriate diuretic therapy in children is hampered by a lack of age-specific pharmacokinetic and pharmacodynamic data, especially in premature neonates. Well-designed clinical trials in neonates, infants, and younger children are necessary prerequisites to safer and more efficacious diuretic therapy.

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.

Randomized, double-blind, controlled trial of long-term diuretic therapy for bronchopulmonary dysplasia

The effects of continuous therapy with hydrochlorothiazide and spironolactone on pulmonary function in 34 premature infants with severe bronchopulmonary dysplasia were assessed in a randomized double-blind controlled trial. Subjects were greater than or equal to 30 days old, were supported by mechanical ventilation in greater than or equal to 30% oxygen, and had radiographic evidence of bronchopulmonary dysplasia. The treatment group (n = 19) and the placebo group (n = 15) were similar in all respects except for distribution of gender. Anthropometrics, ventilatory measurements, and the results of pulmonary function tests were evaluated at study entry and at 1, 4, and 8 weeks into therapy. Poststudy chest radiographs were compared with those obtained before the study. The proportion of infants alive at discharge was significantly increased (84%) in the treatment group compared with the placebo group (47%) (p = 0.05). There were no statistically significant differences in total hospital days or in total ventilator days. Total respiratory system compliance at 4 weeks was higher in the treatment group (0.61 +/- 0.18) than in the placebo group (0.45 +/- 0.13) (p = 0.016). No difference in outcome was detected between male and female infants in the treatment group. These results suggest that long-term diuretic therapy improves outcome in infants with bronchopulmonary dysplasia.

Pharmacology of diuretics in the newborn

Diuretics are used in various conditions with fluid overload. Their efficacy in the management of congestive heart failure is well documented. In contrast, the indication of diuretics in chronic lung disease and central nervous system disorders of the newborn have not been clearly established. Substantial pharmacologic knowledge of diuretics in the young infant remains to be described. Most investigations on diuretics in the sick newborn infant have examined furosemide. In contrast, the pharmaco-dynamics, pharmacokinetics, clinical indications, and toxicity of other diuretics used in the newborn require considerable further evaluation. Future studies using a combination of diuretics, acting at different segments of the nephron, also may provide newer therapeutic modalities to overcome or prevent the development of frequently observed tolerance to diuretics, as well as to treat refractory edema.

Effect of spironolactone-hydrochlorothiazide on lung function in infants with chronic bronchopulmonary dysplasia

To test the hypothesis that spironolactone-hydrochlorothiazide (Aldactazide) will improve urine output and lung function in infants with bronchopulmonary dysplasia, we studied 21 hospitalized, spontaneously breathing, oxygen-dependent infants with chronic bronchopulmonary dysplasia. Infants were randomly assigned to receive either a 1:1 mixture of spironolactone and hydrochlorothiazide orally (n = 12) (3 mg/kg/day of both compounds) or no treatment (n = 9) for 6 to 8 days each. Dynamic lung compliance, total pulmonary resistance, and hemoglobin oxygen saturation were measured on the first and last days of each study period. Fluid intake and urine output were measured each day. Although the treatment significantly increased urine output, neither lung mechanics nor oxygenation were improved by the drug. The magnitude of the diuresis achieved with spironolactone-hydrochlorothiazide treatment was comparable to the diuresis achieved in a previous study of furosemide treatment (J Pediatr 1986:109;1034-9). Statistical analysis indicated that a type II error was an unlikely explanation for our failure to detect a beneficial effect. In three patients, doubling the oral dose did not improve lung mechanics or oxygenation. We speculate that diuresis per se is not responsible for lung function improvement during treatment with other drugs with diuretic properties.