Pulmonary effects of furosemide in preterm infants with lung disease

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.

Pharmacotherapy in Bronchopulmonary Dysplasia: What Is the Evidence?

Bronchopulmonary Dysplasia (BPD) is a multifactorial disease affecting over 35% of extremely preterm infants born each year. Despite the advances made in understanding the pathogenesis of this disease over the last five decades, BPD remains one of the major causes of morbidity and mortality in this population, and the incidence of the disease increases with decreasing gestational age. As inflammation is one of the key drivers in the pathogenesis, it has been targeted by majority of pharmacological and non-pharmacological methods to prevent BPD. Most extremely premature infants receive a myriad of medications during their stay in the neonatal intensive care unit in an effort to prevent or manage BPD, with corticosteroids, caffeine, and diuretics being the most commonly used medications. However, there is no consensus regarding their use and benefits in this population. This review summarizes the available literature regarding these medications and aims to provide neonatologists and neonatal providers with evidence-based recommendations.

Optimizing respiratory management in preterm infants: a review of adjuvant pharmacotherapies

Adjuvant respiratory therapies in preterm neonates aim to reduce long-term morbidities and mortality. Commonly utilized therapies include caffeine, systemic glucocorticosteroids, inhaled steroids, inhaled bronchodilators, and diuretics. This review discusses the available literature that supports some of these practices and points out where clinical practices are not corroborated by evidence. Therapies with no proven clinical benefit must be weighed against potential adverse effects.

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).

Use of calcimimetics in children with normal kidney function

The calcium-sensing receptor (CaSR) plays an important role in the homeostasis of serum ionized calcium by regulating parathyroid hormone (PTH) secretion and tubular calcium handling. Calcimimetics, which act by allosteric modulation of the CaSR, mimic hypercalcemia resulting in suppression of PTH release and increase in calciuria. Mostly used in children to treat secondary hyperparathyroidism associated with advanced renal failure, we have shown that calcimimetics can also be successfully used in children with bone and mineral disorders in which elevated PTH plays a detrimental role in skeletal pathophysiology in the face of normal kidney function. The current review briefly discusses the role of the CaSR and calcimimetics in calcium homeostasis, and then addresses the potential applications of calcimimetics in children with normal kidney function with disorders in which suppression of PTH is beneficial.

Bronchopulmonary Dysplasia: An Update of Current Pharmacologic Therapies and New Approaches

Bronchopulmonary dysplasia (BPD) remains the most prevalent long-term morbidity of surviving extremely preterm infants and is associated with significant health care utilization in infancy and beyond. Recent advances in neonatal care have resulted in improved survival of extremely low birth weight (ELBW) infants; however, the incidence of BPD has not been substantially impacted by novel interventions in this vulnerable population. The multifactorial cause of BPD requires a multi-pronged approach for prevention and treatment. New approaches in assisted ventilation, optimal nutrition, and pharmacologic interventions are currently being evaluated. The focus of this review is the current state of the evidence for pharmacotherapy in BPD. Promising future approaches in need of further study will also be reviewed.

Successful Reversal of Furosemide-Induced Secondary Hyperparathyroidism With Cinacalcet

Secondary hyperparathyroidism (SHPT) is a rare complication of furosemide therapy that can occur in patients treated with the loop diuretic for a long period of time. We report a 6-month-old 28-weeks premature infant treated chronically with furosemide for his bronchopulmonary dysplasia, who developed hypocalcemia and severe SHPT, adversely affecting his bones. Discontinuation of the loop diuretic and the addition of supplemental calcium and calcitriol only partially reversed the SHPT, bringing serum parathyroid hormone level down from 553 to 238 pg/mL. After introduction of the calcimimetic Cinacalcet, we observed a sustained normalization of parathyroid hormone concentration at 27 to 63 pg/mL and, with that correction, of all biochemical abnormalities and healing of the bone disease. No adverse effects were noted. We conclude that in cases of SHPT due to furosemide in which traditional treatment fails, there may be room to consider the addition of a calcimimetic agent.

Strategies for managing transient tachypnoea of the newborn - a systematic review

OBJECTIVE

To conduct a systematic review of strategies for the management of transient tachypnoea of the newborn (TTN).

METHODS

The Cochrane Collaboration and PRISMA guidelines were used for conducting and reporting this systematic review, respectively. The Cochrane Central Register of Controlled Trials, PubMed, CINAHL and EMBASE databases were searched in February 2016. Only randomised and quasi-randomised controlled trials (RCTs) assessing any intervention for the management of TTN in infants <7 days of age, born at 35 or more weeks with a clinical diagnosis of TTN were eligible for inclusion. Primary outcomes included the duration of respiratory support, oxygen support, tachypnoea and hospitalisation.

RESULTS

Nine RCTs with moderate risk of bias were included. The interventions assessed included furosemide (2 trials, n = 100), inhaled salbutamol (2 trials, n = 94), inhaled epinephrine (1 trial, n = 20), restrictive fluids (2 trials, n = 146) and non-invasive ventilation (2 trials, n = 80). Amongst all interventions, inhaled salbutamol significantly reduced the duration of hospitalisation (2 trials, n = 94) [mean difference (MD) - 1.63 days (95% CI -2.71 to -0.55); p = 0.003] and duration of oxygen requirement (1 trial, n = 37) [MD - 43.10 h (95% CI -81.82 to -4.38; p = 0.03] without adverse effects.

CONCLUSION

Limited low-quality evidence exists on the effects of different management strategies for TTN. The safety and efficacy of inhaled salbutamol in the treatment of TTN can be assessed in a large RCT.

Point Prevalence, Clinical Characteristics, and Treatment Variation for Infants with Severe Bronchopulmonary Dysplasia

OBJECTIVES

Despite improvements in survival of preterm infants, bronchopulmonary dysplasia (BPD) remains a persistent morbidity. The incidence, clinical course, and current management of severe BPD (sBPD) remain to be defined. To address these knowledge gaps, a multicenter collaborative was formed to improve outcomes in this population.

STUDY DESIGN

We performed a "snapshot" in eight neonatal intensive care units (NICUs) on December 17, 2013. A standardized clinical data form for each inpatient born at < 32 weeks was completed and collated centrally for analysis. sBPD was defined as receiving ≥ 30% supplemental oxygen and/or receiving positive pressure ventilation at 36 weeks postmenstrual age (PMA).

RESULTS

Of a total census of 710 inpatients, 351 infants were born at < 32 weeks and 128 of those (36.5%) met criteria for sBPD. The point prevalence of sBPD varied between centers (11-58%; p < 0.001). Among infants with sBPD there was a variation among centers in the use of mechanical ventilation at 28 days of life (p < 0.001) and at 36 weeks PMA (p = 0.001). We observed differences in the use of diuretics (p = 0.018), inhaled corticosteroids (p < 0.001), and inhaled β-agonists (p < 0.001).

CONCLUSION

The high point prevalence of sBPD and variable management among NICUs emphasizes the lack of evidence in guiding optimal care to improve long-term outcomes of this high-risk, understudied population.

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.

Current pharmacologic approaches for prevention and treatment of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a major complication of preterm birth and has serious adverse long-term health consequences. The etiology of BPD is complex, multifactorial, and incompletely understood. Contributing factors include ventilator-induced lung injury, exposure to toxic oxygen levels, and infection. Several preventive and therapeutic strategies have been developed with variable success. These include lung protective ventilator strategies and pharmacological and nutritional interventions. These strategies target different components and stages of the disease process and they are commonly used in combination. The purpose of this review is to discuss the evidence for current pharmacological interventions and identify future therapeutic modalities that appear promising in the prevention and management of BPD. Continued improved understanding of BPD pathogenesis leads to opportunities for newer preventive approaches. These will need to be evaluated in the setting of current clinical practice in order to assess their efficacy.

Diuretics for very low birth weight infants in the first 28 days: a survey of the U.S. neonatologists

OBJECTIVE

The objective of this study was to describe factors influencing diuretic use by neonatologists caring for very low birth weight neonates.

STUDY DESIGN

We surveyed 400 U.S. neonatologists. Respondents made therapeutic decisions in clinical scenarios involving very low birth weight infants at 7, 14 and 28 days of age.

RESULT

Response rate was 39%. Diuretic therapy was chosen in 31% of scenario decisions, with pro re nata dosing selected early and regular dosing more common at later ages. Diuretic use was strongly associated with method of respiratory support, and was chosen less often by those also choosing fluid restriction and those concerned about patent ductus arteriosus risk. After adjusting for these factors, excessive weight gain, expected improvement in work of breathing and expected decrease in ventilator days were also associated with diuretic use.

CONCLUSION

The extent of and expectations for diuretic therapy by neonatologists caring for very low birth weight neonates may exceed evidence for efficacy.

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.

Nebulized Furosemide in the Treatment of Bronchopulmonary Dysplasia in Preterm Infants

Bronchopulmonary dysplasia (BPD) is a chronic pulmonary disease commonly seen in preterm infants who require supplemental oxygen and/or assisted mechanical ventilation. BPD, a major cause of morbidity and mortality among premature infants, occurs in 5,000 to 10,000 premature infants in the United States each year. Despite numerous medical advances, no single intervention will prevent or treat BPD; hence, premature infants have an increased risk for developing significant sequelae that affect both cognitive and motor function. This article provides a brief overview of BPD and reviews the available literature regarding the safe and effective use of nebulized furosemide in the treatment of this disorder.

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.

Intravenous frusemide for transient tachypnoea of the newborn: a randomised controlled trial

AIM

To investigate the effect of intravenous frusemide on the course of transient tachypnoea of the newborn (TTN).

METHODS

Fifty term infant with TTN were randomised at the time of diagnosis to receive either intravenous frusemide 2 mg/kg or saline placebo. Outcomes assessed included duration of supplemental oxygen requirement, the period of tachypnoea, time to discharge from hospital and weight loss in the first 24 h of life and before discharge.

RESULTS

The two groups were similar with respect to sex, birthweight, mode of delivery and age at presentation. The study group lost significantly more weight in the first 24 h after birth. There were no significant differences between the two groups in the duration of oxygen requirements, the period of tachypnoea and the time to hospital discharge.

CONCLUSION

A single dose of intravenous frusemide (2 mg/kg) does not improve the clinical course of TTN. This finding suggests that either frusemide is not effective in promoting resorption of lung fluid or factors other than delayed resorption of this fluid contribute to the pathogenesis of TTN.

Pharmacological strategies in the prevention and management of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a disease of complex and multifactorial etiology and a major cause of morbidity in premature infants. Contributing factors include infection, exposure to toxic oxygen levels, and ventilator-induced lung injury, resulting in arrested lung development and impaired lung function. Several preventive and therapeutic strategies have been employed and include lung protective ventilator strategies, pharmacological and nutritional interventions. These strategies target different components and stages of the disease process, and their success has been variable. This review intends to bring together prior and current pharmacological interventions and future therapeutic modalities that appear promising in the prevention and management of BPD. Better understanding of the pathogenesis has given hope for newer treatment options. Newer studies need to be designed to assess the efficacy of combination therapies that target multiple steps of the disease process.

Immunolocalization of a Na-K-2Cl cotransporter in human tracheobronchial smooth muscle

Inhibition of the Na-K-2Cl (NKCC) cotransporter by loop diuretics is associated with airway relaxation, but there has been no direct evidence for the expression of this protein in airway smooth muscle. Thus we hypothesized that a NKCC cotransporter is present and functional in airway smooth muscle cells. Monoclonal and polyclonal antibodies were used first to demonstrate the presence of a NKCC cotransporter protein in isolated human fetal trachea and normal human bronchial smooth muscle cells (BSMC) by Western blotting. The cotransporter protein was then localized by immunohistochemical staining to airway smooth muscle cells in culture and in situ. The localization was confirmed by indirect immunofluorescence and laser confocal microscopy in the BSMC. Cotransporter function in BSMC was also confirmed in vitro by bumetanide-mediated inhibition of rubidium uptake. Our present findings thus document the presence of a functional NKCC cotransporter in human airway smooth muscle, providing a basis for defining the role of this ion cotransporter in airway smooth muscle function.

Inhaled furosemide: a whole new mechanism of action

The use of aerosolized furosemide has been increasing throughout Mexico, primarily because of its mechanism and site of action as well as its local and systemic effect. We hypothesize that its effect on the respiratory system is totally independent from its diuretic activity and that it is primarily caused by its interaction with the chlorine channels. Furthermore, there is also evidence that furosemide induces prostaglandin synthesis, blocks the sodium-calcium pump, producing relaxation of the smooth muscle that narrows the airway and causes reduced nerve responsiveness to the Neurokinin A produced in acute asthma attacks.

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.

Loop diuretics and in vitro relaxation of human fetal and newborn mouse airways

This study was designed to test the hypotheses that furosemide directly causes relaxation in human fetal airway and that delivery of loop diuretics to either the adventitial or epithelial surface of newborn mouse airway results in equivalent relaxation. Isometric tension changes were measured in human fetal (11-16 wk) trachea and mainstem bronchus rings exposed to furosemide (300 microM) or saline after acetylcholine or leukotriene D(4) constriction. Significant decreases in isometric tension to furosemide were demonstrated after constriction with acetylcholine or leukotriene D(4). To examine the site of effect and mimic aerosolized and systemic administration, furosemide (3-300 microM) and bumetanide (0.3-30 microM) were applied separately to epithelial and adventitial surfaces of newborn mouse airways. No differences in airway diameter changes to epithelial or adventitial furosemide or bumetanide were observed, but a 10-fold difference in potency was found. In summary, human fetal airway relaxed to furosemide when constricted with either neurotransmitter or inflammatory mediator in vitro. Further, no differences in relaxation to equimolar epithelial and adventitial furosemide were observed in isolated newborn mouse airway. Taken together, this provides evidence that furosemide has a direct, nonepithelial-dependent effect on airway smooth muscle tone.

Neonatal Chronic Lung Disease

Chronic lung disease (CLD), formerly known as bronchopulmonary dysplasia, is presently defined as the need for oxygen therapy either at 28 days of age or greater than 36 weeks postmenstrual age. Clinical signs and symptoms include tachypnea, retractions, apnea, and radiographic findings of poorly inflated lungs with reticulogranular opacities. The disease develops as a result of chronic pulmonary inflammation and continuous lung injury induced by oxygen, positive pressure ventilation, and other causes. Fifty to sixty-five percent of neonates with CLD are rehospitalized with respiratory problems, and 21% of very low birth weight neonates are diagnosed with asthma or other respiratory disorders by the age of five. These infants are at risk of adverse neurodevelopmental sequelae as they have a more complicated neonatal course. Many studies have explored various preventive therapies including α1-proteinase inhibitors, superoxide dismutase, antioxidants, and ventilatory management. Although the results from these trials are promising, further studies are needed to define which patients are most likely to benefit from preventive therapy. Two preventive treatment approaches that have shown a decrease in morbidity and an improvement in mortality are antenatal steroids and surfactant therapy. Postnatal corticosteroid therapy continues to be the mainstay of treatment for CLD, however, there are a number of detrimental side effects associated with this treatment. Due to the increased incidence in periventricular leukomalacia, early treatment of steroid therapy cannot be recommended. The optimal time to start steroid therapy appears to be after the first week of life. In addition, the lowest dose and shortest duration of treatment needs to be implemented in order to minimize potential complications. Although bronchodilators and diuretics continue to be used extensively in infants with CLD, there are surprisingly few well-controlled studies that have evaluated the clinical impact of this therapy. Further trials are needed in order to support the routine use of these therapies in CLD. Unfortunately, inhaled steroids have not shown an improvement in long-term outcomes of CLD, however, they have shown a decrease in systemic steroid usage. CLD is a complex disease with many unanswered questions. Further studies are needed to evaluate the effects of various treatment modalities with particular focus on the long-term outcomes such as oxygen and ventilator dependency as well as the incidence of CLD.

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.

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.

Approaching the management of the neonatal intensive care unit graduate through history and physical assessment

NICU graduates, often ex-premature infants, offer unusual challenges to the primary care provider. History and physical assessment require an organized approach with meticulous attention to detail. These infants are at high risk for multiple problems including growth delays, nutrition and feeding problems, pulmonary sequelae, neurological sequelae and developmental delays, vision and hearing disturbances, as well as abnormalities in parent-infant bonding. This article emphasizes particular aspects of the history and physical examination that signify pathophysiology and sequelae common to the NICU graduate.

The effect of aerosolized furosemide in infants with chronic lung disease

To investigate whether aerosolized furosemide would improve pulmonary function in premature infants with chronic lung disease, we enrolled eight preterm ventilator-dependent infants in a cross-over, double-blind, placebo-controlled trial. Either aerosolized furosemide (2 mg/kg) or placebo (0.9% saline) was administered, and serial pulmonary function tests were performed before and at 1 and 2 h after each inhalation. After furosemide inhalation, static respiratory compliance increased significantly by 24.3% and 23.2% as percentage change from the baseline value at 1 and 2 h (p = 0.014 and 0.022, respectively). Also, tidal volume increased significantly by 33.8% and 28.7% at 1 and 2 h, respectively (p = 0.004 and 0.009). In contrast, no changes were observed in them after placebo inhalation. Total respiratory resistance was unchanged after both furosemide and placebo inhalation. There were no differences in urine volume in two groups. These data suggested that aerosolized furosemide improved pulmonary function in infants with chronic lung disease without excessive 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.

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.

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.

Mineral excretion in premature infants receiving various diuretic therapies

The association of various diuretic therapies with the renal handling of minerals, important factors in the development of nephrocalcinosis and osteopenia, was studied in low birth weight infants. Twenty-four-hour urine specimens (n = 65) were collected from 30 patients who were treated with (1) furosemide with or without spironolactone and hydrochlorothiazide (2) spironolactone with hydrochlorothiazide, (3) spironolactone alone, or (4) no diuretic (control; i.e., after diuretic). Hypercalciuria (urinary calcium greater than or equal to 0.15 mmol/kg/day) was observed in all but the control group. Covariate analysis demonstrated a significant effect of sodium, calcium, and vitamin D intakes (p less than 0.01) and sodium excretion (p less than 0.05) on urinary calcium excretion. Treatment with any of these diuretics in neonates may be associated with abnormal renal losses of calcium, sodium, chloride, and potassium. From a nutritional perspective, neonates requiring long-term diuretic therapy thereby require special consideration, including monitoring of mineral excretion and renal ultrasonography.

Renal calcification in preterm infants: pathophysiology and long-term sequelae

We examined the clinical course of 17 preterm infants with chronic lung disease who received loop diuretics and developed nephrocalcinosis; nine of them were followed for up to 4.5 years. The mean gestational age was 26.8 weeks (SD 2.2 weeks), and mean birth weight was 830 gm (SD 276 gm). The diagnosis of renal calcification was made at a mean age of 12 weeks (SD 6.5 weeks) by abdominal x-ray examination, screening abdominal ultrasound studies or, both. Calcification was associated with both furosemide therapy and the presence of multiple potential risk factors. Renal calcification, length, and function were subsequently evaluated in nine patients at a mean age of 21.3 months (SD 15.3 months). Improvement in calcification occurred in five patients, with total resolution in four. Renal length, determined by ultrasound examination and corrected for body length, was normal in 17 of 18 kidneys. Serum creatinine values and calculated glomerular filtration rates were abnormal in four of nine patients. We conclude that renal calcification in preterm infants is associated with multiple risk factors, including furosemide usage, and tends to diminish during the first year of life. However, renal function may remain compromised in some patients.

Respiratory distress syndrome

Increasing knowledge of the pathophysiology of respiratory distress syndrome has led to improvements in clinical management. Future advances in prevention and therapy, including administration of agents to prevent prematurity or to accelerate lung maturation, provision of surfactant replacement, and new techniques of mechanical ventilation, will further decrease mortality and morbidity.

Modern fluid and electrolyte management of the critically ill premature infant

In this article, the authors introduce the concept of a transitional physiology which governs fluid and electrolyte balance in the immediate postnatal period. The important impact of the extrauterine environment on fluid balance is also discussed. Finally, the pathophysiology of diuresis in RDS, and fluid shifts in the VLBW infant with therapeutic recommendations are presented.

Diuretic therapeutics in the pediatric patient

Careful management of fluid and electrolytes has long been an intrinsic part of pediatric practice. However, the augmentation of these manipulations through the rational use of diuretic agents requires considerable skill. In pediatric medicine, the regulation of pharmacokinetic processes and their interface with pharmacodynamic processes show dramatic age-related changes. These ontogenetic processes and their modification by various disease states must be considered carefully before selection and application of diuretic agents. The available data concerning the ontogeny of renal function and the attempts to apply diuretic therapy to pediatric disease are reviewed. It is concluded that results obtained to date suffer from the absence of a rigorous attempt to answer the fundamental therapeutic questions: What drug? What dose? What duration of therapy? A rational "target-effect" strategy is proposed for the application of diuretic agents to pediatric medicine.

Bronchodilators and diuretics in children with bronchopulmonary dysplasia

Pulmonary function tests (PFT) were obtained during the course of a self-controlled study of six children aged 5 to 43 months who had moderate to severe bronchopulmonary dysplasia (BPD). Changes after the administration of intravenous (IV) furosemide (2 mg/kg), inhaled isoproterenol (0.2 cc, 1:200), inhaled atropine sulfate (0.05 mg/kg), and a placebo were assessed. The study indicated the furosemide and atropine significantly (P less than 0.05) increased dynamic compliance (CL) for the group. A decrease in total pulmonary resistance (RL) and work of breathing (W) was observed after isoproterenol, although the responses were not significant (P = 0.08 and P = 0.09, respectively). It was speculated that pulmonary edema and increased vagal tone may contribute to small airway dysfunction in children who have BPD.

Controlled trial of furosemide therapy in infants with chronic lung disease

To study the effects of furosemide therapy in infants with chronic lung disease (CLD), a double-blind controlled trial was designed. Seventeen infants with evidence of CLD (oxygen requirements greater than 30% at greater than 3 weeks of age and chest radiographic findings consistent with CLD) were studied. Pulmonary function was measured immediately before, and after 48 hours and 7 days of treatment with furosemide (1 mg/kg/12 hr intravenously or 2 mg/kg/12 hr orally) or placebo. Clinical status improved in six of seven infants who received furosemide and in two of 10 infants who received placebo (P less than 0.002). In the furosemide group, ventilator and oxygen requirements decreased (P less than 0.003); minute ventilation, alveolar ventilation, and dynamic compliance increased; and venous admixture decreased (P less than 0.05). There were no significant changes in the placebo group. Our findings suggest that furosemide significantly improves lung function during therapy in infants with CLD and allows earlier weaning from ventilatory support and supplemental oxygen.