Decreased pulmonary transvascular fluid filtration in awake newborn lambs after intravenous furosemide

Neonatal perspective on central lymphatic disorders

Lymphatic disorders presenting in the first year of life are difficult to identify and manage given the broad range of underlying etiologies. Neonatal lymphatic disease arising from congenital or acquired conditions results in the abnormal accumulation of lymph fluid in the pleura (chylothorax), peritoneum (chylous ascites) and skin (edema/anasarca). There is also increasing recognition of lymphatic losses through the intestine resulting in protein-losing enteropathy (PLE). While the incidence of lymphatic disorders in neonates is unclear, advances in genetic testing and lymphatic imaging are improving our understanding of the underlying pathophysiology. Despite these advancements, medical management of neonatal lymphatic disorders remains challenging and variable among clinicians.

Interventions for the management of transient tachypnoea of the newborn - an overview of systematic reviews

BACKGROUND

Transient tachypnoea of the newborn (TTN) is characterised by tachypnoea and signs of respiratory distress. It is caused by delayed clearance of lung fluid at birth. TTN typically appears within the first two hours of life in term and late preterm newborns. Although it is usually a self-limited condition, admission to a neonatal unit is frequently required for monitoring, the provision of respiratory support, and drugs administration. These interventions might reduce respiratory distress during TTN and enhance the clearance of lung liquid. The goals are reducing the effort required to breathe, improving respiratory distress, and potentially shortening the duration of tachypnoea. However, these interventions might be associated with harm in the infant.

OBJECTIVES

The aim of this overview was to evaluate the benefits and harms of different interventions used in the management of TTN.

METHODS

We searched the Cochrane Database of Systematic Reviews on 14 July 2021 for ongoing and published Cochrane Reviews on the management of TTN in term (> 37 weeks' gestation) or late preterm (34 to 36 weeks' gestation) infants. We included all published Cochrane Reviews assessing the following categories of interventions administered within the first 48 hours of life: beta-agonists (e.g. salbutamol and epinephrine), corticosteroids, diuretics, fluid restriction, and non-invasive respiratory support. The reviews compared the above-mentioned interventions to placebo, no treatment, or other interventions for the management of TTN. The primary outcomes of this overview were duration of tachypnoea and the need for mechanical ventilation. Two overview authors independently checked the eligibility of the reviews retrieved by the search and extracted data from the included reviews using a predefined data extraction form. Any disagreements were resolved by discussion with a third overview author. Two overview authors independently assessed the methodological quality of the included reviews using the AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews) tool. We used the GRADE approach to assess the certainty of evidence for effects of interventions for TTN management. As all of the included reviews reported summary of findings tables, we extracted the information already available and re-graded the certainty of evidence of the two primary outcomes to ensure a homogeneous assessment. We provided a narrative summary of the methods and results of each of the included reviews and summarised this information using tables and figures.

MAIN RESULTS

We included six Cochrane Reviews, corresponding to 1134 infants enrolled in 18 trials, on the management of TTN in term and late preterm infants, assessing salbutamol (seven trials), epinephrine (one trial), budesonide (one trial), diuretics (two trials), fluid restriction (four trials), and non-invasive respiratory support (three trials). The quality of the included reviews was high, with all of them fulfilling the critical domains of the AMSTAR 2. The certainty of the evidence was very low for the primary outcomes, due to the imprecision of the estimates (few, small included studies) and unclear or high risk of bias. Salbutamol may reduce the duration of tachypnoea compared to placebo (mean difference (MD) -16.83 hours, 95% confidence interval (CI) -22.42 to -11.23, 2 studies, 120 infants, low certainty evidence). We did not identify any review that compared epinephrine or corticosteroids to placebo and reported on the duration of tachypnoea. However, one review reported on "trend of normalisation of respiratory rate", a similar outcome, and found no differences between epinephrine and placebo (effect size not reported). The evidence is very uncertain regarding the effect of diuretics compared to placebo (MD -1.28 hours, 95% CI -13.0 to 10.45, 2 studies, 100 infants, very low certainty evidence). We did not identify any review that compared fluid restriction to standard fluid rates and reported on the duration of tachypnoea. The evidence is very uncertain regarding the effect of continuous positive airway pressure (CPAP) compared to free-flow oxygen therapy (MD -21.1 hours, 95% CI -22.9 to -19.3, 1 study, 64 infants, very low certainty evidence); the effect of nasal high-frequency (oscillation) ventilation (NHFV) compared to CPAP (MD -4.53 hours, 95% CI -5.64 to -3.42, 1 study, 40 infants, very low certainty evidence); and the effect of nasal intermittent positive pressure ventilation (NIPPV) compared to CPAP on duration of tachypnoea (MD 4.30 hours, 95% CI -19.14 to 27.74, 1 study, 40 infants, very low certainty evidence). Regarding the need for mechanical ventilation, the evidence is very uncertain for the effect of salbutamol compared to placebo (risk ratio (RR) 0.60, 95% CI 0.13 to 2.86, risk difference (RD) 10 fewer, 95% CI 50 fewer to 30 more per 1000, 3 studies, 254 infants, very low certainty evidence); the effect of epinephrine compared to placebo (RR 0.67, 95% CI 0.08 to 5.88, RD 70 fewer, 95% CI 460 fewer to 320 more per 1000, 1 study, 20 infants, very low certainty evidence); and the effect of corticosteroids compared to placebo (RR 0.52, 95% CI 0.05 to 5.38, RD 40 fewer, 95% CI 170 fewer to 90 more per 1000, 1 study, 49 infants, very low certainty evidence). We did not identify a review that compared diuretics to placebo and reported on the need for mechanical ventilation. The evidence is very uncertain regarding the effect of fluid restriction compared to standard fluid administration (RR 0.73, 95% CI 0.24 to 2.23, RD 20 fewer, 95% CI 70 fewer to 40 more per 1000, 3 studies, 242 infants, very low certainty evidence); the effect of CPAP compared to free-flow oxygen (RR 0.30, 95% CI 0.01 to 6.99, RD 30 fewer, 95% CI 120 fewer to 50 more per 1000, 1 study, 64 infants, very low certainty evidence); the effect of NIPPV compared to CPAP (RR 4.00, 95% CI 0.49 to 32.72, RD 150 more, 95% CI 50 fewer to 350 more per 1000, 1 study, 40 infants, very low certainty evidence); and the effect of NHFV versus CPAP (effect not estimable, 1 study, 40 infants, very low certainty evidence). Regarding our secondary outcomes, duration of hospital stay was the only outcome reported in all of the included reviews. One trial on fluid restriction reported a lower duration of hospitalisation in the restricted-fluids group, but with very low certainty of evidence. The evidence was very uncertain for the effects on secondary outcomes for the other five reviews. Data on potential harms were scarce, as all of the trials were underpowered to detect possible increases in adverse events such as pneumothorax, arrhythmias, and electrolyte imbalances. No adverse effects were reported for salbutamol; however, this medication is known to carry a risk of tachycardia, tremor, and hypokalaemia in other settings.

AUTHORS' CONCLUSIONS

This overview summarises the evidence from six Cochrane Reviews of randomised trials regarding the effects of postnatal interventions in the management of TTN. Salbutamol may reduce the duration of tachypnoea slightly. We are uncertain as to whether salbutamol reduces the need for mechanical ventilation. We are uncertain whether epinephrine, corticosteroids, diuretics, fluid restriction, or non-invasive respiratory support reduces the duration of tachypnoea and the need for mechanical ventilation, due to the extremely limited evidence available. Data on harms were lacking.

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.

Fluid restriction in the management of transient tachypnea of the newborn

BACKGROUND

Transient tachypnea of the newborn (TTN) is caused by delayed clearance of lung fluid at birth. TTN typically appears within the first two hours of life in term and late preterm neonates and is characterized by tachypnea and signs of respiratory distress. Although it is usually a self-limited condition, admission to a neonatal unit is frequently required for monitoring and providing respiratory support. Restricting intake of fluids administered to these infants in the first days of life might improve clearance of lung liquid, thus reducing the effort required to breathe, improving respiratory distress, and potentially reducing the duration of tachypnea.

OBJECTIVES

To evaluate the efficacy and safety of restricted fluid therapy as compared to standard fluid therapy in decreasing the duration of oxygen administration and the need for noninvasive or invasive ventilation among neonates with TTN.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 12), in the Cochrane Library; Ovid MEDLINE and electronic ahead of print publications, in-process & other non-indexed citations, Daily and Versions(R); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL), on December 6, 2019. We also searched clinical trial databases and the reference lists of retrieved articles for randomized controlled trials and quasi-randomized trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs), quasi-RCTs, and cluster trials on fluid restriction in term and preterm neonates with the diagnosis of TTN or delayed adaptation during the first week after birth.

DATA COLLECTION AND ANALYSIS

For each of the included trials, two review authors independently extracted data (e.g. number of participants, birth weight, gestational age, duration of oxygen therapy, need for continuous positive airway pressure [CPAP], need for mechanical ventilation, duration of mechanical ventilation) and assessed the risk of bias (e.g. adequacy of randomization, blinding, completeness of follow-up). The primary outcome considered in this review was the duration of supplemental oxygen therapy in hours or days. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

Four trials enrolling 317 infants met the inclusion criteria. Three trials enrolled late preterm and term infants with TTN, and the fourth trial enrolled only term infants with TTN. Infants were on various methods of respiratory support at the time of enrollment including room air, oxygen, or nasal CPAP. Infants in the fluid-restricted group received 15 to 20 mL/kg/d less fluid than those in the control group for varying durations after enrollment. Two studies had high risk of selection bias, and three out of four had high risk of performance bias. Only one study had low risk of detection bias, with two at high risk and one at unclear risk. The certainty of evidence for all outcomes was very low due to imprecision of estimates and unclear risk of bias. Two trials reported the primary duration of supplemental oxygen therapy. We are uncertain whether fluid restriction decreases or increases the duration of supplemental oxygen therapy (mean difference [MD] -12.95 hours, 95% confidence interval [CI] -32.82 to 6.92; I² = 98%; 172 infants). Similarly, there is uncertainty for various secondary outcomes including incidence of hypernatremia (serum sodium > 145 mEq/L, risk ratio [RR] 4.0, 95% CI 0.46 to 34.54; test of heterogeneity not applicable; 1 trial, 100 infants), hypoglycemia (blood glucose < 40 mg/dL, RR 1.0, 95% CI 0.15 to 6.82; test of heterogeneity not applicable; 2 trials, 164 infants), endotracheal ventilation (RR 0.73, 95% CI 0.24 to 2.23; I² = 0%; 3 trials, 242 infants), need for noninvasive ventilation (RR 0.40, 95% CI 0.14 to 1.17; test of heterogeneity not applicable; 2 trials, 150 infants), length of hospital stay (MD -0.92 days, 95% CI -1.53 to -0.31; test of heterogeneity not applicable; 1 trial, 80 infants), and cumulative weight loss at 72 hours of age (%) (MD 0.24, 95% CI -1.60 to 2.08; I² = 89%; 2 trials, 156 infants). We did not identify any ongoing trials; however, one trial is awaiting classification.

AUTHORS' CONCLUSIONS

We found limited evidence to establish the benefits and harms of fluid restriction in the management of TTN. Given the very low certainty of available evidence, it is impossible to determine whether fluid restriction is safe or effective for management of TTN. However, given the simplicity of the intervention, a well-designed trial is justified.

Diuretic Use and Subsequent Electrolyte Supplementation in a Level IV Neonatal Intensive Care Unit

OBJECTIVES

To evaluate the relationship between diuretic use, serum electrolyte concentrations, and supplementation requirements in infants admitted to the neonatal intensive care unit.

METHODS

This was a single-center retrospective cohort study conducted in a freestanding children's hospital Level IV NICU. Data were collected for all infants younger than 6 months, admitted to the NICU between January 2015 and May 2017, who received 2 or more consecutive doses of furosemide, chlorothiazide, hydrochlorothiazide, and/or hydrochlorothiazide/spironolactone. The primary outcome was the composite of the incidence of electrolyte abnormalities and/or electrolyte supplementation requirement within 30 days of diuretic exposure.

RESULTS

A total of 72 patients met inclusion criteria, with a median gestational age of 30 weeks. Overall, 92% of patients exposed to diuretics experienced derangement in at least 1 serum electrolyte and/or required electrolyte supplementation during diuretic therapy. Patients born at 36 to 41 weeks' gestational age, receiving thiazide diuretics, experienced a significantly lower rate of the primary outcome (37%, p ≤ 0.001). The most common electrolytes affected by diuretic use were potassium and bicarbonate, with the highest incidence of the primary outcome for potassium occurring in patients receiving furosemide (p = 0.0196). Last, the median total daily dose of chlorothiazide in patients with an adverse event was 15 mg/kg/day, compared with 10 mg/kg/day in patients without an adverse event (p = 0.0041).

CONCLUSIONS

Use of diuretics in young infants is likely to cause electrolyte derangements and/or require electrolyte supplementation. Patients born at earlier gestational ages may be at higher risk for developing such adverse effects.

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.

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.

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.

Variation in the use of diuretic therapy for infants with bronchopulmonary dysplasia

OBJECTIVES

To determine (1) between-hospital variation in diuretic use for infants with bronchopulmonary dysplasia (BPD), including hospital-specific treatment frequency, treatment duration, and percentage of infants receiving short (≤5 consecutive days) versus longer (>5 days) courses, and to determine (2) demographic and clinical variables associated with diuretic administration.

METHODS

A retrospective cohort study was conducted with the use of the Pediatric Health Information System to determine between-hospital variation in diuretic utilization patterns (primary outcome) and variables associated with diuretic use among <29-week-gestation infants with evolving BPD at age 28 days who were discharged between January 2007 and June 2011.

RESULTS

During the 54-month study period, 1429 infants within 35 hospitals met the inclusion criteria for BPD at age 28 days, with 1222 (86%) receiving diuretic therapy for a median of 9 days (25th-75th percentile: 2-33 days). Short courses were administered to 1203 (83%) infants, and 570 (40%) infants received treatment for >5 consecutive days. Furosemide was the most widely prescribed diuretic (1218 infants; 85%), although chlorothiazide had the longest median duration of use (21 days; 25th-75th percentile: 8-46 days). The range of infants receiving a diuretic course of >5 days duration varied by hospital from 4% to 86%, with wide between-hospital variation even after adjustment for confounding variables.

CONCLUSIONS

The frequency of diuretic administration to infants with BPD at US children's hospitals, as well as the specific diuretic regimen used, varies markedly by institution. Safety and effectiveness research of long-term diuretic therapy for BPD patients is needed to develop evidence-based recommendations.

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.

Diuretics for respiratory distress syndrome in preterm infants

BACKGROUND

Lung edema may complicate respiratory distress syndrome (RDS) in preterm infants.

OBJECTIVES

The aim of this review was to assess the risks and benefits of diuretic administration in preterm infants with RDS.

SEARCH METHODS

The standard search method of the Cochrane Neonatal Review Group was used. The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE and EMBASE were searched. These searches were updated in April 2003, March 2007, January 2011. In addition, the abstract books of the American Thoracic Society and Society for Pediatric Research were searched. MEDLINE and CENTRAL search was conducted using the keyword "Respiratory Distress Syndrome" alone, to find studies of medications recently classified as diuretics, such as theophylline. In addition, EMBASE, controlled-trials.com and clinicaltrials.gov searches were completed in January 2011. MEDLINE search updated to August 2011.

SELECTION CRITERIA

Trials were included in which preterm infants with RDS and less than five days of age were randomly allocated to diuretic administration. Of those trials, studies were only included in which at least one of the following outcomes measures was evaluated: mortality, patent ductus arteriosus, hypovolemic shock, intraventricular hemorrhage, renal failure, duration of oxygen supplementation, duration of mechanical ventilation, need for oxygen supplementation at 28 days of life, oxygen supplementation at 36 weeks of postmenstrual age (gestational age + postnatal age), length of stay, number of rehospitalizations during the first year of life, and neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

The standard method for the Cochrane Collaboration, which is described in the Cochrane Collaboration Handbook, was used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

MAIN RESULTS

Seven studies met inclusion criteria. Six studies using furosemide were done before the current era of prenatal steroids, surfactant and fluid restriction. Furosemide administration had no long-term benefits. Furosemide-induced transient improvement in pulmonary function did not outweigh an increased risk for patent ductus arteriosus and for hemodynamic instability. In one recent study, theophylline had no long-term benefits. Theophylline significantly decreased the risk of oligoanuria and transiently increased renal function, but did not significantly affect renal function at discharge or other outcomes.

AUTHORS' CONCLUSIONS

There are no data to support routine administration of furosemide in preterm infants with RDS. Elective administration of furosemide to any patient with RDS should be carefully weighed against the risk of precipitating hypovolemia or developing a symptomatic patent ductus arteriosus. There are not enough data to support routine administration of low-dose theophylline in preterm infants with RDS.

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.

Diuretics for respiratory distress syndrome in preterm infants

BACKGROUND

Lung edema may complicate respiratory distress syndrome (RDS) in preterm infants.

OBJECTIVES

The aim of this review was to assess the risks and benefits of diuretic administration in preterm infants with RDS.

SEARCH STRATEGY

The standard search method of the Cochrane Neonatal Review Group was used. MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) were searched using the following keywords: <exp respiratory distress syndrome> and <exp diuretics>. These searches were updated in April 2003 and March 2007. In addition, the abstract books of the American Thoracic Society and Society for Pediatric Research were searched. A MEDLINE and CENTRAL search was conducted in March 2007 using the keyword "Respiratory Distress Syndrome" alone, to make sure to find studies medications recently classified as diuretics, such as theophylline.

SELECTION CRITERIA

Trials were included in which preterm infants with RDS and less than 5 days of age were randomly allocated to diuretic administration. Of those trials, studies were only included in which at least one of the following outcomes measures was evaluated: mortality, patent ductus arteriosus, hypovolemic shock, intraventricular hemorrhage, renal failure, duration of oxygen supplementation, duration of mechanical ventilation, need for oxygen supplementation at 28 days of life, oxygen supplementation at 36 weeks of postmenstrual age (gestational age + postnatal age), length of stay, number of rehospitalizations during the first year of life, and neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

The standard method for the Cochrane Collaboration, which is described in the Cochrane Collaboration Handbook, was used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

MAIN RESULTS

Seven studies met inclusion criteria. Six studies using furosemide were done before the current era of prenatal steroids, surfactant and fluid restriction. Furosemide administration had no long-term benefits. Furosemide-induced transient improvement in pulmonary function did not outweigh an increased risk for patent ductus arteriosus and for hemodynamic instability. In one recent study, theophylline had no long-term benefits. Theophylline significantly decreased the risk of oligoanuria and transiently increased renal function, but did not significantly affect renal function at discharge or other outcomes.

AUTHORS' CONCLUSIONS

There are no data to support routine administration of furosemide in preterm infants with RDS. Elective administration of furosemide to any patient with RDS should be carefully weighed against the risk of precipitating hypovolemia or developing a symptomatic patent ductus arteriosus. There are not enough data to support routine administration of low-dose theophylline in preterm infants with RDS.

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.

Age-dependent cardiovascular, renal and endocrine responses to furosemide in conscious lambs

1. The present study was performed to investigate some of the physiological responses to furosemide during postnatal maturation. 2. In 1- (n = 8) and 6-week old (n = 10) conscious, chronically instrumented lambs at least 3 days after surgery, three experiments were performed at intervals of 24-48 h and in random order. Various parameters of cardiovascular and endocrine function, as well as cumulative urinary flow rates, were measured before and after intravenous injection of 0 mg/kg (experiment one), 0.25 mg/kg (experiment two; low dose) and 5 mg/kg (experiment three; high dose) furosemide. 3. After high-dose furosemide, mean venous pressure decreased and there was a transient increase in mean arterial pressure in lambs aged 6 weeks. At 1 week of age, heart rate increased after high-dose furosemide and renal blood flow decreased. After high-dose furosemide, plasma renin activity increased in both groups of lambs, although the effects were greater in 1-week-old lambs. Plasma levels of arginine vasopressin increased after high-dose furosemide in lambs aged 1 but not 6 weeks. Cumulative urinary flow rate responses to furosemide were similar in 1- and 6-week-old lambs. 4. These data provide new information that cardiovascular and endocrine responses to furosemide are developmentally regulated.

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.

Mitochondrial thiol status in the liver is altered by exposure to hyperoxia

Patients with poorly functioning lungs often require treatment with high concentrations of supplemental oxygen, which, although often necessary to sustain life, can cause lung injury. The mechanisms responsible for hyperoxic lung injury have been investigated intensely and most probably involve oxidant stress responses, but the details are not well understood. In the present studies, we exposed adult male C57/Bl6 mice to >95% O2 for up to 72 h and obtained lung and liver samples for assessment of lung injury, measurements of tissue concentrations of coenzyme A (CoASH) and the corresponding mixed disulfide with glutathione (CoASSG), as possible biomarkers of intramitochondrial thiol redox status. Subcellular fractions were prepared from both tissues for determination of glutathione reductase (GR) activities. Lung injury in the hyperoxic mice was demonstrated by increases in lung weight to body weight ratios at 48 h and by increases in bronchoalveolar lavage protein concentrations at 72 h. Lung CoASH concentrations declined in the hyperoxic mice, but CoASSG concentrations were not increased nor were CoASH/CoASSG ratios decreased, as would be expected for an oxidant shift in mitochondrial thiol-disulfide status. Interestingly, CoASSG concentrations increased (from 6.72+/-0.54 to 14.10+/-1.10 nmol/g of liver in air-breathing controls and 72 h of hyperoxia, respectively, P<0.05), and CoASH/CoASSG ratios decreased in the livers of mice exposed to hyperoxia. Some apparent effects of duration of hyperoxia on GR activities in lung or liver cytosolic, mitochondrial, or nuclear fractions were observed, but the changes were not consistent or progressive. Yields of isolated hepatic nuclear protein were decreased in the hyperoxic mice within 24 h of exposure, and by 72 h of hyperoxia, protein recoveries in purified nuclear fractions had declined from 41.8 to 14.8 mg of protein/g animal body weight. Concentrations of 10-formyltetrahydrofolate dehydrogenase were diminished in hepatic mitochondria of hyperoxic mice. A second protein in hepatic mitochondria of approximately 25 kDa showed apparent decreases in thiol content, as determined by fluorescence intensities of monobromobimane derivatives separated by SDS-PAGE. The mechanisms responsible for the observed effects and the possible implications for the adverse effects of hyperoxic therapies are not known and need to be investigated.

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.

Diuretics for respiratory distress syndrome in preterm infants

BACKGROUND

Lung edema may complicate respiratory distress syndrome (RDS) in preterm infants.

OBJECTIVES

The aim of this review was to assess the risks and benefits of diuretic administration in preterm infants with RDS.

SEARCH STRATEGY

We used the standard search method of the Cochrane Neonatal Review Group. We searched Medline, Embase and the Cochrane Controlled Trials Register from the Cochrane Library, using the following keywords: <exp respiratory distress syndrome> and <exp diuretics>. In addition, we searched the abstract books of the American Thoracic Society and Pediatric Research Societies.

SELECTION CRITERIA

We only included trials in which preterm infants with RDS and less than 5 days of age were randomly allocated to diuretic administration. Of those trials, we only included studies in which at least one of the following outcomes measures was evaluated: mortality, patent ductus arteriosus, hypovolemic shock, intraventricular hemorrhage, renal failure, duration of oxygen supplementation, duration of mechanical ventilation, need for oxygen supplementation at 28 days of life, oxygen supplementation at 36 weeks of postconceptional age (gestational age + postnatal age), length of stay, number of rehospitalizations during the first year of life, and neurodevelopmental outcome.

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. Any disagreement was resolved by discussion.

MAIN RESULTS

Six studies met inclusion criteria. Studies available for this systematic review were all done before the current era of prenatal steroids, surfactant, indomethacin and fluid restriction. Furosemide administration had no long-term benefits. Furosemide-induced transient improvement in pulmonary function did not outweigh an increased risk for patent ductus arteriosus and for hemodynamic instability.

REVIEWER'S CONCLUSIONS

There are no current data to support routine diuretic administration in preterm infants with RDS. Elective administration of furosemide or any diuretic to any patient with RDS should be carefully weighed against the risk of precipitating hypovolemia. In addition, elective administration of furosemide should be weighed against the risk of developing a symptomatic patent ductus arteriosus.

High-dose furosemide alters gas exchange in a model of acute lung injury

PURPOSE

Furosemide is often used to reduce edema in patients with acute respiratory distress syndrome (ARDS). It was hypothesized that furosemide would reduce lung water and improve gas exchange in a phorbol-myristate acetate (PMA) model of acute lung injury.

METHODS

Two groups of mongrel dogs received PMA (25 to 30 micrograms/kg) and continuous saline at 10 mL/kg/h; one group received PMA plus two 1-mg/kg doses of furosemide at 1 and 2 hours after PMA. Arterial blood gases on F1O2 = 1.0 and double-dilution lung water were measured at intervals over 7 hours.

RESULTS

In dogs receiving PMA+furosemide, AaDO2 and shunt fraction increased compared with dogs receiving PMA only (AaDO2, P = .014; shunt, P = .017). There were no significant differences between the groups in lung water (P = .34) during the experiment or in wet/dry weight postmortem. Urine flow was markedly reduced in both groups; the kidneys appeared unresponsive to the diuretic effects of furosemide. Significant elevations in hematocrit and pulmonary vascular resistance were seen in furosemide-treated compared with PMA-only dogs.

CONCLUSIONS

In this model of ARDS, which results in the absence of effective kidney function and multiple organ failure, furosemide compromises alveolar-capillary gas exchange and fails to influence the time course of lung water accumulation. The results suggest that the nondiuretic affects of furosemide cannot explain its purported clinical utility in ARDS.

Nebulized furosemide in infants with bronchopulmonary dysplasia

The effects of 0.1 mg, 0.25 mg, 0.50 mg, and 1.0 mg of nebulized furosemide per kilogram of body weight on pulmonary functions were studied in eight preterm infants with bronchopulmonary dysplasia who were supported by mechanical ventilation. Doses of 1 mg/kg significantly improved lung compliance (51% at 2 hours after nebulization), pulmonary resistance (28% at 1 hour), and tidal volume (43% at 1 hour), starting as early as 30 minutes after the dose; the effect lasted for at least 4 hours in many of the infants and was not associated with diuresis or renal side effects.

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.

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.

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.

Ovine fetal lung fluid response to atrial natriuretic factor

The fetal lung is an important site of fluid production and is postulated to serve a regulatory role in fetal fluid balance. To assess the role of atrial natriuretic factor on fetal lung liquid production, we studied the effect of intravenous atrial natriuretic factor infusion on tracheal fluid production in fetal sheep with chronic vascular and tracheal catheters. Ovine fetuses (mean gestation = 130 days +/- 1 day) received successive 40-minute intravenous infusions of increasing doses of synthetic fragment 1-28 atrial natriuretic factor (5, 25, and 100 ng/min.kg-1). In response to the 25 ng/min.kg-1 infusion, fetal tracheal fluid production decreased from 1.2 +/- 0.3 ml/10 min to 0.6 +/- 0.2 ml/10 min (p less than 0.05), and remained suppressed during the 100 ng/min.kg-1 infusion (0.5 +/- 0.2 ml/10 min). There was a significant inverse correlation between tracheal fluid production and fetal plasma atrial natriuretic factor levels (r = -0.61, p less than 0.001). Basal tracheal fluid sodium and potassium concentrations (147 +/- 1 mEq/L and 5 +/- 1 mEq/L) and osmolality (291 +/- 3 mOsm) did not change during the atrial natriuretic factor infusion periods. The observation that atrial natriuretic factor acts to decrease fetal lung fluid production suggests that atrial natriuretic factor may be important in the fetal adaptive response to extrauterine life.

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.

Oral theophylline and diuretics improve pulmonary mechanics in infants with bronchopulmonary dysplasia

We studied the effects of orally administered theophylline and diuretics (chlorothiazide and spironolactone) on pulmonary mechanics in 16 infants with bronchopulmonary dysplasia. Their gestational age (mean +/- SD) was 28.5 +/- 3.4 weeks, and postnatal age at the time of study 19.5 +/- 10.7 weeks. The infants were randomized to two groups. Group 1 received successively placebo, theophylline, and theophylline plus diuretics; Group 2 received theophylline, placebo, and placebo plus diuretics on successive 4-day periods. Pulmonary function was measured before beginning the study (baseline) and at the end of each 4-day period. No significant changes in pulmonary function were noted after treatment with placebo. After treatment with theophylline, dynamic compliance (Cdyn) increased from baseline (mean +/- SD) 0.075 +/- 0.017 to 0.091 +/- 0.028 mL/cm H2O/cm (P less than 0.01), airway resistance (Raw) decreased from 67.19 +/- 36.71 to 41.44 +/- 22.50 cm H2O/L/sec (P less than 0.001), maximal expiratory flow at functional residual capacity (VmaxFRC) increased from 0.261 +/- 0.240 to 0.357 +/- 0.299 thoracic gas volume (TGV)/sec (P less than 0.01), and time constant decreased from 0.312 +/- 0.224 to 0.275 +/- 0.247 sec (P less than 0.02). After treatment with combined placebo and diuretics, Cdyn increased to 0.103 +/- 0.023 mL/cm H2O/cm (P less than 0.05), Raw decreased to 31.76 +/- 24.90 cm H2O/L/sec (P less than 0.001), VmaxFRC increased to 0.638 +/- 0.595 TGV/sec (P less than 0.02), and time constant decreased to 0.180 +/- 0.141 sec (P less than 0.05). After treatment with combined theophylline and diuretics, Cdyn increased to 0.118 +/- 0.017 mL/cm H2O/cm (P less than 0.001), Raw decreased to 35.98 +/- 25.85 cm H2O/L/sec (P less than 0.02), VmaxFRC increased to 0.479 +/- 0.377 TGV/sec (P less than 0.02), and time constant decreased to 0.180 +/- 0.137 sec (P less than 0.01). We conclude that theophylline and diuretics have additive effects on the improvement of pulmonary function in infants with bronchopulmonary dysplasia.

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.

Furosemide decreases ventilation in young rabbits

To test the hypothesis that furosemide would cause metabolic alkalosis and thus alveolar hypoventilation, normal rabbit pups were given either furosemide (4 mg/kg/day) or saline solution for the first 8 to 10 days of life. Pups given furosemide developed primary metabolic alkalosis and reduced ventilation, which resulted in secondary respiratory acidosis. Lung compliance was improved by furosemide, and the ventilatory response to CO2 was unaffected. KCl injection in alkalotic pups increased ventilation and decreased pH. The data show that conventional doses of furosemide can (1) cause metabolic alkalosis and reduce ventilation; (2) increase the PaCO2, which reflects changes in acid-base status and not changes in lung function; and (3) increase lung compliance, perhaps by decreasing lung water. When these effects occur in infants with chronic lung disease, the beneficial effect of furosemide may be obscured.

Early furosemide therapy in premature infants (less than or equal to 2000 gm) with respiratory distress syndrome: a randomized controlled trial

Pulmonary edema has been demonstrated in the early stages of respiratory distress syndrome in premature infants. To evaluate whether early furosemide therapy (0 to 8 hours after birth) would affect the electrolyte balance, pulmonary status, and outcome, 57 infants (less than or equal to 2000 gm) with respiratory distress syndrome who required mechanical ventilation shortly after birth were randomized into two groups: 29 given furosemide (1 mg/kg/day intravenously for three doses) and 27 control. The clinical, biochemical, and laboratory characteristics of the groups were comparable before entry into the study. Administration of furosemide significantly enhanced the urinary excretion of Na and Cl at 0 to 24, 24 to 48 and 48 to 72 hours and of Ca at 24 to 48 and 48 to 72 hours after drug administration. There was no significant difference between the groups in urinary excretion of K and in serum Na, Cl, K, and Ca values. A spontaneous increase in urine output occurred in the control group at 48 to 72 hours after the initiation of the study (mean +/- SD 7.0 +/- 3.5 hours postnatal age), along with a decrease in mean airway pressure for mechanical ventilation. The use of furosemide (7.3 +/- 3.5 hours postnatal age) enhanced urine output at 24 to 48 and 48 to 72 hours after medication, resulting in further decrease in mean airway pressure and facilitating extubation. There was, however, no significant difference between the groups with respect to incidence of patent ductus arteriosus, morbidity from bronchopulmonary dysplasia, and mortality.

Blood volume following diuresis induced by furosemide

Changes in blood volume were investigated following intravenous injection of a single dose of furosemide in 21 patients with pulmonary edema. In a subset of 10 patients in whom the blood urea nitrogen level was 11.4 +/- 2.2 mg/dl and the serum creatinine level was 1.3 +/- 0.1 mg/dl and in whom total urine output exceeded 1 liter over a four- to six-hour interval ("diuretic" group), no significant change in plasma or total blood volume was observed, nor were there any significant changes in hematocrit. In a "nondiuretic" group of 11 patients who had moderately decreased renal function (blood urea nitrogen level 59.3 +/- 13.0 mg/dl and serum creatinine level 2.3 +/- 0.3 mg/dl) and in whom total urine output was less than 1 liter over the four- to six-hour interval, there was a significant increase in blood volume with a concomitant decrease in hematocrit and hemoglobin levels. Furosemide-induced diuresis therefore did not deplete intravascular volume. To the contrary, actions of furosemide that were independent of its diuretic action were associated with an expansion of plasma volume in the absence of diuresis. This may be related to the venous capacitance effects of furosemide with lowering of venous resistance and, therefore, lowering of the capillary hydrostatic pressure. In addition, there was an increase in colloid osmotic pressure. Both mechanisms increase the effective oncotic pressure gradient, which favors reabsorption of extravascular (edema) fluid. It is concluded that intravascular volume was therefore replenished at a rate equal to or in excess of the volume removed by diuresis.

The effect of lung edema on pulmonary vasoactivity of furosemide

Previous data suggest that furosemide improves gas exchange in pulmonary edema by preferential perfusion of nonedematous lung units. To test whether this is a direct effect of furosemide on the pulmonary vasculature as opposed to a secondary phenomenon resulting from the known peripheral effects of this drug, the effect of furosemide on the pressure-flow characteristics of the pulmonary vasculature was studied in six isolated perfused canine lungs with different degrees of gravimetrically determined edema. Furosemide shifted the pressure-flow curve by decreasing the mean intercept or average closing pressure of the pulmonary vascular bed from 13.8 +/- 5.3 to 9.5 +/- 5.4 cm H2O and the zero-flow critical closing pressure from 9.3 +/- 4.3 to 4.7 +/- 3.5 cm H2O (P less than 0.05). The slopes of these curves did not change between control and furosemide treatment. The decrease in intercept and the decrease in zero-flow critical closing pressures were closely correlated with the increase in edema (r = 0.895 for average closing pressure and r = -0.928 for critical closing pressure) (P less than 0.05). Furosemide doubled the pulmonary blood flow in the isolated lobe for the same driving pressure and the greater the amount of lobar edema the less pronounced was this furosemide-associated increase in blood flow. This direct effect of furosemide on the pulmonary vasculature could explain the improved gas exchange seen before a decrease in pulmonary edema, since this pulmonary vasoactivity would result in preferential perfusion of nonflooded alveolar units.

Furosemide acutely decreases airways resistance in chronic bronchopulmonary dysplasia

We studied the effects of furosemide on pulmonary mechanics in 10 infants with bronchopulmonary dysplasia aged 41 +/- 1 (SE) weeks post-conception, gestational age at birth 30 +/- 1 wk, birth weight 1370 +/- 200 gm. Thoracic gas volume, airways resistance, and specific airway conductance were measured in an infant body pressure plethysmograph during quiet breathing. Dynamic pulmonary compliance was measured using an esophageal balloon. Infants with BPD had greater Raw, lower SGaw, and lower Cdyn than did 16 normal control infants. Within one hour after administration of furosemide 1 mg/kg IV to infants with BPD, Raw fell 36 +/- 13%, SGaw increased 84 +/- 22%, and Cdyn increased 54 +/- 13%; TGV did not change. Diuretic treatment of BPD in infants is associated with rapid, short-term improvement in Raw and Cdyn.

Pulmonary effects of furosemide in preterm infants with lung disease

Twenty preterm infants recovering from respiratory distress syndrome at 1 week of age were randomized in this study either to a control or a treatment group. Those treated received a single daily dose of furosemide (1 mg/kg) intravenously. Pulmonary compliance was observed to improve significantly at two hours in the treated group, as compared with that in the controls. The calculated alveolar-arterial oxygen gradient was noted to decrease two hours after furosemide and to remain decreased over the four-day period in the treated group. This improvement in lung function was not secondary to diuresis in the infants treated with furosemide. We conclude that furosemide may have a direct pulmonary effect and improve lung function acutely as well as with chronic administration.

Edema formation in the lungs and its relationship to neonatal respiratory distress

Pulmonary edema is an important feature of many newborn lung diseases, including respiratory distress from severe perinatal asphyxia, heart failure, hyaline membrane disease, pneumonitis from group B beta-hemolytic streptococcus, and chronic lung disease (bronchopulmonary dysplasia). Neonatal pulmonary edema often results from increased filtration pressure in the microcirculation of the lungs. This occurs during sustained hypoxia, in left ventricular failure associated with congenital heart disease or myocardial dysfunction, following excessive intravascular infusions of blood, colloid, fat, or electrolyte solution, and in conditions that increase pulmonary blood flow. Low intravascular protein osmotic pressure from hypoproteinemia may predispose infants to pulmonary edema. Hypoproteinemia is common in infants who are born prematurely. Large intravascular infusions of protein-free fluid further decrease the concentration of protein in plasma and thereby facilitate edema formation. Lymphatic obstruction by air (pulmonary interstitial emphysema) or fibrosis (long-standing lung disease) also may contribute to the development of edema. Bacteremia, endotoxemia, and prolonged oxygen breathing injure the pulmonary microvascular endothelium and cause protein-rich fluid to accumulate in the lungs. The risk of neonatal pulmonary edema can be reduced by several therapeutic measures designed to lessen filtration pressure, increase plasma protein osmotic pressure, and prevent or reduce the severity of lung injury.

Furosemide vasodilates the canine gastrointestinal tract

The ability of furosemide to induce vasodilation in the canine gastrointestinal system was studied by quantitative flowmetry. Blood flow and conductance increased maximally by 60 per cent in the stomach and duodenum and by 80 per cent in the small and large intestine. Vasodilation was evident at 2.4 mg/kg furosemide and higher. The onset of vasodilation occurred at 24 to 30 seconds and was maximal at 36 seconds in the stomach, at 66 seconds in the duodenum, at 78 to 84 seconds in the small intestine, and at 90 seconds in the large intestine. Hepatic arterial, splenic, and renal blood flows were unchanged. Simultaneous arteriovenous sampling from the small intestine indicated that the increased blood flow was not associated with increased O2 consumption. However, CO2 addition to the venous effluent decreased by 70 per cent. These data indicate that furosemide has a vasodilatory action on the gastrointestinal tract due either to a delayed effect on the vascular smooth muscle cell or on anaerobic bowel wall metabolism. The CO2 data are compatible with, but do not prove, stimulation of secretion of HCO3- by the intestinal mucosa.

Effect of furosemide in canine low-pressure pulmonary edema

We studied the effect of furosemide on pulmonary oxygen exchange, lung liquid, and central hemodynamics in dogs with pulmonary capillary leak induced by intravenous oleic acid (OA). 2 h after OA, triple indicator-dilution lung liquid volume and pulmonary shunt (Qs/Qt) doubled despite normal pulmonary capillary wedge pressure in 16 dogs compared with dogs not given OA in which no variable change during the same time. Six edematous dogs were then treated with furosemide (1 mg/kg), and 2 h later they showed significant reductions in Qs/Qt and lung liquid. In contrast, six other edematous dogs not given furosemide increased Qs/Qt and lung liquid during the same time. The changes in edema after furosemide could not be attributed to altered wedge or colloid osmotic pressures, and similar changes in Qs/Qt and lung liquid with furosemide were observed in four nephrectomized dogs. We conclude that pulmonary vasoactive effects of furosemide account for reduced shunt and edema in canine pulmonary capillary leak. These effects of furosemide differ from those in cardiogenic pulmonary edema, and suggest a different rationale for diuretic therapy in low-pressure pulmonary edema. Analysis of count rates from 51Cr-labeled erythrocytes and 125I-labeled albumin in lungs excised from 12 dogs indicated that the composition of excess lung liquid did not change with furosemide, and was 50% plasma, 25% blood, and 25% crystalloid.