The effect of sildenafil on retinopathy of prematurity in very preterm infants

First-year outcomes of very low birth weight preterm singleton infants with hypoxemic respiratory failure treated with milrinone and inhaled nitric oxide (iNO) compared to iNO alone: A nationwide retrospective study

BACKGROUND

Inhaled nitric oxide (iNO) has a beneficial effect on hypoxemic respiratory failure. The increased use of concurrent iNO and milrinone was observed. We aimed to report the trends of iNO use in the past 15 years in Taiwan and compare the first-year outcomes of combining iNO and milrinone to the iNO alone in very low birth weight preterm (VLBWP) infants under mechanical ventilation.

METHODS

This nationwide cohort study enrolled preterm singleton infants with birth weight <1500g treated with iNO from 2004 to 2019. Infants were divided into two groups, with a combination of intravenous milrinone (Group 2, n = 166) and without milrinone (Group 1, n = 591). After propensity score matching (PSM), each group's sample size is 124. The primary outcomes were all-cause mortality and the respiratory condition, including ventilator use and duration. The secondary outcomes were preterm morbidities within one year after birth.

RESULTS

After PSM, more infants in Group 2 needed inotropes. The mortality rate was significantly higher in Group 2 than in Group 1 from one month after birth till 1 year of age (55.1% vs. 13.5%) with the adjusted hazard ratio of 4.25 (95%CI = 2.42-7.47, p <0.001). For infants who died before 36 weeks of postmenstrual age (PMA), Group 2 had longer hospital stays compared to Group 1. For infants who survived after 36 weeks PMA, the incidence of moderate and severe bronchopulmonary dysplasia (BPD) was significantly higher in Group 2 than in Group 1. For infants who survived until one year of age, the incidence of pneumonia was significantly higher in Group 2 (28.30%) compared to Group 1 (12.62%) (p = 0.0153).

CONCLUSION

Combined treatment of iNO and milrinone is increasingly applied in VLBWP infants in Taiwan. This retrospective study did not support the benefits of combining iNO and milrinone on one-year survival and BPD prevention. A future prospective study is warranted.

Association of Cardiovascular Disease with Retinopathy of Prematurity

PURPOSE

To determine the associations of presence and types of cardiovascular diseases (CVDs) with development of retinopathy of prematurity (ROP) in premature infants undergoing ROP examinations.

STUDY DESIGN

We performed secondary analyses of data from the multi-center Postnatal Growth and ROP Validation Study (GROP-2). CVD was categorized based on pulmonary blood flow (PBF), systemic blood flow (SBF), pulmonary hypertension (PPHN), or dysrhythmia. Adjusted odds ratios (aOR) and 95% confidence intervals (95% CI) were calculated from multivariable logistic regression models that included any ROP or severe ROP as outcome variable and any CVD or type of CVD as independent variable, with adjustment of covariates including birth weight (BW), gestational age (GA), and days on supplemental oxygen in the first month of postnatal life.

RESULT

Among 3980 infants, 528 (13.3%) had CVD (304 had increased PBF, 101 had decreased PBF, and 49 had PPHN), 1643 (40.4%) developed ROP, and 503 (12.6%) developed severe ROP. In multivariable analyses, presence of CVD was not significantly associated with increased risk of any ROP (aOR = 1.15, 95% CI: 0.90-1.46, p = .26) or severe ROP (aOR = 0.98, 95% CI: 0.72-1.34, p = .92). However, there were trends associating CVD resulting in increased PBF with a higher risk of ROP (aOR = 1.32, 95% CI: 0.97-1.80, p = .08) and PPHN with a higher risk of severe ROP (aOR = 2.04, 95% CI: 0.96-4.35, p = .07). When adjusting only for BW and GA, these associations were significant (aOR = 1.47, 95% CI: 1.09-1.99, and aOR = 2.35, 95% CI: 1.19-4.65, respectively).

CONCLUSION

CVD with increased PBF likely increases the risk of ROP. PPHN likely increases the risk of severe ROP.

Update on the use of sildenafil in neonatal pulmonary hypertension: a narrative review of the history, current administration, and future directions

Pulmonary hypertension (PH) is a life-threatening syndrome in neonates and has multiple and varied etiologies. However, few clinical studies have systematically evaluated the treatment regimens for this population. Phosphodiesterase (PDE) inhibitors, such as milrinone, tadalafil, dipyridamole, and sildenafil, are the most important regulators of vascular relaxation in the normal pulmonary vascular transition after birth, and these agents are widely used in the treatment of PH. Sildenafil, a representative PDE-5 inhibitor, has an important role as a single mode of therapy. However, the lack of evidence from pharmacokinetic and clinical trials has limited the emergence of standardized treatment regimens for sildenafil. There are also differing opinions among researchers regarding the best route of sildenafil administration. Due to the interindividual variability in the neonatal population, it is worth selecting the most suitable route of sildenafil administration according to the specific conditions of the neonatal population. These may be evaluated using the oxygenation index (OI), pulmonary artery pressure, mean blood pressure, and the serological index. This article reviews the clinical data on the use of sildenafil, focusing on the current and promising alternative routes of administration, which may affect subsequent clinical research in term and preterm neonates.

Ophthalmic findings in neonates receiving sildenafil

AIM

To determine the risk of ocular complications of sildenafil therapy in neonates.

METHODS

Retrospective case review of neonates with persistent pulmonary hypertension of the newborn who received sildenafil therapy between 2010 and 2015 in a single, tertiary surgical neonatal intensive care unit in Australia. Ophthalmic examination findings in the neonatal intensive care unit and follow-up were examined.

RESULTS

Twenty-seven neonates with persistent pulmonary hypertension of the newborn received sildenafil. The median gestational age (GA) was 38 weeks (range 24-41 weeks), and median birthweight was 2690 g (range 454-4270 g). Ophthalmic review was undertaken in 23 neonates, and 16 neonates were term or near-term infants (GA 31-40 weeks). All of them had a normal initial ophthalmic examination; one child was later diagnosed with hypermetropia and another with infantile esotropia. Amongst the seven premature infants (GA 24-30 weeks), three had retinopathy of prematurity (ROP) diagnosed at the first ophthalmic review and the other four had normal initial examinations. Two patients later developed ROP, one of whom was also diagnosed with congenital motor nystagmus. All five patients diagnosed with ROP were extremely preterm (<28 weeks) with low birthweight (454-635 g).

CONCLUSIONS

There were no short-term complications attributable to sildenafil therapy identified in term or near-term neonates (GA ≥31 weeks). This cohort of neonates does not typically undergo ophthalmic review as part of the ROP screening protocol in our institution. Routine ophthalmic review of neonates on sildenafil therapy, who are not at risk of ROP, is therefore unlikely to be warranted. Further research is required to clarify the relationship between sildenafil and ROP.

Sildenafil Exposure in the Neonatal Intensive Care Unit

OBJECTIVE

Pulmonary hypertension causes substantial morbidity and mortality in infants. Although Food and Drug Administration approved to treat pulmonary arterial hypertension in adults, sildenafil is not approved for infants. We sought to describe sildenafil exposure and associated diagnoses and outcomes in infants.

STUDY DESIGN

Retrospective cohort of neonates discharged from more than 300 neonatal intensive care units from 2001 to 2016.

RESULTS

Sildenafil was administered to 1,336/1,161,808 infants (0.11%; 1.1 per 1,000 infants); 0/35,977 received sildenafil in 2001 versus 151/90,544 (0.17%; 1.7 per 1,000 infants) in 2016. Among infants <32 weeks' gestational age (GA) with enough data to determine respiratory outcome, 666/704 (95%) had bronchopulmonary dysplasia (BPD). Among infants ≥32 weeks GA, 248/455 (55%) had BPD and 76/552 (14%) were diagnosed with meconium aspiration. Overall, 209/921 (23%) died prior to discharge.

CONCLUSION

The use of sildenafil has increased since 2001. Exposed infants were commonly diagnosed with BPD. Further studies evaluating dosing, safety, and efficacy of sildenafil are needed.

Sildenafil and Retinopathy of Prematurity in Preterm Infants with Bronchopulmonary Dysplasia

OBJECTIVE

To assess whether sildenafil is associated with worsening retinopathy of prematurity (ROP) in very low birth weight (VLBW) infants (≤1500 g) with bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This retrospective case-control study included VLBW infants admitted to the neonatal intensive care unit between January 1, 2006, and December 31, 2012. Each infant treated with sildenafil was assigned 3 unexposed controls matched for gestational age, birth weight, and BPD diagnosis. Severe ROP was defined as stage ≥3 ROP. Worsening ROP was defined as increased stage of ROP within 8 weeks + 4 days after initiation of sildenafil or matched postmenstrual age.

RESULTS

Twenty-three exposed infants and 69 matched controls met the inclusion criteria for the study (mean birth weight, 715 ± 210 g; mean gestational age, 25 ± 1 weeks). The mean postmenstrual age at sildenafil treatment was 42 ± 8 weeks. Exposed infants had more days of respiratory support (mean, 208 ± 101 days vs 102 ± 33 days; P < .001). Exposed infants had a higher prevalence of severe ROP (26% [6 of 23] vs 7% [5 of 69]; OR, 6.4; 95% CI, 1.2-32.9; P = .026). Five exposed infants and 2 unexposed infants had severe ROP before starting sildenafil and were excluded from the analysis for worsening ROP. The rate of worsening ROP did not differ significantly between exposed infants and unexposed infants ((41% [7 of 17] vs 24% [12 of 51]; OR, 8.4; 95% CI, 0.9-78.6; P = .061).

CONCLUSION

Although sildenafil treatment was not statistically significantly associated with worsening of ROP, the raw difference in ROP rate is concerning. Larger studies are warranted to confirm this finding.

Retinopathy of prematurity: a review of risk factors and their clinical significance

Retinopathy of prematurity (ROP) is a retinal vasoproliferative disease that affects premature infants. Despite improvements in neonatal care and management guidelines, ROP remains a leading cause of childhood blindness worldwide. Current screening guidelines are primarily based on two risk factors: birth weight and gestational age; however, many investigators have suggested other risk factors, including maternal factors, prenatal and perinatal factors, demographics, medical interventions, comorbidities of prematurity, nutrition, and genetic factors. We review the existing literature addressing various possible ROP risk factors. Although there have been contradictory reports, and the risk may vary between different populations, understanding ROP risk factors is essential to develop predictive models, to gain insights into pathophysiology of retinal vascular diseases and diseases of prematurity, and to determine future directions in management of and research in ROP.

Controversies in the identification and management of acute pulmonary hypertension in preterm neonates

It is increasingly recognized that the abnormal physiologic consequences of pulmonary hypertension (PH) may contribute to poor cardiopulmonary health in premature babies. Conflicting literature has led to clinical uncertainty, pathological misinterpretation, and variability in treatment approaches among practitioners. There are several disorders with overlapping and interrelated presentations, and other disorders with a similar clinical phenotype but diverse pathophysiological contributors. In this review, we provide a diagnostic approach for acute hypoxemic respiratory failure in the preterm neonate, outline the pathophysiological conditions that may present as acute PH, and discuss the implications of high pulmonary vascular resistance (PVR) on the cardiovascular system. Although PVR and respiratory management are highly interrelated, there may be a population of preterm neonates in whom inhaled nitric oxide may improve illness severity and may relate to outcomes. A management approach based on physiology that considers common clinical conundrums is provided. A more comprehensive understanding of the physiology may help in informed decision-making in clinical situations where conclusive scientific evidence is lacking. Regardless, high-quality research is required, and appropriate definition of the target population is paramount. A thoughtful approach to cardiovascular therapy may also provide an avenue to improve neurodevelopmental outcomes while awaiting more clear answers.

Pulmonary Hypertension Therapy and a Systematic Review of Efficacy and Safety of PDE-5 Inhibitors

Pulmonary hypertension (PH) is a syndrome that is of growing concern to pediatricians worldwide. Recent data led to concerns about the safety of phosphodiesterase type 5 (PDE5) inhibitors in children and a US Food and Drug Administration safety advisory. Our objective is to provide insight into therapies for PH in children and to systematically review the comparative effectiveness and safety of PDE5 inhibitors in the management of pediatric patients with PH. We searched the following databases through February 2015: Medline, Embase, SCOPUS, and the Cochrane Central Register of Controlled Trials. We included studies that examined PDE5 inhibitor use in children with PH. Allowed comparators were either no medication or other classes of medication for management of PH. Study inclusion was via a 2-stage process with 2 reviewers and a predesigned form. Of 1270 papers identified by the literature search, 21 were included: 8 randomized controlled trials and 13 observational studies (9 retrospective, 4 prospective). There is strong evidence that PDE5 inhibitor use improves echocardiography measurements, cardiac catheterization parameters, and oxygenation compared with baseline or placebo in pediatric patients with PH. Evidence suggests that low- and moderate-dose sildenafil are safe regimens for children. There are a relatively small number of randomized controlled trials that address use of PDE5 inhibitors in pediatric patients with PH. PDE5 inhibitors are effective agents for cardiovascular and oxygenation end points in pediatric PH and important components of a multimodal pharmacotherapeutic approach to this growing challenge. Additional studies are needed to define optimal PH therapy in childhood.

Pharmacoepidemiological safety studies in children: a systematic review

Purpose

In order to identify challenges in pediatric pharmacoepidemiological safety studies, we assessed the characteristics of such (published) studies.

Methods

Relevant articles from inception to 2013 were retrieved from Embase and Medline. We sequentially screened titles, abstracts and full texts with independent validation. We systematically collected data regarding general information, study methods and results.

Results

Out of 4825 unique articles, 268 full texts (5.6%) were retained; 147 (54.9%) pertained to drugs rather than vaccines. Considering the 268 studies, 202 (75.4%) concerned children and adolescents (2 to 11 years) and 14 (5.3%) included preterm newborns. Most studies originated from North America (154 [57.5%]) or Europe (92 [34.3%]). Only 47 studies (17.5%) were privately funded. The majority (174 [64.9%]) were cohort studies. Out of 268 studies, 196 (73.1%) collected data retrospectively; paper medical charts were the most common data source for the exposures (85 [31.7%]) and outcomes (122 [45.5%]). Only 3 (2.0%) drug‐only studies investigated rarely used drugs. Considering all 268 studies, only 27 (10.1%) reported sample size or power calculation. Most (75 [51.0%]) drug‐only studies corrected confounding by multivariate modeling unlike stratification in 66 (55.9%) vaccine‐only studies. Considering 75 child‐only studies without any statistically significant result, 41 (54.7%) did not discuss lack of power.

Conclusions

Although the field of pediatric pharmacoepidemiology is steadily developing evaluation seldom includes neonates, is mainly focused on few drug classes and safety outcomes and concerns mainly drug use in developed countries. Small study size is a specific challenge in pediatrics. Reporting should be improved. © 2016 The Authors. Pharmacoepidemiology and Drug Safety Published by John Wiley & Sons Ltd.

Sildenafil and retinopathy of prematurity risk in very low birth weight infants

OBJECTIVE

To examine the effect of sildenafil therapy on development of severe retinopathy of prematurity (ROP) requiring surgical intervention in premature infants.

STUDY DESIGN

We identified premature infants who were discharged from Pediatrix Medical Group neonatal intensive care units from 2003 to 2012 and who received an ophthalmologic exam. We matched each infant exposed to sildenafil before first eye exam to three nonexposed infants using propensity scoring to control for differences in baseline infant characteristics. We evaluated the association between sildenafil exposure and development of severe ROP using conditional logistic regression.

RESULT

Of the 57 815 infants meeting inclusion criteria, 88 were exposed to sildenafil. We matched 81/88 (92%) sildenafil-exposed with 243 nonexposed infants. There was no difference in the proportion of infants who developed severe ROP in the sildenafil-exposed vs nonexposed groups (17/81 (21%) vs 38/243 (16%), P=0.27). On adjusted analysis, there was no difference in severe ROP in the sildenafil-exposed vs nonexposed infants (odds ratio=1.46, 95% confidence interval=0.76 to 2.82, P=0.26).

CONCLUSION

We did not observe an association between risk of severe ROP and sildenafil exposure before first eye exam in this cohort of premature infants.

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

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

CONCLUSION

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

Sildenafil for the Treatment of Pulmonary Arterial Hypertension in Infants with Bronchopulmonary Dysplasia

Sildenafil, a phosphodiesterase-5 inhibitor, is a controversial treatment option for pulmonary arterial hypertension (PAH), a significant complication of bronchopulmonary dysplasia (BPD). The objective of this study was to evaluate the use of sildenafil in infants with PAH secondary to BPD. This was a retrospective review of medical records of all premature infants with PAH associated with BPD treated with sildenafil between January 2009 and May 2013 in a level 3 neonatal intensive care unit. The primary outcomes were clinical response (20 % decreases in respiratory support score or oxygen requirements) and echocardiographic response (20 % decrease in tricuspid regurgitation gradient or change of at least 1° of septal flattening). Twenty-three infants were included in the study. Significant echocardiographic and clinical responses were, respectively, observed in 71 and 35 % of cases. Most clinical responses were observed in the first 48 h of treatment, and the median time to an echocardiographic response was of 19 days. The median dose of sildenafil used was 4.4 mg/kg/day, with a median time to reach the maximum dose of 9 days. Transient hypotension was the primary reported side effect, and it was observed in 44 % of our study population. Sildenafil treatment in patients with PAH secondary to BPD was associated with an echocardiographic improvement in the majority of patients, whereas clinical improvement was observed in a minority of patients. Many infants presented with transient hypotension during the course of the treatment. Further prospective studies are required to better assess safety and efficacy of this treatment in this population.

Sildenafil for pulmonary hypertension complicating bronchopulmonary dysplasia

Sildenafil, a phospohodiesterase-5 inhibitor, is widely used to treat pulmonary hypertension in infants with bronchopulmonary dysplasia despite a lack of evidence to support either safety or efficacy and US FDA advice against its use.

Sildenafil attenuates vaso-obliteration and neovascularization in a mouse model of retinopathy of prematurity

PURPOSE

We sought to determine the effect of sildenafil on retinal vascular changes in a mouse model of oxygen-induced retinopathy (OIR).

METHODS

Vascular defects in OIR mice were quantified by measuring vaso-obliteration at postnatal days 12 and 17 (P12 and P17) and neovascularization at P17 to compare sildenafil-treated to dextrose-treated OIR mice. Retinal HIF1α protein expression was quantified by Western blotting and normalized to that of β-actin. Right ventricular hypertrophy was measured by Fulton's index as a surrogate for hyperoxia-induced pulmonary hypertension.

RESULTS

At P12, OIR mice treated with sildenafil demonstrated a 24% reduction in vaso-obliteration (P < 0.05), whereas at P17, treated animals showed a 50% reduction in neovascularization (P < 0.05) compared to dextrose-treated controls. Sildenafil-treated OIR mice had stabilization of retinal HIF1α at P12, immediately after hyperoxia. At P17, sildenafil-treated OIR mice had decreased HIF1α relative to untreated mice. OIR mice developed right ventricle hypertrophy that was significant compared to that in room air controls, which was abrogated by sildenafil.

CONCLUSIONS

Sildenafil treatment significantly decreased retinal vaso-obliteration and neovascularization in a mouse OIR model. These effects are likely due to sildenafil-induced HIF1α stabilization during hyperoxia exposure. Furthermore, we confirm disease overlap by showing that OIR mice also develop hyperoxia-induced right ventricular hypertrophy, which is prevented by sildenafil. This study is a first step toward delineating a potential therapeutic role for sildenafil in OIR and further suggests that there may be common pathophysiologic mechanisms underlying hyperoxia-induced retinal and pulmonary vascular disease.

The utility of sildenafil in pulmonary hypertension: a focus on bronchopulmonary dysplasia

The treatment of pulmonary hypertension (PH) secondary to bronchopulmonary dysplasia (BPD) in infants has evolved in recent years, improving both quality of life and survival for patients. One of the potential agents for this condition is sildenafil, a phosphodiesterase-V inhibitor with proven efficacy within the idiopathic PH population. However, only limited evidence exists for its use as either monotherapy or part of a combination approach towards the management of PH in BPD. This review summarises the evidence base for sildenafil alone and in combination with other recognised therapeutic agents for ameliorating paediatric PH in the presence of BPD. It also examines the suitability for current practice with the aim of clarifying regimens that produce improved patient outcomes. We conclude that sildenafil is both safe and effective in this utility. Doses should be started at 0.5 mg/kg every 8 h before titrating up towards 2 mg/kg every 6 h to effect reductions in pulmonary vascular resistance and arterial pressure. Evidence suggests that if continued until PH resolution, this improves survival from 61% to 81% at 12 months. Furthermore, there are also data suggesting that in treatment refractory PH cases, the addition of endothelin antagonists and prostacyclin analogues to sildenafil therapy can also be considered.

An update on pharmacologic approaches to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most prevalent long-term morbidity in surviving extremely preterm infants and is linked to increased risk of reactive airways disease, pulmonary hypertension, post-neonatal mortality, and adverse neurodevelopmental outcomes. BPD affects approximately 20% of premature newborns, and up to 60% of premature infants born before completing 26 weeks of gestation. It is characterized by the need for assisted ventilation and/or supplemental oxygen at 36 weeks postmenstrual age. Approaches to prevention and treatment of BPD have evolved with improved understanding of its pathogenesis. This review will focus on recent advancements and detail current research in pharmacotherapy for BPD. The evidence for both current and potential future experimental therapies will be reviewed in detail. As our understanding of the complex and multifactorial pathophysiology of BPD changes, research into these current and future approaches must continue to evolve.