Intratracheal sildenafil in the newborn with pulmonary hypertension

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.

Efficacy and safety of a novel nitric oxide generator for the treatment of neonatal pulmonary hypertension: Experimental and clinical studies

Persistent pulmonary hypertension of the newborn (PPHN) is a complex pathology resulting from a failure of the post-natal reduction in pulmonary vascular resistance leading to hypoxemia. The standard therapy is inhaled Nitric Oxide (NO) improving oxygenation but its availability is limited, especially in hospitals with restricted financial resources. We evaluated the efficacy and safety of a new device generating NO (TAS + PLUS), in three experimental piglet models of pulmonary hypertension (PH), and we later tested its application in a pilot study of newborn patients suffering from PPHN. Piglets with experimentally induced PH showed a decrease in pulmonary arterial pressure (PAP) after breathing NO. Both acute and chronic exposure of piglets and rats did not cause any adverse effect in blood gas levels and biological parameters. A pilot study including 32 patients suffering from PPHN showed an increase in oxygen saturation (SatO₂) and partial pressure of oxygen in arterial blood (PaO₂) leading to a decrease of Oxygenation Index (OI) after compassionate treatment with NO from TAS + PLUS device. The device showed effectiveness and safety both in experimental PH and in the clinical setting. Therefore, it represents an excellent alternative for PPHN management in conditions where commercial NO is unavailable.

Sildenafil in pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening disease of varied etiologies. Although PAH has no curative treatment, a greater understanding of pathophysiology, technological advances resulting in early diagnosis, and the availability of several newer drugs have improved the outlook for patients with PAH. Sildenafil is one of the therapeutic agents used extensively in the treatment of PAH in children, as an off-label drug. In 2012, the United States Food and Drug Administration (USFDA) issued a warning regarding the of use high-dose sildenafil in children with PAH. This has led to a peculiar situation where there is a paucity of approved therapies for the management of PAH in children and the use of the most extensively used drug being discouraged by the regulator. This article provides a review of the use of sildenafil in the treatment of PAH in children.

Changes in mean arterial blood pressure during sildenafil use in neonates with meconium aspiration syndrome or sepsis

The aim of this study was to evaluate changes in mean blood pressure (MBP) in late preterm and term newborns with meconium aspiration syndrome (MAS) or sepsis who, in addition to inhaled nitric oxide (iNO), received enteral sildenafil for treatment of persistent pulmonary hypertension of the newborn. Data on sildenafil dosing, MBP, and vasopressor/inotrope use were collected for 72 hours after initiation of sildenafil. Groups were compared between "low dose" (<3 mg·kg·d) versus "high dose" (≥ 3 mg·kg·d) and "early" (<7 postnatal days) versus "late" (≥ 7 postnatal days) administration of sildenafil. Seventeen patients were identified. Ten and 7 patients received "low-dose" and "high-dose" sildenafil, respectively, and 8 and 9 patients were started on sildenafil "early" and "late," respectively. At the doses used, sildenafil treatment of infants with MAS and sepsis was not associated with changes in MBP. In addition, vasopressor/inotropic support was weaned in all groups. During the first 72 hours of enteral sildenafil administration in neonates with pulmonary hypertension of the newborn secondary to MAS or sepsis, no significant decrease in MBP or increase in vasopressor/inotrope requirement occurred.

Is sildenafil an effective therapy in the management of persistent pulmonary hypertension?

Persistent pulmonary hypertension of the newborn (PPHN) is a life-threatening neonatal pathology resulting from poor hemodynamic and respiratory transition to extra uterine life. Inhaled nitric oxide (iNO) is a current, commonly used treatment of PPHN. However, iNO is not available therapy in many developing countries and around 50% of infants with PPHN do not respond to iNO therapy. Sildenafil is a phosphodiesterase inhibitor type 5 (PDE5) that has been shown to selectively reduce pulmonary vascular resistance in both animal models and adult humans. Recent studies have found that in PPHN, administration of Sildenafil was associated with a significant increase in the oxygenation and a reduction in mortality with no clinically important side effects.

A comparison of magnesium sulphate and sildenafil in the treatment of the newborns with persistent pulmonary hypertension: a randomized controlled trial

The aim of this prospective, randomized and controlled study was to compare the clinical efficacy of intravenous magnesium sulfate (MgSO₄) and oral sildenafil therapies with persistent pulmonary hypertension of the newborn. A total of 34 infants in the MgSO₄ group and 31 infants in the sildenafil group completed the study. The time to reach the adequate clinical response [defined as oxygen index (OI) level of <15, a pulmonary artery pressure of < 20 mmHg) was significantly shorter in the sildenafil group (p = 0.002). Duration of mechanical ventilation was longer and the number of the patients requiring inotropic support was higher in the MgSO₄ group (p = 0.001 and p = 0.002, respectively). Although among two groups the difference in OI > 5 as speculated in our hypothesis could only be found at 36 h of the treatment, sildenafil was more effective than MgSO₄ in the treatment of persistent pulmonary hypertension of the newborns with regard to time to adequate clinical response, duration of mechanical ventilation and support requirement with inotropic agents.

Sildenafil prevents the increase of extravascular lung water and pulmonary hypertension after meconium aspiration in newborn piglets

Meconium aspiration syndrome causes respiratory failure after birth and in vivo monitoring of pulmonary edema is difficult. The objective of the present study was to assess hemodynamic changes and edema measured by transcardiopulmonary thermodilution in low weight newborn piglets. Additionally, the effect of early administration of sildenafil (2 mg/kg vo, 30 min after meconium aspiration) on this critical parameter was determined in the meconium aspiration syndrome model. Thirty-eight mechanically ventilated anesthetized male piglets (Sus scrofa domestica) aged 12 to 72 h (1660 ± 192 g) received diluted fresh human meconium in the airway in order to evoke pulmonary hypertension (PHT). Extravascular lung water was measured in vivo with a PiCCO monitor and ex vivo by the gravimetric method, resulting in an overestimate of 3.5 ± 2.3 mL compared to the first measurement. A significant PHT of 15 Torr above basal pressure was observed, similar to that of severely affected humans, leading to an increase in ventilatory support. The vascular permeability index increased 57%, suggesting altered alveolocapillary membrane permeability. Histology revealed tissue vessel congestion and nonspecific chemical pneumonitis. A group of animals received sildenafil, which prevented the development of PHT and lung edema, as evaluated by in vivo monitoring. In summary, the transcardiopulmonary thermodilution method is a reliable tool for monitoring critical newborn changes, offering the opportunity to experimentally explore putative therapeutics in vivo. Sildenafil could be employed to prevent PHT and edema if used in the first stages of development of the disease.

Current and future therapeutic options for persistent pulmonary hypertension in the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a potentially life-threatening condition that is characterized by supra-systemic pulmonary vascular resistance causing right-to-left shunting through the ductus arteriosus and/or foramen ovale, leading to a vicious cycle of hypoxemia, acidosis and further pulmonary vasoconstriction. Advances in neonatology including surfactant instillation, high-frequency ventilation, extracorporeal membrane oxygenation and, most importantly, inhaled nitric oxide (INO), have revolutionized the management of PPHN. However, given that INO does not improve oxygenation in a significant proportion (30-40%) of cases, there is an urgent need to consider other therapeutic options for PPHN. The issue is more important for developing nations with a higher PPHN-related health burden and limited resources. This article discusses the evidence about INO in term and preterm neonates in brief, and focuses mainly on the potential alternative drugs in the management of PPHN.

Pediatric Pulmonary Hypertension: A Pharmacotherapeutic Review

Pulmonary hypertension in children is a disorder associated with increased pulmonary vascular resistance and arterial pressure, decreased cardiac output, and right-sided cardiac dysfunction that is caused by numerous etiologies. Although treatment will vary with underlying cause, pharmacological treatment has historically included inhaled nitric oxide and prostacyclin analogues. Over the past several years new agents have been added to the treatment armamentarium, including phosphodiesterase V inhibitors (eg sildenafil) and endothelin antagonists (eg bosentan). Further, more agents are currently under investigation for pulmonary hypertension in children including immunosuppressives and other endothelin antagonist entities. Limitations to treatment include the availability of appropriate, robust pediatric pharmacological data and constraints with dosage forms.

Pharmacotherapy for meconium aspiration

In this article we have attempted to review the current pharmacological treatment options for infants with meconium aspiration syndrome with or without persistent pulmonary hypertension. These treatments include ventilatory support, surfactant treatment and inhaled nitric oxide (INO), in addition to older and newer pharmacological treatments. These include sedatives, muscle relaxants, alkali infusion, antibiotics and the newer vasodilators. Many aspects of treatment, including ventilatory care, surfactant treatment and the use of INO, are reviewed in great detail in this issue. On the other hand, many newer pharmacological modalities of treatment described here have not been evaluated with randomized control trials. We have given an overview of these emerging therapies.

Sildenafil acutely reverses the hypoxic pulmonary vasoconstriction response of the newborn pig

Sildenafil is a pulmonary vasodilator shown to be effective in neonates, but conflicting data exist regarding its effect on arterial oxygenation. To address this issue, we tested the sildenafil effect on the piglet's hypoxic pulmonary vasoconstriction (HPV) response. A segmental lung atelectasis was created by obstructing the corresponding bronchus. Total pulmonary and specific flows to the atelectatic and contra-lateral lobes were measured by magnetic resonance (MR) before and 30-min post sildenafil (0.2 and 1 mg/kg i.v.) or saline administration. Flow was reduced (p < 0.01) in the atelectatic and increased in the contra-lateral lobe indicating an effective HPV response. Sildenafil at both doses significantly (p < 0.01) increased flow solely to the atelectatic lobe. At a dose of 1 mg/kg, sildenafil induced a decrease in Pao2 from 285 +/- 37 to 161 +/- 22 mm Hg (p < 0.01). We conclude that the HPV response in the newborn is capable of almost completely reducing blood flow to nonventilated lung units and is reversed following sildenafil i.v. administration in a dose-dependent manner. In the presence of lung parenchymal disease, the use of i.v. sildenafil as a pulmonary vasodilator may worsen arterial oxygenation by reversing the HPV response in nonventilated lung units.