Clinical approach to inhaled nitric oxide therapy in newborn with hypoxemia

Oral sildenafil in infants with persistent pulmonary hypertension of the newborn: a pilot randomized blinded study

BACKGROUND

Persistent pulmonary hypertension (PPHN) occurs in as many as 6.8 of 1000 live births. Mortality is approximately 10% to 20% with high-frequency ventilation, surfactant, inhaled nitric oxide, and extracorporeal membrane oxygenation but is much higher when these therapies are not available. Sildenafil is a phosphodiesterase inhibitor type 5 that selectively reduces pulmonary vascular resistance.

OBJECTIVE

Our goal was to evaluate the feasibility of using oral sildenafil and its effect on oxygenation in PPHN.

DESIGN

This study was a proof-of-concept, randomized, masked study in infants >35.5 weeks' gestation and <3 days old with severe PPHN and oxygenation index (OI) >25 admitted to the NICU (Hospital Niño Jesús, Barranquilla, Colombia). The sildenafil solution was prepared from a 50-mg tablet. The first dose (1 mg/kg) or placebo was given by orogastric tube <30 minutes after randomization and every 6 hours. Preductal saturation and blood pressure were monitored continuously. OI was calculated every 6 hours. The main outcome variable was the effect of oral sildenafil on oxygenation. Sildenafil or placebo was discontinued when OI was <20 or if there was no significant change in OI after 36 hours.

RESULTS

Six infants with an OI of >25 received placebo, and 7 received oral sildenafil at a median age of 25 hours. All infants were severely ill, on fraction of inspired oxygen 1.0, and with similar ventilatory parameters. Intragastric sildenafil and placebo were well tolerated. In the treatment group, OI improved in all infants within 6 to 30 hours, all showed a steady improvement in pulse oxygen saturation over time, and none had noticeable effect on blood pressure; 6 of 7 survived. In the placebo group, 1 of 6 infants survived.

CONCLUSIONS

Oral sildenafil was administered easily and tolerated as well as placebo and improved OI in infants with severe PPHN, which suggests that oral sildenafil may be effective in the treatment of PPHN and underscores the need for a large, controlled trial.

Recombinant human superoxide dismutase enhances the effect of inhaled nitric oxide in persistent pulmonary hypertension

We investigated the pulmonary vascular effects of superoxide dismutase (SOD) alone and in combination with inhaled nitric oxide (iNO) in newborn lambs with persistent pulmonary hypertension (PPHN) following prenatal ligation of the ductus arteriosus. In in vitro experiments, pretreatment with SOD significantly enhanced vascular relaxation in response to the NO donor S-nitrosyl-acetylpenicillamine (SNAP) in fifth-generation pulmonary arteries isolated from lambs with PPHN. In vivo treatment of fully instrumented newborn lambs with a single intratracheal dose of recombinant human CuZn SOD (rhSOD; 5 mg/kg) produced selective dilation of the pulmonary circulation. Further studies, of the combination of rhSOD and iNO, showed enhancement of the pulmonary vascular effects of iNO after brief periods of inhalation of 5 ppm and 80 ppm NO. We conclude that rhSOD reduces pulmonary vascular resistance and facilitates the action of iNO in a lamb model of PPHN. This suggests that rhSOD may prove to be an effective adjunctive treatment for newborns with PPHN.