Sildenafil 1

Running head: Sildenafil in the NICU

The Use of Sildenafil for patients with Persistent Pulmonary Hypertension in the NICU

Jessica Sterr

Victoria College RSPT 2147

Sildenafil 2

Abstract

Background In the Neonatal Intensive Care Unit, there are term and near term infants who suffer

from Persistent Pulmonary Hypertension (PPHN) that require expensive treatment options to

control or reverse this condition. Such a treatment being used within the hospital is inhaled Nitric

Oxide (iNO). This is an excellent treatment option, but it is expensive and not always effective as

a treatment by itself to treat PPHN. In these three studies, Sildenafil is introduced to infants with

PPHN. Sildenafil is an effective treatment option by itself to treat PPHN as well as an effective

treatment option combined with iNO.

Methods In study 1, 13 infants were chosen to be in a randomized study. The patients were

infants over the age of 35.5 weeks gestation to under the age of 3 years that had severe PPHN

and an oxygen index (OI) over 25. In study 2, 30 ventilated infants and children were

randomized to receive 0.4 mg/kg of Sildenafil or placebo before discontinuing 10 ppm of iNO.

Pulmonary artery pressures (PA) and arterial blood gases were measured in both groups before

and after the study to rule out rebound PPHN. In study 3, 15 ventilated infants were chosen to be

in a randomized study. All 15 infants were recovering from recent closure of ventricular or

atrioventricular septal defects. Eight infants received 20 ppm of iNO with the addition of

intravenous Sildenafil (0.35 mg/kg over 20 min). Seven infants received intravenous Sildenafil

(0.35 mg/kg over 20 mins) with the addition of 20 ppm of iNO.

Results Study 1 found that Sildenafil improved OI within 6 to 30 hours, and steadily improved

pulse oxygen saturation over time with no fluctuations in the patients’ blood pressure. In the

treatment group, 6 of 7 patients survived. In the placebo group, 1 of 6 patients survived. Study 2

Sildenafil 3

found that rebound of PPHN was found in 10 of 14 patients in the placebo group with an

increase PA pressure of 25% (14-67). Rebound PPHN occurred in 0 of 15 Sildenafil patients

with an increase of 1% (-9-5). 4 patients from the placebo group could not be weaned from iNO

where as all Sildenafil patients could be weaned off of iNO. Lastly, the duration of mechanical

ventilation for the placebo group was 98 hours compared to the duration of the Sildenafil group

which was 28.2 hours. Study 3 showed that the group receiving the iNO with the addition of

Sildenafil had a decrease of Pulmonary vascular resistance index from 3.45 to 2.45 units. In the

group receiving Sildenafil with the addition of iNO, there was a decrease of pulmonary vascular

resistance index from 2.84 to 2.15 units. In both groups, Sildenafil reduced systemic blood

pressure and systemic vascular resistance, and worsened arterial oxygenation and the alveolar-

arterial gradient.

Discussion/Conclusion The results of study 1 suggests that Sildenafil as an only treatment option

can improve Oxygen Index and steadily improve pulse arterial oxygen saturation without causing

any fluctuations in systemic blood pressure. Study 2 suggests that Sildenafil, if used before

discontinuing iNO, can completely prevent rebound PPHN, decrease duration of mechanical

ventilation and shorten the wean time on iNO. Unexpectedly, Study 3 results showed that

Sildenafil can lead to hypotension, lowered systemic vascular resistance, and worsened the

patient’s oxygenation. For the exception of study 3 results, Sildenafil is an effective drug in

reducing pulmonary vascular resistance, therefore increasing arterial oxygenation as a treatment

by itself or in combination with iNO.

Sildenafil 4

Introduction

Sildenafil is an effective treatment option for patients with Persistent Pulmonary

Hypertension. This drug is a vasodilator that decreases pulmonary vascular resistance, therefore

increasing systemic arterial oxygenation. This is an excellent treatment option that has been

shown to decrease mechanical ventilation time, increase oxygenation, and decrease weaning time

of inhaled nitric oxide. Sildenafil is an effective treatment option in itself or combined with

inhaled nitric oxide. This paper will discuss more in detail how the intervention of Sildenafil

used in patients with PPHN improves patients’ health and decreases hospital stay.

Sildenafil 5

Methods and Results

Study 1 (Baquero, H., Soliz, A., Neira, F., Venegas, M. E., Sola, A., 2006).

This proof-of-concept pilot study was randomized, prospective, and masked and

performed between 2003 and 2004 in the NICU of Hospital Nin˜ o Jesu´ s in Barranquilla,

Colombia. This is a regional NICU serving a population of _10 000 deliveries per year, which is

well equipped with modern technology but in which surfactant used is limited for preterm infants

with respiratory distress syndrome, and there is no iNO, HFV, or ECMO available. Eligible

infants for the study were term or near-term gestation (_35.5 weeks’ gestation) with severe

hypoxemia and pulmonary hypertension confirmed by echocardiogram. Only very sick and

critically ill term or nearterm newborn infants with PPHN were considered candidates for the

study. The infants had to be on mechanical ventilation with an oxygenation index (OI) _40, show

clinical signs of severe refractory hypoxemia, and have a known high risk for mortality at this

center. The echocardiogram (Sonosite 180 plus) performed before entry had to show evidence of

right-to-left shunt and estimated pulmonary artery pressures _40 mm Hg. Exclusion criteria

included congenital abnormalities. Congenital heart disease of any type was excluded, including

pulmonic stenosis, atrial septal defect, anomalous pulmonary venous drainage, and ventricular

septal defect. Arterial blood gases were monitored from an umbilical arterial catheter, and OI

was calculated in every arterial blood gas using the PaO2 from the umbilical arterial catheter and

the classic formula to calculate OI: OI _ (fraction of inspired oxygen _ mean airway

pressure)/PaO2. For this protocol, we decided a priori to also obtain a blood gas 2 hours after

each dose of drug or placebo and analyze and report the OI at this time to ensure consistency and

accurate comparisons. Pulse oxygen saturation (SpO2) and mean arterial blood pressure (BP)

Sildenafil 6

were monitored continuously. For consistency and to avoid including a large number of data

points at many different times, we chose to report the data on SpO2 and BP at these

preestablished set points of time, 2 hours after each dose, after the predesigned protocol.

Clinical management protocols used in the NICU by attending physicians caring for infants with

PPHN were not altered if the infant was a study subject. The clinical approach for all of the

infants included: no “hyperventilation” but avoidance of hypercarbia (ie, PacO2: 35–50 mm Hg),

manual ventilation when needed (ie, severe episode of hypoxemia or of low pH with high

PaCO2), avoidance of significant acidosis, (ie, maintain pH_7.30), no alkalosis (ie, not aiming to

keep pH _7.45), inotropes (dopamine), and volume infusion to try to preserve intravascular

volume and maintain mean arterial BP _50th percentile, and no nitroprusside or tolazoline were

used. Improvement in OI was defined as a decrease in OI of _6 from the previous calculated

value. Although this is an arbitrary measure, we agreed a priori on the significance of a reduction

_10%. For infants with an initial OI value of 40, a decrease of 6 would be a 15% effect.

The preparations and schedule for administration of drug and placebo were as follows. A 50-mg

tablet of sildenafil was diluted in Orabase as much as will suffice to 25 mL for a final

concentration of 2 mg/mL. (If this compound is refrigerated, it would expire 1 month after

preparation.) For placebo, an equal volume of diluents (0.5–1 mL/kg) was used. Both drug and

placebo were given by orogastric tube, and the protocol for dosing schedule was (a) first dose of

1 mg/kg (0.5 mL/kg) _30 minutes after randomization, (b) dosing every 6 hours,

(c) dose could be doubled (2.0 mg/kg or 1.0 mL/kg) if the OI did not improve and the mean BP

remained stable after the previous dose, and (d) discontinuation of treatment decided according

to 1 of 2 criteria, whichever is earlier: an OI of _20 or maximum number of doses of 8 (ie, a

Sildenafil 7

maximum period of 42 hours after the first dose). Randomization was by simple allocation of

presealed numbers. Pharmacy prepared the oral preparations in the same containers for placebo

and medication and had the sealed code for identification. The administration of drug or placebo

was randomly assigned, masked, and bedside clinicians were unaware of group assignment. At

the onset of the study it was elected to enter only very sick and critically ill newborn infants with

PPHN (OI _ 40), with a known high mortality rate. The initial sample size calculated to assess

feasibility, and OI response was 25 infants in each group. Stopping rules for breaking of the

codes and analyzing the data included potential significant adverse effects like hypotension,

gastric intolerance or bleeding, renal failure, or death in 6 infants. The main outcome variable

was the feasibility of administration, gastric tolerance, and the effect of oral sildenafil on OI

values. Other variables analyzed were SpO2, PaO2, BP, and survival. Statistical methods used

were analysis of variance for comparison of repeated measurements of OI, BP, and SpO2 and

Newman-Keuls for posthoc analyses. Fisher’s test was used to compare baseline characteristics

and survival between study groups. Significance was set at P _ .05. The research protocol was

reviewed by the institutional review board and approved by the ethics committee at Hospital

Nin˜ o Jesu´ s, with the stopping rules mentioned above. Eligible infants were entered only after

parental informed consent was obtained.

There were 42 infants with significant refractory hypoxemia, and 22 met entry criteria

with severe PPHN (OI _ 40). Of the 22 infants, 2 died, for 3 the parents were not approached for

consent, and for 4 the parents refused. Thirteen infants with an OI of _40 had been enrolled in

Sildenafil 8

the study when the study was stopped at institutional review board request for detailed analysis

because of 6 deaths. The median age of the 13 infants at the time of entry was close to 25 hours

(range: 3–72 hours). Six of the infants had received placebo, and 7 had received oral

sildenafil. Table 1 summarizes the characteristics of the infants enrolled, the ventilator

parameters, and the initial blood gases and OI at the time of entry. The gender distribution,

gestational age, birth weight, Apgar scores, route of delivery, and condition associated with

severe refractory hypoxemia, as well as the ventilatory parameters and blood gases were

comparable in both groups (Table 1). The mean OI was 56 in the treatment group and 46 in the

placebo group with low PaO2 at entry; 34.2 (_12.5) mm Hg and 42.7 (_11.3) mm Hg,

respectively. All of the infants were critically ill, receiving fraction of inspired oxygen 1.0 and

dopamine for inotropic support. All had been treated at least once with manual ventilation,

sodium bicarbonate, and volume infusion. In the treatment group, oxygenation improved in all

of the infants sometime between 6 and 30 hours after initiation of treatment, and all of the infants

showed a steady and significant improvement in SpO2 over time, different from the placebo

group. Figures 1 and 2 show the changes in oxygenation after placebo and sildenafil. The

differences were significant (P _ .05) at different times, as shown in the figures. The first dose

induced an improvement in OI compared with baseline and with the placebo group, and the

significant differences persisted until the last measurement (Figs 1 and 2). There were

also differences in PaO2 between the groups, and this became significant over time after 4 doses

or 36 hours after entry. In addition, Table 2 shows the individual OI values for each infant in

relation to the dose of sildenafil or placebo. Figure 3 shows that oral sildenafil produced

Sildenafil 9

no noticeable effect on BP during the study period with the doses used. All of the infants in both

groups received dopamine (dose range: 6–20 _g/kg per minute). There was no difference in

pressure support or volume infusions between groups. Furthermore, we were unable to identify

any adverse effect that could be associated with the treatment. In the treatment group, 6 (85%) of

7 infants survived; the infant who died did so at 72 hours because of a pneumopericardium. In

the placebo group, 1 (17%) of 6 infants survived (P _ .02 versus sildenafil group). The infants

who died with refractory hypoxemia in the placebo group did so at various postnatal ages (36,

45, 74, 102, or 139 hours). The intragastric administration of the prepared solution was simple

and easily accomplished, and the doses were equally well tolerated in the placebo and treatment

groups. The number of doses received per infant varied based on the study protocol as described

in the “Methods” section. In the sildenafil group, 2 infants had an OI of _20 after the sixth dose

by 36 hours. In 1 of these infants, all of the doses were of 1.0 mg/kg per dose, and in the other

infant, the dose was 1.0 mg/kg for the first dose and 2.0 mg/kg per dose for the next 5 doses

(Table 2). The other 5 infants in the sildenafil group received 7 doses before the OI was _20

(Table 2). Four of them received all 7 doses at 0.5 mL/kg per dose (1 mg/kg), and 1 received the

first 2 doses of 0.5 mL/kg and the other 5 of 1.0 mL/kg (2 mg/kg; Table 2). Therefore, the total

amount of sildenafil per kilogram varied between infants from 6 to 12 mg/kg (median: 7 mg/kg).

In the placebo group, the 6 infants received 0.5 mL/kg as the first dose. All but 1 of the infants

received all of the other doses at 1.0 mL/kg (Table 2). No evidence of rebound hypoxemia was

found in any of the infants in whom sildenafil was discontinued because of achievement of the

prespecified improvement in OI (ie, OI _ 20). We cannot comment on the degree of change in

Sildenafil 10

pulmonary artery pressure, because we did not perform repeated echocardiograms before and

after each dose.

Sildenafil 11

Study 2 (Namachivayam, P., Theilen, U., Butt,, W. W., Cooper, S. M., Penny, D. J.,

Shekerdemian, L. S., 2006).

The institutional ethics committee at the Royal Children’s Hospital, Melbourne, approved

this prospective, randomized, double-blinded, placebo-controlled study. This study was

performed between August 2003 and November 2005 in the pediatric ICU at the Royal

Children’s Hospital, Melbourne. Identification of potential participants and randomization were

performed before any attempt was made to reduce inhaled NO below the therapeutic dose.

Parents were given information about the study protocol, and written consent was obtained

before randomization. All infants and children who were mechanically ventilated on the pediatric

ICU and who had been receiving inhaled NO at a dose of 10 ppm or more for at least 12 h, and

who did not have any of the exclusion criteria, were eligible for this study. The exclusion criteria

were as follows: previous failure to wean from NO, the use of intravenous nitrovasodilators,

hepatic failure, an inspired oxygen fraction of greater than 0.6 at the time of recruitment, CHD

with obstructed pulmonary or systemic blood flow, or no measurable PA or right ventricular

pressure. Thirty children were recruited for the study between July 2003 and September 2005.

All participants were intubated, sedated, and ventilated in the ICU, and receiving inhaled NO at 5

ppm or greater at the time of consent. They all had measurable PA pressures, either by

echocardiographic estimation of right ventricular systolic pressure from the Doppler-derived

tricuspid regurgitant jet velocity (in 14 patients) or from a direct PA line (in 16 patients). Inhaled

NO concentration was measured using a bedside chemiluminescence analyzer. The study

protocol commenced when participants were receiving 5 ppm of NO; the weaning of NO until

Sildenafil 12

this level was entirely at the discretion of the attending ICU physician. The patient, parents, all

clinical staff, and investigators were blinded as to the study drug allocation. The study drug was

prepared by the Royal Children’s Hospital pharmacy department, and block randomization was

performed so that each group of 10 children contained equal numbers of sildenafil or study drug

recipients. Each participant was allocated a “study number,” which corresponded to an envelope

containing a range of study drug capsules. The study drug was formulated into 1-mg and 5-mg

capsules, and each participant’s dose was calculated at 0.4 mg/kg, and then rounded up or down

to the nearest 1 mg. Thus, the final dose range was 0.3 to 0.5 mg/kg. All patients had continuous

monitoring of systemic arterial blood pressure and central venous pressure via indwelling

catheters, and monitoring of heart rate and oxygen saturation. Patients with an indwelling PA

pressure–monitoring catheter also had continuous monitoring of PA pressure. Hemodynamic

parameters were recorded at 30-min intervals. In our ICU, it is standard practice to wean inhaled

NO by 1 ppm every 30 min, and increase the inspired oxygen fraction by 0.2 (20%) during the

final 2 ppm of the NO weaning process. The study drug was given by the bedside nurse, via the

nasogastric tube, when the patients were receiving 2 ppm inhaled NO, 1 h before the expected

discontinuation of NO. An arterial blood gas and PA pressures were recorded at three time

points. These were as follows: just before the study drug being given, 1 h after stopping the NO,

and 4 h after stopping NO. In patients without a PA catheter, systolic PA pressure was measured

using standard equations: from the peak instantaneous echocardiographic Doppler-derived

pressure difference between the right ventricle and right atrium, and the simultaneous central

venous pressure. None of these patients had obstruction to the right ventricular outflow tract, or

intracardiac shunts, which would influence the accuracy of PA pressure measurement. The

Sildenafil 13

primary outcome measure was the development of rebound PHT. Rebound PHT was defined as

an increase in PA pressure of greater than 20% after discontinuing NO or the urgent need to

recommence NO therapy within 4 h of discontinuing NO. Other outcome measures included

changes in oxygenation, systemic blood pressure, and duration of mechanical ventilation and

ICU stay. Descriptive data are expressed as mean (SD), if normally distributed, or as median

(interquartile range). Within-group and between-group comparisons were made using t tests,

Wilcoxon rank sum test, or oneway analysis of variance, as appropriate. Using the primary

outcome measure of a change in PA pressure after discontinuation of NO between the sildenafil

and placebo groups, the following factors were considered in calculating sample size: first, an

increase in PA pressure of 20% was used to define rebound; and second, it was assumed that

90% of untreated (placebo) patients would demonstrate increases in PA pressure of between 10

and 40%. Finally, we considered that a reduction by one-third in the incidence of rebound

would be the minimum reduction that is likely to be of clinical importance, and was used as the

basis for sample size calculation. With a study power of 83%, assuming a standard two-sided _

level of 0.05, then a total sample size of 40 participants (20 participants per study arm) would be

necessary. However, it was agreed that interim analysis would be permitted after the first 30

patients were recruited.

Interim analysis was performed after the first 30 patients had been randomized, and the

study was then stopped based on the significant findings discussed below. The enrollment flow

chart is given in Figure 1. One infant who had been randomized to receive placebo died after

randomization, but before the weaning process had started (Figure 1). Patient details and

indications for NO therapy are given in Tables 1 and 2. Baseline demographic and

Sildenafil 14

cardiopulmonary data were similar for the two groups. There were no adverse events associated

with the study drug administration.

Sildenafil 15

Study 3 (Stocker, C., et al. 2003).

This prospective, clinical randomised trial was approved by the local Ethics in Human

Research Committee. All infants at our hospital undergoing surgical repair of ventricular septal

defects or atrioventricular septal defects with a large left-to-right shunt, diagnosed on pre-

operative echocardiography, were eligible for entry to this study. We initially intended to enrol

30 infants, but the trial was terminated early after interim analysis of the first 15 completed

studies (see Results). The parents of 18 infants were approached for participation in the study;

written consent was obtained from the parents of 17 infants (median age 132 days, range 48–262

days; mean weight 4.8 kg) and studies were carried out in 15 (see Fig. 1 for trial profile). Nine

infants had Down’s syndrome. Studies were commenced between 3.8 and 6.7 h after separation

from cardiopulmonary bypass. The infants were sedated and musclerelaxed (vecuronium,

midazolam and morphine) and mechanically ventilated during the study. All infants were

receiving an inspired oxygen fraction of 0.5 at the start of the study. They were receiving a

single inotropic agent, either intravenous dopamine or dobutamine (between 1 and 5 μg/kg per

min)during the study and doses were not adjusted during the study period. No patient received

alpha-blockers, other phosphodiesterase inhibitors or nitrovasodilators at any time prior to or

during the study. Any residual intracardiac shunt or significant atrioventricular valve

regurgitation was excluded by intra-operative transoesophageal or epicardial echocardiography

and by postoperative transthoracic echocardiography. A 3F catheter (Model 94–011–3F,

American Laboratories, CA, USA), which incorporated a thermistor, was placed intra-

operatively into the pulmonary artery for monitoring pressure and the measurement of CO by

thermodilution [17]. Additional catheters were placed directly in the right and left atria and in a

Sildenafil 16

peripheral artery, for injectate, pressure monitoring and for blood gas analysis (Ciba Corning

Diagnostic Corp, Massachusetts, USA). Systemic and pulmonary arterial, as well as central

venous and left atrial pressures, were directly measured with electromechanical pressure

transducers (Abbott, Sligo, Ireland), which were calibrated before each study. Cardiac output

was measured in triplicate at each data point by thermodilution. (Baxter-Edwards cardiac output

monitor, Irvine, CA, USA). One millimetre of 0.9% NaCl at 0–40C was injected into the right

atrial catheter and cardiac output was measured using the change in temperature recorded by the

pulmonary arterial thermistor. Where PPA, PLA, PArt and PCV are mean pulmonary arterial,

left atrial, systemic arterial and central venous pressures, respectively (mmHg); CI is cardiac

index (l/min per m2); PAW is mean airway pressure (cmH2O); FiO2 is the fraction of oxygen in

inspired gas; PaO2 is the arterial partial pressure of oxygen (mmHg) and PaCO2 is arterial

partial pressure of carbon dioxide. Sixteen infants were randomly assigned to one of two study

protocols, and 15 infants entered the clinical study (Fig. 1). Randomisation was done by ‘block

allocation’ and, prior to the patient returning from the operating theatre, the envelope containing

the patient’s group assignment was opened by one of the investigators. The total study duration

was 40 min for all participants. Eight infants were randomised to receive nitric oxide first (20

ppm), with fused over 20 min). The other eight infants were randomised to receive

intravenous sildenafil first (dose as above), with the addition of nitric oxide at 20 min. A

complete set of haemodynamics and an arterial blood gas were recorded, and cardiac output was

measured in triplicate, at 0 min (baseline) and at 20 and 40 min (following each intervention).

Intravenous sildenafil was provided by Pfizer Pharmaceuticals, Sandwich, UK and the dose (per

kg) was based on a pharmacokinetic study in healthy adults [20]. The results were analysed using

Sildenafil 17

Sigmastat for Windows, version 2.03 (SPSS, Chicago, IL). The results are expressed as means +-

standard errors of the mean (SEM). Student’s t-test was used to compare between group data at

baseline and for changes between baseline and each time point, and paired t-tests to compare

withingroup data at different time points. Probability values of less than 0.05 were considered

statistically significant.

One infant developed early post-operative arrhythmias with significant haemodynamic

compromise prior to baseline data collection and was excluded from the study. Data were

therefore collected for 15 infants: 7 received iNO first and 8 received intravenous sildenafil first.

Demographic variables, baseline systemic and pulmonary haemodynamics, and gas exchange

data were similar in the two patient groups (Tables 1 and 2). In patients receiving nitric oxide

first, by 20 min, the mean PA pressure had fallen by 1.4+- 0.4 mmHg (by 7.8+-2.1%; p=0.008),

while mean systemic arterial, left atrial and central venous pressures and cardiac index were

all unchanged. The addition of sildenafil to these patients did not further influence PA pressure.

However, systemic blood pressure fell by 8.9+- 2 mmHg (13.4+- 2.7%; p=0.004), while left

atrial pressure, central venous pressure and cardiac index were unchanged (Table 2, Fig. 2).

In patients receiving sildenafil first, by 20 min PA pressure tended to fall (by 10+- 4.1%;

p=0.055). Mean systemic arterial pressure fell by 12+- 1.2 mmHg (17+- 1.8%; p<0.001); left

atrial and central venous pressures, and cardiac index were unchanged. The addition of nitric

oxide resulted in a further reduction in PA pressure to levels which were significantly below

baseline (p=0.001) (Table 2, Fig. 2). In infants receiving nitric oxide first, within 20 min of

treatment, PVRI fell to 0.54+- 0.16 units below baseline (17+- 5.0%; p=0.01), while SVRI was

unchanged. Addition of sildenafil reduced PVRI by a further 0.41+- 0.16 units (16+-5.2%;

Sildenafil 18

p=0.04), but also reduced SVRI significantly (by 22+-5.4%; p=0.03; (Table 2, Fig 2)). In infants

receiving sildenafil first, PVRI fell by 0.44+-0.16 units (12.8+-5.7%; p=0.03) between 0 and

20 min. However, SVRI also fell by 4.02+-0.58 units (by 23+-2.1%; p<0.001), therefore the

pulmonary to systemic vascular resistance ratio was unchanged. The addition of nitric oxide in

these infants further reduced PVRI, by 0.25+-0.07 units (7.8+-2.0%; p=0.01), without

influencing SVRI. There was no difference in relative reduction of PVRI between the two

treatment groups during the first treatment period with nitric oxide or sildenafil alone (p=0.7).

Arterial partial pressure of CO2 and pH did not change significantly during any of the

therapeutic interventions in either group (Table 2, Fig 3). In patients receiving nitric oxide first,

there was a trend towards an improvement in PaO2; and oxygenation index and alveolar-arterial

gradient both fell significantly during nitric oxide inhalation alone. However, the addition of

intravenous sildenafil in these children reduced PaO2 by 38.2+- 15.9 mmHg (p=0.045) and, as a

result, increased the oxygenation index by 1.4+-0.5 (p=0.04) and increased the alveolar-arterial

gradient by a mean of 47+-14 mmHg (p=0.03). In those infants receiving sildenafil first,

sildenafil reduced the PaO2 by 29.9+-6.9 mmHg (p=0.003), increased the oxygenation index by

2.0+-0.8 (p=0.003) and increased the alveolar-arterial gradient by 30+-6 mmHg (p=0.007).

Administration of nitric oxide did not produce any further changes in these variables.

Sildenafil 19

Discussion

The main goal in study 1 was to see if Sildenafil, as an only treatment option, could

reverse refractory hypoxemia in patients with severe PPHN when HFV, ECMO, and iNO were

not available. The study’s results showed that Sildenafil was effective in increasing oxygen index

and arterial oxygenation without causing fluctuations in systemic blood pressure, although

dopamine was administered to all patients. All patients receiving Sildenafil survived without

rebound refractory hypoxemia.

In study 2 the goal was to see if Sildenafil could decrease the likelihood or completely

prevent a rebound of PPHN when iNO is discontinued. The results show that giving Sildenafil

before discontinuing iNO decreased pulmonary artery pressures, decreased weaning time from

the iNO treatment, and decreased duration on the ventilator. The majority of the placebo group

had a rebound of PPHN whereas in the Sildenafil group, none of the patients experienced

rebound PPHN.

The purpose of study 3 was to see if a treatment option of iNO with the addition of

Sildenafil was more effective than the treatment option of Sildenafil with the addition of iNO. It

was concluded that iNO with the addition of Sildenail resulted in a greater reduction in

pulmonary vascular resistance index than did the treatment option of Sildenafil with the addition

of iNO. It was also concluded in this particular study that Sildenafil was linked to reduced

systemic blood pressure and arterial oxygenation whereas iNO did not produce any changes to

the systemic blood pressure or decreases in oxygenation.

Sildenafil 20

Conclusion

The use of Sildenafil was an effective treatment option for patients with elevated

pulmonary artery pressures in all 3 studies, although Sildenafil was shown to reduce systemic

blood pressure as well as the patients’ oxygenation in the last study. In studies 1 and 2, there was

a great improvement in oxygenation values. I think Sildenafil is a revolutionary drug that should

be more vastly used in the NICU and PICU. It is as effective as iNO, more cost effective, and if

combined with iNO, heightens the vasodilatory effects iNO. Despite the drop in systemic blood

pressure and oxygenation in Study 3, Sildenafil should be researched further and, if research

permits, should be used more frequently with patients.

Sildenafil 21

References

Baquero, H., Soliz, A., Neira, F., Venegas, M. E., Sola, A. (2006).

Oral Sildenafil in Infants With Persistent Pulmonary Hypertension of the Newborn: A

Pilot Randomized Blinded Study. Pediatrics, 117(4), 1077-1083. Retrieved April 22,

2010 from

Namachivayam, P., Theilen, U., Butt, W. W., Cooper, S. M., Penny, D. J., Shekerdemian, L. S.

(2006). Sildenafil Prevents Rebound Pulmonary Hypertension after Withdrawal of Nitric

Oxide in Children. American Journal of Respiratory and Critical Care Medicine, 74,

1042-1047. Retrieved April 22, 2010 from

Stocker, C., Penny, D. J., Brizard, C. P., Cochrane, A. D., Soto, R., Shekerdemian, L. S.

(2003). Intravenous sildenafil and inhaled nitric oxide: a randomised trial in infants after

cardiac surgery Intensive Care Med, 29, 1696-2003. Retrieved April 22, 2010 from