Inhaled nitric oxide reduces the utilization of extracorporeal membrane oxygenation in persistent pulmonary hypertension of the newborn

Epidemiologic evaluation of inhaled nitric oxide use among neonates with gestational age less than 35 weeks

BACKGROUND AND OBJECTIVES

The use of inhaled nitric oxide (iNO) in +late preterm and term infants with pulmonary hypertension is Food and Drug Administration (FDA) approved and has improved outcomes and survival. iNO use is not FDA approved for preterm infants and previous studies show no mortality benefit. The objectives were 1) to determine the usage of iNO among preterm neonates <35 weeks before and after the 2010 National Institutes of Health consensus statement and 2) to evaluate characteristics and outcomes among preterm neonates who received iNO.

METHODS

This is a population-based cross-sectional study. Billing and procedure codes were used to determine iNO usage. Data were queried from the National Inpatient Sample from 2004 to 2016. Neonates were included if gestational age was <35 weeks. The epochs were spilt into 2004-2010 (Epoch 1) and 2011-2016 (Epoch 2). Prevalence of iNO use, mortality, bronchopulmonary dysplasia (BPD), intraventricular hemorrhage, length of stay, mechanical ventilation, and cost of hospitalization.

RESULTS

There were 4865 preterm neonates <35 weeks who received iNO. There was a significant increase in iNO use during Epoch 2 (p < 0.001). There was significantly higher use in Epoch 2 among neonates small for gestational age (SGA) 2.3% versus 7.2%, congenital heart disease (CHD) 11.1% versus 18.6%, and BPD 35.2% versus 46.8%. Mortality was significantly lower in Epoch 2 19.8% versus 22.7%.

CONCLUSION

Usage of iNO was higher after the release of the consensus statement. The increased use of iNO among preterm neonates may be targeted at specific high-risk populations such as SGA and CHD neonates. There was lower mortality in Epoch 2; however, the cost was doubled.

A Review of Pulmonary Arterial Hypertension Treatment in Extracorporeal Membrane Oxygenation: A Case Series of Adult Patients

BACKGROUND

Little data is published describing the use of medications prescribed for pulmonary arterial hypertension (PAH) in patients receiving extracorporeal membrane oxygenation (ECMO). Even though many patients with PAH may require ECMO as a bridge to transplant or recovery, little is reported regarding the use of PAH medications in this setting.

METHODS

This retrospective case series summarizes the clinical experience of 8 patients with PAH receiving ECMO and reviews medication management in the setting of ECMO.

RESULTS

Eight PAH patients, 5 of whom were female, ranging in age from 21 to 61 years old, were initiated on ECMO. Veno-arterial (VA) ECMO was used in 4 patients, veno-venous (VV) ECMO and hybrid ECMO configurations in 2 patients respectively. Common indications for ECMO included cardiogenic shock, bridge to transplant, and cardiac arrest. All patients were on intravenous (IV) prostacyclin therapy at baseline. Refractory hypotension was noted in 7 patients of whom 5 patients required downtitration or discontinuation of baseline PAH therapies. Three patients had continuous inhaled epoprostenol added during their time on ECMO. In patients who were decannulated from ECMO, PAH therapies were typically resumed or titrated back to baseline dosages. One patient required no adjustment in PAH therapy while on ECMO. Two patients were not able to be decannulated from ECMO.

CONCLUSION

The treatment of critically ill PAH patients is challenging given a variety of factors that could affect PAH drug concentrations. In particular, PAH patients on prostacyclin analogues placed on VA ECMO appear to have pronounced systemic vasodilation requiring vasopressors which is alleviated by temporarily reducing the intravenous prostacyclin dose. Patients should be closely monitored for potential need for rapid titrations in prostacyclin therapy to maintain hemodynamic stability.

Nitric oxide for respiratory failure in infants born at or near term

BACKGROUND

Nitric oxide (NO) is a major endogenous regulator of vascular tone. Inhaled nitric oxide (iNO) gas has been investigated as treatment for persistent pulmonary hypertension of the newborn.

OBJECTIVES

To determine whether treatment of hypoxaemic term and near-term newborn infants with iNO improves oxygenation and reduces rate of death and use of extracorporeal membrane oxygenation (ECMO), or affects long-term neurodevelopmental outcomes.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 1), MEDLINE via PubMed (1966 to January 2016), Embase (1980 to January 2016) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to January 2016). We searched clinical trials databases, conference proceedings and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. We contacted the principal investigators of studies published as abstracts to ascertain the necessary information.

SELECTION CRITERIA

Randomised studies of iNO in term and near-term infants with hypoxic respiratory failure, with clinically relevant outcomes, including death, use of ECMO and oxygenation.

DATA COLLECTION AND ANALYSIS

We analysed trial reports to assess methodological quality using the criteria of the Cochrane Neonatal Review Group. We tabulated mortality, oxygenation, short-term clinical outcomes (particularly use of ECMO) and long-term developmental outcomes.

STATISTICS

For categorical outcomes, we calculated typical estimates for risk ratios and risk differences. For continuous variables, we calculated typical estimates for weighted mean differences. We used 95% confidence intervals and assumed a fixed-effect model for meta-analysis.

MAIN RESULTS

We found 17 eligible randomised controlled studies that included term and near-term infants with hypoxia.Ten trials compared iNO versus control (placebo or standard care without iNO) in infants with moderate or severe severity of illness scores (Ninos 1996; Roberts 1996; Wessel 1996; Davidson 1997; Ninos 1997; Mercier 1998; Christou 2000; Clark 2000; INNOVO 2007; Liu 2008). Mercier 1998 compared iNO versus control but allowed back-up treatment with iNO for infants who continued to satisfy the same criteria for severity of illness after two hours. This trial enrolled both preterm and term infants but reported most results separately for the two groups. Ninos 1997 studied only infants with congenital diaphragmatic hernia.One trial compared iNO versus high-frequency ventilation (Kinsella 1997).Six trials enrolled infants with moderate severity of illness scores (oxygenation index (OI) or alveolar-arterial oxygen difference (A-aDO2)) and randomised them to immediate iNO treatment or iNO treatment only after deterioration to more severe criteria (Barefield 1996; Day 1996; Sadiq 1998; Cornfield 1999; Konduri 2004; Gonzalez 2010).Inhaled nitric oxide appears to have improved outcomes in hypoxaemic term and near-term infants by reducing the incidence of the combined endpoint of death or use of ECMO (high-quality evidence). This reduction was due to a reduction in use of ECMO (with number needed to treat for an additional beneficial outcome (NNTB) of 5.3); mortality was not affected. Oxygenation was improved in approximately 50% of infants receiving iNO. The OI was decreased by a (weighted) mean of 15.1 within 30 to 60 minutes after the start of therapy, and partial pressure of arterial oxygen (PaO2) was increased by a mean of 53 mmHg. Whether infants had clear echocardiographic evidence of persistent pulmonary hypertension of the newborn (PPHN) did not appear to affect response to iNO. Outcomes of infants with diaphragmatic hernia were not improved; outcomes were slightly, but not significantly, worse with iNO (moderate-quality evidence).Infants who received iNO at less severe criteria did not have better clinical outcomes than those who were enrolled but received treatment only if their condition deteriorated. Fewer of the babies who received iNO early satisfied late treatment criteria, showing that earlier iNO reduced progression of the disease but did not further decrease mortality nor the need for ECMO (moderate-quality evidence). Incidence of disability, incidence of deafness and infant development scores were all similar between tested survivors who received iNO and those who did not.

AUTHORS' CONCLUSIONS

Inhaled nitric oxide is effective at an initial concentration of 20 ppm for term and near-term infants with hypoxic respiratory failure who do not have a diaphragmatic hernia.

Adapted ECMO criteria for newborns with persistent pulmonary hypertension after inhaled nitric oxide and/or high-frequency oscillatory ventilation

PURPOSE

Early prediction of extracorporeal membrane oxygenation (ECMO) requirement in term newborns with persistent pulmonary hypertension (PPHN), partially responding to inhaled nitric oxide (iNO) and/or high-frequency oscillatory ventilation (HFOV), based on oxygenation parameters.

METHODS

This was a retrospective cohort study in 53 partial responders from among 133 term newborns with PPHN born between 2002 and 2007. Alveolar-to-arterial oxygen gradient (AaDO₂) values were determined in these 53 partial responders during the initial 72 h of iNO and/or HFOV treatment and compared between newborns who ultimately did (n = 11) and did not (n = 42) need ECMO.

RESULTS

Over 72 h, partial responders not requiring ECMO showed a more profound AaDO₂ decrease than those who needed ECMO (median decline 242.5 mmHg, IQR 144 to 353 mmHg, vs. 35 mmHg, IQR -15 to 123 mmHg; p = 0.0007). A decline of <123 mmHg over 72 h predicted the need for ECMO (sensitivity 82 %, specificity 79 %). At 72 h, AaDO₂ was significantly lower in partial responders without the need for ECMO than in those who did need ECMO (median 369 mmHg, IQR 258 to 478 mmHg, vs. 570 mmHg IQR 455 to 590 mmHg; p = 0.0008). An AaDO₂ >561 mmHg at 72 h predicted the need for ECMO (sensitivity 64 %, specificity 95 %, positive predictive value 78 %).

CONCLUSIONS

In term newborns with PPHN partially responding to iNO and/or HFOV, oxygenation-based prediction of the need for ECMO appears to be possible after 72 h. ECMO centers are encouraged to develop their own prediction model in order to prevent both lung damage and unnecessary ECMO runs.

Cost-effectiveness of early compared to late inhaled nitric oxide therapy in near-term infants

OBJECTIVE

The purpose of this study was to determine the cost-effectiveness of early versus late inhaled nitric oxide (INO) therapy in neonates with hypoxic respiratory failure initially managed on conventional mechanical ventilation.

RESEARCH DESIGN

A decision analytic model was created to compare the use of early INO compared to delayed INO for neonates receiving mechanical ventilation due to hypoxic respiratory failure. The perspective of the model was that of a hospital. Patients who did not respond to either early or delayed INO were assumed to have been treated with extracorporeal membrane oxygenation (ECMO). The effectiveness measure was defined as a neonate discharged alive without requiring ECMO therapy. A Monte Carlo simulation of 10,000 cases was conducted using first and second order probabilistic analysis. Direct medical costs that differed between early versus delayed INO treatment were estimated until time to hospital discharge. The proportion of successfully treated patients and costs were determined from the probabilistic sensitivity analysis.

RESULTS

The mean (± SD) effectiveness rate for early INO was 0.75 (± 0.08) and 0.61 (± 0.09) for delayed INO. The mean hospital cost for early INO was $21,462 (± $2695) and $27,226 (± $3532) for delayed INO. In 87% of scenarios, early INO dominated delayed INO by being both more effective and less costly. The acceptability curve between products demonstrated that early INO had over a 90% probability of being the most cost-effective treatment across a wide range of willingness to pay values.

CONCLUSIONS

This analysis indicated that early INO therapy was cost-effective in neonates with hypoxic respiratory failure requiring mechanical ventilation compared to delayed INO by reducing the probability of developing severe hypoxic respiratory failure. There was a 90% or higher probability that early INO was more cost-effective than delayed INO across a wide range of willingness to pay values in this analysis.

Nonventilatory strategies for patients with life-threatening 2009 H1N1 influenza and severe respiratory failure

Severe respiratory failure (including acute lung injury and acute respiratory distress syndrome) caused by 2009 H1N1 influenza infection has been reported worldwide. Refractory hypoxemia is a common finding in these patients and can be challenging to manage. This review focuses on nonventilatory strategies in the advanced treatment of severe respiratory failure and refractory hypoxemia such as that seen in patients with severe acute respiratory distress syndrome attributable to 2009 H1N1 influenza. Specific modalities covered include conservative fluid management, prone positioning, inhaled nitric oxide, inhaled vasodilatory prostaglandins, and extracorporeal membrane oxygenation and life support. Pharmacologic strategies (including steroids) investigated for the treatment of severe respiratory failure are also reviewed.

Extracorporeal membrane oxygenation: current clinical practice, coding, and reimbursement

Extracorporeal membrane oxygenation (ECMO) is a technique for providing life support for patients experiencing both pulmonary and cardiac failure by maintaining oxygenation and perfusion until native organ function is restored. ECMO is used routinely at many specialized hospitals for infants and less commonly for children with respiratory or cardiac failure from a variety of causes. Its usage is more controversial in adults, but select medical centers have reported favorable findings in patients with ARDS and other causes of severe pulmonary failure. ECMO is also rarely used as a rescue therapy in a small subset of adult patients with cardiac failure. This article will review the current uses and techniques of ECMO in the critical care setting as well as the evidence supporting its usage. In addition, current practice management related to coding and reimbursement for this intensive therapy will be discussed.

Airway function in infants treated with inhaled nitric oxide for persistent pulmonary hypertension

RATIONALE

Inhaled nitric oxide (iNO), used for treatment of persistent pulmonary hypertension of newborn (PPHN), is an oxygen free radical with potential for lung injury. Deferring ECMO with iNO in these neonates could potentially have long-term detrimental effects on lung function. We studied respiratory morbidity (defined as occurrence of respiratory infections requiring treatment, episodes of wheezing, and/or need for ongoing medications following discharge) and airway function at 1 year postnatal age in term neonates treated with iNO but not ECMO for PPHN, and compared data from similar infants recruited to the UK ECMO Trial randomized to receive ECMO or conventional management (CM).

METHODS

Maximal expiratory flow at FRC (V(') (maxFRC)) was measured in infants treated with iNO for PPHN (oxygenation index >or=25) at birth.

RESULTS

V(') (maxFRC) was measured in 23 infants and expressed as z-scores, to adjust for sex and body size and compared to data from 71 (46 ECMO, 25 CM) infants studied at a similar age in the ECMO Trial. Respiratory morbidity was low in iNO group. V(') (maxFRC) z-score was lower than predicted in all groups (P < 0.001), with no significant difference between those treated with iNO [mean (SD) z-score: -1.65 (1.2)] and those treated with ECMO [-1.59 (1.2)] or CM [-2.1(1.0)]. Within iNO, ECMO and CM groups; 26%, 37% and 56%, respectively, had V(') (maxFRC) z-scores below normal.

CONCLUSIONS

Respiratory outcome at 1 year in iNO treated neonates with moderately severe PPHN is encouraging, with no apparent increase in respiratory morbidity when compared to the general population. Sub-clinical reductions in airway function are evident at 1 year, suggesting that continuing efforts to minimize lung injury in the neonatal period are warranted to maximize lung health in later life.

Inhaled nitric oxide therapy during the transport of neonates with persistent pulmonary hypertension or severe hypoxic respiratory failure

Our aim was to determine whether starting inhaled nitric oxide (iNO) on critically ill neonates with severe hypoxemic respiratory failure and/or persistent pulmonary hypertension (PPH), at a referring hospital at the start of transport, decreases the need for extracorporeal membrane oxygenation (ECMO), lessens the number of hospital days and improves survival in comparison with those patients who were started on iNO only at the receiving facility. The study was a retrospective review of 94 charts of neonates that had iNO initiated by the transport team at a referring hospital or only at the tertiary neonatal intensive care unit (NICU) of the receiving hospital. Data collected included demographics, mode of transport, total number of hospital days, days on inhaled nitric oxide and ECMO use. Of the 94 patients, 88 were included. Of these, 60 were started on iNO at the referring facility (Field-iNO) and 28 were started at the receiving NICU (CHLA-iNO). All patients survived transport to the receiving NICU. Death rates and ECMO use were similar in both groups. Overall, patients who died were younger and had lower birth weights and Apgar scores. For all surviving patients who did not require ECMO, the length of total hospital stay (median days 22 versus 38, P = 0.018), and the length of the hospital stay at the receiving hospital (median days 18 versus 29, P = 0.006), were significantly shorter for the Field-iNO patients than for the CHLA-iNO patients, respectively. Earlier initiation of iNO may decrease length of hospital stay in surviving neonates with PPH not requiring ECMO.

Persistent pulmonary hypertension of the newborn: pathogenesis, etiology, and management

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by severe hypoxemia shortly after birth, absence of cyanotic congenital heart disease, marked pulmonary hypertension, and vasoreactivity with extrapulmonary right-to-left shunting of blood across the ductus arteriosus and/or foramen ovale. In utero, a number of factors determine the normally high vascular resistance in the fetal pulmonary circulation, which results in a higher pulmonary compared with systemic vascular pressure. However, abnormal conditions may arise antenatally, during, or soon after birth resulting in the failure of the pulmonary vascular resistance to normally decrease as the circulation evolves from a fetal to a postnatal state. This results in cyanosis due to right-to-left shunting of blood across normally existing cardiovascular channels (foramen ovale or ductus arteriosus) secondary to high pulmonary versus systemic pressure. The diagnosis is made by characteristic lability in oxygenation of the infant, echocardiographic evidence of increased pulmonary pressure, with demonstrable shunts across the ductus arteriosus or foramen ovale, and the absence of cyanotic heart disease lesions. Management of the disease includes treatment of underlying causes, sedation and analgesia, maintenance of adequate systemic blood pressure, and ventilator and pharmacologic measures to increase pulmonary vasodilatation, decrease pulmonary vascular resistance, increase blood and tissue oxygenation, and normalize blood pH. Inhaled nitric oxide has been one of the latest measures to successfully treat PPHN and significantly reduce the need for extracorporeal membrane oxygenation.

Nitric oxide for respiratory failure in infants born at or near term

BACKGROUND

Nitric oxide is a major endogenous regulator of vascular tone. Inhaled nitric oxide gas has been investigated as a treatment for persistent pulmonary hypertension of the newborn.

OBJECTIVES

To determine whether treatment of hypoxaemic term and near-term newborn infants with inhaled nitric oxide (iNO) improves oxygenation and reduces the rates of death, the requirement for extracorporeal membrane oxygenation (ECMO), or affects long term neurodevelopmental outcomes.

SEARCH STRATEGY

Electronic and hand searching of pediatric/neonatal literature and personal data files. In addition we contacted the principal investigators of articles which have been published as abstracts to ascertain the necessary information.

SELECTION CRITERIA

Randomized and quasi-randomized studies of inhaled nitric oxide in term and near term infants with hypoxic respiratory failure. Clinically relevant outcomes, including death, requirement for ECMO, and oxygenation.

DATA COLLECTION AND ANALYSIS

Trial reports were analysed for methodologic quality using the criteria of the Cochrane Neonatal Review Group. Results of mortality, oxygenation, short term clinical outcomes (particularly need for ECMO), and long term developmental outcomes were tabulated.

STATISTICS

For categorical outcomes, typical estimates for relative risk and risk difference were calculated. For continuous variables, typical estimates for weighted mean difference were calculated. 95% confidence intervals were used. A fixed effect model was assumed for meta-analysis.

MAIN RESULTS

Fourteen eligible randomized controlled studies were found in term and near term infants with hypoxia. Seven of the trials compared iNO to control (placebo or standard care without iNO) in infants with moderate or severe severity of illness scores. Four of the trials compared iNO to control, but allowed back up treatment with iNO if the infants continued to satisfy the same criteria for severity of illness after a defined period of time. Two trials enrolled infants with moderate severity of illness score (OI or AaDO2) and randomized to immediate iNO treatment or iNO treatment only if they deteriorated to more severe criteria. One trial studied only infants with congenital diaphragmatic hernia (Ninos 1997), and one trial enrolled both preterm and term infants (Mercier 1998), but reported the majority of the results separately for the two groups. Inhaled nitric oxide appears to improve outcome in hypoxaemic term and near term infants by reducing the incidence of the combined endpoint of death or need for ECMO. The reduction seems to be entirely a reduction in need for ECMO; mortality is not reduced. Oxygenation improves in approximately 50% of infants receiving nitric oxide. The Oxygenation Index decreases by a (weighted) mean of 15.1 within 30 to 60 minutes after commencing therapy and PaO2 increases by a mean of 53 mmHg. Whether infants have clear echocardiographic evidence of persistent pulmonary hypertension of the newborn (PPHN) or not does not appear to affect outcome. The outcome of infants with diaphragmatic hernia was not improved; indeed there is a suggestion that outcome was slightly worsened. The incidence of disability, incidence of deafness and infant development scores are all similar between tested survivors who received nitric oxide or not.

AUTHORS' CONCLUSIONS

On the evidence presently available, it appears reasonable to use inhaled nitric oxide in an initial concentration of 20 ppm for term and near term infants with hypoxic respiratory failure who do not have a diaphragmatic hernia.

Mean airway pressure and response to inhaled nitric oxide in neonatal and pediatric patients

Inhaled nitric oxide (iNO) can improve oxygenation and ventilation-perfusion (V/Q) matching by reduction of shunt (Qs/Qt) in patients with hypoxemic lung disease. Because the improvement in V/Q matching must occur by redistribution of pulmonary blood flow, and because high airway pressure (Paw) increases physiologic dead space (Vd/Vt), we hypothesized that high Paw may limit the improvement in V/Q matching during iNO treatment. iNO 0-50 ppm was administered during mechanical ventilation. Mechanical ventilator settings were at the discretion of the attending physician. Qs/Qt and Vd/Vt were derived from a tripartite lung model with correction for shunt-induced dead space. Data from 62 patients during 153 trials were analyzed for effects of Paw and iNO on Qs/Qt and Vd/Vt. Baseline Qs/Qt was slightly increased at Paw 16-23 cmH2O (p < 0.05), while Vd/Vt increased progressively with higher Paw (p < 0.002). Therapy with iNO significantly reduced Qs/Qt (p < 0.001) at all levels of mean Paw, reaching a maximum reduction at 16-23 cmH2O (p < 0.05), such that Qs/Qt during iNO treatment was similar at all levels of Paw. During iNO treatment, a reduction in Vd/Vt occurred only at Paw of 8-15 cmH2O (p < 0.05), and the positive relationship between Vd/Vt and Paw was maintained. These differential effects on Qs/Qt and Vd/Vt suggest that both high and low Paw may limit improvement in gas exchange with iNO. Analysis of gas exchange using this corrected tripartite lung model may help optimize ventilatory strategies during iNO therapy.

Modulation of pulmonary cytochrome P4501A1 expression by hyperoxia and inhaled nitric oxide in the newborn rat: implications for lung injury

Inhaled nitric oxide (iNO), with supplemental oxygen, is used in the treatment of hypoxic respiratory failure of the newborn. In this study, we tested the hypothesis that exposure of newborn rats to iNO, hyperoxia, or iNO + hyperoxia would modulate the expression of pulmonary cytochrome P450 (CYP)1A1 in relation to acute lung injury. Newborn Fischer 344 rats were maintained in room air, or exposed to iNO, hyperoxia (>95%), or iNO (20 or 40 ppm) + hyperoxia for up to 168 h, and lung injury parameters and CYP1A1 expression were studied. Animals given iNO (40 ppm) + hyperoxia were more susceptible to lung injury than those exposed to hyperoxia or iNO alone. On the other hand, animals exposed to iNO (20 ppm) + hyperoxia did not elicit lung damage. Pulmonary CYP1A1 protein and mRNA expression were induced by hyperoxia, iNO (20 or 40 ppm), or iNO (20 ppm) + hyperoxia for up to 168 h, compared with air-breathing controls. In animals given iNO (40 ppm) + hyperoxia, pulmonary CYP1A1 was enhanced at 48 h, followed by down-regulation at later time points. Immunohistochemistry experiments showed localization of CYP1A1 in the pulmonary epithelial and endothelial cells. In conclusion, because previous studies have shown beneficial effects of CYP1A1 induction in hyperoxic lung injury, our current observations showing maintenance of pulmonary CYP1A1 induction by iNO (20 ppm) + hyperoxia through the 168-h period support the hypothesis that this phenomenon may contribute to the protective effects of iNO against hyperoxic injury.

Gene transfer with inducible nitric oxide synthase decreases production of urea by arginase in pulmonary arterial endothelial cells

Nitric oxide (NO) is a vasodilator produced from L-arginine (L-Arg) by NO synthase (NOS). Gene therapy for hypertensive disorders has been proposed using the inducible isoform of NOS (iNOS). L-Arg also can be metabolized to urea and L-ornithine (L-Orn) by arginase, and L-Orn can be metabolized to proline and/or polyamines, which are vital for cellular proliferation. To determine the effect of iNOS gene transfer on arginase, we transfected bovine pulmonary arterial endothelial cells (bPAEC) with an adenoviral vector containing the gene for iNOS (AdiNOS). As expected, NO production in AdiNOS bPAEC was substantially greater than in control bPAEC. Although urea production was significantly less in the AdiNOS bPAEC than in the control bPAEC, despite similar levels of arginase I protein, AdiNOS transfection of bPAEC had no effect on the uptake of L-Arg. Inhibiting NO production with Nomega-nitro-L-arginine methyl ester increased urea production, and inhibiting urea production with L-valine increased nitrite production, in AdiNOS bPAEC. The addition of L-Arg to the medium increased urea production by AdiNOS bPAEC in a concentration-dependent manner. Thus, in these iNOS-transfected bPAEC, the transfected iNOS and native arginase compete for a common intracellular pool of L-Arg. This competition for substrate resulted in impaired proliferation in the AdiNOS-transfected bPAEC. These findings suggest that the use of iNOS gene therapy for pulmonary hypertensive disorders may not only be beneficial through NO-mediated pulmonary vasodilation but also may decrease vascular remodeling by limiting L-Orn production by native arginase.

Hypoxic respiratory failure in term newborns: clinical indicators for inhaled nitric oxide and extracorporeal membrane oxygenation therapy

PURPOSE

The criteria for starting extracorporeal membrane oxygenation (ECMO) therapy in term newborn patients with hypoxemic respiratory failure consist of an oxygenation index (OI) of 25 or higher and alveolar-arterial oxygen (Aao(2)) gradient of more than 600 at sea level. In such conditions, inhaled nitric oxide (iNO) may improve oxygenation and reduce the need for ECMO therapy. We studied early changes in OI and Aao(2) gradients in response to iNO treatment that may indicate a need to continue iNO treatment or the necessity to start an ECMO therapy.

MATERIALS AND METHODS

In this prospective study, we used 34 outborn neonatal patients that were referred to our pediatric critical care unit in a children's hospital for ECMO therapy with diagnosis of hypoxemic respiratory failure. In all patients, iNO therapy, starting at 80 ppm, was instituted either during transport or on arrival to hospital. Response to iNO was assessed after 1 hour, at which time, iNO concentration was reduced to 40 ppm, provided there was more than 20% improvement in either or both oxygenation indices. Patients who did not respond positively to continuous iNO therapy and met ECMO criteria were given ECMO therapy.

RESULTS

Inhaled nitric oxide therapy alone was successful in 10 (29%) of 34 patients. Eighteen patients (53%) required ECMO therapy within the first 10 hours of iNO treatment (early ECMO therapy), whereas 6 other neonates (18%) became eligible for ECMO therapy after prolonged (2-4 days) iNO treatment (late ECMO therapy). No mortality occurred with any treatment. Within 4 hours after iNO therapy, patients who required early ECMO therapy had significantly higher OI and Aao(2) gradients than patients who were treated with iNO therapy alone (P<.01, analysis of variance followed by Tukey-Kramer multiple comparison test). Six of 34 patients (18%), categorized as late ECMO therapy, on the average, had initially higher levels of OI and mean airway pressure than neonates in iNO treatment and early ECMO therapy.

CONCLUSION

Persisting levels of OI of more than 20 or Aao(2) gradients of more than 600 after 4 hours of iNO therapy could be indicative of an immediate need for ECMO therapy.

Systemic hypertension associated with venovenous extracorporeal membrane oxygenation for pediatric respiratory failure

BACKGROUND/PURPOSE

Arterial hypertension (HTN) is common in neonates on venoarterial (VA) extracorporeal membrane oxygenation (ECMO), but HTN in pediatric venovenous (VV) ECMO has not been well described. The authors noted HTN in their VV ECMO experience and hypothesized that HTN was associated with fluid status, steroid use, and renal insufficiency.

METHODS

Records of 50 patients receiving VV ECMO for respiratory failure were reviewed. HTN was defined as systolic blood pressure greater than 95th percentile for age for > or =1 hour, unresponsive to sedation/analgesia. Hypertensive index (HI) is defined as total hypertensive hours per total ECMO hours. Fluid status was estimated by a fluid index (FI = total fluid balance during ECMO per ECMO hours per weight).

RESULTS

Forty-seven of 50 patients (94%) had HTN. Median HI was 0.21 (range, 0.01 to 1.0). Thirteen patients had renal insufficiency, 39 received steroids, and 23 received continuous venovenous hemofiltration (CVVH). There was no association between HI and FI, steroid use, or renal insufficiency. Thirty-three patients were treated for HTN, often requiring multiple agents. Bleeding complicated the course of 18 patients, and HI was significantly higher in those patients (P = .03). HI was not different between survivors (37 of 39 with HTN) and nonsurvivors (10 of 11 with HTN).

CONCLUSIONS

Hypertension is a common complication associated with VV ECMO with unclear etiology. HTN was frequently difficult to control. This study emphasizes the need for the development of treatment protocols to decrease the incidence, severity, and associated morbidity. Improved insight into the etiology of HTN associated with pediatric VV ECMO, including evaluation of the renin-angiotensin system, would help guide therapy.

Évolution sur 15 ans de l’assistance respiratoire extra-corporelle dans la prise en charge des détresses respiratoires néonatales sévères

Over the last decade, several new therapies including exogenous surfactant therapy, inhaled nitric oxide and high-frequency ventilation have become available for the treatment of neonatal pulmonary failure. The aim of this retrospective study was to evaluate to what extent these modalities have impacted the use of neonatal extracorporeal membrane oxygenation at our institution and to discuss the role of ECMO in 2003 in the management of newborn infants with refractory hypoxemia.

POPULATION AND METHODS

Two hundred and twenty six newborn infants treated by ECMO before 15 days of life and during more than 24 h in our intensive care unit were retrospectively included from two time periods (group 1: 1988-1993 and group 2: 1996-2003).

RESULTS

As compared with the first group, the number of newborns supported by ECMO in the second group has clearly diminished and their severity has increased. Overall survival rate was 80% in the first group and 69% in the second group. Meconium aspiration syndrome remains the major indication for ECMO (44%). Pulmonary sequelae, assessed by bronchopulmonary dysplasia rate (41%) are more frequent that neurologic sequelae (4.8%).

CONCLUSION

ECMO remains an useful technique in the management of newborn infants with refractory hypoxemia, with a consideration to institute ECMO early in order to increase survival rate.

The effect of inhaled nitric oxide and oxygen on the hydroxylation of salicylate in rat lungs

Inhaled nitric oxide (iNO) is used as a selective pulmonary vasodilator, and often under conditions when a high fraction of inspired oxygen is indicated. However, little is known about the potential toxicity of iNO therapy with or without concomitant oxygen therapy. NO can combine with superoxide (O2-) to form peroxynitrite (ONOO-), which can in turn decompose to form hydroxyl radical (OH.). Both OH. and ONOO- are involved in various forms of lung injury. To begin evaluation of the effect of iNO under either normoxic or hyperoxic conditions on OH. and/or ONOO- formation, rats were exposed for 58 h to either 21% O2, 21% O2 + 10 parts per million (ppm) NO, 21% O2 + 100 ppm NO, 50% O2, 90% O2, 90% O2 + 10 ppm NO, or 90% O2 + 100 ppm NO. We used a salicylate hydroxylation assay to detect the effects of these exposures on lung OH. and/or ONOO- formation measured as the appearance of 2,3-dihydroxybenzoic acid (2,3-DHBA). Exposure to 90% O2 and 90% O2 + 100 ppm NO resulted in significantly (p < 0.05) greater lung wet weight (1.99 +/- 0.14 g and 3.14 +/- 0.30 g, respectively) compared with 21% O2 (1.23 +/- 0.01 g). Exposure to 21% O2 + 100 ppm NO led to 2.5 times the control (21% O2 alone) 2,3 DHBA formation (p < 0.05) and exposure to 90% O2 led to 2.4 times the control 2,3-DHBA formation (p < 0.05). However, with exposure to both 90% O2 and 100 ppm NO, the 2,3-DHBA formation was no greater than the control condition (21% O2). Thus, these results indicate that, individually, both the hyperoxia and the 100 ppm NO led to greater salicylate hydroxylation, but that the combination of hyperoxia and 100 ppm NO led to less salicylate hydroxylation than either did individually. The production of OH. and/or ONOO- in the lung during iNO therapy may depend on the ratio of NO to O2.

The impact of changing neonatal respiratory management on extracorporeal membrane oxygenation utilization

BACKGROUND

The introduction of inhaled nitric oxide (INO) and high-frequency oscillatory ventilation (HFV) has had a profound effect on the use of extracorporeal membrane oxygenation (ECMO) for respiratory failure in neonates without congenital diaphragmatic hernia (CDH). The purpose of this study was to evaluate the changes in the demographics and outcome of non-CDH neonates who underwent ECMO for hypoxemic respiratory failure.

METHODS

All neonates (non-CDH and noncardiac) who underwent ECMO between January 1, 1989 and January 1, 2001 were reviewed. Patients were separated into 3, 4-year periods for comparison (period A, 1989 through 1992; B, 1993 through 1996; C, 1997 through 2000). Data were examined by analysis of variance and contingency table analysis.

RESULTS

There was a progressive decline in the total number of neonates requiring ECMO over time (period A, 172; B, 114; C, 56; P <.01). The utilization of pre-ECMO alternate respiratory therapies such as INO (period A, 0%; B, 23%; C, 98%; P <.01) and HFV (period A, 9%; B, 61%; C, 89%; P <.01) have increased significantly associated with an increase in the age of ECMO initiation (Period A, 40.5 hours; B, 58.3 hours; C, 68.5 hours; P <.01). The length of ECMO run also has increased (period A, 154.7 hours; B, 193.0 hours; C, 174.5 hours; P <.01), but the overall mortality rate has remained unchanged.

CONCLUSIONS

With the increasing use of INO and HFO, the absolute number of non-CDH, noncardiac neonates with hypoxemic respiratory failure requiring ECMO has decreased. Initiation of ECMO has become progressively later likely because of the use of these rescue therapies, but the overall mortality rate remains unchanged despite this delay.

Beneficial effects of inhaled nitric oxide in adult cardiac surgical patients

BACKGROUND

Pulmonary hypertension with associated right ventricular dysfunction may complicate the postoperative cardiac patient despite maximum pharmacologic and ventilatory support. The purpose of this study was to retrospectively review our experience with inhaled nitric oxide (INO) in adult postoperative cardiac patients with pulmonary hypertension.

METHODS

We retrospectively reviewed the medical records of 17 adult cardiac patients treated with INO postoperatively between November 1998 and February 2000. The INO was used to manage pulmonary hypertension postoperatively in patients who had undergone coronary artery bypass graft (CABG) (n = 13), valve operation (n = 3), and combined CABG/aortic valve replacement (n = 1). Hemodynamic and respiratory measurements before INO and again 6 hours after administration were examined. Student's t test was used to analyze the data.

RESULTS

Inhaled nitric oxide (20 ppm to 30 ppm) was administered for a median duration of 30.2 hours. The group, as a whole, demonstrated a significant decrease in both mean pulmonary artery pressure and right ventricular stroke work index. In addition, a significant increase in posttherapeutic cardiac index and Pao2/Fio2 ratio was observed. The vasodilatory effects of nitric oxide were specific to the pulmonary circulation as no significant change in mean arterial pressure was noted. Overall mortality was 6%.

CONCLUSIONS

Inhaled nitric oxide effectively and selectively lowered right ventricular afterload and right ventricular work in critically ill adult cardiac patients with acute pulmonary hypertension.

Residual pulmonary vasoreactivity to inhaled nitric oxide in patients with severe obstructive pulmonary hypertension and Eisenmenger syndrome

OBJECTIVE

To determine whether inhaled NO (iNO) can reduce pulmonary vascular resistance in adults with congenital heart disease and obstructive pulmonary hypertension or Eisenmenger syndrome.

DESIGN

23 patients received graded doses of iNO. Pulmonary and systemic haemodynamic variables and circulating cyclic guanosine monophosphate (cGMP) concentrations were measured at baseline and after 20 and 80 ppm iNO. Patients were considered responders when total pulmonary resistance was reduced by at least 20%, and rebound was defined as a greater than 10% increase in total pulmonary resistance upon withdrawal from iNO.

RESULTS

In response to 20 ppm iNO, total pulmonary resistance decreased in four patients (18%, 95% confidence interval (CI), 2% to 34%), while in response to 80 ppm iNO it decreased in six patients (29%, 95% CI 10% to 38%). Systemic blood pressure did not change. Withdrawal resulted in rebound in three patients (16%, 95% CI 0% to 32%) after cessation of 20 ppm iNO, and in six patients (35%, 95% CI 12% to 58%) after cessation of 80 ppm iNO. Patients with predominant right to left shunting did not respond. In all patients cGMP increased from (mean (SD)) 28 (13) micromol/l at baseline to 55 (30) and 78 (44) micromol/l after 20 and 80 ppm iNO (p < 0.05 v baseline).

CONCLUSIONS

NO inhalation is safe and is associated with a dose dependent increase in circulating cGMP concentrations. Pulmonary vasodilatation in response to iNO was observed in 29% of patients and was influenced by baseline pulmonary haemodynamics. Responsiveness to acute iNO may identify patients with advanced obstructive pulmonary hypertension and Eisenmenger syndrome who could benefit from sustained vasodilator treatment.

Combined-modality therapy with inhaled nitric oxide and exogenous surfactant in term infants with acute respiratory failure

OBJECTIVE

To report cases of neonates successfully treated with both exogenous surfactant and inhaled nitric oxide (INO).

DESIGN

Retrospective chart review of full term infants treated between January and May 1999 in the neonatal intensive care unit of The Children's Hospital at Strong, University of Rochester, Rochester, New York.

PATIENTS

Three full-term infants treated with surfactant and INO were identified. Each infant had severe acute respiratory failure (as a result of severe aspiration syndromes) and a clinical diagnosis of pulmonary hypertension and parenchymal lung disease in the absence of congenital malformations.

INTERVENTIONS

One infant received INO (20-40 ppm) followed by exogenous surfactant (100mg/kg); the other two received surfactant followed by INO.

MAIN RESULTS

All three infants exhibited a favorable response to treatment with these agents in terms of improved arterial oxygenation as summarized by oxygenation index and all survived to discharge home without referral for extracorporeal membrane oxygenation.

CONCLUSIONS

No adverse interactions were observed related to INO plus surfactant therapy. The responses of these critically ill infants were consistent with the hypothesis that the actions of INO in dilating the pulmonary microvasculature and of exogenous surfactant in stabilizing and recruiting alveoli are complementary and may lead to additive clinical benefits. These case results suggest that more extensive clinical studies are warranted for combined-modality therapy with INO and exogenous surfactant in patients with the acute respiratory distress syndrome.

Nitric oxide for respiratory failure in infants born at or near term

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To determine whether treatment of hypoxemic newborn infants with inhaled nitric oxide (INO) improves oxygenation and reduces the rates of death, or the requirement for ECMO.

SEARCH STRATEGY

Electronic and hand searching of pediatric/neonatal literature and personal data files. In addition we contacted the principal investigators of articles which have been published as abstracts to ascertain the necessary information.

SELECTION CRITERIA

Randomized and quasi randomized studies in term and near term infants. Administration of inhaled nitric oxide. Clinically relevant outcomes, including death, requirement for ECMO, and oxygenation.

DATA COLLECTION AND ANALYSIS

Eight randomized controlled studies were found in term and near term infants with hypoxia. Entry criteria were reasonably consistent except for the one trial that studied only infants with congenital diaphragmatic hernia (Ninos 1997).

MAIN RESULTS

Inhaled nitric oxide appears to improve outcome in hypoxemic term and near term infants by reducing the incidence of the combined endpoint of death or need for ECMO. The reduction seems to be entirely a reduction in need for ECMO; mortality is not reduced. Oxygenation improves in approximately 50% of infants receiving nitric oxide. The Oxygenation Index decreases by a (weighted) mean of 15.1 within 30 to 60 minutes after commencing therapy and PaO2 increases by a mean of 53 mmHg. It does not appear to affect outcome whether infants have clear echocardiographic evidence of PPHN or not. The outcome of infants with diaphragmatic hernia was not improved; indeed there is a suggestion that outcome was slightly worsened.

REVIEWER'S CONCLUSIONS

On the evidence presently available, it appears reasonable to use inhaled nitric oxide in a concentration of 20 ppm for term and near term infants with hypoxic respiratory failure who do not have a diaphragmatic hernia. Longterm neurodevelopmental and pulmonary followup of surviving infants enrolled in randomized trials of INO are required to establish more firmly the role of INO in the treatment of neonatal respiratory failure.

Randomized, controlled trial of low-dose inhaled nitric oxide in the treatment of term and near-term infants with respiratory failure and pulmonary hypertension

Recent reports indicate that inhaled nitric oxide (iNO) causes selective pulmonary vasodilation, increases arterial oxygen tension, and may decrease the use of extracorporeal membrane oxygenation (ECMO) in infants with persistent pulmonary hypertension of the newborn (PPHN). Despite these reports, the optimal dose and timing of iNO administration in PPHN remains unclear.

OBJECTIVES

To test the hypotheses that in PPHN 1) iNO at 2 parts per million (ppm) is effective at acutely increasing oxygenation as measured by oxygenation index (OI); 2) early use of 2 ppm of iNO is more effective than control (0 ppm) in preventing clinical deterioration and need for iNO at 20 ppm; and 3) for those infants who fail the initial treatment protocol (0 or 2 ppm) iNO at 20 ppm is effective at acutely decreasing OI.

STUDY DESIGN

A randomized, controlled trial of iNO in 3 nurseries in a single metropolitan area. Thirty-eight children, average gestational age of 37.3 weeks and average age <1 day were enrolled. Thirty-five of 38 infants had echocardiographic evidence of pulmonary hypertension. On enrollment, median OI in the control group, iNO at 0 ppm, (n = 23) was 33.1, compared with 36.9 in the 2-ppm iNO group (n = 15).

RESULTS

Initial treatment with iNO at 2 ppm for an average of 1 hour was not associated with a significant decrease in OI. Twenty of 23 (87%) control patients and 14 of 15 (92%) of the low-dose iNO group demonstrated clinical deterioration and were treated with iNO at 20 ppm. In the control group, treatment with iNO at 20 ppm decreased the median OI from 42.6 to 23.8, whereas in the 2-ppm iNO group with a change in iNO from 2 to 20 ppm, the median OI did not change (42.6 to 42.0). Five of 15 patients in the low-dose nitric oxide group required ECMO and 2 died, compared with 7 of 23 requiring ECMO and 5 deaths in the control group.

CONCLUSION

In infants with PPHN, iNO 1): at 2 ppm does not acutely improve oxygenation or prevent clinical deterioration, but does attenuate the rate of clinical deterioration; and 2) at 20 ppm acutely improves oxygenation in infants initially treated with 0 ppm, but not in infants previously treated with iNO at 2 ppm. Initial treatment with a subtherapeutic dose of iNO may diminish the clinical response to 20 ppm of iNO and have adverse clinical sequelae.

Nitric oxide inhalation in pulmonary hypertension and severe respiratory failure

Inhalation of nitric oxide (NO) can cause selective pulmonary vasodilation in aerated lung regions; thus, it may be of benefit in the treatment of various forms of pulmonary hypertension and respiratory distress due to a mismatch of pulmonary ventilation and perfusion. The specific characteristics of inhaled NO exclude long-term treatment, but NO has been successfully used as a test substance to screen patients for response to oral vasodilators. Furthermore, inhalation of NO has been shown to improve gas exchange and right ventricular performance and to reduce the need for other, more invasive therapies in various settings of acute pulmonary hypertension. However, the improvement of arterial oxygenation seen in patients with the acute respiratory distress syndrome does not result in increased survival, questioning the future importance of inhaled NO in the treatment of this pulmonary disorder.

Combined effects of inhaled nitric oxide and hyperoxia on pulmonary vascular permeability and lung mechanics

OBJECTIVE

To determine whether inhaled nitric oxide (NO) may alter pulmonary vascular permeability and respiratory function in an in vivo model.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

University experimental pharmacology laboratory.

SUBJECTS

Mechanically ventilated newborn piglets, 1 to 2 days old, exposed to 100% oxygen for 76 hrs.

INTERVENTIONS

The piglets were randomly assigned either to a treatment group receiving 20 ppm inhaled NO from the onset of ventilation (n = 5) or to a control group (n = 6) receiving no treatment.

MEASUREMENTS AND MAIN RESULTS

The main variables studied were gas exchange (PaO2/F(IO2) ratio, lung diffusing capacity), respiratory mechanics (static compliance of the respiratory system, stat, quasi-static hysteresis area, functional residual capacity), and pulmonary vascular permeability assessed by simultaneous intravenous administration of iodine-125-labeled albumin and chromium-51-labeled red blood cells. Extravascular albumin space of the lung and dry lung weight were significantly higher in the NO group vs. the control group (albumin space, 1.08+/-0.16 vs. 0.70+/-0.26 [SD] mL/kg body weight [p < .05]; dry lung weight, 3.20+/-0.34 vs. 2.66+/-0.14 g/kg body weight [p < .05]). Moreover, the hysteresis area was higher from 24 hrs of NO exposure. Conversely, NO inhalation altered neither the extravascular lung water content (12.98+/-2.79 mL/kg body weight in the NO group vs. 12.18+/-2.26 mL/kg body weight in the control group [not significant]) nor the main respiratory mechanical variables (static compliance, functional residual capacity) and gas exchange (lung diffusing capacity, PaO2/F(IO2) ratio).

CONCLUSION

These results do not support the hypothesis that NO inhalation combined with hyperoxia can alter the main lung-function variables in neonates. However, it may induce an increase in lung vascular protein leakage. The pathophysiologic consequences of this finding remain to be elucidated.

Low-dose inhaled nitric oxide improves the oxygenation and ventilation of infants and children with acute, hypoxemic respiratory failure

OBJECTIVE

To describe the effects of inhaled nitric oxide on oxygenation and ventilation in patients with acute, hypoxic respiratory failure and to characterize those who respond to low doses with a significant improvement in PaO2.

DESIGN

Prospective dose response trial of inhaled nitric oxide. Patients who demonstrated a > or =15% improvement in PaO2 were randomized to receive conventional mechanical ventilation with or without prolonged inhaled nitric oxide.

SETTING

Pediatric intensive care unit of a tertiary care children's hospital serving as a regional referral center for respiratory failure.

PATIENTS

Pediatric patients with an acute parenchymal lung disease requiring mechanical ventilation, an F(IO2) of > or =0.5, a positive end-expiratory pressure of > or =7 cm H2O, and whose PaO2/FIO2 ratio was < or =160.

INTERVENTIONS

PaO2, PaCO2, pH, heart rate, blood pressure, and methemoglobin were recorded at baseline and after inhaling 1, 5, 10, and 20 ppm of nitric oxide. Peak expiratory flow rate and mean airway resistance were measured while subjects received 0 and 20 ppm of inhaled nitric oxide. Patients were followed up until extubation or death.

MEASUREMENTS AND MAIN RESULTS

Twenty-six patients (median age, 2.6 yrs [range, 1 mo-18.2 yrs]) were enrolled in the study. PaO2 increased (p< .001) and Pa(CO2) fell (p< .0001) from baseline with the administration of inhaled nitric oxide. There was no statistical difference among 1, 5, 10, and 20 ppm with regard to effects on oxygenation. Sixteen patients (62%) responded to inhaled nitric oxide with a > or =15% improvement in PaO2; 14 of these responses occurred at a dose of 1 or 5 ppm. Response to inhaled nitric oxide was not associated with age, length of intubation, presence of primary lung disease, chest radiograph, or illness severity. Among patients weighing < or =20 kg, responders showed a greater fall in mean airway resistance (p < .05) than nonresponders. Mortality was not influenced by prolonged inhaled nitric oxide when analyzed by intention to treat. Patients receiving prolonged inhaled nitric oxide at doses of < or =20 ppm maintained methemoglobin levels of <3.0% and circuit concentrations of NO2 of <1 ppm.

CONCLUSIONS

Inhaled nitric oxide at doses of < or =5 ppm improves the oxygenation and (to a lesser extent) ventilation of most children with acute, hypoxic respiratory failure. The unpredictable response of patients necessitates individualized dosing of inhaled nitric oxide, starting at concentrations of < or =1 ppm. Inhaled nitric oxide at < or =20 ppm may exert a small salutary effect on bronchial tone. The benefits of prolonged inhaled nitric oxide remain unknown.

Inhaled vasodilator therapy for treatment of acute lung injury

In randomized controlled trials, inhaled nitric oxide failed to provide significant clinical benefit in patients with acute lung injury. Despite temporary improvement in oxygenation, inhaled nitric oxide neither improved survival, nor decreased length of mechanical ventilation. Thus, with the exception of severe hypoxaemia refractory to conventional therapy, inhaled nitric oxide is not indicated in patients with acute lung injury. Inhalation of prostacyclin and prostaglandin E1, respectively, has been associated with an improvement in oxygenation and a decrease in pulmonary artery pressure. Prospective randomized trials are warranted to assess the impact of inhaled prostaglandins on the outcome of patients with acute lung injury.

Vasodilators in mechanical ventilation

Vasodilators that affect the pulmonary vasculature are appealing adjuncts in many cardiopulmonary conditions that require mechanical ventilation such as ARDS, COPD, PPHN, and cardiothoracic surgery. The adverse systemic effects of parenteral PGE1 and parenteral prostacyclin limit their usefulness in critically ill patients. Liposomal PGE1 has few systemic effects, but thus far has not resulted in a significant clinical benefit in patients with ARDS. Inhaled NO and aerosolized prostacyclin offer the advantage of selective pulmonary vasodilation with minimal systemic effects. Both agents decrease PAP and in many clinical situations improve oxygenation; however, the physiologic effects of inhaled NO and aerosolized prostacyclin have not convincingly led to improved clinical outcomes. Currently, use of vasodilators in mechanically ventilated patients remains investigational.

Nitric oxide inhalation therapy for newborn infants

Binding of NO to heavy metal-containing proteins probably accounts for many of its physiologic actions. NO inhalation is a promising new treatment for various disorders of neonates. The therapy is most likely to benefit premature neonates who are hypoxemic despite breathing pure oxygen and those who suffer from impaired carbon dioxide elimination. Newborn infants who have congenital heart disease may benefit from inhaled NO therapy if their disease involves some form of pulmonary venous hypertension or if they have recently undergone surgery involving cardiopulmonary bypass grafting. The use of NO in infants with PPHN might obviate the need for ECMO or other invasive treatment methods. Neonates with CDH seem likely to benefit marginally from NO therapy. Minimizing the toxicities of NO inhalation therapy requires that the physicians understand the nuances of infant care. The therapeutic value of increasing carbon dioxide elimination with NO inhalation warrants further investigation.

Aerosolization of novel nitric oxide donors selectively reduce pulmonary hypertension

OBJECTIVES

Inhaled nitric oxide (NO) reduces pulmonary hypertension in acute respiratory failure. Soluble nitric oxide donors (NO/nucleophile adducts-NONOates) are less cumbersome to deliver and may offer clinical advantage compared with inhaled NO. The objective of this study was to examine the pulmonary and systemic hemodynamic effects of tracheal aerosolization of a new class of NONOates in a porcine model of experimentally induced pulmonary hypertension.

DESIGN

Prospective, randomized, controlled study.

SETTING

Research laboratory.

SUBJECTS

Yorkshire pigs (n = 18), weighing 11.4 to 16.4 kg.

INTERVENTIONS

In anesthetized, mechanically ventilated, instrumented pigs, steady-state pulmonary hypertension (SSPH) was induced using a thromboxane agonist (U46619). Control animals received tracheal aerosolization of saline (n = 6); EP/NO animals received tracheal aerosolization of ethylputreanine NONOate (EP/ NO, n = 6); and DMAEP/NO animals received aerosolized 2-(dimethylamino) ethylputreanine NONOate (DMAEP/NO, n = 6).

MEASUREMENTS AND MAIN RESULTS

Mean pulmonary (MPAP) and mean systemic arterial pressures (MAP), atrial pressures, cardiac output, and arterial blood gases were measured following drug instillation. DMAEP/NO animals had significant reductions in pulmonary vascular resistance index (PVRI) and MPAP at all time points compared with SSPH and control animals (p < .05), while systemic vascular resistance index did not change. EP/NO animals had a significant reduction in PVRI and MPAP at some time points compared with SSPH and control animals. For both NONOate-treated animal groups, MAP and cardiac index did not change significantly compared with SSPH and control animals (p < .05).

CONCLUSIONS

In this porcine model of pulmonary hypertension, intratracheal aerosolization of soluble NO donors results in sustained reduction of pulmonary hypertension without reducing systemic arterial pressure. Intermittent aerosolization of NONOates may be an alternative to continuously inhaled NO in the treatment of acute pulmonary hypertension.

Nitric oxide increases the survival of rats with a high oxygen exposure

The purpose of this study was to begin to examine the influence of inhaled NO on O2 toxicity. The survival of Sprague-Dawley rats exposed to >95% O2, >95% O2 + 10 ppm NO, >95% O2 + 100 ppm NO, and >95% O2 + 3 ppm NO2 was determined. Survival at 120 h was 2/24 in >95% O2, 2/12 in >95% O2 + 10 ppm NO, and 1/12 in >95% O2 + 3 ppm NO2. Survival at 120 h was 21/30 in >95% O2 + 100 ppm NO (p < 0.01 compared with >95% O2). Three additional groups of rats were exposed for 60 h to: 21% O2, >95% O2, or >95% O2 + 100 ppm NO. The lungs were then assayed for total protein, reduced (GSH) and oxidized glutathione (GSSG), and 4-hydroxy-2(E)-nonenal. Both of the high O2 groups had significantly (p < 0.05) lower GSH/mg protein and GSH/GSSG ratios compared with the 21% O2 group. The >95% O2 group had a higher 4-hydroxy-2(E)-nonenal/mg of protein than either the 21% O2 group (p < 0.05), or the >95% O2 + 100 ppm NO group (p < 0.05 compared with >95% O2, not different from the 21% O2 group). Additional groups of rats were exposed to either 21% O2, >95% O2, or >95% O2 + 100 ppm NO for 0, 24, 48, and 60 h. The lungs were examined for neutrophil accumulation, which was increased at 60 h in the two groups exposed to >95% O2, but adding NO had no effect. Thus, the overall result was that 100 ppm inhaled NO improved the survival of rats in high O2.

Advances in neonatal care and surgery

Neonatology has seen many advances over the past decade. Exogenous surfactant therapy is now a mainstay treatment for respiratory distress syndrome. Partial liquid ventilation, high-frequency ventilation, and inhaled nitric oxide are all relatively new modalities, which have enabled neonatologists to treat with varying degrees of success ever younger and smaller patients. The purpose of this review is to examine studies regarding the long-term outcome of high-risk neonates, the various treatment modalities, and current neonatal surgical techniques, all of which will influence our care of the neonate.

The use of inhaled nitric oxide in a wide variety of clinical problems

Inhaled nitric oxide (NO) clearly decreased pulmonary vascular resistance in pediatric patients with pulmonary hypertension, regardless of the underlying origin of the pulmonary hypertension. In persistent pulmonary hypertension of the neonate (PPHN) and CHD, the use of inhaled NO appears to improve the outcome of these patients. In acute respiratory distress syndrome (ARDS) and surfactant deficiency the role of inhaled NO therapy remains unclear. The use of inhaled NO is safe in a carefully monitored setting with a delivery system designed to minimize the generation of NO2.

Nitric oxide in respiratory failure in the newborn infant

Nitric oxide given as an inhalation (INO) is a novel selective pulmonary vasodilator without effects on the systemic circulation. Preliminary observations indicated that INO treatment was associated with improvements in oxygenation in near-term newborn infants with hypoxic respiratory failure and persistent pulmonary hypertension of the newborn (PPHN). Subsequently, at least eight prospective randomized controlled trials evaluating the use of INO in the near-term neonate with hypoxic respiratory failure have been presented or published. A meta-analysis of these trials has provided evidence that INO improves the PaO2 in the INO-treated infants by 52.8 mm Hg (weighted mean difference) compared with controls (95% CI, 38.2, 67.4), and significantly decreases the oxygenation index by 16.9 compared with controls (95% CI, -22.2, -11.6). The incidence of death or need for ECMO is significantly reduced by treatment with INO, relative risk 0.71 compared to control (95% CI, 0.57, 0.87), with the majority of the improvement observed in the reduction in the need for ECMO. A single study of infants with congenital diaphragmatic hernia (CDH) did not show a benefit for early INO therapy, with treated infants having a greater requirement for ECMO (P = .043). At present, there are no long-term evaluations of infants who have received INO as part of these prospective trials. INO improves oxygenation and reduces the need for ECMO in the near-term hypoxic neonate, but further research is required to evaluate the ultimate safety and benefit of this therapy.