A Multicenter Collaborative to Improve Postoperative Pain Management in the NICU

OBJECTIVES

This quality improvement initiative aimed to decrease unrelieved postoperative pain and improve family satisfaction with pain management.

METHODS

NICUs within the Children's Hospitals Neonatal Consortium that care for infants with complex surgical problems participated in this collaborative. Each of these centers formed multidisciplinary teams to develop aims, interventions, and measurement strategies to test in multiple Plan-Do-Study-Act cycles. Centers were encouraged to adopt evidence-based interventions from the Clinical Practice Recommendations, which included pain assessment tools, pain score documentation, nonpharmacologic treatment measures, pain management guidelines, communication of a pain treatment plan, routine discussion of pain scores during team rounds, and parental involvement in pain management. Teams submitted data on a minimum of 10 surgeries per month, spanning from January to July 2019 (baseline), August 2019 to June 2021 (improvement work period), and July 2021 to December 2021 (sustain period).

RESULTS

The percentage of patients with unrelieved pain in the 24-hour postoperative period decreased by 35% from 19.5% to 12.6%. Family satisfaction with pain management measured on a 3-point Likert scale with positive responses ≥2 increased from 93% to 96%. Compliance with appropriate pain assessment and numeric documentation of postoperative pain scores according to local NICU policy increased from 53% to 66%. The balancing measure of the percentage of patients with any consecutive sedation scores showed a decrease from 20.8% at baseline to 13.3%. All improvements were maintained during the sustain period.

CONCLUSIONS

Standardization of pain management and workflow in the postoperative period across disciplines can improve pain control in infants.

Analgesia, Sedation, and Neuromuscular Blockade in Infants with Congenital Diaphragmatic Hernia

OBJECTIVE

The aim of this study was to describe the use, duration, and intercenter variation of analgesia and sedation in infants with congenital diaphragmatic hernia (CDH).

STUDY DESIGN

This is a retrospective analysis of analgesia, sedation, and neuromuscular blockade use in neonates with CDH. Patient data from 2010 to 2016 were abstracted from the Children's Hospitals Neonatal Database and linked to the Pediatric Health Information System. Patients were excluded if they also had non-CDH conditions likely to affect the use of the study medications.

RESULTS

A total of 1,063 patients were identified, 81% survived, and 30% were treated with extracorporeal membrane oxygenation (ECMO). Opioid (99.8%), sedative (93.4%), and neuromuscular blockade (87.9%) use was common. Frequency of use was higher and duration was longer among CDH patients treated with ECMO. Unadjusted duration of use varied 5.6-fold for benzodiazepines (median: 14 days) and 7.4-fold for opioids (median: 16 days). Risk-adjusted duration of use varied among centers, and prolonged use of both opioids and benzodiazepines ≥5 days was associated with increased mortality (p < 0.001) and longer length of stay (p < 0.001). Use of sedation or neuromuscular blockade prior to or after surgery was each associated with increased mortality (p ≤ 0.01).

CONCLUSION

Opioids, sedatives, and neuromuscular blockade were used commonly in infants with CDH with variable duration across centers. Prolonged combined use ≥5 days is associated with mortality.

KEY POINTS

· Use of analgesia and sedation varies across children's hospital NICUs.. · Prolonged opioid and benzodiazepine use is associated with increased mortality.. · Postsurgery sedation and neuromuscular blockade are associated with mortality..

Variability for Age at Successful Extubation in Infants with Congenital Diaphragmatic Hernia

OBJECTIVE

The objective of this study was to characterize clinical factors associated with successful extubation in infants with congenital diaphragmatic hernia.

STUDY DESIGN

Using the Children's Hospitals Neonatal Database, we identified infants with congenital diaphragmatic hernia from 2017 to 2020 at 32 centers. The main outcome was age in days at the time of successful extubation, defined as the patient remaining extubated for 7 consecutive days. Unadjusted Kaplan-Meier and multivariable Cox proportional hazards ratio equations were used to estimate associations between clinical factors and the main outcome. Observations occurred through 180 days after birth.

RESULTS

There were 840 eligible neonates with a median gestational age of 38 weeks and birth weight of 3.0 kg. Among survivors (n = 693), the median age at successful extubation was 15 days (interquartile range [IQR]: 8-29 days, 95th percentile: 71 days). For nonsurvivors (n = 147), the median age at death was 21 days (IQR: 11-39 days, 95th percentile: 110 days). Center (adjusted hazards ratio: 0.22-15, P < .01), low birth weight, intrathoracic liver position, congenital heart disease, lower 5-minute Apgar score, lower pH upon admission to Children's Hospitals Neonatal Database center, and use of extracorporeal support were independently associated with older age at successful extubation. Tracheostomy was associated with multiple failed extubations.

CONCLUSION

Our findings suggest that infants who have not successfully extubated by about 3 months of age may be candidates for tracheostomy with chronic mechanical ventilation or palliation. The variability of timing of successful extubation among our centers supports the development of practice guidelines after validating clinical criteria.

Central Line Utilization and Complications in Infants with Congenital Diaphragmatic Hernia

OBJECTIVE

Infants with congenital diaphragmatic hernia (CDH) require multiple invasive interventions carrying inherent risks, including central venous and arterial line placement. We hypothesized that specific clinical or catheter characteristics are associated with higher risk of nonelective removal (NER) due to complications and may be amenable to efforts to reduce patient harm.

STUDY DESIGN

Infants with CDH were identified in the Children's Hospital's Neonatal Database (CHND) from 2010 to 2016. Central line use, duration, and complications resulting in NER are described and analyzed by extracorporeal membrane oxygenation (ECMO) use.

RESULTS

A total of 1,106 CDH infants were included; nearly all (98%) had a central line placed, (average of three central lines) with a total dwell time of 22 days (interquartile range [IQR]: 14-39). Umbilical arterial and venous lines were most common, followed by extremity peripherally inserted central catheters (PICCs); 12% (361/3,027 central lines) were removed secondary to complications. Malposition was the most frequent indication for NER and was twice as likely in infants with intrathoracic liver position. One quarter of central lines in those receiving ECMO was placed while receiving this therapy.

CONCLUSION

Central lines are an important component of intensive care for infants with CDH. Careful selection of line type and location and understanding of common complications may attenuate the need for early removal and reduce risk of infection, obstruction, and malposition in this high-risk group of patients.

KEY POINTS

· Central line placement near universal in congenital diaphragmatic hernia infants.. · Mean of three lines placed per patient; total duration 22 days.. · Clinical patient characteristics affect risk..

Improving timeliness of hepatitis B vaccine administration in an urban safety net level III NICU

OBJECTIVE

To avoid preventable consequences of perinatal hepatitis B infection, all infants should be given hepatitis B vaccine (HBV) within 24 hours of birth if birth weight is ≥2 kg and at 30 days of life or at discharge if <2 kg, to provide highest seroprotection rates while ensuring universal vaccination prior to discharge. We aimed to achieve timely HBV administration in >80% of eligible infants in both birthweight groups and decrease infants discharged home without receiving HBV to <1% over an 18-month period and sustain results for an additional 15 months.

METHODS

Data were collected from June 2016 to May 2020 in a level III neonatal intensive care unit. A multidisciplinary team identified barriers and interventions through Plan-Do-Study-Act cycles from September 2017 to February 2019: using pharmacists as champions, overcoming legal barriers, staff education and best practice alerts (BPAs) embedded in electronic health records. Statistical process control (SPC) p charts were used to evaluate the primary outcome measure, monthly percentage of infants receiving timely HBV administration stratified by birthweight categories (≥2 and <2 kg). For infants receiving HBV outside the time frame, absolute difference of timeliness was calculated.

RESULTS

Mean timely HBV administration improved from 45% to 95% (≥2 kg) and from 45% to 85% (<2 kg) with special cause variation in SPC charts. Infants discharged without receiving HBV decreased from 4.6% to 0.22%. Of those given HBV outside the recommended time frame, median absolute time between recommended and actual administration time decreased significantly: from 3.5 days (IQR 1.6, 8.6) to 0.3 day (IQR 0.1, 0.8) (p<0.001) in ≥2 kg group and from 6 days (IQR 1, 15) to 1 day (IQR 1, 6.5) (p=0.009) in <2 kg group.

CONCLUSIONS

Using a multidisciplinary approach, we significantly improved and sustained timely HBV administration and nearly eliminated infants discharged home without receiving HBV. Pharmacists as champions and BPAs were critical to our success.

Treatment of pulmonary hypertension during initial hospitalization in a multicenter cohort of infants with congenital diaphragmatic hernia (CDH)

OBJECTIVE

Describe inpatient pulmonary hypertension (PH) treatment and factors associated with therapy at discharge in a multicenter cohort of infants with CDH.

METHODS

Six years linked records from Children's Hospitals Neonatal Database and Pediatric Health Information System were used to describe associations between prenatal/perinatal factors, clinical outcomes, echocardiographic findings and PH medications (PHM), during hospitalization and at discharge.

RESULTS

Of 1106 CDH infants from 23 centers, 62.8% of infants received PHM, and 11.6% of survivors were discharged on PHM. Survivors discharged on PHM more frequently had intrathoracic liver, small for gestational age, and low 5 min APGARs compared with those discharged without PHM (p < 0.0001). Nearly one-third of infants discharged without PHM had PH on last inpatient echo.

CONCLUSIONS

PH medication use is common in CDH. Identification of infants at risk for persistent PH may impact ongoing management. Post-discharge follow-up of all CDH infants with echocardiographic evidence of PH is warranted.

Cardiopulmonary resuscitation in quaternary neonatal intensive care units: a multicenter study

BACKGROUND

The reported incidence of cardiopulmonary resuscitation (CPR) in quaternary NICU is approximately 10-times higher than in the delivery room. However, the etiologies and outcomes of CPR in quaternary NICUs are poorly understood. We hypothesized that demographic characteristics, diagnoses, interventions, and arrest etiologies would be associated with survival to discharge after CPR.

METHODS

Multicenter retrospective cohort study of four quaternary NICUs over six years (2011-2016). Demographics, resuscitation event data, and post-arrest outcomes were analyzed. The primary outcome was survival to discharge.

RESULTS

Of 17,358 patients admitted to four NICUs, 200 (1.1%) experienced a CPR event, and 45.5% of those survived to discharge. Acute respiratory compromise leading to cardiopulmonary arrest occurred in 182 (91%) of the CPR events. Most neonates requiring CPR were on mechanical ventilation (79%) and had central venous access (90%) at the time of arrest. Treatments at the time of the arrest associated with decreased survival to discharge included mechanical ventilation, antibiotics, or vasopressor therapy (p < 0.01). Etiologies of arrest associated with decreased survival to discharge included multisystem organ failure, septic shock, and pneumothorax (p < 0.05). Longer duration of CPR was associated with decreased survival to discharge. The odds of surviving to discharge decreased for infants who had a primarily cardiac arrest and for infants who received epinephrine during the arrest.

CONCLUSION

Approximately 1% of neonates admitted to quaternary NICUs require CPR. The most common etiology of arrest is acute respiratory compromise on a ventilator. CPR events with respiratory etiology have a favorable outcome as compared to non-respiratory causes.

STEPP IN: Working Together to Keep Infants Warm in the Perioperative Period

OBJECTIVES

Reduce postoperative hypothermia by up to 50% over a 12-month period in children's hospital NICUs and identify specific clinical practices that impact success.

METHODS

Literature review, expert opinion, and benchmarking were used to develop clinical practice recommendations for maintaining perioperative euthermia that included the following: established euthermia before transport to the operating room (OR), standardized practice for maintaining euthermia on transport to and from the OR, and standardized practice to prevent intraoperative heat loss. Process measures were focused on maintaining euthermia during these time points. The outcome measure was the proportion of patients with postoperative hypothermia (temperature ≤36°C within 30 minutes of a return to the NICU or at the completion of a procedure in the NICU). Balancing measures were the proportion of patients with postoperative temperature >38°C or the presence of thermal burns. Multivariable logistic regression was used to identify key practices that improved outcome.

RESULTS

Postoperative hypothermia decreased by 48%, from a baseline of 20.3% (January 2011 to September 2013) to 10.5% by June 2015. Strategies associated with decreased hypothermia include >90% compliance with patient euthermia (36.1-37.9°C) at times of OR arrival (odds ratio: 0.58; 95% confidence interval [CI]: 0.43-0.79; P < .001) and OR departure (odds ratio: 0.0.73; 95% CI: 0.56-0.95; P = .017) and prewarming the OR ambient temperature to >74°F (odds ratio: 0.78; 95% CI: 0.62-0.999; P = .05). Hyperthermia increased from a baseline of 1.1% to 2.2% during the project. No thermal burns were reported.

CONCLUSIONS

Reducing postoperative hypothermia is possible. Key practices include prewarming the OR and compliance with strategies to maintain euthermia at select time points throughout the perioperative period.

Diuretic Use and Subsequent Electrolyte Supplementation in a Level IV Neonatal Intensive Care Unit

OBJECTIVES

To evaluate the relationship between diuretic use, serum electrolyte concentrations, and supplementation requirements in infants admitted to the neonatal intensive care unit.

METHODS

This was a single-center retrospective cohort study conducted in a freestanding children's hospital Level IV NICU. Data were collected for all infants younger than 6 months, admitted to the NICU between January 2015 and May 2017, who received 2 or more consecutive doses of furosemide, chlorothiazide, hydrochlorothiazide, and/or hydrochlorothiazide/spironolactone. The primary outcome was the composite of the incidence of electrolyte abnormalities and/or electrolyte supplementation requirement within 30 days of diuretic exposure.

RESULTS

A total of 72 patients met inclusion criteria, with a median gestational age of 30 weeks. Overall, 92% of patients exposed to diuretics experienced derangement in at least 1 serum electrolyte and/or required electrolyte supplementation during diuretic therapy. Patients born at 36 to 41 weeks' gestational age, receiving thiazide diuretics, experienced a significantly lower rate of the primary outcome (37%, p ≤ 0.001). The most common electrolytes affected by diuretic use were potassium and bicarbonate, with the highest incidence of the primary outcome for potassium occurring in patients receiving furosemide (p = 0.0196). Last, the median total daily dose of chlorothiazide in patients with an adverse event was 15 mg/kg/day, compared with 10 mg/kg/day in patients without an adverse event (p = 0.0041).

CONCLUSIONS

Use of diuretics in young infants is likely to cause electrolyte derangements and/or require electrolyte supplementation. Patients born at earlier gestational ages may be at higher risk for developing such adverse effects.

Utility of echocardiography in predicting mortality in infants with severe bronchopulmonary dysplasia

OBJECTIVE

To determine the relationship between interventricular septal position (SP) and right ventricular systolic pressure (RVSP) and mortality in infants with severe BPD (sBPD).

STUDY DESIGN

Infants with sBPD in the Children's Hospitals Neonatal Database who had echocardiograms 34-44 weeks' postmenstrual age (PMA) were included. SP and RVSP were categorized normal, abnormal (flattened/bowed SP or RVSP > 40 mmHg) or missing.

RESULTS

Of 1157 infants, 115 infants (10%) died. Abnormal SP or RVSP increased mortality (SP 19% vs. 8% normal/missing, RVSP 20% vs. 9% normal/missing, both p < 0.01) in unadjusted and multivariable models, adjusted for significant covariates (SP OR 1.9, 95% CI 1.2-3.0; RVSP OR 2.2, 95% CI 1.1-4.7). Abnormal parameters had high specificity (SP 82%; RVSP 94%), and negative predictive value (SP 94%, NPV 91%) for mortality.

CONCLUSIONS

Abnormal SP or RVSP is independently associated with mortality in sBPD infants. Negative predictive values distinguish infants most likely to survive.

Neonates Hospitalized with Community-Acquired SARS-CoV-2 in a Colorado Neonatal Intensive Care Unit

IMPORTANCE

The novel coronavirus 2019 (SARS-CoV-2) has been well described in adults. Further, the impact on older children and during the perinatal time is becoming better studied. As community spread increases, it is important to recognize that neonates are vulnerable to community spread as well. The impact that community-acquired SARS-CoV-2 has in the neonatal time period is unclear, as this population has unique immunity considerations.

OBJECTIVE

To report on a case series of SARS-CoV-2 in neonates through community acquisition in the USA.

DESIGN

This is an early retrospective study of patients admitted to the Neonatal Intensive Care Unit (NICU) identified as having SAR-CoV-2 through positive real-time polymerase chain reaction assay of nasopharyngeal swabs.

FINDINGS

Three patients who required admission to the NICU between the ages of 17 and 33 days old were identified. All 3 had ill contacts in the home or had been to the pediatrician and presented with mild to moderate symptoms including fever, rhinorrhea, and hypoxia, requiring supplemental oxygen during their hospital stay. One patient was admitted with neutropenia, and the other 2 patients became neutropenic during hospitalization. None of the patients had meningitis or multiorgan failure.

CONCLUSIONS AND RELEVANCE

Infants with community-acquired SARS-CoV-2 may require hospitalization due to rule-out sepsis guidelines if found to have fever and/or hypoxia. Caregivers of neonates should exercise recommended guidelines before contact with neonates to limit community spread of SARS-CoV-2 to this potentially vulnerable population, including isolation, particularly as asymptomatic cases become prevalent.

Extracorporeal membrane oxygenation in infants with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly which impairs normal pulmonary development leading to acute and chronic respiratory failure, pulmonary hypoplasia, pulmonary hypertension, and mortality. CDH is the most common non-cardiac indication for neonatal ECMO. Prenatal and postnatal predictors of CDH severity aid in patient selection. Centers vary in preferred mode of ECMO and timing of CDH repair. Survivors of severe CDH with ECMO are at risk for long-term sequelae including neurodevelopmental delays.

Sustaining SLUG Bug CLABSI Reduction: Does Sterile Tubing Change Technique Really Work?

OBJECTIVES

To evaluate the ability to sustain and further reduce central line-associated bloodstream infection (CLABSI) rates in NICUs participating in a multicenter CLABSI reduction collaborative and to assess the impact of the sterile tubing change (TC) technique as an important component in CLABSI reduction.

METHODS

A multi-institutional quality improvement collaborative lowered CLABSI rates in level IV NICUs over a 12-month period. During the 19-month sustain phase, centers were encouraged to monitor and report compliance measures but were only required to report the primary outcome measure of the CLABSI rate. Four participating centers adopted the sterile TC technique during the sustain phase as part of a local Plan-Do-Study-Act cycle.

RESULTS

The average aggregate baseline NICU CLABSI rate of 1.076 CLABSIs per 1000 line days was sustained for 19 months across 17 level IV NICUs from January 2013 to July 2014. Four centers transitioning from the clean to the sterile TC technique during the sustain phase had a 64% decrease in CLABSI rates from the baseline (1.59 CLABSIs per 1000 line days to 0.57 CLABSIs per 1000 line days).

CONCLUSIONS

Sustaining low CLABSI rates in a multicenter collaborative is feasible with team engagement and ongoing collaboration. With these results, we further demonstrate the positive impact of the sterile TC technique in CLABSI reduction efforts.

Inter-center variation in death or tracheostomy placement in infants with severe bronchopulmonary dysplasia

OBJECTIVE

To estimate the presence and sources of inter-center variation (ICV) in the risk of death or tracheostomy placement (D/T) among infants with severe bronchopulmonary dysplasia (sBPD)Study design:We analyzed the Children's Hospitals Neonatal Database between 2010 and 2013 to identify referred infants born <32 weeks' gestation with sBPD. The association between center and the primary outcome of D/T was analyzed by multivariable modeling. Hypothesized diagnoses/practices were included to determine if these explained any observed ICV in D/T.

RESULTS

D/T occurred in 280 (20%) of 1383 eligible infants from 21 centers. ICV was significant for D/T (range 2-46% by center, P<0.001) and tracheostomy placement (n=187, range 2-37%, P<0.001), but not death (n=93, range 0-19%, P=0.08). This association persisted in multivariable analysis (adjusted center-specific odds ratios for D/T varied 5.5-fold, P=0.009).

CONCLUSIONS

ICV in D/T is apparent among infants with sBPD. These results highlight that the indications for tracheostomy (and subsequent chronic ventilation) remain uncertain.

Short-term weight gain velocity in infants with congenital diaphragmatic hernia (CDH)

BACKGROUND

Appropriate post-natal growth remains a mainstay of therapeutic goals for infants with CDH, with the hypothesis that optimizing linear growth will improve survival through functional improvements in pulmonary hypoplasia. However, descriptions of growth and the effect on survival are limited in affected infants.

OBJECTIVE

Describe in-hospital weight gain related to survival among infants with CDH.

DESIGN/METHODS

Children's Hospitals Neonatal Database (CHND) identified infants with CDH born ≥34weeks' gestation (2010-14). Exclusion criteria were: admission age>7days, death/discharge age<14days, or surgical CDH repair prior to admission. Weight gain velocity (WGV: g/kg/day) was calculated using an established exponential approximation and the cohort stratified by Q1: <25%ile, Q2-3: 25-75%ile, and Q4: >75%ile. Descriptive measures and unadjusted Kaplan-Meier analyses describe the implications of WGV on mortality/discharge.

RESULTS

In 630 eligible infants, median WGV was 4.6g/kg/day. After stratification by WGV [Q1: (n=156; <3.1g/kg/day); Q2-3 (n=316; 3.1-5.9g/kg/day), and Q4 (n=158, >5.9g/kg/day)] infants in Q1 had shortest median length of stay, less time on TPN and intervention for gastro-esophageal reflux relative to the other WGV strata (p<0.01 for all). Unadjusted survival estimates revealed that Q1 [hazard ratio (HR)=9.5, 95% CI: 5.7, 15.8] and Q4 [HR=2.9, 95% CI: 1.7, 5.1, p<0.001 for both] WGV were strongly associated with NICU mortality relative to Q2-3 WGV.

CONCLUSION

Variable WGV is evident in infants with CDH. Highest and lowest WGV appear to be related to adverse outcomes. Efforts are needed to develop nutritional strategies targeting optimal growth.

Orchestrated Testing

Health care quality improvement collaboratives implement care bundles to target critical parts of a complex system to improve a specific health outcome. The quantitative impact of each component of the care bundle is often unknown. Orchestrated testing (OT) is an application of planned experimentation that allows simultaneous examination of multiple practices (bundle elements) to determine which intervention or combination of interventions affects the outcome. The purpose of this article is to describe the process needed to design and implement OT methodology for improvement collaboratives. Examples from a multicenter collaborative to reduce central line-associated bloodstream infections highlight the practical application of this approach. The key components for implementation of OT are the following: (1) define current practice and evidence, (2) develop a factorial matrix and calculate power, (3) formulate structure for engagement, (4) analyze results, and (5) replicate findings.

SLUG Bug: Quality Improvement With Orchestrated Testing Leads to NICU CLABSI Reduction

OBJECTIVE

Reduce central line-associated bloodstream infection (CLABSI) rates 15% over 12 months in children's hospital NICUs. Use orchestrated testing as an approach to identify important CLABSI prevention practices.

METHODS

Literature review, expert opinion, and benchmarking were used to develop clinical practice recommendations for central line care. Four existing CLABSI prevention strategies (tubing change technique, hub care monitoring, central venous catheter access limitation, and central venous catheter removal monitoring) were identified for study. We compared the change in CLABSI rates from baseline throughout the study period in 17 participating centers. Using orchestrated testing, centers were then placed into 1 of 8 test groups to identify which prevention practices had the greatest impact on CLABSI reduction.

RESULTS

CLABSI rates decreased by 19.28% from 1.333 to 1.076 per 1000 line-days. Six of the 8 test groups and 14 of the 17 centers had decreased infection rates; 16 of the 17 centers achieved >75% compliance with process measures. Hub scrub compliance monitoring, when used in combination with sterile tubing change, decreased CLABSI rates by 1.25 per 1000 line-days.

CONCLUSIONS

This multicenter improvement collaborative achieved a decrease in CLABSI rates. Orchestrated testing identified infection prevention practices that contribute to reductions in infection rates. Sterile tubing change in combination with hub scrub compliance monitoring should be considered in CLABSI reduction efforts.

Short-term outcomes and medical and surgical interventions in infants with congenital diaphragmatic hernia

OBJECTIVE

The aim of this study is to characterize medical and surgical therapies and short-term outcomes in infants with congenital diaphragmatic hernia (CDH).

STUDY DESIGN

Retrospective analysis of CDH infants admitted to 27 children's hospitals submitting data to Children's Hospital Neonatal Database (CHND) from 2010 to 2013, stratified by gestational age, birth weight, and survival.

RESULTS

A total of 572 infants were identified, 508 (89%) born ≥ 34 weeks' gestation and ≥ 2 kg. More mature infants had higher APGAR scores, shorter duration of mechanical ventilation, and were more likely to receive extracorporeal membrane oxygenation (ECMO). Overall, mortality for the cohort was 29%, with mortality lower in infants born ≥ 34 weeks' gestation and ≥ 2 kg (26 vs. 50%, p < 0.01). Nonsurvivors were more likely to receive treatment with high-frequency oscillatory ventilation (HFOV), vasopressors, pulmonary vasodilators, and ECMO, and to have associated major congenital anomalies than survivors. In hospital morbidity and complications were relatively uncommon among survivors.

CONCLUSION

Infants with CDH have a high risk of morbidity and mortality, and for preterm infants with CDH those risks are amplified. Patterns of respiratory and circulatory support appeared to be different for survivors. In addition to established data registries, this consortium of regional neonatal intensive care units provides a new collaborative effort to describe short-term outcomes for infants referred with CDH.

High surgical burden for infants with severe chronic lung disease (sCLD)

BACKGROUND/PURPOSE

Infants with severe chronic lung disease (sCLD) may require surgical procedures to manage their medical problems; however, the scope of these interventions is undefined. The purpose of this study was to characterize the frequency, type, and timing of operative interventions performed in hospitalized infants with sCLD.

METHODS

The Children's Hospital Neonatal Database was used to identify infants with sCLD from 24 children's hospital's NICUs hospitalized over a recent 16-month period.

RESULTS

556 infants were diagnosed with sCLD; less than 3% of infants had operations prior to referral and 30% were referred for surgical evaluation. In contrast, 71% of all sCLD infants received ≥1 surgical procedure during the CHND NICU hospitalization, with a mean of 3 operations performed per infant. Gastrostomy insertion (24%), fundoplication (11%), herniorrhaphy (13%), and tracheostomy placement (12%) were the most commonly performed operations. The timing of gastrostomy (PMA 48±10 wk) and tracheostomy (PMA 47±7 wk) insertions varied, and for infants who received both devices, only 33% were inserted concurrently (13/40 infants).

CONCLUSIONS

A striking majority of infants with sCLD received multiple surgical procedures during hospitalizations at participating NICUs. Further work regarding the timing, coordination, perioperative complications, and clinical outcomes for these infants is warranted.

Predicting death or tracheostomy placement in infants with severe bronchopulmonary dysplasia

OBJECTIVE

To estimate the risk of death or tracheostomy placement (D/T) in infants with severe bronchopulmonary dysplasia (sBPD) born < 32 weeks' gestation referred to regional neonatal intensive care units.

STUDY DESIGN

We conducted a retrospective cohort study in infants born < 32 weeks' gestation with sBPD in 2010-2011, using the Children's Hospital Neonatal Database. sBPD was defined as the need for FiO2 ⩾ 0.3, nasal cannula support >2 l min(-1) or positive pressure at 36 weeks' post menstrual age. The primary outcome was D/T before discharge. Predictors associated with D/T in bivariable analyses (P < 0.2) were used to develop a multivariable logistic regression equation using 80% of the cohort. This equation was validated in the remaining 20% of infants.

RESULT

Of 793 eligible patients, the mean gestational age was 26 weeks' and the median age at referral was 6.4 weeks. D/T occurred in 20% of infants. Multivariable analysis showed that later gestational age at birth, later age at referral along with pulmonary management as the primary reason for referral, mechanical ventilation at the time of referral, clinically diagnosed pulmonary hypertension, systemic corticosteroids after referral and occurrence of a bloodstream infection after referral were each associated with D/T. The model performed well with validation (area under curve 0.86, goodness-of-fit χ(2), P = 0.66).

CONCLUSION

Seven clinical variables predicted D/T in this large, contemporary cohort with sBPD. These results can be used to inform clinicians who counsel families of affected infants and to assist in the design of future prospective trials.

Therapeutic interventions and short-term outcomes for infants with severe bronchopulmonary dysplasia born at <32 weeks' gestation

OBJECTIVE

To characterize the treatments and short-term outcomes in infants with severe bronchopulmonary dysplasia (sBPD) referred to regional neonatal intensive care units.

STUDY DESIGN

Infants born <32 weeks' gestation with sBPD were identified using the Children's Hospital Neonatal Database. Descriptive outcomes are reported.

RESULT

A total of 867 patients were eligible. On average, infants were born at 26 weeks' gestation and referred 43 days after birth. Infants frequently experienced lung injury (pneumonia: 24.1%; air leak: 9%) and received systemic corticosteroids (61%) and mechanical ventilation (median duration 37 days). Although 91% survived to discharge, the mean post-menstrual age was 47 weeks. Ongoing care such as supplemental oxygen (66%) and tracheostomy (5%) were frequently needed.

CONCLUSION

Referred infants with sBPD sustain multiple insults to lung function and development. Because affected infants have no proven, safe or efficacious therapy and endure an exceptional burden of care even after referral, urgent work is required to observe and improve their outcomes.

Pulmonary vascular effects of serotonin and selective serotonin reuptake inhibitors in the late-gestation ovine fetus

Maternal use of selective serotonin (5-HT) reuptake inhibitors (SSRIs) is associated with an increased risk for persistent pulmonary hypertension of the newborn (PPHN), but little is known about 5-HT signaling in the developing lung. We hypothesize that 5-HT plays a key role in maintaining high pulmonary vascular resistance (PVR) in the fetus and that fetal exposure to SSRIs increases 5-HT activity and causes pulmonary hypertension. We studied the hemodynamic effects of 5-HT, 5-HT receptor antagonists, and SSRIs in chronically prepared fetal sheep. Brief infusions of 5-HT (3-20 μg) increased PVR in a dose-related fashion. Ketanserin, a 5-HT 2A receptor antagonist, caused pulmonary vasodilation and inhibited 5-HT-induced pulmonary vasoconstriction. In contrast, intrapulmonary infusions of GR127945 and SB206553, 5-HT 1B and 5-HT 2B receptor antagonists, respectively, had no effect on basal PVR or 5-HT-induced vasoconstriction. Pretreatment with fasudil, a Rho kinase inhibitor, blunted the effects of 5-HT infusion. Brief infusions of the SSRIs, sertraline and fluoxetine, caused potent and sustained elevations of PVR, which was sustained for over 60 min after the infusion. SSRI-induced pulmonary vasoconstriction was reversed by infusion of ketanserin and did not affect the acute vasodilator effects of acetylcholine. We conclude that 5-HT causes pulmonary vasoconstriction, contributes to maintenance of high PVR in the normal fetus through stimulation of 5-HT 2A receptors and Rho kinase activation, and mediates the hypertensive effects of SSRIs. We speculate that prolonged exposure to SSRIs can induce PPHN through direct effects on the fetal pulmonary circulation.

Cinaciguat, a soluble guanylate cyclase activator, causes potent and sustained pulmonary vasodilation in the ovine fetus

Impaired nitric oxide-cGMP signaling contributes to severe pulmonary hypertension after birth, which may in part be due to decreased soluble guanylate cyclase (sGC) activity. Cinaciguat (BAY 58-2667) is a novel sGC activator that causes vasodilation, even in the presence of oxidized heme or heme-free sGC, but its hemodynamic effects have not been studied in the perinatal lung. We performed surgery on eight fetal (126 +/- 2 days gestation) lambs (full term = 147 days) and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic flow transducer was placed on the left pulmonary artery to measure blood flow, and a catheter was placed in the left pulmonary artery for drug infusion. Cinaciguat (0.1-100 microg over 10 min) caused dose-related increases in pulmonary blood flow greater than fourfold above baseline and reduced pulmonary vascular resistance by 80%. Treatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an sGC-oxidizing inhibitor, enhanced cinaciguat-induced pulmonary vasodilation by >120%. The pulmonary vasodilator effect of cinaciguat was prolonged, decreasing pulmonary vascular resistance for >1.5 h after brief infusion. In vitro stimulation of ovine fetal pulmonary artery smooth muscle cells with cinaciguat after ODQ treatment resulted in a 14-fold increase in cGMP compared with non-ODQ-treated cells. We conclude that cinaciguat causes potent and sustained fetal pulmonary vasodilation that is augmented in the presence of oxidized sGC and speculate that cinaciguat may have therapeutic potential for severe neonatal pulmonary hypertension.

Hypoxia-inducible factors HIF-1alpha and HIF-2alpha are decreased in an experimental model of severe respiratory distress syndrome in preterm lambs

Respiratory distress syndrome (RDS) secondary to preterm birth and surfactant deficiency is characterized by severe hypoxemia, lung injury, and impaired production of nitric oxide (NO) and vascular endothelial growth factor (VEGF). Since hypoxia-inducible factors (HIFs) mediate the effects of both NO and VEGF in part through regulation by prolyl-hydroxylase-containing domains (PHDs) in the presence of oxygen, we hypothesized that HIF-1alpha and -2alpha in the lung are decreased following severe RDS in preterm neonatal lambs. To test this hypothesis, fetal lambs were delivered at preterm gestation (115-day gestation, term = 145 days; n = 4) and mechanically ventilated for 4 h. Lambs developed respiratory failure characterized by severe hypoxemia despite treatment with mechanical ventilation with high inspired oxygen concentrations. Lung samples were compared with nonventilated control animals at preterm (115-day gestation; n = 3) and term gestation (142-day gestation; n = 3). We found that HIF-1alpha protein expression decreased (P < 0.05) and PHD-2 expression increased (P < 0.005) at birth in normal term animals before air breathing. Compared with age-matched controls, HIF-1alpha protein and HIF-2alpha protein expression decreased by 80% and 55%, respectively (P < 0.005 for each) in preterm lambs with RDS. Furthermore, VEGF mRNA was decreased by 40%, and PHD-2 protein expression doubled in RDS lambs. We conclude that pulmonary expression of HIF-1alpha, HIF-2alpha, and the downstream target of their regulation, VEGF mRNA, is impaired following RDS in neonatal lambs. We speculate that early disruption of HIF and VEGF expression after preterm birth and RDS may contribute to long-term abnormalities in lung growth, leading to bronchopulmonary dysplasia.

Rho kinase activation maintains high pulmonary vascular resistance in the ovine fetal lung

Mechanisms that maintain high pulmonary vascular resistance (PVR) in the fetal lung are poorly understood. Activation of the Rho kinase signal transduction pathway, which promotes actin-myosin interaction in vascular smooth muscle cells, is increased in the pulmonary circulation of adult animals with experimental pulmonary hypertension. However, the role of Rho kinase has not been studied in the fetal lung. We hypothesized that activation of Rho kinase contributes to elevated PVR in the fetus. To address this hypothesis, we studied the pulmonary hemodynamic effects of brief (10 min) intrapulmonary infusions of two specific Rho kinase inhibitors, Y-27632 (15-500 microg) and HA-1077 (500 microg), in chronically prepared late-gestation fetal lambs (n = 9). Y-27632 caused potent, dose-dependent pulmonary vasodilation, lowering PVR from 0.67 +/- 0.18 to 0.16 +/- 0.02 mmHg x ml(-1) x min(-1) (P < 0.01) at the highest dose tested without lowering systemic arterial pressure. Despite brief infusions, Y-27632-induced pulmonary vasodilation was sustained for 50 min. HA-1077 caused a similar fall in PVR, from 0.39 +/- 0.03 to 0.19 +/- 0.03 (P < 0.05). To study nitric oxide (NO)-Rho kinase interactions in the fetal lung, we tested the effect of Rho kinase inhibition on pulmonary vasoconstriction caused by inhibition of endogenous NO production with nitro-L-arginine (L-NA; 15-30 mg), a selective NO synthase antagonist. L-NA increased PVR by 127 +/- 73% above baseline under control conditions, but this vasoconstrictor response was completely prevented by treatment with Y-27632 (P < 0.05). We conclude that the Rho kinase signal transduction pathway maintains high PVR in the normal fetal lung and that activation of the Rho kinase pathway mediates pulmonary vasoconstriction after NO synthase inhibition. We speculate that Rho kinase plays an essential role in the normal fetal pulmonary circulation and that Rho kinase inhibitors may provide novel therapy for neonatal pulmonary hypertension.

Recombinant human VEGF treatment enhances alveolarization after hyperoxic lung injury in neonatal rats

VEGF signaling inhibition decreases alveolar and vessel growth in the developing lung, suggesting that impaired VEGF signaling may contribute to decreased lung growth in bronchopulmonary dysplasia (BPD). Whether VEGF treatment improves lung structure in experimental models of BPD is unknown. The objective was to determine whether VEGF treatment enhances alveolarization in infant rats after hyperoxia. Two-day-old Sprague-Dawley rats were placed into hyperoxia or room air (RA) for 12 days. At 14 days, rats received daily treatment with rhVEGF-165 or saline. On day 22, rats were killed. Tissue was collected. Morphometrics was assessed by radial alveolar counts (RAC), mean linear intercepts (MLI), and skeletonization. Compared with RA controls, hyperoxia decreased RAC (6.1 ± 0.4 vs. 11.3 ± 0.4, P < 0.0001), increased MLI (59.2 ± 1.8 vs. 44.0 ± 0.8, P < 0.0001), decreased nodal point density (447 ± 14 vs. 503 ± 12, P < 0.0004), and decreased vessel density (11.7 ± 0.3 vs. 18.9 ± 0.3, P < 0.001), which persisted despite RA recovery. Compared with hyperoxic controls, rhVEGF treatment after hyperoxia increased RAC (11.8 ± 0.5, P < 0.0001), decreased MLI (42.2 ± 1.2, P < 0.0001), increased nodal point density (502 ± 7, P < 0.0005), and increased vessel density (23.2 ± 0.4, P < 0.001). Exposure of neonatal rats to hyperoxia impairs alveolarization and vessel density, which persists despite RA recovery. rhVEGF treatment during recovery enhanced vessel growth and alveolarization. We speculate that lung structure abnormalities after hyperoxia may be partly due to impaired VEGF signaling.

Inhibition of 20-HETE abolishes the myogenic response during NOS antagonism in the ovine fetal pulmonary circulation

Mechanisms that maintain high pulmonary vascular resistance (PVR) and oppose vasodilation in the fetal lung are poorly understood. In fetal lambs, increased pulmonary artery pressure evokes a potent vasoconstriction, suggesting that a myogenic response contributes to high PVR in the fetus. In adult systemic circulations, the arachidonic acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) has been shown to modulate the myogenic response, but its role in the fetal lung is unknown. We hypothesized that acute increases in pulmonary artery pressure release 20-HETE, which causes vasoconstriction, or a myogenic response, in the fetal lung. To address this hypothesis, we studied the hemodynamic effects of N-methylsufonyl-12,12-dibromododec-11-enamide (DDMS), a specific inhibitor of 20-HETE production, on the pulmonary vasoconstriction caused by acute compression of the ductus arteriosus (DA) in chronically prepared fetal sheep. An inflatable vascular occluder around the DA was used to increase pulmonary artery pressure under three study conditions: control, after pretreatment with nitro-l-arginine (l-NA; to inhibit shear-stress vasodilation), and after combined treatment with both l-NA and a specific 20-HETE inhibitor, DDMS. We found that DA compression after l-NA treatment increased PVR by 44 ± 12%. Although intrapulmonary DDMS infusion did not affect basal PVR, DDMS completely abolished the vasoconstrictor response to DA compression in the presence of l-NA (44 ± 12% vs. 2 ± 4% change in PVR, l-NA vs. l-NA + DDMS, P < 0.05). We conclude that 20-HETE mediates the myogenic response in the fetal pulmonary circulation and speculate that pharmacological inhibition of 20-HETE might have a therapeutic role in neonatal conditions characterized by pulmonary hypertension.

Pulmonary vascular effects of nitric oxide-cGMP augmentation in a model of chronic pulmonary hypertension in fetal and neonatal sheep

Persistent pulmonary hypertension of the newborn (PPHN) is partly due to impaired nitric oxide (NO)-cGMP signaling. BAY 41-2272 is a novel direct activator of soluble guanylate cyclase, but whether this drug may be an effective therapy for PPHN is unknown. We hypothesized that BAY 41-2272 would cause pulmonary vasodilation in a model of severe PPHN. To test this hypothesis, we compared the hemodynamic response of BAY 41-2272 to acetylcholine, an endothelium-dependent vasodilator, and sildenafil, a selective inhibitor of PDE5 in chronically instrumented fetal lambs at 1 and 5 days after partial ligation of the ductus arteriosus. After 9 days, we delivered the animals by cesarean section to measure their hemodynamic responses to inhaled NO (iNO), sildenafil, and BAY 41-2272 alone or combined with iNO. BAY 41-2272 caused marked pulmonary vasodilation, as characterized by a twofold increase in blood flow and a nearly 60% fall in PVR at day 1. Effectiveness of BAY 41-2272-induced pulmonary vasodilation increased during the development of pulmonary hypertension. Despite a similar effect at day 1, the pulmonary vasodilator response to BAY 41-2272 was greater than sildenafil at day 5. At birth, BAY 41-2272 dramatically reduced PVR and augmented the pulmonary vasodilation induced by iNO. We concluded that BAY 41-2272 causes potent pulmonary vasodilation in fetal and neonatal sheep with severe pulmonary hypertension. We speculate that BAY 41-2272 may provide a novel treatment for severe PPHN, especially in newborns with partial response to iNO therapy.

rhVEGF treatment preserves pulmonary vascular reactivity and structure in an experimental model of pulmonary hypertension in fetal sheep

We have previously shown that lung VEGF expression is decreased in a fetal lamb model of PPHN and that VEGF165 inhibition causes severe pulmonary hypertension in fetal lambs. Therefore, we hypothesized that treatment with rhVEGF165 would preserve endothelium-dependent vasodilation and reduce the severity of pulmonary vascular remodeling in an experimental model of PPHN. We studied the effects of daily intrapulmonary infusions of rhVEGF after partial ligation of the ductus arteriosus (DA). We performed surgery in 24 late-gestation fetal lambs and placed catheters in the main pulmonary artery, left atrium, and aorta for pressure measurements and in the left pulmonary artery for drug infusions. A pressure transducer was placed around the LPA to measure blood flow to the left lung (Qp), and the DA was surgically constricted to induce pulmonary hypertension. rhVEGF165 or vehicle was infused for 7 or 14 days. ACh or 8-BrcGMP was infused on days 2 and 13 to assess endothelium-dependent and -independent vasodilation, respectively. ACh-induced vasodilation was reduced in PPHN lambs after 14 days (change in Qp from baseline, 106% vs. 11%). In contrast, the response to ACh was preserved in lambs treated with rhVEGF (change in Qp, 94% vs. 90%). Pulmonary vasodilation to 8-BrcGMP was not altered in PPHN lambs or enhanced by VEGF treatment. rhVEGF treatment increased expression of lung eNOS protein and decreased pulmonary artery wall thickness by 34% vs. PPHN lambs. We conclude that VEGF165 preserves endothelium-dependent vasodilation, upregulates eNOS expression, and reduces the severity of pulmonary vascular remodeling in experimental PPHN.

Effects of BAY 41-2272, a soluble guanylate cyclase activator, on pulmonary vascular reactivity in the ovine fetus

Nitric oxide (NO)-cGMP signaling plays a critical role during the transition of the pulmonary circulation at birth. BAY 41-2272 is a novel NO-independent direct stimulator of soluble guanylate cyclase that causes vasodilation in systemic and local circulations. However, the hemodynamic effects of BAY 41-2272 have not been studied in the perinatal pulmonary circulation. We hypothesized that BAY 41-2272 causes potent and sustained fetal pulmonary vasodilation. We performed surgery on 14 fetal lambs (125-130 days gestation; term = 147 days) and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic flow transducer was placed on the left pulmonary artery (LPA) to measure blood flow, and a catheter was placed in the LPA for drug infusion. Pulmonary vascular resistance (PVR) was calculated as pulmonary artery pressure minus left atrial pressure divided by LPA blood flow. BAY 41-2272 caused dose-related increases in pulmonary blood flow up to threefold above baseline and reduced PVR by 75% (P < 0.01). Prolonged infusion of BAY 41-2272 caused sustained pulmonary vasodilation throughout the 120-min infusion period. The pulmonary vasodilator effect of BAY 41-2272 was not attenuated by N(omega)-nitro-l-arginine, a NO synthase inhibitor. In addition, compared with sildenafil, a phosphodiesterase 5 inhibitor, the pulmonary vasodilator response to BAY 41-2272 was more prolonged. We conclude that BAY 41-2272 causes potent and sustained fetal pulmonary vasodilation independent of NO release. We speculate that BAY 41-2272 may have therapeutic potential for pulmonary hypertension associated with failure to circulatory adaptation at birth, especially in the setting of impaired NO production.

Pulmonary hypertension impairs alveolarization and reduces lung growth in the ovine fetus

Persistent pulmonary hypertension of the newborn (PPHN) is a clinical disorder characterized by abnormal vascular structure, growth, and reactivity. Disruption of vascular growth during early postnatal lung development impairs alveolarization, and newborns with lung hypoplasia often have severe pulmonary hypertension. To determine whether pulmonary hypertension can directly impair vascular growth and alveolarization in the fetus, we studied the effects of chronic intrauterine pulmonary hypertension on lung growth in fetal lambs. We performed surgery, which included partial constriction of the ductus arteriosus (DA) to induce pulmonary hypertension (PH, n = 14) or sham surgery (controls, n = 13) in fetal lambs at 112-125 days (term = 147 days). Tissues were harvested near term for measurement of right ventricular hypertrophy (RVH), radial alveolar counts (RAC), mean linear intercepts (MLI), wall thickness, and vessel density of small pulmonary arteries. Chronic DA constriction caused RVH (P < 0.0001), increased wall thickness of small pulmonary arteries (P < 0.002), and reduced small pulmonary artery density (P < 0.005). PH also reduced alveolarization, causing a 27% reduction in RAC and 20% increase in MLI. Furthermore, prolonged DA constriction (21 days) not only decreased RAC and increased MLI by 30% but also caused a 25% reduction of lung-body weight ratio. We conclude that chronic PH reduces pulmonary arterial growth, decreases alveolar complexity, and impairs lung growth. We speculate that chronic hypertension impairs vascular growth, which disrupts critical signaling pathways regulating lung vascular and alveolar development, thereby interfering with alveolarization and ultimately resulting in lung hypoplasia.

Role of platelet-derived growth factor in vascular remodeling during pulmonary hypertension in the ovine fetus

Platelet-derived growth factor (PDGF) is a potent smooth muscle cell mitogen that may contribute to smooth muscle hyperplasia during the development of chronic pulmonary hypertension (PH). We studied changes in PDGFalpha- and beta-receptor and ligand expression in lambs with chronic intrauterine PH induced by partial ligation of the ductus arteriosus (DA) at gestational age 124-128 days (term = 147 days). Western blot analysis performed on whole lung homogenates from PH animals after 8 days of DA ligation showed a twofold increase in PDGFalpha- and beta-receptor proteins compared with age-matched controls (P < 0.05). Lung PDGF-A and -B mRNA expression did not differ between PH and control animals. We treated PH animals with NX1975, an aptamer that selectively inhibits PDGF-B, by infusion into the left pulmonary artery for 7 days after DA ligation. NX1975 reduced the development of muscular thickening of small pulmonary arteries by 47% (P < 0.05) and right ventricular hypertrophy (RVH) by 66% (P < 0.02). Lung PDGFalpha- and beta-receptor expression is increased in perinatal PH, and NX1975 reduces the increase in wall thickness of small pulmonary arteries and RVH in this model. We speculate that PDGF signaling contributes to structural vascular remodeling in perinatal PH and that selective PDGF inhibition may provide a novel therapeutic strategy for the treatment of chronic PH.

Intrauterine hypertension decreases lung VEGF expression and VEGF inhibition causes pulmonary hypertension in the ovine fetus

Although vascular endothelial growth factor (VEGF) plays a vital role in lung vascular growth in the embryo, its role in maintaining endothelial function and modulating vascular structure during late fetal life has not been studied. We hypothesized that impaired lung VEGF signaling causes pulmonary hypertension, endothelial dysfunction, and structural remodeling before birth. To determine whether lung VEGF expression is decreased in an experimental model of persistent pulmonary hypertension of the newborn (PPHN), we measured lung VEGF and VEGF receptor protein content from fetal lambs 7-10 days after ductus arteriosus ligation (132-140 days gestation; term = 147 days). In contrast with the surge in lung VEGF expression during late gestation in controls, chronic intrauterine pulmonary hypertension reduced lung VEGF expression by 78%. To determine whether VEGF inhibition during late gestation causes pulmonary hypertension, we treated fetal lambs with EYE001, an aptamer that specifically inhibits VEGF(165). Compared with vehicle controls, EYE001 treatment elevated pulmonary artery pressure and pulmonary vascular resistance by 22 and 50%, respectively, caused right ventricular hypertrophy, and increased wall thickness of small pulmonary arteries. EYE001 treatment reduced lung endothelial nitric oxide synthase protein content by 50% and preferentially impaired the pulmonary vasodilator response to ACh, an endothelium-dependent agent. We conclude that chronic intrauterine pulmonary hypertension markedly decreases lung VEGF expression and that selective inhibition of VEGF(165) mimics the structural and physiological changes of experimental PPHN. We speculate that hypertension downregulates VEGF expression in the developing lung and that impaired VEGF signaling may contribute to the pathogenesis of PPHN.

Vascular endothelial growth factor causes pulmonary vasodilation through activation of the phosphatidylinositol-3-kinase-nitric oxide pathway in the late-gestation ovine fetus

Vascular endothelial growth factor (VEGF) causes vasodilation in adult models of peripheral vascular disease and myocardial ischemia through the acute release of nitric oxide (NO). However, the hemodynamic effects of VEGF and its effects on NO production have not been studied in the developing lung circulation. We hypothesized that VEGF causes fetal pulmonary vasodilation, and that its actions are mediated through the release of endogenous NO. We performed surgery in 16 fetal lambs (125-135 d gestation; term = 147 d), and placed catheters in the main pulmonary artery, aorta, and left atrium to measure pressures. An ultrasonic flow transducer was placed on the left pulmonary artery (LPA) to measure blood flow, and a catheter was placed in the LPA for local drug infusion. Pulmonary vascular resistance in the left lung was calculated as pulmonary artery pressure minus left atrial pressure divided by LPA flow. Fetal lambs were treated with brief infusions of recombinant human VEGF (dose, 0.5-2.0 micro g) into the LPA. Recombinant human VEGF infusions acutely increased LPA flow by up to 3-fold (p < 0.02) and decreased pulmonary vascular resistance by 65% (p < 0.05) in a dose-related fashion, without affecting aortic pressure or heart rate. To determine the mechanism of VEGF-induced vasodilation, we studied the effects of nitro-L-arginine, an NO synthase inhibitor, and LY294002, a phosphatidylinositol-3-kinase inhibitor, on the response to VEGF. We found that pretreatment with either nitro-L-arginine or LY294002 completely inhibited the vasodilator response to recombinant human VEGF (p < 0.005). These findings suggest that recombinant human VEGF causes fetal pulmonary vasodilation, and that this response is likely mediated by the release of NO through activation of phosphatidylinositol-3-kinase.

Case report: infantile hemangioendothelioma

During a routine physical exam, an 18-day-old male infant was noted to have persistent abdominal distention and prominent vascular markings over his abdominal wall. Laboratory studies were significant for an elevated alpha-fetoprotein level of 7051 ng/ml and mild anemia. Abdominal ultrasound and CT scan demonstrated a large, heterogeneous mass in the lateral segment of the left lobe of the liver. Although the patient did not have congestive heart failure or coagulopathy, surgical resection was performed to rule out malignancy. Histopathologic examination revealed a type I infantile hemangioendothelioma. This case report reviews the presentation and treatment of infantile hemangioendotheliomas and the differential diagnosis of neonatal hepatic neoplasms.

NO and prostaglandin interactions during hemodynamic stress in the fetal ovine pulmonary circulation

Nitric oxide (NO) and prostacyclin (PGI(2)) are potent fetal pulmonary vasodilators, but their relative roles and interactions in the regulation of the perinatal pulmonary circulation are poorly understood. We compared the separate and combined effects of nitric oxide synthase (NOS) and cyclooxygenase (COX) inhibition during acute hemodynamic stress caused by brief mechanical compression of the ductus arteriosus (DA) in chronically prepared fetal lambs. Nitro-L-arginine (L-NNA; NOS antagonist), meclofenamate (Mec; COX inhibitor), combined drugs (L-NNA-Mec), or saline (control) was infused into the left pulmonary artery (LPA) before DA compression. In controls, DA compression decreased pulmonary vascular resistance (PVR) by 43% (P < 0.01). L-NNA, but not Mec, treatment completely blocked vasodilation and caused a paradoxical increase in PVR (+31%; P < 0.05). The effects of L-NNA-Mec and L-NNA on PVR were similar. To determine if the vasodilator effect of PGI(2) is partly mediated by NO release, we studied PGI(2)-induced vasodilation before and after NOS inhibition. L-NNA treatment blocked the PGI(2)-induced rise in LPA blood flow by 73% (P < 0.001). We conclude that NO has a greater role than PGs in fetal pulmonary vasoregulation during acute hemodynamic stress and that PGI(2)-induced pulmonary vasodilation is largely mediated by NO release in the fetal lung.

Effects of chronic estrogen-receptor blockade on ovine perinatal pulmonary circulation

Prolonged infusions of 17beta-estradiol reduce fetal pulmonary vascular resistance (PVR), but the effects of endogenous estrogens in the fetal pulmonary circulation are unknown. To test the hypothesis that endogenous estrogen promotes pulmonary vasodilation at birth, we studied the hemodynamic effects of prolonged estrogen-receptor blockade during late gestation and at birth in fetal lambs. We treated chronically prepared fetal lambs with ICI-182,780 (ICI, a specific estrogen-receptor blocker, n = 5) or 1% DMSO (CTRL, n = 5) for 7 days and then measured pulmonary hemodynamic responses to ventilation with low- and high-fraction inspired oxygen (FI(O(2))). Treatment with ICI did not change basal fetal PVR or arterial blood gas tensions. However, treatment with ICI abolished the vasodilator response to ventilation with low FI(O(2)) [change in PVR -30 +/- 6% (CTRL) vs. +10 +/- 13%, (ICI), P < 0.05] without reducing the vasodilator response to ventilation with high FI(O(2)) [change in PVR, -73 +/- 3% (CTRL) vs. -77 +/- 4%, (ICI); P = not significant]. ICI treatment reduced prostacyclin synthase (PGIS) expression by 33% (P < 0.05) without altering expression of endothelial nitric oxide synthase or cyclooxygenase-1 and -2. In situ hybridization and immunohistochemistry revealed that PGIS is predominantly expressed in the airway epithelium of late gestation fetal lambs. We conclude that prolonged estrogen-receptor blockade inhibits the pulmonary vasodilator response at birth and that this effect may be mediated by downregulation of PGIS. We speculate that estrogen exposure during late gestation prepares the pulmonary circulation for postnatal adaptation.

Repetitive prenatal glucocorticoids increase lung endothelial nitric oxide synthase expression in ovine fetuses delivered at term

Antenatal administration of glucocorticoids has been shown to improve postnatal lung function after preterm birth in the ovine fetus. Mechanisms of steroid-induced lung maturation include increased surfactant production and altered parenchymal lung structure. Whether steroid treatment also affects lung vascular function is unclear. Because nitric oxide contributes to the fall in pulmonary vascular resistance at birth, we hypothesized that the improvement of postnatal lung function of preterm lambs after treatment with prenatal glucocorticoids may be in part caused by an increase in endothelial nitric oxide synthase (eNOS) activity. To determine whether glucocorticoid treatment increases lung eNOS expression, we measured eNOS protein content by Western blot analysis of distal lung homogenates and immunostaining of formalin-fixed lungs from ovine fetuses delivered at preterm and term gestation after prenatal administration of glucocorticoids. Treatment protocols were followed in which ewes were treated with intramuscular betamethasone (0.5 mg/kg) at single or multiple doses at weekly intervals, and fetuses were delivered at 125, 135, or 145 d gestation. All groups were compared with saline-treated controls. Western blot analysis of whole lung homogenates demonstrated a 4-fold increase in eNOS protein content in lambs treated with repetitive doses of glucocorticoids and delivery at term (145 d; p < 0.002). In addition, a small increase in lung eNOS protein content was seen in lambs treated with a single dose of betamethasone at 128 d gestation with delivery at 135 d gestation. In comparison with control animals, there were no differences in lung eNOS content from the remaining lambs treated with glucocorticoids when delivery occurred at preterm ages (125 and 135 d). Immunostaining showed eNOS predominantly in the vascular endothelium in all vessel sizes. Pattern of staining was not altered by treatment with antenatal glucocorticoids. We conclude that maternal treatment with glucocorticoids increases lung eNOS content after multiple doses and delivery at term gestation. We speculate that antenatal glucocorticoids may up-regulate eNOS but that the timing and duration of steroid administration appears to be critical to this response.

Inhaled carbon monoxide does not cause pulmonary vasodilation in the late-gestation fetal lamb

As observed with nitric oxide (NO), carbon monoxide (CO) binds and may activate soluble guanylate cyclase and increase cGMP levels in smooth muscle cells in vitro. Because inhaled NO (I(NO)) causes potent and sustained pulmonary vasodilation, we hypothesized that inhaled CO (I(CO)) may have similar effects on the perinatal lung. To determine whether I(CO) can lower pulmonary vascular resistance (PVR) during the perinatal period, we studied the effects of I(CO) on late-gestation fetal lambs. Catheters were placed in the main pulmonary artery, left pulmonary artery (LPA), aorta, and left atrium to measure pressure. An ultrasonic flow transducer was placed on the LPA to measure blood flow to the left lung. After baseline measurements, fetal lambs were mechanically ventilated with a hypoxic gas mixture (inspired O(2) fraction < 0.10) to maintain a constant fetal arterial PO(2). After 60 min (baseline), the lambs were treated with I(CO) [5-2,500 parts/million (ppm)]. Comparisons were made with I(NO) (5 and 20 ppm) and combined I(NO) (5 ppm) and I(CO) (100 and 2,500 ppm). We found that I(CO) did not alter left lung blood flow or PVR at any of the study doses. In contrast, low-dose I(NO) decreased PVR by 47% (P < 0.005). The combination of I(NO) and I(CO) did not enhance the vasodilator response to I(NO). To determine whether endogenous CO contributes to vascular tone in the fetal lung, zinc protoporphyrin IX, an inhibitor of heme oxygenase, was infused into the LPA in three lambs. Zinc protoporphyrin IX had no effect on baseline PVR, aortic pressure, or the pressure gradient across the ductus arteriosus. We conclude that I(CO) does not cause vasodilation in the near-term ovine transitional circulation, and endogenous CO does not contribute significantly to baseline pulmonary vascular tone or ductus arteriosus tone in the late-gestation ovine fetus.

Estradiol improves pulmonary hemodynamics and vascular remodeling in perinatal pulmonary hypertension

Partial ligation of the ductus arteriosus (DA) in the fetal lamb causes sustained elevation of pulmonary vascular resistance (PVR) and hypertensive structural changes in small pulmonary arteries, providing an animal model for persistent pulmonary hypertension of the newborn. Based on its vasodilator and antimitogenic properties in other experimental studies, we hypothesized that estradiol (E(2)) would attenuate the pulmonary vascular structural and hemodynamic changes caused by pulmonary hypertension in utero. To test our hypothesis, we treated chronically instrumented fetal lambs (128 days, term = 147 days) with daily infusions of E(2) (10 microg; E(2) group, n = 6) or saline (control group, n = 5) after partial ligation of the DA. We measured intrauterine pulmonary and systemic artery pressures in both groups throughout the study period. After 8 days, we delivered the study animals by cesarean section to measure their hemodynamic responses to birth-related stimuli. Although pulmonary and systemic arterial pressures were not different in utero, fetal PVR immediately before ventilation was reduced in the E(2)-treated group (2.43 +/- 0.79 vs. 1.48 +/- 0.26 mmHg. ml(-1). min, control vs. E(2), P < 0.05). During the subsequent delivery study, PVR was lower in the E(2)-treated group in response to ventilation with hypoxic gas but was not different between groups with ventilation with 100% O(2). During mechanical ventilation after delivery, arterial partial O(2) pressure was higher in E(2) animals than controls (41 +/- 11 vs. 80 +/- 35 Torr, control vs. E(2), P < 0. 05). Morphometric studies of hypertensive vascular changes revealed that E(2) treatment decreased wall thickness of small pulmonary arteries (59 +/- 1 vs. 48 +/- 1%, control vs. E(2), P < 0.01). We conclude that chronic E(2) treatment in utero attenuates the pulmonary hemodynamic and histological changes caused by DA ligation in fetal lambs.