Vasopressin as a rescue therapy for refractory pulmonary hypertension in neonates: case series

The effect of heart rate on systolic and diastolic time intervals and cardiac function in stable and sick preterm infants

BACKGROUND

Diastolic function includes relaxation and filling of the heart and is dependent on heart rate (HR) and time spent in either systole (St) or diastole (Dt). The St/Dt ratio increases as HR increased and is a marker of overall cardiac function in children with heart failure. The aim of this study is to describe cardiac cycle events in preterm infants.

METHODS

Cardiac ultrasounds of preterm infants <32 weeks were retrospectively reviewed for cardiac cycle events from Tissue Doppler images and grouped by clinical indication of the scan as stable or as clinical deterioration with significant illness.

RESULTS

412 scans in 201 preterm infants were analyzed. St/Dt ratio increased with increasing HR. St increased from 50 to 54 % of the cardiac cycle length with shortened diastolic duration. Isovolumetric contraction and relaxation remained unchanged at 9 and 12 % of the cardiac cycle respectively. Mean St, Dt and St/Dt ratio in stable infants were 195(19) msec, Dt 175(24) msec and 1.13 (0.16) respectively. Sick infants without cardiovascular medications showed a significantly shorter St and lower St/Dt ratio. Cardiovascular medications increased isovolumetric times, Dt, and early diastolic duration.

CONCLUSION

Reference values for cardiac cycle durations and St/Dt ratio are presented. Preterm hearts adapt to higher HR by shifting towards systole and shortened early diastole by optimising its force frequency relationship and enhanced relaxation. The St/Dt ratio was altered in preterm infants with significant illness. This simple ultrasound marker could be tested in further studies that investigate cardiovascular medications in preterm infants.

Cardiorespiratory interactions during the transitional period in extremely preterm infants: a narrative review

We aimed to review the physiology and evidence behind cardiorespiratory interactions during the transitional circulation of extremely preterm infants with fragile physiology and to propose a framework for future research. Cord clamping strategies have a great impact on initial haemodynamic changes, and appropriate transition can be facilitated by establishing spontaneous ventilation before cord clamping. Mechanical ventilation modifies preterm transitional haemodynamics, with positive pressure ventilation affecting the right and left heart loading conditions. Pulmonary vascular resistances can be minimized by ventilating with optimal lung volumes at functional residual capacity, and other pulmonary vasodilator treatments such as inhaled nitric oxide can be used to improve ventilation/perfusion mismatch. Different cardiovascular drugs can be used to provide support during transition in this population, and it is important to understand both their cardiovascular and respiratory effects, in order to provide adequate support to vulnerable preterm infants and improve outcomes. Current available non-invasive bedside tools, such as near-infrared spectroscopy, targeted neonatal echocardiography, or lung ultrasound offer the opportunity to precisely monitor cardiorespiratory interactions in preterm infants. More research is needed in this field using precision medicine to strengthen the benefits and avoid the harms associated to early neonatal interventions. IMPACT: In extremely preterm infants, haemodynamic and respiratory transitions are deeply interconnected, and their changes have a key impact in the establishment of lung aireation and postnatal circulation. We describe how mechanical ventilation modifies heart loading conditions and pulmonary vascular resistances in preterm patients, and how hemodynamic interventions such as cord clamping strategies or cardiovascular drugs affect the infant respiratory status. Current available non-invasive bedside tools can help monitor cardiorespiratory interactions in preterm infants. We highlight the areas of research in which precision medicine can help strengthen the benefits and avoid the harms associated to early neonatal interventions.

Vasopressin as adjunctive therapy in pulmonary hypertension associated with refractory systemic hypotension in term newborns

OBJECTIVE

The use of vasopressin as an adjunctive therapy in pulmonary hypertension associated with refractory systemic hypotension has increased. The objective of our study is to describe its effects on term infants.

STUDY DESIGN

Retrospective observational study. Setting in a referral level IV neonatal intensive care unit from a middle-income region. The patients are term neonates admitted to our NICU who required vasopressin due to severe Pulmonary Hypertension and refractory hypotension during a 49-month period (December 2019 and December 2023).

RESULTS

We identified 68 term infants, all in mechanical ventilation, receiving inhaled nitric oxide (iNO), and a phased protocol management for hypotension. Vasopressin was a started at a mean of 2 days with a mean duration of 80 h. Regarding hemodynamic outcome: diastolic, systolic, and median systemic pressure significantly increased during the first 4 h of treatment, as well as arterial pH and urine output. Accordingly, lactate and Vasoactive Inotropic Score (VIS) score decreased after 4 and 8 h, respectively, after vasopressin was started. Regarding oxygenation markers: oxygen requirements and mean airway pressure decreased significantly (and therefore the oxygenation index decreased in concordance) after 4 h of vasopressin. Echocardiographic indices of pulmonary hypertension progressively improved after vasopressin infusion with a significant decrease of tricuspid ingurgitation velocities and the rate of right-to- left ductal shunt through the ductus arteriosus. In the same way, left and right ventricular output increased after the initiation of vasopressin.

CONCLUSION

This study showed that the use of vasopressin in neonates with persistent pulmonary hypertension was associated with a rapid and significant improvement in oxygenation and hemodynamic markers of perfusion, including blood pressure. Its effects begin early during the first hours of treatment.

Meconium Aspiration Syndrome, Hypoxic-Ischemic Encephalopathy and Therapeutic Hypothermia-A Recipe for Severe Pulmonary Hypertension?

Hypoxic-ischemic encephalopathy (HIE) is the leading cause of mortality among term newborns globally. Infants born through meconium-stained amniotic fluid are at risk of developing meconium aspiration syndrome (MAS) and HIE. Simultaneous occurrence of MAS and HIE is a perilous combination for newborns due to the risk of persistent pulmonary hypertension of the newborn (PPHN). Moreover, therapeutic hypothermia (TH), which is the current standard of care for the management of HIE, may increase pulmonary vascular resistance (PVR) and worsen PPHN. Infants with MAS and HIE require close cardiorespiratory and hemodynamic monitoring for PPHN. Therapeutic strategies, including oxygen supplementation, ventilation, use of surfactant, inhaled nitric oxide and other pulmonary vasodilators, and systemic vasopressors, play a critical role in the management of PPHN in MAS, HIE, and TH. While TH reduces death or disability in infants with HIE, infants with MAS and HIE undergoing TH need close hemodynamic monitoring for PPHN.

Comparative efficacy of volume expansion, inotropes and vasopressors in preterm neonates with probable transitional circulatory instability in the first week of life: a systematic review and network meta-analysis

BACKGROUND

There exists limited agreement on the recommendations for the treatment of transitional circulatory instability (TCI) in preterm neonates OBJECTIVE: To compare the efficacy of various interventions used to treat TCI METHODS: Medline and Embase were searched from inception to 21st July 2023. Two authors extracted the data independently. A Bayesian random effects network meta-analysis was used. Recommendations were formulated using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) framework.

INTERVENTIONS

Dopamine, dobutamine, epinephrine, hydrocortisone, vasopressin, milrinone, volume and placebo.

MAIN OUTCOME MEASURES

Mortality, major brain injury (MBI) (intraventricular haemorrhage > grade 2 or cystic periventricular leukomalacia), necrotising enterocolitis (NEC) ≥stage 2 and treatment response (as defined by the author).

RESULTS

15 Randomized Controlled Trials (RCTs) were included from the 1365 titles and abstracts screened. Clinical benefit or harm could not be ruled out for the critical outcome of mortality. For the outcome of MBI, epinephrine possibly decreased the risk when compared to dobutamine and milrinone (very low certainty). Epinephrine was possibly associated with a lesser risk of NEC when compared with dopamine, dobutamine, hydrocortisone and milrinone (very low certainty). Dopamine was possibly associated with a lesser risk of NEC when compared with dobutamine (very low certainty). Vasopressin possibly decreased the risk of NEC compared with dopamine, dobutamine, hydrocortisone and milrinone (very low certainty). Clinical benefit or harm could not be ruled out for the outcome response to treatment.

CONCLUSIONS

Epinephrine may be used as the first-line drug in preterm neonates with TCI, the evidence certainty being very low. We suggest future trials evaluating the management of TCI with an emphasis on objective criteria to define it.

Use of Vasopressin as Rescue Therapy in Refractory Hypoxia and Refractory Systemic Hypotension in Term Neonates with Severe Persistent Pulmonary Hypertension-A Prospective Observational Study

OBJECTIVE

Persistent pulmonary hypertension of the newborn (PPHN) is a serious cardiorespiratory problem. PPHN is frequently associated with refractory hypoxia and hypotension, and optimal management has the potential to improve important clinical outcomes including mortality. The primary objective is to evaluate the efficacy and safety of rescue vasopressin (VP) therapy in the management of severe (refractory) hypoxia and refractory systemic hypotension in term neonates with severe PPHN.

STUDY DESIGN

Neonates with refractory hypoxia and refractory hypotension due to severe PPHN needing VP were prospectively enrolled in the study. Refractory hypoxia was defined as oxygenation index (OI) ≥ 25 for at least 4 hours after the commencement of high-frequency oscillatory ventilation and nitric oxide at 20 ppm. Refractory hypotension was defined as mean blood pressure lesser than mean gestational age lasting for more than 15 minutes in spite of dopamine infusion at 10 µg/kg/min, adrenaline infusion at 0.3 µg/kg/min, and noradrenaline infusion at 0.1 µg/kg/min.

RESULTS

Thirty-two neonates with PPHN were recruited. The baseline OI (mean ± standard deviation [SD]) before starting VP was 33.43 ± 16.54 which started decreasing significantly between 1 and 6 hours after the commencement of VP (p < 0.05). The mean blood pressure also increased concomitantly with a significant effect seen by 1 hour (p < 0.05). The vasoactive infusion score before the commencement of VP was mean 46.07 (SD = 25.72) and started decreasing after 12 to 24 hours of commencement of VP (p < 0.05). Lactate levels (mean ± SD) before starting VP were 7.8 ± 8.6 mmol/L and started decreasing between 6 and 12 hours (p < 0.05). Two neonates died due to refractory hypoxia and refractory hypotension (overall mortality 6.2%) CONCLUSION:  Rescue VP therapy is a useful adjunct in the management of neonates with severe PPHN with refractory hypoxia and/or refractory hypotension. Improvement in oxygenation and hemodynamics with the use of VP results in reduced mortality.

KEY POINTS

· Rescue vasopressin is a useful adjunct in the management of neonates with severe PPHN.. · Vasopressin helps reduce OI.. · Vasopressin reduces the vasoactive inotrope score..

Vasopressin in newborns with refractory acute pulmonary hypertension

BACKGROUND

Acute pulmonary hypertension (aPH) in newborns can be life threatening and challenging to manage. In newborns with refractory aPH, there is currently limited therapeutic agents.

METHODS

Retrospective single-center cohort study in newborns less than one month old who were treated with vasopressin for a minimum of one hour in the context of refractory aPH in the neonatal and pediatric intensive care units of a tertiary university center between 2016 and 2022. The objective was to evaluate the efficacy and safety of vasopressin in newborns as an adjuvant treatment for refractory aPH.

RESULTS

Twenty-five patients met inclusion criteria. In patients who received vasopressin, oxygenation index improved from 28.4 to 14.4 (p = 0.004) after twelve hours of continuous infusion. Oxygen requirements (FiO2) decreased from 0.91 to 0.50 (p = 0.004) and mean arterial pressure increased from 41 to 51 mmHg (p = 0.001). In our cohort, 68% of patients presented an episode of hyponatremia (serum sodium <130 mmol/L).

CONCLUSIONS

The use of vasopressin may be associated with improvement in oxygenation and hemodynamic status of neonatal patients with aPH refractory to initial therapy. Further prospective studies are needed to establish the safety profile of vasopressin in newborns, particularly in preterm infants.

IMPACT

Vasopressin may be an effective cardiotropic agent to improve oxygenation and hemodynamic status in newborns with acute pulmonary hypertension. Careful monitoring of serum sodium levels are warranted in newborns who are receiving vasopressin infusion. This provides additional evidence for the consideration of vasopressin in newborns with acute pulmonary hypertension refractory to inhaled nitric oxide.

Targeted Neonatal Echocardiography in the Management of Neonatal Pulmonary Hypertension

Pulmonary hypertension (PH) in neonates, originating from a range of disease states with heterogeneous underlying pathophysiology, is associated with significant morbidity and mortality. Although the final common pathway is a state of high right ventricular afterload leading to compromised cardiac output, multiple hemodynamic phenotypes exist in acute and chronic PH, for which cardiorespiratory treatment strategies differ. Comprehensive appraisal of pulmonary pressure, pulmonary vascular resistance, cardiac function, pulmonary and systemic blood flow, and extrapulmonary shunts facilitates delivery of individualized cardiovascular therapies in affected newborns.

The impact of a care bundle with an emphasis on hemodynamic assessment on the short-term outcomes in neonates with congenital diaphragmatic hernia

OBJECTIVE

To evaluate the short-term outcomes of implementing a care bundle emphasizing frequent hemodynamic assessments by echocardiography in neonates with congenital diaphragmatic hernia (CDH).

STUDY DESIGN

This was a retrospective cohort study of infants with CDH admitted to a quaternary perinatal unit from January 2013 to March 2021. The primary composite outcome was defined as mortality or use of extracorporeal membrane oxygenation or need for respiratory support at discharge.

RESULTS

We identified 37 and 20 CDH infants in Epoch I and II, respectively. More patch repairs (50% vs. 21.9%, p = 0.035) and echocardiograms (6[4-8] vs. 1[0-5], p = 0.003) were performed in Epoch II. While there were no differences in the primary outcome, there was a reduction in mortality in Epoch II (0% vs. 27%, p = 0.01).

CONCLUSION

With the implementation of a CDH care bundle with an emphasis on hemodynamic assessment, we demonstrated a significant reduction in mortality.

Early Pulmonary Hypertension in Preterm Infants

Pulmonary hypertension (PH) in preterm neonates has multifactorial pathogenesis with unique characteristics. Premature surfactant-deficient lungs are injured following exposure to positive pressure ventilation and high oxygen concentrations resulting in variable phenotypes of PH. The prevalence of early PH is variable and reported to be between 8% and 55% of extremely preterm infants. Disruption of the lung development and vascular signaling pathway could lead to abnormal pulmonary vascular transition. The management of early PH and the off-label use of selective pulmonary vasodilators continue to be controversial.

Haemodynamic assessment and management of hypotension in the preterm

The management of low blood flow states in premature neonates is fraught with many challenges. We remain over-reliant on regimented stepwise protocols that use mean blood pressure as a threshold for intervention to guide treatment, without giving due consideration to the underlying pathophysiology. The current available evidence does not reflect the need to concentrate on the unique pathophysiology of the preterm infant and thus leads to widespread misuse of vasoactive agents that often do not provide the desired clinical effect. Therefore, understanding the underlying pathophysiological underpinnings of haemodynamic compromise may better guide choice of agent and assess physiological response to the selected intervention.

Meconium aspiration syndrome: a comprehensive review

Meconium aspiration syndrome (MAS) is a complex respiratory disease that continues to be associated with significant morbidities and mortality. The pathophysiological mechanisms of MAS include airway obstruction, local and systemic inflammation, surfactant inactivation and persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen and non-invasive respiratory support are the main therapies for many patients. The management of the patients requiring invasive mechanical ventilation could be challenging because of the combination of atelectasis and air trapping. While studies have explored various ventilatory modalities, evidence to date does not clearly support any singular modality as superior. Patient's pathophysiology, symptom severity, and clinician/unit expertise should guide the respiratory management. Early identification and concomitant management of PPHN is critically important as it contributes significantly to mortality and morbidities.

Evidence-Based Guidelines for Acute Stabilization and Management of Neonates with Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of the newborn, or PPHN, represents a challenging condition associated with high morbidity and mortality. Management is complicated by complex pathophysiology and limited neonatal specific evidence-based literature, leading to a lack of universal contemporary clinical guidelines for the care of these patients. To address this need and to provide consistent high-quality clinical care for this challenging population in our neonatal intensive care unit, we sought to develop a comprehensive clinical guideline for the acute stabilization and management of neonates with PPHN. Utilizing cross-disciplinary expertise and incorporating an extensive literature search to guide best practice, we present an approachable, pragmatic, and clinically relevant guide for the bedside management of acute PPHN. KEY POINTS: · PPHN is associated with several unique diagnoses; the associated pathophysiology is different for each unique diagnosis.. · PPHN is a challenging, dynamic, and labile process for which optimal care requires frequent reassessment.. · Key management goals are adequate tissue oxygen delivery, avoiding harm..

Early vasopressin infusion improves oxygenation in infants with congenital diaphragmatic hernia

Objective

Congenital Diaphragmatic Hernia (CDH) is a complex disease including a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension. Despite its increasing use in neonates, the literature on the use of vasopressin in neonates is limited. The aim of this work is to analyze the changes in clinical and hemodynamic variables in a cohort of CDH infants treated with vasopressin.

Methods

Among CDH infants managed at the Neonatal Intensive Care Unit (NICU) of our hospital from May 2014 to January 2019, all infants who were treated with vasopressin, because of systemic hypotension and pulmonary hypertension, were enrolled in this retrospective study. The primary outcome was the change in oxygenation index (OI) after the start of the infusion of vasopressin. The secondary outcomes were the changes in cerebral and splanchnic fractional tissue oxygen extraction (FTOEc and FTOEs) at near-infrared spectroscopy, to understand the balance between oxygen supply and tissue oxygen consumption after the start of vasopressin infusion. We also reported as secondary outcomes the changes in ratio of arterial oxygen partial pressure (PaO2) to fraction of inspired oxygen (FiO2), heart rate, mean arterial pressure, serum pH, and serum sodium.

Results

We included 27 patients with isolated CDH who received vasopressin administration. OI dramatically dropped when vasopressin infusion started, with a significant reduction according to ANOVA for repeated measures (p = 0.003). A global significant improvement in FTOEc and FTOEs was detected (p = 0.009 and p = 0.004, respectively) as a significant reduction in heart rate (p = 0.019). A global significant improvement in PaO2/FiO2 ratio was observed (p < 0.001) and also at all time points: at 6 h since infusion (p = 0.015), 12 h (p = 0.009), and 24 h (p = 0.006), respectively. A significant reduction in sodium levels was observed as expected side effect (p = 0.012). No significant changes were observed in the remaining outcomes.

Conclusion

Our data suggest that starting early vasopressin infusion in CDH infants with pulmonary hypertension could improve oxygenation index and near-infrared spectroscopy after 12 and 24 h of infusion. These pilot data represent a background for planning future larger randomized trials to evaluate the efficacy and safety of vasopressin for the CDH population.

Pathogenesis, Prognosis and Outcomes of Multiple Organ Failure in Newborns (Review)

Multiple organ failure (MOF) is the leading cause of neonatal mortality in intensive care units. The prevalence of MOF in newborns is currently unclear, since its incidence varies in asphyxia, sepsis, prematurity, and comorbidity, and depends on the level of development and funding of health care in different countries. Sepsis and acute respiratory distress syndrome prevail among the causes of MOF in this category of patients.

Aim of the review. To summarize the available literature data on the pathogenesis, therapeutic strategies and outcomes of MOF in newborns.

Material and methods. We searched PubMed, Scopus, Web of Science, and RSCI databases using the following keywords: «newborns, multiple organ failure, etiology, pathogenesis, premature, diagnosis, treatment, respiratory support, cardiotonic support», without language limitations. A total of 144 full-text sources were selected for analysis, 70% of which were published in the last five years and 50% were published in the last three years. Criteria for exclusion were low information value and outdated data.

Results. The prevalence of MOF in neonates is currently unclear. This could be due to common association of neonatal MOF (as well as the adult one) with various diseases; thus, its incidence is not the same for asphyxia, sepsis, prematurity, and comorbidities. There is no precise data on neonatal mortality in MOF, but according to some reports, it may be as high as 13-50%.

In newborns, MOF can be caused by two major causes, intrapartum/postnatal asphyxia and sepsis, but could also be influenced by other intranatal factors such as intrauterine infections and acute interruption of placental blood flow.

The key element in the pathogenesis of neonate MOF is cytokinemia, which triggers universal critical pathways. Attempts to identify different clinical trajectories of critical illness in various categories of patients have led to the discovery of MOF phenotypes with specific patterns of systemic inflammatory response. This scientific trend is very promising for the creation of new classes of drugs and individual therapeutic pathways in neonates with MOF of various etiologies.

The pSOFA scale is used to predict the outcome of neonatal MOF, however, the nSOFA scale has higher validity in premature infants with low birth weight.

Central nervous system damage is the major MOF-associated adverse outcome in newborns, with gestational age and the timing of treatment initiation being key factors affecting risk of MOF development in both full-term and premature infants.

Conclusion. The study of cellular messengers of inflammation, MOF phenotypes, mitochondrial insufficiency, and immunity in critically ill infants with MOF of various etiologies is a promising area of research. The pSOFA scale is suggested for predicting the outcome of MOF in full-term infants, while the nSOFA scale should be used in premature infants with low birth weight.

Update on pre-ECMO evaluation and treatment for term infants in respiratory failure

The epidemiology, diagnostic and management approach to severe hypoxemic respiratory failure in the term and near-term neonate has evolved over time, as has the need for extracorporeal membrane oxygenation (ECMO) support in this patient population. Many patients who historically would have required ECMO support now respond to less invasive therapies, with patients requiring ECMO generally representing a higher risk and more heterogenous group of underlying diagnoses. This review will highlight these changes over time and the current available evidence for the diagnosis and management of these infants, as well as the current indications and relative contraindications to ECMO support when oxygen delivery cannot meet demand with less invasive management.

How to diagnose and treat acute pulmonary hypertension when you have no cardiology support

Acute pulmonary hypertension (aPH) is a complex, physiology-driven disorder that causes critical illness in newborns, the hallmark of which is elevated pressure in the pulmonary vascular bed. Several underlying hemodynamic phenotypes exist, including classic arterial aPH with resistance-driven elevations in pulmonary arterial pressure (PAP), alongside flow-driven aPH from left-to-right shunt lesions, and primary left ventricular dysfunction with pulmonary venous hypertension and elevated left atrial pressure. Targeted neonatal echocardiography (TnECHO) is an important tool for evaluation of hemodynamics in aPH and is highly useful for evaluating modulators of disease and targeting cardiovascular therapy. The diagnostic approach to aPH includes confirmation of elevation of PAP, evaluation of the cause and exclusion of structural cardiac disease, assessment of the response of the myocardium to adverse loading conditions, and appraisal of the adequacy of systemic blood flow. Therapeutic goals include support of right ventricular (RV) function, RV afterload reduction, and selection of cardiotropic agents that support underlying pathophysiology without adverse effects on heart rate or pulmonary vascular resistance in addition to routine supportive intensive care. Training programs for TnECHO exist across multiple jurisdictions and strong correlation with pediatric cardiology assessment has been demonstrated. Future directions include adapting TnECHO training with a greater focus on achieving competency, and further research into the role of the modality in providing individualized cardiovascular care for patients with heterogenous underlying physiology, and its effect on key neonatal outcomes.

A new physiologic-based integrated algorithm in the management of neonatal hemodynamic instability

Physiologic-based management of hemodynamic instability is proven to guide the logical selection of cardiovascular support and shorten the time to clinical recovery compared to an empiric approach that ignores the heterogeneity of the hemodynamic instability related mechanisms. In this report, we classified neonatal hemodynamic instability, circulatory shock, and degree of compensation into five physiologic categories, based on different phenotypes of blood pressure (BP), other clinical parameters, echocardiography markers, and oxygen indices. This approach is focused on hemodynamic instability in infants with normal cardiac anatomy.Conclusion: The management of hemodynamic instability is challenging due to the complexity of the pathophysiology; integrating different monitoring techniques is essential to understand the underlying pathophysiologic mechanisms and formulate a physiologic-based medical recommendation and approach. What is Known: • Physiologic-based assessment of hemodynamics leads to targeted and pathophysiologic-based medical recommendations. What is New: • Hemodynamic instability in neonates can be categorized according to the underlying mechanism into five main categories, based on blood pressure phenotypes, systemic vascular resistance, and myocardial performance. • The new classification helps with the targeted management and logical selection of cardiovascular support.

Care of the critically ill neonate with hypoxemic respiratory failure and acute pulmonary hypertension: framework for practice based on consensus opinion of neonatal hemodynamics working group

Circulatory transition after birth presents a critical period whereby the pulmonary vascular bed and right ventricle must adapt to rapidly changing loading conditions. Failure of postnatal transition may present as hypoxemic respiratory failure, with disordered pulmonary and systemic blood flow. In this review, we present the biological and clinical contributors to pathophysiology and present a management framework.

Use of vasopressin in persistent pulmonary hypertension of the newborn: A case series

Treatment of neonates with persistent pulmonary hypertension of newborn includes optimization of ventilatory support, use of pulmonary vasodilators, and/or inotropic support. If refractory to this management, some may require extracorporeal membrane oxygenation. We describe a case series of 10 neonates with refractory persistent pulmonary hypertension of newborn treated with vasopressin in a single tertiary center. Mean initiation time of vasopressin was at 30 h of life with a dose ranging from 10 to 85 milliunits/kg/h. Oxygenation index decreased after 12 h of vasopressin exposure (25 to 11) and mean arterial pressure improved after 1 h (45 to 58 mm Hg). Extracorporeal membrane oxygenation was averted in 50% of the cases with transient hyponatremia as the only notable side effect. Although our findings are exploratory and further research is needed to establish safety and efficacy, our experience suggests that vasopressin may have rescue properties in the management of refractory persistent pulmonary hypertension of newborn.

Effect of Vasopressin on Systemic and Pulmonary Hemodynamics in Neonates

OBJECTIVE

Despite its increasing use in neonates, the literature on the use of vasopressin (VP) in neonates is limited. The aim of this study is to evaluate the systemic and pulmonary effects of VP in neonates and to assess its safety among them.

STUDY DESIGN

This retrospective study enrolled all neonates in two level III neonatal intensive care units in Winnipeg, Manitoba, who had received VP therapy between 2011 and 2016. Infants with congenital malformations/chromosomal disorders were excluded. The changes in cardiovascular and pulmonary parameters were collected from patient charts. The primary outcome was the mean blood pressure (MBP) post-VP initiation. Secondary outcomes included systolic blood pressure (SBP) and diastolic blood pressure (DBP), vasoactive inotropic score (VIS), pH, urine output, lactate, base deficit (BD), mean airway pressure (MAP), and oxygen requirement.

RESULTS

A total of 33 episodes from 26 neonates were analyzed. The postnatal age at VP initiation was 14 days (interquartile range [IQR]: 4-25), and the median starting dose was 0.3 mU/kg/min (IQR: 0.2-0.5). MBP improved significantly after VP initiation from 28 to 39 mm Hg 24 hours after VP initiation (p < 0.001). Similar changes are observed with SBP and DBP. VIS declined from 15 to 6 at 24 hours, while pH, lactate, BD, and oxygen requirement improved significantly. While urine output marginally improved, there were no changes to MAP 24 hours post-VP initiation. Hyponatremia was observed in 21 episodes (64%) and severe hyponatremia in 7 episodes (33%).

CONCLUSION

VP appears to be a promising rescue therapy in catecholamine resistant shock or refractory pulmonary hypertension in neonates.

Management of systemic hypotension in term infants with persistent pulmonary hypertension of the newborn: an illustrated review

In persistent pulmonary hypertension of the newborn (PPHN), the ratio of pulmonary vascular resistance to systemic vascular resistance is increased. Extrapulmonary shunts (patent ductus arteriosus and patent foramen value) allow for right-to-left shunting and hypoxaemia. Systemic hypotension can occur in newborns with PPHN due to variety of reasons, such as enhanced peripheral vasodilation, impaired left ventricular function and decreased preload. Systemic hypotension can lead to end organ injury from poor perfusion and hypoxaemia in the newborn with PPHN. Thus, it must be managed swiftly. However, not all newborns with PPHN and systemic hypotension can be managed the same way. Individualised approach based on physiology and echocardiographic findings are necessary to improve perfusion to essential organs. Here we present a review of the physiology and mechanisms of systemic hypotension in PPHN, which can then guide treatment.

Precision in Cardiovascular Care Using Targeted Neonatal Echocardiography in Lethal Neonatal Disseminated Herpes Infection: A Case Series

Neonates with disseminated neonatal herpes simplex virus infection often present with cardiorespiratory failure. The pathophysiological contributors to the disease phenotype, biologic mechanisms underlying the hemodynamic instability and optimal approach to cardiovascular treatment have not been well described. We describe clinical and echocardiography features of cardiovascular dysfunction, in a case series of neonates with disseminated herpes simplex virus, and response to physiology-based hemodynamic management. The biologic phenotype includes low systemic vascular resistance state, hypovolemia secondary to third space losses, myocardial dysfunction and pulmonary hypertension. Early targeted neonatal echocardiography provided hemodynamic insights on blood flow, shunt characterization, vascular resistance and cardiac function, that were difficult to gauge clinically (eg, differentiating parenchymal from pulmonary vascular disease) thereby positively impacted clinical care. All patients were stabilized hemodynamically without utilizing extracorporeal membrane oxygenation, although all patients died of multiorgan failure.

Utility of Low Dose Vasopressin for Persistent Pulmonary Hypertension of Newborn with Catecholamine Refractory Shock

OBJECTIVE

To evaluate the effect of low dose vasopressin on the hemodynamics of neonates with persistent pulmonary hypertension and catecholamine refractory shock.

METHODS

This retrospective study was conducted in a level III NICU of a tertiary care teaching hospital, south India. Eighteen neonates with hypoxemic respiratory failure due to persistent pulmonary hypertension of newborn with catecholamine refractory shock were studied. Neonates were managed for hypotension with conventional inotropic support with the additional use of low dose vasopressin (LDV). Effect of vasopressin on oxygenation index (OI), blood pressure, duration of inotropic usage and survival was evaluated.

RESULTS

Mean OI was 38.2 ± 4.9, and mean blood pressure was 30.7 ± 5.3 mmHg before the start of vasopressin. Initiation of LDV (0.0003 ± 0.0001 IU/kg/min) for a median duration 36.4 ± 17.9 h was followed by a reduction in OI (p < 0.001), control of hypotension (p < 0.001), reduction in lactic acidosis (p < 0.001) and decline in inotropic support.

CONCLUSIONS

In resource-restricted settings, LDV may be useful as a rescue therapy for persistent pulmonary hypertension of newborn with catecholamine refractory shock.

Severe neonatal pulmonary artery hypertension rescued with vasopressin

An inborn term neonate weighing 2600 g developed meconium aspiration syndrome at birth. Baby had respiratory failure requiring high-frequency oscillatory ventilation support at 15 hours of life. He additionally developed hypotension with left ventricular dysfunction noted on point-of-care echocardiography (POCE), which required dopamine and epinephrine infusions. At 28 hours of life, he was started on inhaled nitric oxide (iNO), followed by milrinone due to hypoxaemic respiratory failure and the POCE revealed severe pulmonary artery hypertension (PAH). As PAH was refractory to iNO and milrinone, vasopressin was added which resulted in rapid improvement in oxygenation and normalisation of pulmonary artery pressures. Baby was weaned off from vasoactive support in the next 120 hours. Vasopressin proved to be the rescue agent in this case of iNO refractory PAH without any side effects during therapy. Baby was successfully extubated on day 18 and was discharged with a normal neurological examination finding.

Intensive care management of right ventricular failure and pulmonary hypertension crises

Pulmonary hypertension (PH), an often unrelenting disease that carries with it significant morbidity and mortality, affects not only the pulmonary vasculature but, in turn, the right ventricle as well. The survival of patients with PH is closely related to the right ventricular function. Therefore, having an understanding of how to manage right ventricular failure (RVF) and acute pulmonary hypertensive crises is imperative for clinicians who encounter these patients. This review addresses the management of these patients in detail, addressing: (a) the pathophysiology of RVF, (b) intensive care monitoring of these patients in the intensive care unit, (c) imaging of the right ventricle, (d) intubation and mechanical ventilation, (e) inotrope and vasopressor selection, (f) pulmonary vasodilator use, (g) interventional and surgical procedures for the acutely failing right ventricle, and (h) mechanical support for RVF.

Milrinone Use in Persistent Pulmonary Hypertension of the Newborn

Failure of the normal transition from in utero to ex utero physiology leads to "persistent" pulmonary hypertension of the newborn (PPHN). PPHN is frequently associated with low systemic blood pressure and low cardiac output because of increased right ventricular afterload and myocardial dysfunction. The general management of newborns with PPHN is geared toward maintenance of normothermia, normal serum electrolytes, normal intravascular volume, correction of acidosis, adequate sedation/analgesia, adequate ventilation and oxygenation with optimal lung recruitment, and avoidance of hyperoxia. Inotropic and vasoactive agents are commonly initiated early to increase cardiac output, maintain adequate systemic blood pressure, and enhance oxygen delivery to the tissue. Unfortunately, there is not much evidence on the choice, timing of initiation, dosing, monitoring, and titrating of vasoactive agents in this patient population. In this review, we will discuss the pathophysiology of PPHN and review the use of inotropic, lusitropic, and vasoactive agents in the management of PPHN, with particular attention to milrinone.

Use of vasopressin in neonatal hypertrophic obstructive cardiomyopathy: case series

OBJECTIVE

To determine the effect of vasopressin on arterial blood pressure in infants with neonatal hypertrophic obstructive cardiomyopathy (HOCM).

STUDY DESIGN

Retrospective case study in Neonatal ICU involving six infants; five born to mothers with diabetes mellitus (mean gestational age 37.5 ± 0.9 weeks). Vasopressin infusion was started at a mean dose of 0.3 ± 0.2 mU/kg/min.

RESULT

Initiation of vasopressin was followed by improved mean (p = 0.004), systolic (p = 0.028), and diastolic (p = 0.009) arterial pressure within 2 h. Heart rate (p = 0.025) and oxygen requirement (p = 0.021) also declined after initiation. Serum sodium declined initially and recovered by 72 h (p = 0.017).

CONCLUSION

Although there is limited experience with vasopressin use in neonatal HOCM, our case series suggests it may be beneficial for improving systemic hypotension and stabilization of hemodynamics. The potential for hyponatremia is high, necessitating careful fluid/electrolyte management. A prospective randomized trial is necessary to confirm safety and efficacy of vasopressin treatment in neonatal HOCM.

Cardiovascular management following hypoxic-ischemic encephalopathy in North America: need for physiologic consideration

BACKGROUND

Hypotension and hypoxemic respiratory failure are common among neonates with hypoxic-ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH). Right ventricular (RV) dysfunction is associated with adverse neurodevelopment. Individualized management utilizing targeted neonatal echocardiography (TnECHO) may enhance care.

METHODS

We evaluated the influence of TnECHO programs on cardiovascular practices in HIE/TH patients utilizing a 77-item REDCap survey. Nominated representatives of TnECHO (n = 19) or non-TnECHO (n = 96) sites were approached.

RESULTS

Seventy-one (62%) sites responded. Baseline neonatal intensive care unit characteristics and HIE volume were comparable between groups. Most centers monitor invasive blood pressure; however, we identified 17 unique definitions of hypotension. TnECHO centers were likelier to trend systolic/diastolic blood pressure and request earlier echocardiography. TnECHO responders were less likely to use fluid boluses; TnECHO responders more commonly chose an inotrope first-line, while non-TnECHO centers used a vasopressor. For HRF, TnECHO centers chose vasopressors with a favorable pulmonary vascular profile. Non-TnECHO centers used more dopamine and more extracorporeal membrane oxygen for patients with HRF.

CONCLUSIONS

Cardiovascular practices in neonates with HIE differ between centers with and without TnECHO. Consensus regarding the definition of hypotension is lacking and dopamine use is common. The merits of these practices among these patients, who frequently have comorbid pulmonary hypertension and RV dysfunction, need prospective evaluation.

IMPACT

Cardiovascular care following HIE while undergoing therapeutic hypothermia varies between centers with access to trained hemodynamics specialists and those without. Because cardiovascular dysfunction is associated with brain injury, precision medicine-based care may be an avenue to improving outcomes. Therapeutic hypothermia has introduced new physiological considerations and enhanced survival. It is essential that hemodynamic strategies evolve to keep pace; however, little literature exists. Lack of consensus regarding fundamental definitions (e.g., hypotension) highlights the importance of collaboration among the scientific community to advance the field. The value of enhanced cardiovascular care guided by hemodynamic specialists requires prospective evaluation.

What Inotrope and Why?

Primary function of cardiovascular system is to meet body's metabolic demands. The aim of inotrope therapy is to minimise adverse impact of cardiovascular compromise. Current use of inotropes is primarily guided by the pathophysiology of cardiovascular compromise and anticipated actions of inotropes. Lack of significant reduction in morbidity and mortality associated with cardiovascular compromise despite inotrope use, highlights major gaps in our understanding of circulatory targets, thresholds and choices of inotrope therapy. Thus far, prevention of cardiovascular compromise remains the most effective strategy to optimize outcomes. Studies of alternative design are needed for further advancement in cardiovascular therapy in neonates.

Vasopressin for refractory persistent pulmonary hypertension of the newborn in preterm neonates - a case series

Objective: To describe the clinical outcomes following treatment with vasopressin for a sub-cohort of critically ill preterm neonates who have refractory persistent pulmonary hypertension of the newborn (PPHN).Design: Case seriesSetting: Tertiary neonatal intensive care unit, Toronto, Canada.Population: Neonates born <37 weeks gestational age (GA) who received vasopressin for refractory PPHN (lack of response to inhaled nitric oxide) over a 4-year period.Measurements: Changes in physiological indices of cardio-pulmonary stability during vasopressin therapy were analyzed using one-way repeated measures ANOVA, compared to pretreatment values. Data regarding survival to discharge and neurodevelopmental outcomes at 18-24 months were described.Main Results: Thirteen neonates with a mean GA of 31.4 ± 3.3 weeks were included. Vasopressin was initiated at 28.5 ± 4.5 h of age. Overall, oxygenation and hemodynamic variables improved significantly following vasopressin therapy (p < .05 at 24 h vs. pretreatment). Oxygenation failure resolved in 8 cases, of which 7 patients survived (6 without disability). Among the 5 cases where oxygenation failure persisted despite vasopressin, 4 died while one survived with disability.Conclusions: Vasopressin offers promise as a therapy for preterm neonates with refractory PPHN and hemodynamic instability, but prospective investigation is needed.

Severe Hyponatraemia Associated with the Use of Arginine-Vasopressin in Two Neonates with Complex Congenital Heart Disease

We report two cases of neonates with complex congenital heart disease and volume, catecholamine, and corticosteroid refractory shock treated with arginine-vasopressin. Arginine-vasopressin was able to reverse critical hypotension, but both patients developed severe hyponatremia, which recovered after discontinuation of arginine-vasopressin. Close control and prompt substitution of serum sodium is required in neonates with advanced heart failure on high-dose vasopressin therapy.

The Use of Cardiotonic Drugs in Neonates

There is a distinct lack of age-appropriate cardiotonic drugs, and adult derived formulations continue to be administered, without evidence-based knowledge on their dosing, safety, efficacy, and long-term effects. Dopamine remains the most commonly studied and prescribed cardiotonic drug in the neonatal intensive care unit (NICU), but evidence of its effect on endorgan perfusion still remains. Unlike adult and pediatric critical care, there are significant gaps in our knowledge on the use of various cardiotonic drugs in various forms of circulatory failure in the NICU.

Concurrent Use of Calcium Chloride and Arginine Vasopressin Infusions in Pediatric Patients with Acute Cardiocirculatory Failure

Acute heart failure (AHF) can cause low cardiac output and poor end-organ perfusion. Inotropic agents along with vasodilators can improve organ perfusion. Arginine vasopressin (AVP) and calcium chloride (CaCl) infusions are increasingly being used in low cardiac output states in pediatric AHF. We retrospectively reviewed 77 patients (0-18 years) with AHF admitted between January 2014 and May 2017 who received concurrent AVP and CaCl infusions. Surrogates of cardiac output and organ perfusion included hemodynamic vital signs, laboratory parameters, and urine output (UO). Organ dysfunction and vasopressor inotropic scores were also calculated. Median (IQR) age was 0.88 years (0, 3.75), and median weight was 6.62 kg (3.5, 13.7). Congenital heart disease was present in 70% (46/77) patients. Univentricular physiology was present in 25% (25/77) patients. None of the patients were in the immediate postoperative period. Median durations of AVP and CaCl were 2 days (1, 3) and 3 days (2, 6), respectively. Using Wilcoxon-signed rank test and Bonferroni correction, post hoc comparison showed that at 8 h post infusion, all systolic blood pressure (SBP) and diastolic blood pressure (DBP) results, and UO were greater than those 1 h prior to infusion. Median SBP increased from 79 mm Hg (71, 92) 1 h prior to 97 mm Hg (84, 107) 8 h post. Median DBP increased from 44 mm Hg (35, 52) 1 h prior to 54 mm Hg (44, 62) 8 h post. Heart rate showed a decrease between measurements 1 h prior to infusion and 8 h post, with median scores 146 (127, 162) and 136 (114, 150) beats per minute, respectively. Within first 8 h, median UO continuously increased from 6 mL/h. (0, 25) at 1 h post infusion to 20 mL/h. (2, 62) at 8 h post infusion. Median pediatric logarithmic organ dysfunction scores on days 4 through 7 post infusion were lower compared to day 1; median vasopressor inotropic scores on day 2 through 7 post infusion were lower compared to day 1. Serum lactate level, arterial pH, and base excess all showed favorable trend. Concurrent use of AVP and CaCl infusions may improve surrogates of cardiac output, and intensive care outcomes, and prevent organ dysfunction in children with AHF.

Effect of vasopressin on a porcine model of persistent pulmonary hypertension of the newborn

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is due to a failure of pulmonary vascular relaxation. Vasopressin, a systemic vasoconstrictor acting on smooth muscle AVPR1a receptors, is used in treatment of PPHN. We sought to determine acute effects of vasopressin infusion on pulmonary hemodynamics in a large animal model of hypoxic PPHN.

METHODS

PPHN was induced in 6 newborn piglets by 72 h normobaric hypoxia (FiO2 = 0.10); controls were 7 age-matched 3-day-old piglets. Animals were anesthetized and ventilated with central venous and arterial lines, and after stabilization, randomized using a crossover design to normoxic or hypoxic ventilation, then 30 min infusion of 0.0012 U/kg/min vasopressin, followed by 45 min vasopressin washout period. Echocardiographic parameters and oxygen consumption were measured before and after vasopressin. Relaxation to vasopressin was tested in isolated PPHN and control pulmonary arteries by isometric myography. Expression of AVPR1a receptor mRNA was quantified in arterial and myocardial tissues.

RESULTS

Vasopressin did not alleviate hypoxia-responsiveness of PPHN pulmonary circuit. There were no significant differences in pulmonary hypertension, cardiac function indices, or oxygenation indices after vasopressin infusion. Vasopressin did not dilate control or PPHN pulmonary arteries, and AVPR1 was minimally expressed.

CONCLUSIONS

Vasopressin does not have a direct pulmonary vasodilator effect in PPHN, within the timeframe studied.

Hospital and intensive care unit management of decompensated pulmonary hypertension and right ventricular failure

Pulmonary hypertension and concomitant right ventricular failure present a diagnostic and therapeutic challenge in the intensive care unit and have been associated with a high mortality. Significant co-morbidities and hemodynamic instability are often present, and routine critical care unit resuscitation may worsen hemodynamics and limit the chances of survival in patients with an already underlying poor prognosis. Right ventricular failure results from structural or functional processes that limit the right ventricle’s ability to maintain adequate cardiac output. It is commonly seen as the result of left heart failure, acute pulmonary embolism, progression or decompensation of pulmonary hypertension, sepsis, acute lung injury, or in the perioperative setting. Prompt recognition of the underlying cause and institution of treatment with a thorough understanding of the elements necessary to optimize preload, cardiac contractility, enhance systemic arterial perfusion, and reduce right ventricular afterload are of paramount importance. Moreover, the emergence of previously uncommon entities in patients with pulmonary hypertension (pregnancy, sepsis, liver disease, etc.) and the availability of modern devices to provide support pose additional challenges that must be addressed with an in-depth knowledge of this disease.

Advances in Diagnosis and Management of Hemodynamic Instability in Neonatal Shock

Shock in newborn infants has unique etiopathologic origins that require careful assessment to direct specific interventions. Early diagnosis is key to successful management. Unlike adults and pediatric patients, shock in newborn infants is often recognized in the uncompensated phase by the presence of hypotension, which may be too late. The routine methods of evaluation used in the adult and pediatric population are often invasive and less feasible. We aim to discuss the pathophysiology in shock in newborn infants, including the transitional changes at birth and unique features that contribute to the challenges in early identification. Special emphasis has been placed on bedside focused echocardiography/focused cardiac ultrasound, which can be used as an additional tool for early, neonatologist driven, ongoing evaluation and management. An approach to goal oriented management of shock has been described and how bed side functional echocardiography can help in making a logical choice of intervention (fluid therapy, inotropic therapy or vasopressor therapy) in infants with shock.

Inotropes for Preterm Infants: 50 Years on Are We Any Wiser?

For almost half a century, inotropes have been administered to preterm infants with the ultimate goal of increasing their blood pressure. A number of trials, the majority of which focused on dopamine administration, have demonstrated increased blood pressure following inotrope administration in preterm infants and have led to continued use of inotropes in our neonatal units. We have also seen an increase in the number of potential agents available to the clinician. However, we now know that hypotension is a much broader concept than blood pressure alone, and our aim should instead be focused on improving end organ perfusion, specifically cerebral perfusion. Only a limited number of studies have incorporated the organ-relevant hemodynamic changes and long-term outcomes when assessing inotropic effects in neonates, the majority of which are observational studies or have a small sample size. In addition, important considerations, including the developing/maturing adrenergic receptors, polymorphisms of these receptors, and other differences in the pharmacokinetics and pharmacodynamics of preterm infants, are only recently being recognized. Certainly, there remains huge variation in practice. The lack of well-conducted randomized controlled trials addressing these relevant outcomes, along with the difficulty executing such RCTs, leaves us with more questions than answers. This review provides an overview of the various inotropic agents currently being used in the care of preterm infants, with a particular focus on their organ/cerebral hemodynamic effects both during and after transition.

Cardiovascular Supportive Therapies for Neonates With Asphyxia - A Literature Review of Pre-clinical and Clinical Studies

Asphyxiated neonates often have hypotension, shock, and poor tissue perfusion. Various "inotropic" medications are used to provide cardiovascular support to improve the blood pressure and to treat shock. However, there is incomplete literature on the examination of hemodynamic effects of these medications in asphyxiated neonates, especially in the realm of clinical studies (mostly in late preterm or term populations). Although the extrapolation of findings from animal studies and other clinical populations such as children and adults require caution, it seems appropriate that findings from carefully conducted pre-clinical studies are important in answering some of the fundamental knowledge gaps. Based on a literature search, this review discusses the current available information, from both clinical studies and animal models of neonatal asphyxia, on common medications used to provide hemodynamic support including dopamine, dobutamine, epinephrine, milrinone, norepinephrine, vasopressin, levosimendan, and hydrocortisone.

Use of Vasopressin in Neonatal Intensive Care Unit Patients With Hypotension

OBJECTIVE

To evaluate the safety and efficacy of vasopressin for the treatment of hypotension in patients admitted to neonatal intensive care units (NICUs).

METHODS

Vasopressin use in 69 infants admitted to our NICU between 2011 and 2014 was examined. Data evaluated included demographics; serum creatinine, sodium, and lactate concentrations; urine output; and systolic, diastolic, and mean blood pressures (BPs). Parameters prior to vasopressin use were compared to those at maximum dose.

RESULTS

Vasopressin use was associated with increased urine output (p < 0.05), and increased systolic (p < 0.0005), diastolic (p < 0.01), and mean (p < 0.001) BP. There were no differences in sodium or lactate concentrations before vs during infusion; vasopressin use was not associated with hyponatremia (sodium < 130 mEq/L) at the maximum dose.

CONCLUSIONS

Vasopressin for the treatment of neonatal hypotension appears safe and was efficacious in raising BP. These data suggest that vasopressin could be considered a viable option in the treatment regimen in hypotensive infants in the NICU.

Management of Neonatal Hypotension

Hypotension is a common problem in neonates with complex underlying pathophysiology. Although treatment of low blood pressure is common, clinicians must use all available information to target neonates with compromised perfusion. Pharmacotherapy should be tailored to the specific physiologic perturbations of the individual neonate. Dopamine is the most commonly utilized agent and may be the most appropriate agent for septic shock with low diastolic blood pressure. However, alternative therapies should be considered for other etiologies of hypotension, including milrinone and vasopressin for persistent pulmonary hypertension of the newborn and dobutamine for patent ductus arteriosus. Additional studies are required to refine the approach to neonatal hypotension and document the long-term outcomes of treated neonates.

Integrated Evaluation of Neonatal Hemodynamics, Part 2: Systematic Bedside Assessment

Intact hemodynamics results when there is adequate oxygen uptake by the respiratory system, normal cardiac output, sufficient oxygen-carrying capacity of blood, and intact autoregulatory mechanisms to maintain enough oxygenation for normal end-organ function. The current routine monitoring of cardiovascular dynamics in sick preterm and term infants has been based on incomplete evaluation and relies on nonspecific and sometimes misleading clinical markers such as blood pressure. A thorough understanding of perinatal and neonatal cardiovascular, respiratory, oxygen, and other specific end-organ physiology is also mandatory for proper targeted interpretation.

Treatment of Persistent Pulmonary Hypertension of the Newborn: Use of Pulmonary Vasodilators in Term Neonates

Persistent pulmonary hypertension of the newborn (PPHN) represents a challenging condition associated with significant morbidity. A successful transition from intrauterine to extrauterine life is contingent on adequate pulmonary vasodilation. Several pathophysiologies contribute to the failure of this cascade and may result in life-threatening hypoxia and acidosis in the newborn. Management includes optimal respiratory support, adequate sedation and analgesia, and support of vascular tone and cardiac function. Pulmonary vasodilation has the potential to overcome the cycle of hypoxia and acidosis, improving outcome in these infants. Oxygen and inhaled nitric oxide represent the foundation of therapy. Tertiary pulmonary vasodilators represent a greater challenge, selecting between therapies that include prostanoids, sildenafil, and milrinone. Variable levels of evidence exist for each agent. Thorough review of available data informing efficacy and adverse effects contributes to the development of an informed approach to neonates with refractory PPHN.

Pulmonary Hypertension

OBJECTIVES

To review the clinical classification, diagnosis, and pathophysiology of pulmonary hypertension in children, emphasizing the role of right ventricular function, ventricular interaction, and congenital heart disease in the evolution and progression of disease, as well as management strategies and therapeutic options.

DATA SOURCE

MEDLINE, PubMed.

CONCLUSIONS

Critically ill children with pulmonary hypertension associated with congenital heart disease are a high-risk population. Congenital cardiac defects resulting in either increased pulmonary blood flow or impaired pulmonary venous drainage predispose patients to developing structural and functional aberrations of the pulmonary vasculature. Mortality from pulmonary hypertension is most directly related to right ventricular failure.

Hemodynamic Effects of Phenylephrine, Vasopressin, and Epinephrine in Children With Pulmonary Hypertension: A Pilot Study

OBJECTIVES

During a pulmonary hypertensive crisis, the marked increase in pulmonary vascular resistance can result in acute right ventricular failure and death. Currently, there are no therapeutic guidelines for managing an acute crisis. This pilot study examined the hemodynamic effects of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertension.

DESIGN

In this prospective, open-label, nonrandomized pilot study, we enrolled pediatric patients previously diagnosed with pulmonary hypertensive who were scheduled electively for cardiac catheterization. Primary outcome was a change in the ratio of pulmonary-to-systemic vascular resistance. Baseline hemodynamic data were collected before and after the study drug was administered.

PATIENTS

Eleven of 15 participants were women, median age was 9.2 years (range, 1.7-14.9 yr), and median weight was 26.8 kg (range, 8.5-55.2 kg). Baseline mean pulmonary artery pressure was 49 ± 19 mm Hg, and mean indexed pulmonary vascular resistance was 10 ± 5.4 Wood units. Etiology of pulmonary hypertensive varied, and all were on systemic pulmonary hypertensive medications.

INTERVENTIONS

Patients 1-5 received phenylephrine 1 μg/kg; patients 6-10 received arginine vasopressin 0.03 U/kg; and patients 11-15 received epinephrine 1 μg/kg. Hemodynamics was measured continuously for up to 10 minutes following study drug administration.

MEASUREMENTS AND MAIN RESULTS

After study drug administration, the ratio of pulmonary-to-systemic vascular resistance decreased in three of five patients receiving phenylephrine, five of five patients receiving arginine vasopressin, and three of five patients receiving epinephrine. Although all three medications resulted in an increase in aortic pressure, only arginine vasopressin consistently resulted in a decrease in the ratio of systolic pulmonary artery-to-aortic pressure.

CONCLUSIONS

This prospective pilot study of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertensive showed an increase in aortic pressure with all drugs although only vasopressin resulted in a consistent decrease in the ratio of pulmonary-to-systemic vascular resistance. Studies with more subjects are warranted to define optimal dosing strategies of these medications in an acute pulmonary hypertensive crisis.