Pulmonary hemorrhage (PH) is a rare but potentially fatal condition in pediatric patients, particularly those with congenital heart disease (CHD). The severity of PH can lead to life-threatening respiratory failure, necessitating advanced life-support interventions such as extracorporeal membrane oxygenation (ECMO). While ECMO has proven life-saving in critical cases, limited data exists on survival outcomes for pediatric cardiac patients with PH who require ECMO support. This study seeks to bridge that knowledge gap by analyzing patient data from the Extracorporeal Life Support Organization (ELSO) registry.
Study Background and Objectives
Children with congenital heart defects are at an increased risk for PH due to multiple factors, including abnormal pulmonary vasculature, high pulmonary pressures, and surgical interventions that impact pulmonary circulation. While conventional mechanical ventilation is the standard initial treatment, ECMO is used as a last resort for severe respiratory and cardiac failure. However, patient survival outcomes and the best ventilation strategies before ECMO initiation remain unclear.
This retrospective cohort study aims to characterize pediatric cardiac patients with PH requiring ECMO and identify factors that contribute to survival. Specifically, the study investigates whether the use of high-frequency oscillatory ventilation (HFOV) before ECMO cannulation improves survival rates. Additionally, it evaluates the impact of hemorrhagic and renal complications on patient outcomes.
Methods and Study Design
Using the ELSO registry database, the study analyzed data from pediatric cardiac patients aged birth to 18 years who were placed on ECMO for PH between January 2011 and December 2020. A total of 161 patients met the inclusion criteria. The study examined patient demographics, ventilation strategies, ECMO characteristics, and complications. Statistical methods, including multivariable logistic regression, were applied to identify independent predictors of survival to hospital discharge.
Key Findings
- Patient Demographics and Survival Rates
- The median age of the cohort was 40 days (IQR 7.3–452).
- The median weight was 4.06 kg (IQR 3–9.36).
- Neonates (<30 days old) made up 48.1% of cases.
- Congenital heart disease (CHD) was the most common diagnosis, affecting 77.2% of patients.
- Overall survival to hospital discharge was 35.8%, indicating the high mortality risk associated with PH in pediatric cardiac patients.
- Ventilation Strategies Before ECMO
- One of the most significant findings in this study was the role of HFOV before ECMO cannulation:
- The majority of patients (79.7%) were placed on conventional mechanical ventilation before ECMO.
- 11% received HFOV, a technique that uses small, rapid breaths to improve gas exchange while minimizing lung injury.
- Survivors were significantly more likely to have received HFOV before ECMO (24.4% vs. 2.8% in non-survivors, p < 0.001).
- Logistic regression showed that HFOV before ECMO was an independent predictor of survival (OR 28.44, p < 0.001). This suggests that early use of HFOV may improve lung function and oxygenation before ECMO initiation, leading to better outcomes.
- ECMO Characteristics and Complications
- Veno-arterial (VA) ECMO was used in 94.4% of cases, making it the predominant support mode.
- Extracorporeal cardiopulmonary resuscitation (ECPR) was required in 23.5% of patients.
- Complications were common, with the most frequent being:
- Renal replacement therapy (44%)
- Surgical site bleeding (25.3%). Non-survivors were more likely to experience multiple complications, including cardiovascular, hemorrhagic, metabolic, and neurologic issues.
- Factors Associated with Survival
- Beyond ventilation strategies, the study identified other key predictors of survival:
- Absence of hemorrhagic complications was associated with improved survival (OR 3.51, p = 0.031).
- Absence of renal complications also improved outcomes (OR 3.50, p = 0.027).
This highlights the importance of managing bleeding and kidney function during ECMO treatment.
Discussion and Clinical Implications
This study is the first to establish a link between HFOV before ECMO and improved survival in pediatric cardiac patients with PH. The findings suggest that HFOV may stabilize the lungs and reduce alveolar hemorrhage, leading to better oxygenation and lung compliance before ECMO initiation.
However, the use of HFOV in pediatric cardiac patients has traditionally been debated due to concerns about its impact on hemodynamics. HFOV can increase intrathoracic pressure, potentially reducing pulmonary venous return and increasing right ventricular afterload. Despite these concerns, previous studies have shown that HFOV does not always cause hemodynamic instability in this population.
This study’s findings suggest that, in select patients, early HFOV use could be a beneficial pre-ECMO strategy. The data also reinforce the importance of avoiding hemorrhagic and renal complications, as these significantly reduce survival chances.
Limitations and Future Research
While this study provides valuable insights, several limitations should be noted:
- Retrospective Study Design – The analysis relied on registry data, which may lack granular details on patient management and disease severity.
- Small HFOV Sample – Despite its strong statistical association with survival, HFOV was only used in 11% of cases, meaning further prospective studies are needed to confirm its benefits.
- Center-Specific Variability – Differences in ECMO and ventilation protocols across institutions could influence patient outcomes.
Future research should focus on prospective trials evaluating HFOV in pediatric cardiac patients with PH and strategies to reduce hemorrhagic and renal complications during ECMO.
Conclusion
In pediatric cardiac patients with pulmonary hemorrhage, this study identifies high-frequency oscillatory ventilation (HFOV) before ECMO as an independent predictor of survival. Additionally, avoiding hemorrhagic and renal complications significantly improves outcomes. These findings suggest that a proactive approach to pre-ECMO ventilation could be life-saving for critically ill children.
Given the high mortality rates associated with PH in CHD patients, optimizing ventilation strategies, complication management, and ECMO protocols is crucial. Future prospective studies could help refine these strategies and improve survival rates in this vulnerable population.
