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Mechanisms of change in cardiac performance in infants undergoing extracorporeal membrane oxygenation
D G Holley1, B L Short, S S Karr
1Department of Cardiology, Children's National Medical Center, Washington, DC 20010.
Insights
Cardiac performance changes in infants during extracorporeal membrane oxygenation (ECMO) are not caused by the disease or bypass itself. Instead, these changes are linked to altered cardiac loading conditions during partial bypass, impacting infant cardiac function.
Area of Science:
- Pediatric Cardiology
- Neonatal Intensive Care
- Cardiopulmonary Support
Background:
- Infants undergoing extracorporeal membrane oxygenation (ECMO) can exhibit altered cardiac performance.
- The precise causes of these cardiac changes during ECMO are not fully understood.
Purpose of the Study:
- To investigate the factors contributing to cardiac performance changes in infants during ECMO.
- To differentiate between disease effects, bypass procedure effects, loading conditions, and myocardial hypoxia-reoxygenation.
Main Methods:
- A consecutive case series of infants with meconium aspiration syndrome was studied.
- Cardiac performance was assessed at varying bypass flow rates using load-dependent and load-independent indices.
- Measurements included heart rate, mean arterial blood pressure, left ventricular shortening fraction, and stroke volume.
Main Results:
- Cardiac performance indices remained normal and stable across increasing bypass flow rates.
- No significant changes were observed in heart rate, blood pressure, or cardiac performance metrics with altered bypass flow.
Conclusions:
- Decreased cardiac performance during ECMO is not attributable to the underlying disease or the bypass procedure.
- Altered loading conditions during partial bypass are the primary cause of observed cardiac performance changes in infants.
Objective:
To determine whether changes in cardiac performance observed in infants early during extracorporeal membrane oxygenation are due to the underlying disease process, the partial bypass procedure, changes in cardiac loading conditions, or due to a direct myocardial effect of hypoxia-reoxygenation.
Design:
Consecutive case series.
Patients:
Infants with meconium aspiration syndrome were studied at the end of their extracorporeal membrane oxygenation course (veno-arterial, n = 12; veno-venous, n = 8), after lung compliance and pulmonary arterial pressure returned toward normal and they were ready to have extracorporeal membrane oxygenation discontinued.
Interventions:
Heart rate, mean arterial blood pressure, and load-dependent indices, and a load-independent index of cardiac performance were measured at increasing bypass flow rates (25, 50, 75, 100, 125 mL/kg/min).
Measurements And Main Results:
Heart rate, mean arterial blood pressure, and load-dependent indices of cardiac performance (left ventricular shortening fraction and stroke volume) were normal at 25 mL/kg/min bypass flow rate and did not change significantly with increasing bypass flow rates. The load-independent index of performance was within the normal range for infants and did not change significantly with increasing bypass flow rates.
Conclusions:
The previously described decreases in cardiac performance during extracorporeal membrane oxygenation are not due to the underlying disease process or the bypass procedure but are due to changes in loading conditions during partial bypass.