Mechanisms of change in cardiac performance in infants undergoing extracorporeal membrane oxygenation.

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.