MECHANISMS OF CHANGE IN CARDIAC-PERFORMANCE IN INFANTS UNDERGOING EXTRACORPOREAL MEMBRANE-OXYGENATION

Objective: To determine whether changes in cardiac performance observe d in infants early during extracorporeal membrane oxygenation are due to the underlying disease process, the partial bypass procedure, chang es 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 t heir extracorporeal membrane oxygenation course (veno-arterial, n = 12 ; veno-venous, n = 8), after lung compliance and pulmonary arterial pr essure returned toward normal and they were ready to have extracorpore al membrane oxygenation discontinued. Interventions: Heart rate, mean arterial blood pressure, and load-dependent indices, and a load-indepe ndent index of cardiac performance were measured at increasing bypass flow rates (25, 50, 75, 100, 125 mL/kg/min). Measurements and Main Res ults: Heart rate, mean arterial blood pressure, and load-dependent ind ices of cardiac performance (left ventricular shortening fraction and stroke volume) were normal at 25 mL/kg/min bypass now rate and did not change significantly with increasing bypass now rates. The load-indep endent index of performance was within the normal range for infants an d did not change significantly with increasing bypass flow rates. Conc lusions: The previously described decreases in cardiac performance dur ing extracorporeal membrane oxygenation are not due to the underlying disease process or the bypass procedure but are due to changes in load ing conditions during partial bypass.