Institution of cardiac bypass has resulted in cardiac dysfunction in some studies of ECMO. We hypothesize that pre-bypass oxygenation level (and possibly antioxidants) determines cardiac effect.

Methods: 21 newborn (4-7d) Dorsett lambs were anesthetized with pentobarbital and ventilated with 100% or 15% FiO2. Arterial, PA, RA, LV(Millar) and coronary sinus catheters were placed. Lambs were then cannulated, exposed to a 5 min dose of ECMO with hyperoxygenated sheep blood prime, assessed off ECMO, given a one hour dose of ECMO, and assessed on and off ECMO. LV dp/dt, shortening fraction (SF), rate corrected velocity of circumferential fiber shortening (mVCFc) and end- systolic wall stress were measured.

Results: PO2 increased from 38±4 torr to 126±38 (p=0.04, paired t-test) for the 15% group. Table shows LV results. A significant (p<0.05) decrease in SF and mVCFc is present for all points for 15% FiO2 lambs. dp/dt max shows significant decrease for 15% lambs for 5 min only (p=0.008) and for all points for 100% FiO2 lambs. LV end- diastolic dimension and wedge pressures were unchanged.

Table 1 No caption available.
Full size table

Conclusions: Echo plus hemodynamic indices of cardiac function suggest decreased function after a 5 minute exposure of hypoxic animals to hyperoxygenated extracorporeal circulation. Data supports the concept of cardiac reoxygenation injury in hypoxic newborns exposed to extracorporeal oxygenation.