EARLY DETERMINANTS OF RIGHT AND LEFT-VENTRICULAR OUTPUT IN VENTILATEDPRETERM INFANTS

One hundred and twenty ventilated preterm infants, birthweight < 1500 g, were examined within the first 36 hours with colour Doppler echocar diography, to determine the cardiorespiratory influences on right (RVO ) and left ventricular output (LVO). Forty nine of these infants had t hree further daily scans. Measurements included left ventricular (LV) ejection fraction, Doppler determination of RVO and LVO, and ductal an d interatrial shunt direction, velocity and colour Doppler diameter. I nfants were grouped by respiratory disease severity: mild, mean FIO2 i n first 24 hours < 0.5; moderate/severe, mean FIO2 < 0.5; and fatal, d eath resulting directly from acute respiratory distress. In the early studies ventricular outputs varied widely (RVO: 62-412 ml/kg/minute, L VO: 75-505 ml/kg/minute). The incidence of low ventricular outputs (< 150 ml/kg/ minute) increased with worsening respiratory disease. The i ncidence of low RVO in the mild group was 19%, in the moderate/severe group 42%, and in the fatal group 85%. More infants had a low RVO than a low LVO, reflecting the impact of ductal shunting. Ductal and atria l shunting was predominantly left to right except in those with fatal respiratory disease. In those studied longitudinally, RVO and LVO incr eased with age and low outputs were not seen after day 3. Multilinear regression analyses, with RVO as the dependent variable, revealed incr easing LVO and atrial shunt diameter as significant positive influence s increasing ductal shunt diameter mean airway pressure as a significa nt negative influence. With LVO as the dependent variable, increasing RVO, ductal shunt diameter, and age were significant positive influenc es and increasing atrial shunt diameter was a significant negative inf luence. Low ventricular outputs are more common with worsening respira tory disease. Mean airway pressure and ductal shunting are two negativ e influences on ventricular outputs over which there is some therapeut ic control.