Early determinants of right and left ventricular output in ventilated preterm infants.

Abstract

One hundred and twenty ventilated preterm infants, birthweight <1500 g, were examined within the first 36 hours with colour Doppler echocardiography, to determine the cardiorespiratory influences on right (RVO) and left ventricular output (LVO). Forty nine of these infants had three further daily scans. Measurements included left ventricular (LV) ejection fraction, Doppler determination of RVO and LVO, and ductal and interatrial shunt direction, velocity and colour Doppler diameter. Infants were grouped by respiratory disease severity: mild, mean F102 in first 24 hours <0 5; moderate/severe, mean FI02 <05; and fatal, death resulting directly from acute respiratory distress.In the early studies ventricular outputs varied widely (RVO: 62-412 ml/kg/minute, LVO: 75-505 ml/kg/minute). The incidence of low ventricular outputs (<150 ml/kg/ minute) increased with worsening respiratory disease. The incidence 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 atrial shunting was predominantly left to right except in those with fatal respiratory disease. In those studied longitudinally, RVO and LVO increased with age and low outputs were not seen after day 3.Multilinear regression analyses, with RVO as the dependent variable, revealed increasing LVO and atrial shunt diameter as significant positive influences and increasing ductal shunt diameter and mean airway pressure as a significant negative influence. With LVO as the dependent variable, increasing RVO, ductal shunt diameter, and age were significant positive influences and increasing atrial shunt diameter was a significant negative influence.Low ventricular outputs are more common with worsening respiratory disease. Mean airway pressure and ductal shunting are two negative influences on ventricular outputs over which there is some therapeutic control.(Arch Dis Child 1996; 74: F88-F94) Keywords: cardiac output, ductus arteriosus, respiratory disease, Doppler echocardiography.A fundamental aim in intensive care of preterm infants is the maintenance of adequate and stable systemic and pulmonary perfusion. The haemodynamics of the preterm cardiovascular system are complex with the problems of the transitional circulation and changing pulmonary vascular resistance being compounded by an immature myocardium1 and shunting across the fetal channels of the ductus arteriosus and foremen ovale.2 3 Such shunting usually diverts blood left to right from the systemic back into the pulmonary circulation. For the ductus arteriosus, such shunting has been shown to 'steal' blood from the systemic circulation4; atrial shunting could have a similar effect. Occasionally these shunts are right to left and so divert blood from the pulmonary to the systemic circulation with resultant hypoxaemia. Positive pressure ventilation, often essential to maintain oxygenation, can also compromise cardiac output.5The output from each ventricle will refl...

Cardiac troponin T and N-terminal-pro-B type natriuretic peptide reflect myocardial function in preterm infants

“…Poor myocardial function is common in these preterm infants, 21 and may be mediated by hypoxia and/or ischemia. 1 Infants requiring inotropes had higher cTnT compared to those who were normotensive but this did not reach statistical significance possibly due to the relatively small number of subjects. Clark SJ et al 18,22 showed a similar effect of inotropes on cTnT levels.…”

“…The higher cTnT levels in infants with RDS may therefore reflect the previously reported association between RDS and poor myocardial performance. 1 There was no relationship between cTnT and PDA diameter or LA:Ao suggesting that cTnT is less influenced by volume loading of the heart. N-terminal-pro-natriuretic peptide NTpBNP levels were not influenced by gestation, birth weight, gender, mode of delivery or antenatal factors.…”

“…1,14 (c) Shortening fraction: measured using M-mode echocardiography. 15 (d) Ductal diameter: absolute diameter in millimeters from the high parasternal view.…”

“…Respiratory distress syndrome and perinatal asphyxia are associated with low cardiac output and poor myocardial contractility. 1 Echocardiography is currently the best diagnostic tool available to assess cardiovascular function. 2 B-type natriuretic peptide (BNP) and N-terminal-Pro-BNP (NTpBNP) are released by the stressed myocardium in response to volume and pressure loading.…”

Cerebral Fractional Oxygen Extraction is Inversely Correlated with Oxygen Delivery in the Sick, Newborn, Preterm Infant

“…A previous study has shown that preterm infants have a significantly higher cerebral OEF on the first day after birth when compared with day 2 (Kissack et al, 2004). Left ventricular output (LVO) increases during the days after birth (Evans and Kluckow, 1996) and there is a significant correlation between cerebral OEF and LVO on the first day after birth (Kissack et al, 2004). The likely mechanism that links low LVO and increased cerebral OEF is that low LVO causes reduced cerebral oxygen delivery, but this has not previously been established.…”