Although cardiac function in the neonatal period has been relatively well-studied, controversy still exists about cardiac function in the premature neonate, particularly with respect to left ventricular (LV) diastolic function.
Dopamine is commonly used in the treatment of preterm neonates with hypotension refractory to volume loading, its use is accompanied by variable effects on global heamodynamics as well as anterior cerebral and superior mesenteric artery perfusion. This variability may reflect differences in the relative magnitudes of the cardiac and peripheral actions of dopamine.
The first aim of the studies in this thesis was to evaluate the effects of patent ductus arterisus and gestational age on LV diastolic function in the premature newborn. The second aim was to investigate the mechanisms of blood pressure increase induced by dopamine in hypotensive preterm neonates.
An echocardiographic examination including digitized M-mode indices and Doppler indices of transmitral flow and aortic flow were used to assess cardiac function.
The main findings were:
1) use of M-mode echocardiography to assess cardiac function in preterm neonates is constrained by the presence of abnormal motion of the intraventricular septum. Doppler transmitral flow variables are more accurate and sensitive to assess cardiac diastolic function in the human preterm infant;
2) diastolic function is not affected by a small ductus arteriosus in the
3) cardiac function improves with gestational age in newborn neonates and
this improvement is in part due to gestation-related changes in heart rate;
4) in a portion of hypotensive preterm neonates receiving inotropic therapy
with dopamine, the increase in blood pressure induced by dopamine is related to a predominant vasoconstrictor action and is associated with a fall in bowel perfusion;
The major conclusion is that diastolic function in the neonate improves with gestational age. The increase in blood pressure induced by dopamine in hypotensive preterm neonates may be related to either a predominant inotropic or vasoconstrictor action of this agent.