PH and the heart in preterms

Abstract

Cardiac function in preterm infants has been minimally evaluated. From the clinicians' perspective, if the blood pressure is normal—and normal is difficult to define—the heart function will be normal. Conversely, if blood pressure is low, then cardiac function likely is abnormal. In contrast to older children or adults, drugs are selected for blood pressure and myocardial support of preterm infants without evaluations of myocardial function. But the preterm heart differs even from the term heart and has unique challenges during transition after birth. Cardiac function deteriorates as pH falls in the mature heart, but, in this issue of The Journal, Noori et al report that the preterm heart is insensitive to changes in pH for about 2 weeks after birth. Subsequently, contractility degrades as acidosis increases, as with the mature heart. Vascular responses to acidosis change toward a mature pattern relatively rapidly after birth. The treatment of a low pH with bicarbonate has been discouraged in preterm newborns in recent years; a pH-insensitive myocardium is another reason not to treat acidosis with bicarbonate.Article page 958▶ Cardiac function in preterm infants has been minimally evaluated. From the clinicians' perspective, if the blood pressure is normal—and normal is difficult to define—the heart function will be normal. Conversely, if blood pressure is low, then cardiac function likely is abnormal. In contrast to older children or adults, drugs are selected for blood pressure and myocardial support of preterm infants without evaluations of myocardial function. But the preterm heart differs even from the term heart and has unique challenges during transition after birth. Cardiac function deteriorates as pH falls in the mature heart, but, in this issue of The Journal, Noori et al report that the preterm heart is insensitive to changes in pH for about 2 weeks after birth. Subsequently, contractility degrades as acidosis increases, as with the mature heart. Vascular responses to acidosis change toward a mature pattern relatively rapidly after birth. The treatment of a low pH with bicarbonate has been discouraged in preterm newborns in recent years; a pH-insensitive myocardium is another reason not to treat acidosis with bicarbonate. Article page 958▶ pH Effects on Cardiac Function and Systemic Vascular Resistance in Preterm InfantsThe Journal of PediatricsVol. 162Issue 5PreviewTo investigate the effect of pH on cardiac function and systemic vascular resistance (SVR) in preterm infants. Full-Text PDF